Journal of the American Mosquito Contol Association, l7(3):166-180, 2001The copyright of the publication does not extend to this article.

MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATINAMERICA-AN ELEVENTH SYMPOSIUM

GARY G. CLARK' eNo HUMBERTO QUIROZ MARTiNEZ' (ORGANIZERS)

ABSTRACT, The llth annual Latin American symposium presented by the American Mosquito ControlAssociation (AMCA) was held as part of the 67th Annual Meeting in Dallas, TX, in February 2001. The principalobjective, as fbr the previous 10 symposia, was to promote participation in the AMCA by vector control spe-cialists, public health workers, and academicians fiom Latin America. This publication includes summaries of45 presentations that were given orally in Spanish or presented as posters by participants from 8 countries rnLatin America. Topics addressed in the symposium included results fiom chemical and biological control pro-grams and studies; studies of insecticide resistance; and population genetics, molecular, ecological, and behav-ioral studies of vectors of dengue (Aedes aegypti), malaria (Anopheles albimanus and Anopheles aquasalis),leishmaniasis (Lutzomyia), murine typhus, and Chagas' disease (Triatona). Related topics included biology andcontrol of Rhodnius, scorpions, Loxosceles spp., Chironomus plumosus, and Musca domestica.

KEY WORDS Mosquitoes, mosquito control, Aedes, Anopheles, Culer, Lutzomyia, Triatoma, scorpions, lox-osce le s, M ust:a dome stica, C hirrnomu.s. resistance

INTRODUCTION

The American Mosquito Control Association(AMCA) is dedicated to the study and control ofmosquitoes, other vectors, and other arthropods andpromotes cooperation and interaction among pro-fessionals and students in this field both in the USAand internationally. To promote greater and moreactive participation among and with a portion of itsinternational membership, a Spanish language sym-posium was held at the AMCA Annual Meeting in1991 and symposia have been held at subsequentmeetings. In addition to providing a fbrum for sci-entists whose primary language is Spanish, the ses-sion promoted interaction and esprit de corps withinthis group; interaction with control industry repre-sentatives; and interaction with prof'essional col-leagues in the USA who are involved in mosquitovector control, training, and research at the univer-sity level, and with state and federal governmentofficials-

This publication includes summaries of 45 pre-sentations that were given in Spanish by partici-pants from 8 countries in Latin America. Topicsaddressed in the symposium included results fromchemical and biological control programs and stud-ies; studies of insecticide resistance; and populationgenetics, molecular, ecological, and behavioralstudies of scorpions, Loxosceles spp., Chironomusspp., and Musca domestica, and vectors of dengue(Aedes aegypti (L.)), malaria (Anopheles albimanusWiedemann and Anopheles aquasalis Curry), leish-maniasis (Lutzomyia), and Chagas' disease (Triat-orra). Summaries of 9 previous symposia havebeen published (Clark and Suarez 1991, 1992,

I Dengue Branch, Centers for Disease Control and Pre-vention, 1324 Calle Cafrada, San Juan. PR 00920-3860.

'�Laboratorio de Entomologia, Facultad Ciencias Biol-6gicas, Universidad Aut6noma de Nuevo Le6n, San Ni-col6s de los Garza, Nuevo Le6n. M6xico.

1993; Clark 1995, 1996; Clark and Rangel 1997,1998, 1999; Clark et al. 2000).

Financial support for this session was providedby the following sponsors and individuals: Aventis(Robin Slatter), Clarke Mosquito Control Producrs(Lyell Clarke III), Curtis DynaFog (Mike de Lara),H. D. Hudson (Manuel Lluberas), Summit Chemi-cals (Jonathan Cohen), Zoecon Prof'essional Prod-ucts (John Neberz), Rockefeller Foundation, andthe Pan American Health Organization. Funds fromthese sponsors provided Annual Meeting registra-tion and partially defrayed travel expenses formany symposium participants. Enthusiasm and in-terest fbr this symposium among Spanish and non-Spanish speaking participants was high and it willcontinue to be a part of future meetings.

PRESENTATIONS

Vector populations (order: Diptera) in thePanama Canal areas (1999-2000)

Gloria D6vila de Obaldia, L,eopoldo De Le6n,Ricardo Carrasco and Victor Young

Autrtridad Canal Panama, Secci6n de Sanidad yEntomologia, Panama City, Panama.

The Panama Canal Authority maintains a sur-veillance program of mosquito and sand fly popu-lations within its operational areas. The need forthis program is to protect its clients, visitors, andthe workforce against vector-borne diseases. Forthis purpose, 19 New Jersey light traps are locatedin difTerent areas, supplemented by the activesearch for mosquito larvae along the 50 mi of prop-erty along the waterway. Collections were identi-fied daily and results were analyzed weekly. Resultsobtained during the wet and dry seasons are pre-sented. Major vectors of diseases are in the generaAnopheles, Culex, Aedes, Mansonia, and Lutzo-myia. The most important mosquito vectors are

SEprevsen 2001 Svvposturvr oN Moseurro CoNrnol ru LetlN Aurntce t67

Anopheles albimanus and Aedes aegypti. Monitor-ing insect vector populations is a very importantstep before implementing routine control opera-tions, which are structured on an integrated pestmanagement system that always attempts to protectthe environment. The program is based on the elim-ination or control of breeding sites and a continuedmonitoring of the incidence of disease within thePanama Canal areas.

Entomological surveillance of Aedes aegypti andAe. albopictus ovitrapping program inVeracruz, M6xico, during 1998-1999

C. Martinez-Campos, A. P€rez-Garcia,C. Pdrez-Renteria,

L. Hidalgo and J. Escobar

Departamento de Entomologia, Instituto deD iagn6stico y Referenc ia Epidemio 16 gicas, " D r.

Manuel Martinez Bdez," Secretarla de Salud,Mdxico, Distrito Federal: and Deportamento de

Control de Vectores, Secretaria de Salud delEstado de Veracruz, Mdxico

From 272 mosquito samples received from thestate of Yeracruz, 3 samples from Martfnez de laTorre had Aedes albopicras. This is the lst recordof this species in the state. The entomological sur-veillance program was enhanced and included thecollection of mosquito larvae from artificial con-tainers and the use of ovitraps in outdoor and in-door urban areas to detect Ae. albopictus popula-tions in selected communities throughout the state.Eggs from ovipaddles were hatched and reared withdog food powder to obtain 4th-stage larvae oradults for species identification. A total of 5,424ovipaddles from 10 sanitary districts was receivedat the laboratory during 2 years. In 1998, 1,743samples (627o) had Aedes aegypti and I,O87 (387o)were negative. During 1999, 1,884 (73Vo) ovipad-dles were positive for Ae. aegypti,696 (21Vo) werenegative, and 2 were positive for Ae. albopictus andAe. aegypti in I district. This finding confirms therecord of Ae. albopictus in M6xico and suggests thespecies is spreading toward southern M6xico.

Rapid spray of insecticide in high-risk housesas an alternative for the control of Aedes

aegypti

Juan I. Arredondo-Jim1nez. Juan G. Bond.Norma E. Rivero, Silvany Rios,

Esther Cruz and Mario H. Rodrfguez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas,

Mdxico; and Centro de Investigaciones sobreEnfermedades Infecciosas, Instituto Nacional de

Salud Priblica, Cuernavaca, Morelos, Mdxico

We evaluated the rapid spray of insecticide forthe control of Aedes aegypti in 6 cities in southern

M6xico. Tleatments were insecticide application ofall the houses within a city; focal treatment of high-risk houses, classified by the premise condition in-dex (PCI); and larval control with conventional lar-viciding (temephos). The PCI was based on thegood, moderate, or bad appearance ofhouse, shade,and tidiness of backyard. Insecticide droplets of50-l0O pm were applied with a mistblower at ratesof 13 and 2O mg active ingredient/mz for delta-methrin and bifenthrin, respectively. Insecticide im-pact was measured on larval and adult aedine in-dicators, whereas insecticide residuality effect wasestimated. Each house was treated in l0 min. In-secticide residual effect with 75Vo rnortality lastedfor up to 19 wk. All aedine indices were reducedin insecticide-treated houses as compared to controlareas, and adult populations were suppressed frompremises for up to 12 wk. These reductions weremore apparent in the full treatment areas, but notdifferent than in focally treated cities. Therefore,the full or focal rapid spray to control Ae. aegypriproved more effective than conventional larvicid-ing. These strategies remain to be evaluated onwhether I or the other reduces or suppresses den-gue transmission.

Laboratory evaluation of permethrin-irnpregnated bed-nets against Aedes aegypti

K. L. Saavedra-Rodriguez, H. Quiroz-M arlinez,K. M. Valdez-Delgado, V. A. Rodriguez-Castro,R. Mercado-Hern6ndez and I. Fern6ndez-Salas

Laboratorio de Entomologta and I'aboratorio deEntomologia Mddica, Facuhad de Ciencias

Biol1gicas, Universidad Aut1noma de NuevoLe6n, San Nicolds tle los Garza, Nuevo Le6n,

Mdxico

Impregnated bed-nets have been an importanttool to prevent mosquito-biting activity. The effi-cacy of permethrin on impregnated nets of 100%nylon ( l-mm mesh), 7O0Vo nylon (0.1-mm mesh),and lOOTo polyester (2-mm mesh) was evaluatedagainst Aedes aegypri under laboratory conditions.All 3 types of bed-net material were impregnatedwi th 1 , O.5 , 0 .25 ,0 .15 , 0 .1 , 0 .05 , and O.OlVo o fpermethrin. The knockdown time and knockdownand mortality rates were registered weekly for 2months after impregnation. The test material im-pregnated with l, 0.5, and O.257o permethrincaused 1007a knockdown and 100% mortality ratesduring the 2 months after impregnation and the av-erage time required for complete knockdown wasbetween 2.25 and 4.50 min. Mortality registeredwith permethrin concentrations of O.l5 and O.lVowere 85-l00%o and 6O-95Vo during the 2 monthsafter treatment, respectively. Knockdown time wasbetween 5.75 and 10.0 min during the 1st and 8thwk after impregnation, respectively. No significantdifference in mortality rates was found among the3 materials tested.

r68 JounNal op rHe AMenrcaN Mosgurro CoNrnol Assocr.lrroN VoL. 17, No. 3

Chlorine bleach as an ovicide for Aedes aegyptieggs

Jos6 R. Albaine Pons, Guillermo Gonzalvez,Angel Solis y Juana de los Santos

Centro de Control de Enfermedades Tropicales(CENCE:|), Ministerio de Salud Prtbhca y

Asistencia Socictl, Santo Domingo, DominicanRepublic

Chlorine bleach (5.25Vo sodium hypochlorite so-lution) was studied as an ovicide for Aedes aegypri.Strips of paper towels with 100 or 200 eggs wereset on the bottom or the side of 6-liter plastic con-tainers. Pure or 5OVo bleach was added with a sy-r inge to the eggs and after 5, 10, 15, 20,3O,45, or60 min the recipient was filled with tap water cov-ering the eggs. Each test was replicated 3 timeswith controls (recipient with eggs and tap water).Larvae were counted I wk after the onset of trials.The longer the time of exposure to the bleach thefewer larvae were counted after I wk in the exper-imental containers. Exposure to pure chloridebleach for 15 min produced an average of 4.67 lar-vae and a similar exposure to 50Vo bleach for thesame time produced 64.53 larvae versus a mean of105.0 in the conrrols (P < 0.05). Tiials with six 55-gal metal drums, which are widely used in the Do-minican Republic for water storage, were dividedin half by plastic walls. One half was used as acontrol and the other was treated with pure bleachfor 15 min. A mean of 3.3 larvae was found in thebleached half versus a mean of 58 larvae, pupae,or both in the controls (P < 0.05). Utilizing 8 metaldrums full of eggs, 3 were treated with pure bleachthat was applied with a sponge to soak the innerwalls and 15 min later filled with tap water. Fivecontrols were used. Our results showed that the ex-perimental drums had 1.0 and 3larvae, whereas thecontrols had hundreds of larvae.

Larvicidal activity of extracts of four species ofAgave on Aedes aegypli larvae

Susana De la Torre, Azucena Oranday,Marfa L. Rodrfguez,

Maria J. Verde and Catalina Rivas

Laboratorio de Fitoquimica and Laboratorio deEntomologfa, Facultad de Ciencias Biol1gicas,

Universidad Aut6noma de Nuevo Le6n, SanNicohis de kts Garza, Mdxico.

The toxic impacts of natural products obtainedfrom algae and plants on insect larvae were studiedas a possible strategy for dengue vector control inM6xico. In 1999, M6xico experienced 14,655 casesof classical dengue and 25 cases of dengue hem-orrhagic fever;63.6Vo of these cases were reportedin the northern states of Nuevo Le6n and Tamau-lipas. These states have many species of plants inthe family Agavaceae, which has shown different

biological effects on bacteria, fungi, insects, ani-mals, and humans. The purpose of this study wasto evaluate the larvicidal impact of extracts ob-tained with acetone and methanol of Agave amer-icana, A. lechuguilla, A. lophanta, and A. scabra.The greatest toxicity was found at 100 ppm in themethanolic extract of A. lophanta (67Vo mortality)and A. scabra (>SOVo). The extracts obtained withacetone at 100 ppm from A. americana and A. le-chuguilla registered low larvicidal effects (<35Vo).The active extracts were tested with colorometricchemical reactions to identify functional groups andsecondary metabolites (possible toxic compounds).Both extracts (methanol and acetone) were positiveto esterols, terpenes, and saponins, whereas cou-marins were positive only for the methanolic ex-tracts.

Why doesn't dengue exist in Ponciano Arriaga,M6xico?

J. F Martinez-Perales, H. Quiroz-Martinez,V. A. Rodriguez-Castro, F. Gonz6lez-Jim6nez,

M. H. Badii and L.O. Tejada.

Departamento de Control de Vectores, Serviciosde Salud de San Luis Potosi; Laboratorio de

Entomologfa, Facultad de Ciencias Biol6gicas,Universidad Aut6noma de Nuevo Le6n, San

Nicokis de los Garza, Nuevo Le6n; and Programade Graduados de la Divisi6n de Agricultura y

Tecnologfa de Alimentos, Monterrey, Nuevo Le6n,Mdxico

Although several cases ofdengue were registeredin the Huasteca Potosina in 1998, no case was re-corded in the small town of Ponciano Arriaga. Be-cause of that, an entomological survey was under-taken to better understand why dengue was notfound there. We found that people from PoncianoArriaga store water in cement containers that havebeen closed with materials such as cement, metalliccovers, or plastic films. In the open containers, wefound 2 notonectid species, Notonecta irrorata anldBuenoet scimitra, and although the containers werecleaned monthly, the predators apparently persisted.Accordingly, community members and health min-istry personnel gave information abottt Aedes ae-gypti, dengue fever, and vector control without in-secticides.

Murine typhus in the state of Veracruz,M6xico

B. Salceda-S6nchez, E. Argott, C. Martinez-Campos and B. Brisefro Garcfa

Departamento de Virologia Diagn6stica, Institutode Diagn6stico y Referencia Epidemiol6gicos

(INDRE) "Dr. Manuel Martinez Bdez,"Secretaria de Salud, Mdxico, Distrito Federal,

Mdxico

Between 1990 and 1996,667 cases of rickettsi-osis (867o of which were murine typhus), were re-

SEPTEMBER 2001 Svvposruv oN Moseurro CoNrnoL rl LenN AMERTCA r69

corded in M6xico. Previous observations indicatedthat this disease had a higher incidence in femalesolder than 25 years of age. ln 1997, a case of mu-rine typhus was identified in Zaragoza, a smallcommunity (8,000 inhabitants) in the state of Ver-acntz. A total of l30 serum samples from patientswith clinical symptoms associated with this diseasewere sent to INDRE. Indirect inmunofluorescence(lIF) fbr immunoglobulin M was positive in 106samples (25 males and 81 females). One of 3 ratscollected in Zaragoza was highly positive by IIF inliver and kidney extracts and the other 2 were lowpositives. Twenty-two ectoparasites were obtainedfrom the rats, including the natural vector of Rick-ettsia typhi, Xenopsylla cheopis. These results in-dicate that an outbreak of murine typhus occurredin 1997 in Zaragoza, Veracruz. As a control mea-sure, rats were almost completely eliminated fromthe community by baited traps.

Egg production, fertility, and defecationpatterns of four Mexican Triatominae(Hemiptera: Reduviidae) species under

laboratory conditions

Jos6 Alejandro Martinez-Ibzrra, Josefi na CeciliaTrujillo and Yunuen Grant Guill6n

Laboratorio de Salud Prtbhca, CentroUniversitario d.el Sur, Universidad de

Guadalajara, Guadalajara, JaLisco; Laboratoriode Salud Prtblica, Servicios de Salud en el Estado

de Oaxaca, Oaxaca, Oaxaca; and Servicios deSalud en el Estado de Jalisco, Guadalajara,

Jalisco, Mdxico

In M6xico, Triatoma pallidipennis, T. longipennis,T. picturata, and T. phyllosoma are considered to bethe most important vectors of Chagas' disease. Stud-ies of their biology can increase the understandingof their role in Trypanosoma cruzi ftansmission tohumans and could improve control programs. Forthese reasons, research on mean egg production, fer-tility of eggs, and defecation patterns was conductedin these 4 species. The species have been maintainedunder laboratory conditions at 27 + 2"C and 55 +

5Vo relative humidity, and fed on New Zealand whiterabbit weekly. During a study period of 90 days, amean of 2.O eggslfemalelday and egg fertility of98.8Vo (n : 1,757) were recorded for T. pallidipen-nis, 2.2 eggs/female/day and egg fertility of l8.3Vo(n : 1,953) were recorded for Z. longipennis, 2.Oleggs/female/day and fertility of 65.lVo (n : 1,853)were recorded for T. picturata, and 1.8 eggs/female/day and fertility of 84.27o (n : 1597) were recordedfor T. phyllosoma. Most lst-stage bugs (70-807o)defecated 1 min after feeding. These baseline datasuggest that these 4 species can be considered asimpoftant vectors of T. cruzi to humans.

Triatome bugs infected with Trypanosoma cruzifrom dwellings in M6xico

V. Vidal-Acosta, C. A. Cano-Reveles, J. L. Tellez-Rend6n and G. Aquino-Rubio

Departamento de Entomologfa, Instituto deDiagnri st ico y Refe rencia Epide mioki g ico s " Dr.Manuel Mart{nez Bdez," Secretarta de Salud,

Mdxico, Distrito Federal, Mdxico

Chagas' disease is an important public healthproblem in Latin America. Triatomine bugs are nat-ural vectors of Trypanosoma cruzi, the etiologicagent of Chagas' disease. Vector transmission is themain source of int'ection to humans. In the presentstudy, the frequency of infection and the distribu-tion of triatomine bugs was obtained to identify riskareas. During 1999 and 2000, we received 946 tia-tomine bugs collected from dwellings in 9 states inM6xico. The frequency of infection was determinedby searching for T. cruzi in the bugs' feces. ThreeTriatoma picturata collected in Nayarit were posi-tive. The Triatoma pallidipennis collected in Mo-relos were also positive, as were 487o of those re-ceived from Michoacan. Positivity of Triatomadimidiata was 26Vo in Hidalgo, l5%o in Veracruz,and zero in Puebla. Ten percent of Triatoma sp.were positive and the remaining species were neg-ative. Collection sites with triatomine bugs identi-fied in Veracruz State included bedrooms. beds, andwalls. We found that T. pallidipennis had the high-est percentage of T. cruzi, followed by T. dimidiata.

Association of scorpion sting cases with highlytoxic scorpion species in M6xico

V. Vidal-Acosta and C. Martinez-Campos

Departamento de Entomologia, Instituto deDiagn6stico y Referencia Epidemiol6gicos " Dr.Manuel Martinez Bdez," Secretaria de Salud,

M€xico, Distrito Federal, M€xico

Scorpions may sting any human but most fre-quently sting children and older people. After eval-uating annual scorpion sting reports, 16 states lo-cated on the Paciflc coast and inland are consideredendemic. The purpose of this study was to associatethe frequency of scorpion stings with the occur-rence of highly toxic species. For this, taxonomicidentification of scorpions was performed and com-pared to the distribution and number of scorpionstings in l0 endemic states. Between 1995 and2000, we received 855 scorpions specimens from17 states. The following data were obtained: Nay-arit (4 species), Oaxaca (3), M6xico (2), Puebla (2),Guerrero (2), Sinaloa (2), Queretaro (l), Colima(l), Durango (l), and Guanajuato (1). Of thesestates, Guerrero, Guanajuato, Colima, and Pueblahave had more than 50,000 cases in the last 5 years.In Nayarit, although 5 species were found and I ofthem (Centruroides noxius) is the most toxic, the

t70 JounNlr- oF rne AuenlcAN Moseurro CoNrnor- AssocrATroN Vol. 17, No. 3

number of stings reported was low compared toGuerrero, where 2 species were found. Apparently,no correlation exists between the number or varietyof toxic scorpion species found and the number ofsting cases reported by the state.

Mortality by sting intoxication of scorpions inGuerrero, M6xico (1998-2000)

A. Herniindez-Ramirez and V. Vidal-Acosta

Direcci6n General de Epidemiologia andDepartamento de Entomologfu, Instituto de

Diagn6stico y Referencia Epidemiol6gicos "Dr.

Manuel Martinez Bdez" Secretaria de Salud,Mixico, Distrito Federal, Mdxico

During 1998, scorpion sting intoxication was thel5th greatest cause of morbidity in M6xico. Guer-rero is one of the 16 states with highly toxic scor-pions, including many important species and sub-species in the genus Centruroides. The objective ofthis project was to establish risk areas by studyingmorbidity and mortality. We conducted a transversestudy to determine deaths by sting, cases, and dis-tribution of death by scorpion species, through theanalysis of death certificates and morbidity andpopulation data, and by collection of scorpions. Thestudy was performed in 6 of Guerrero's 7 sanitarydistricts. The highest morbidity rate was in the 2nddistrict, with 86.5 cases per 10,000 inhabitants. The3rd district had a mortality rate of 1.8 deaths per10,000 inhabitants and the 4th district had a lethal-ity rate of 2.9 deaths per 1,000 cases registered.This district has the county with the highest mor-bidity rate (Olinal6 with 4'/7 cases), mortality rate(Copanatoyac with 15 stinging deaths), and lethal-ity (Zapotitlfln Tablas with 333 deaths by sting).Centruroides limpidus was the most abundant spe-cies. Mortality and lethality did not share the samehyperendemic zones.

Distribution of Loxoscelidae (Araneae:Araneomorphae) in Nuevo Le6n, M6xico

Carlos Solis-Rojas, Jos6 Juan Flores-Maldonado,Alfonso Flores Leal and Katiushka Ar6valo Nifro

Colecci6n Aracnol6gica, Laboratorio deEntomologia y Artrdpodos, Facuhad de Ciencias

Biol6gicas, Universidad Autdnoma de NuevoLetin, San Nicolas cle los Garza, Nuevo Le6n,

Mdxico

The family Loxoscelidae includes the genus Zox-osceles, which has about 9O species in the Ameri-cas. In the USA and northern M6xico, Loxoscelesprisoner, L. arizonica, and L. deserts have been re-ported, whereas in South America, L. laeta, L.spadicea, L. rufescens, and L. gaucho have beenreported and found to cause severe cutaneous ne-crosis in man. All species in this genus have beenrepofted to produce "loxoscelism." The objectives

of our study were to conduct studies to charactertzeand inventory the species the Loxosceles in NuevoLe6n, M6xico; to provide elements to assist in theidentification of Loxosceles species; and to gatherdata on their distribution and biology. A total of204 specimens belonging to the ArachnologicalCollection were reviewed. Of these, 447o weremales, 367o were females, and the remaining 2O7owere juveniles. We confirmed the presence of Z.devia and L. candela in Nuevo Le6n, as well as thelst record of L. belli. According to the collectionrecords, L. devia and L. candle are present in urbanhabitats and they are commonly found on the floor,and hidden between or under stones, or in cracks.

Malaria vectorial capacity of Anophelespunctimacula in southern Chiapas, M6xico

Armando Ulloa and Juan I. Arredondo-Jimlnez

Centro de Investigaci4n de Paludismo, InstitutoNacional de Salud Prtblica, Tapachula, Chiapas,

Mdxico

We studied the bionomics of Anopheles puncti-macula, an abundant species that readily bites hu-mans, along the coastal plain of Chiapas, M6xico.This mosquito has been reported elsewhere as a sec-ondary malaria vector. Human landing collectionswere conducted to assess its abundance and bitingcycle. Blood-engorged mosquitoes from indoor andoutdoor resting collections were assayed to establishthe human blood index. Daily changes in the parous-nulliparous ratios in An. punctimacala females wereused to calculate daily survivorship and gonotrophiccycle and the vectorial capacity was calculated. Theresulting human biting rate was 18.65 (4.53 mosqui-toes/man/night). The biting cycle showed an earlyevening peak by An. punctimacula, with 5O7o of lhebites occurring before 22OOh. The daily survival rateof An. punctimacula was 0.68 and a 4-day gonotroph-ic cycle was found (r : 0.709; P : 0.0067). Thesporogonic cycle was calculated based on a meantemperature of 26.2"C, and was 8.97 days for Plas-modium vivax and 10.88 days for P. falciparum. Re-sulting vectorial capacity was 1.08 and 0.49, respec-tively, for P. vivax and P. .falciparum. Tltis figure washigher than those reported for other confirmed anoph-eline vectors in the area.

Colonization of Anopheles darlingi from theLacandon Forest, Chiapas, M6xico

Cuauht6moc Villarreal, Juan I. Arredondo-Jim6nez, Iliana R. Malo and M. H. Rodriguez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas;

Instituto de Fitosanidad, Colegio deP o st g,raduados, Montecillos, Es tado de M dxico ;Centro de Investigaciones sobre Enfermedades

Infecciosas, Instituto Nacional de Salud Ptiblica,Cue rnavaca, Morelos, Mdxico

Anopheles darlingi, the main vector of malariain the Americas, has a limited distribution in M6x-

Seprerr{srn 2001 SyMposrr,\4 oN Moseutro CoNrnol N LATIN AMERICA

ico, although it has not been found to be infectedwith Plasmodium. The low population density ofAn. darlingi in the field and the difficulty in estab-lishing laboratory colonies have contributed to alimited knowledge of this species. In March 2000,we collected An. darlingi on animals and humansin the Lacand6n Forest in Chiapas State. Eggs ob-tained from 5 females through induced ovipositionwere taken to an insectary situated 280 km to thesouthwest. Larvae were reared and mating was in-duced in 270 F, adults with 12:12 h light: dark pho-toperiod, 30"C:25'C day:night thermoperiod, andaided from 1930 to 2O3O h with a flashlight hori-zontally set at 0.15 m from the edge of a standardcage (0.6 x 0.6 x 0.6 m). Females were allowedto oviposit, and eggs were incubated for 48-120 hand had a 45Va hatching rate. The F, larvae werefed with mouse feed. Larval survivorship was98Vo,with mean pupation time of 11 days. Adults wereoffered blood meals every 48 h and female longev-ity averaged 30 days. Insemination in femalesranged from 25Vo (Fr) through 367o (F). The col-ony has been maintained for 7 generations, with aproduction of 25 larvae in the F, generation to 510in the Fu generation.

Phase III trials of bifenthrin to controlAnopheles in southern M6xico

Juan I. Arredondo-Jim1nez, Norma E. Rivero,Iliana R. Malo, Antonio Tiejo, LTlia GonzSlez-

Cer6n and Mario H. Rodriguez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Prtblica, Tapachula, Chiapas;

and Centro de Investigaciones sobreEnfermedade s Infe ccio s as, Instituto Nacional de

Salud Piblica, Cuernavaca, Morelos, Mdxico

Although use of DDT in M6xico must be dis-continued by 2OO7, it has already been replaced bydeltamethrin for malaria vector control. However,considering a rotation scheme for the long term isnecessary to define which product(s), includingnew insecticides, can be used. Desired attributes ofnew insecticides are high killing and low repellenteffect against mosquitoes; sustained residual effecton walls; low toxicity and persistence in the envi-ronment, wildlife, and humans; and acceptance byresidents and spraymen. In this study, we conductedphase III studies (village-scale) to compare the ef-ficacy of the indoor residual spray of the novel py-rethroid bifenthrin (OMS 3024) with deltamethrinagainst the malaria vectors Anopheles albimanusand An. pseudopunctipennls. Studies included base-line anopheline susceptibility against bifenthrin,and village-scale trials in 2 epidemiological situa-tions where An. albimanus or An. pseudopunctipen-nis were the prevalent vectors, to establish the im-pact of bifenthrin on the mosquito populations andthe appropriate frequency of insecticide application.Methods of evaluation included insecticide perfor-

mance, entomological impact, and acceptance oftreatments by residents and spraymen. Overall re-sults confirmed the potential of bifenthrin as a re-sidual insecticide for the control of both malariavectors in southern M6xico.

Morphological differences among Anophelesvestipennis populations

Arnoldo Orozco, Armando Ulloa, Mario H.Rodrfguez and Juan I. Anedondo-Jim6nez

Centro de Investigaci6n de Paludismo, InstitutoNacional de Salud Priblica, Tapachula, Chiapas;

and Centro de Investigaciones sobreEnfermedades Infecciosas, Instituto Nacional de

Salud Pilblica, Cuemavaca, Morelos, Mdxico

Evidence for the existence of a species complexwithin Anopheles vestipennis is coming from manysources, including isozyme and random amplifiedpolymorphic DNA polymorphism, egg ultrastruc-ture, and ecology. In this study, we compared thewing length and sector dark spot (SD) length ofsympatric anthropophilic and zoophTlic An. vesti'pennis populations. The F, mosquitoes from fe-males collected on human or animal hosts in Chia-pas, M6xico, were released in the center of anexperimental hut. Side compartments contained 2humans and an animal host. Faithful mosquitoes,that is, those selecting the same host from whichparental females were collected, were recorded.The wing and SD lengths of anthropophilic mos-quitoes (4,001.38 + 18.73 pm, range 3,571-4,333pm;, and 703.36 -r 8.17 pm, range 547-857 p'm,respectively) were significantly greater than thoseof zoophilic mosquitoes (3,919.47 + 18.19 pum,range 3,428-4,285 p.m, lt : 49.87, df : 137, P <0.051, and 676.81 -r 7.67 li,m, range 571-809 pm,respectively, l t : 30.17, df : I19, P < 0.051). Theratio of wing length to SD length was lower in an-thropophilic mosquitoes (5.717O + 0.16, range4.84-6.78) compared with zoophilic mosquitoes(5.7238 + 4.94-6.83; t = 14.06, df : 93, P <0.05). These results suggest segregation amongpopulations with different feeding preferences.

Morphometric variation in Colombianpopulations of Anopheles d.arlingi

Ranulfo Gonzfllez, Heiber Cdrdenas, Marco ESuiirez, Felipe Garcia and Richard Wilkerson

Facultad de Ciencias y Facultad de Salud,Universidad del Valle, Cali, Colombia: and

Department of Entomology, Walter Reed ArmyInstitute of Research, Washington, DC

In the present study morphometric variation wasevaluated to determine heterogeneity and to iden-tify characters that have a genetically detectablecomponent in a population of Anopheles darlingifrom Colombia. The morphometric variation of the

t 7 2 JounNal or rHs ANnenrc,qN M<lseuno Conrnol AssocrlrroN VoL. 17, No. 3

costal patterns and hind tarsus II in eastern andwestern subpopulations was analyzed. Three hun-dred ninety-two offspring (257 t'emales and 135males) and 249 females from the Museum of En-tomology of the Universidad del Valle were includ-ed in the analysis. According to the variation of thecostal patterns, it was possible to detect up to 15different types. The highest frequency was recordedin only 2 patterns, which actually were defined fbrall costal areas (:type I) and the junction ofPSD+SP+PRSD (:type II) . Type I was predomi-nant in the eastern subpopulation, whereas type IIwas predominant in the western subpopulation. Thesex as well as the costal patterns (I, II) aff'ected thevariation in some of the analyzed characters; ananalysis of variance with the data of the offspringshowed that only some characters of the costal spot(PHD, HP, PSR SP) but they did not presenr sexualdimorphism. Independently of the coastal patternand of sex, of the 16 characters analyzed, only 3were consistent with the differentiation of subooo-ulat ions, and this was sustained in a senetic com-ponent. Of the total variation of the phenotype. be-tween 54 and 62Vo of the variation of the character(appraising dark area of the Tlll-2llongitude of theTIII-2) was due to significant diff'erences among thesubpopulations. Other costal characters are popu-lation-specific depending on the analyzed patternand the sex.

Population genetics of Anopheles albimanususing microsatellite markers

Carolina Schoua, Maria Marta Yurrita, Ana Mariade Merida, Alvaro Molina-Cruz and

Wil l iam C. Black IV

Universidad del Valle. Guatemala Citv.Guatemala; and Department rf Microbiology,Colorado State University, Fort Collins, CO

In a previous study, we examined the distributionof mitochondrial DNA haplotypes among popula-tions of Anopheles albimanus from Guatemala totest for gene flow barriers using a -350-base pairsequence of the mitochondrial reduced nicotin-amide adenine dinucleotide dehydrogenase subunir5 (ND5) gene. Little variation was found amongsamples of populations or regions across 3 seasons.We have developed microsatellite markers to fur-ther analyze the population structure of An. albi-manus with an independent marker. Three micro-satel l i te primers ( l-9O, 2-14, and 6-41) producedconsistent polymerase chain reaction products andpresented 18,20, and 12 alleles, respectively. Pop-ulations from different regions of Guatemala(northern, southern, and eastern) presented varia-tions in the frequency of alleles for the 2 microsat-ellite markers analyzed. Comparison between the 3regions using analysis of variance showed that92.857o of variation in allele frequency aroseamong individuals in a collection, whereas only

4.23Vc of variation arose among collections in aregion, and 2.92Vo of variation arose among re-gions. This analysis indicates that small variationexists among populations from northern, southern,and eastern Guatemala; this variation is higher thanthat detected with mitochondrial markers (l.67%avariation among regions), but is smaller than thatdetected with intergenic spacers of nuclear ribo-somal DNA (8.7Vo variatton among regions).

A population genetics study of Anophelesdarlingi from Colomtria based on random

amplified polymorphic DNA*polymerase chainreaction and amplified fragment length

polymorphism (AFLP) molecular markers

Ranulfo GonzLlez, Marco E Su6rez, FelipeGarcia, Richard Wilkerson, Gerardo Gallego,

Carmen E. Posso and Myrian C. Duque

Facultad de Ciencias y FacuLtad de Salud,Universidad del Valle, Cali, Colombia:

Department of Ennmology, Walter Reed ArmyInstitute of Research, Washington, DC; and

Centro Internacional de Agricultura Tropical,CIAT, Cali, Colombia

A molecular genetic study of 3 ColombianAnopheles darlingi subpopulations (2 western andI eastern) was performed with random amplifiedpolymorphic DNA-polymerase chain reaction(RAPD-PCR) and amplified fragmenr length poly-morphism (AFLP) molecular markers to clarify thetaxonomic status of this species in Colombia. Inthis study, 46 polymorphic RAPD-PCR fragmenrsproduced by 6 primers were obtained for 64 DNAsamples. A total of 202 AFLP polymorphic frag-ments from the 2 primer combinations was obtainedfor 7l DNA samples. Cluster analysis using a dis-tance matrix with Phylip 3.5C and multiple corre-spondence analysis were used. For RAPD-PCRfragments, the consensus tree and multiple corre-spondence results showed significantly low evi-dence of geographical separation between easternand western subpopulations; nevertheless the Fstdata showed a high genetic flow between the 2 Col-ombian western subpopulations (Fst : 0.008). Aclear geographic partitioning was obtained with theAFLP fragments. The geographical isolation be-tween the eastern Colombian subpopulation and the2 western Colombian supopulations was better ad-justed with Fst data obtained from the AFLP frag-ments (Fst : 0.213 and O.22O) than the Fst dataobtained from RAPD fragments. These resultsshowed evidence of a high genetic flow betweenthe 2 western Colombian subpopulations (Fst :

0.096).

Seprsveen 2001 Svvpostuv oN Mosqurro Covrnor rN Lntrr Avenrca 1 7 3

Random amplified polymorphic DNA analysisof Colombian Anopheles nuneztovari

populations

Carmen E. Posso, Ranulfo Gonzillez, GerardoGallego, Myrian C. Duque and Marco E Su6rez

Departamento de Biologfa, Universidad del Valle,Cali, Colombia; Department of Entomology,

Walter Reed Army Institute of Research,Washington, DC; Centro Internacional de

Agricuhura Tropical, CIAT, Cali; and Escuela deSafud Prtbhca, Universidad del Valle, Cali,

Colombia

Random amplified polymorphic DNA (RAPD)markers were used to analyze 119 samples of 3Colombian Anopheles nuneztovari subpopulationsto establish the possible existence of cryptic orcomplex species. Of the 554 RAPD primersscreened, 9 produced a total of 65 polymorphicfragments ranging in size from 478 to 1,778 basepairs. A RAPDPLOT program analysis showedsmall genetic distances between the 3 subpopula-tions and did not allow a clear separation, using a1-S distance matrix. Neverlheless, the genetic flowwas significantly different. lt was higher betweenwestern Colombian subpopulations (Lynch andMilligan Fst : 0.035; Nm : 6.8) and smaller be-tween those and the eastern Colombian subpopu-lation (Fst = 0.08; Nm : 2.8). A distance dendro-gram of the 65 fragments, using a Nei's unbiasedgenetic distance analysis, showed evidence that the2 western subpopulations clustered separately fromthe eastern subpopulation in a consensus tree de-rived from the 100 unweighted pair-group methodusing arithmetic averages (UPGMA) trees. A mul-tiple correspondence analysis generated 16 clustersand also depicted the geographical separation be-tween the 2 western subpopulations and the easternsubpopulation. These results indicate that the sub-populations of Colombian An. nuneztovari are con-specific.

Enzyme polymorphism among Triatomapicturata (Hemiptera: Reduviidae) populations

from western M6xico

Jos6 Alejandro Martinez-Ibarra, Nina MalenaBiircenas-Ortega, Mario Henry Rodriguez-L6pez

and Porfirio Ramfrez-Vallejo

Laboratorio de Marcado res Moleculares,IREGEP, Colegio de Postgraduados,

Guadalajara, Jalisco; Laboratorio de SaludPrtblica, Centro Universitario del Sur,

Univ e rsidad de G uadalaj ara, Guadalaj ara,Jalisco; and Centro de Investigaciones Sobre

Enfennedades Infecciosas, Instituto Nacional deSalud Piblica, Cuernavaca, Morelas, Mdxico

Isozyme variability in populations of the Chagas'disease vector Triatoma Dicturata was determined

by means of starch gel electrophoresis. Sampleswere taken from 5 localities across the range of thisspecies in western M6xico, where this species isone of the most important vectors. Zymograms forproteins coded by a total of 4 loci of 3 enzymes(esterases [Es EC 3. l. l. l], malate dehydrogenase

IMDH EC 1.1 1. 371, and malic enzyme [Me EC1.1.1.401) were obtained. Proportion of polymor-phism loci, endogamy, mean heterozygocity per lo-cus, gene flow, and Nei's genetic distance amongpopulations were calculated. Only I (337o) locuswas polymorphic; endogamy was 1, heterozygocitywas 0. Gene flow was 0.9376 and Nei's geneticdistances were minimal (0-0.002) among popula-tions. According to the data above, all of the sub-populations of T. picturata that were studied couldbe considered a single widely distributed popula-tion.

Oviposition preference of Anopheles albimanusfor 5 plant species under laboratory conditions

Jos6 L. Torres-Espada, Juan I. Arredondo-Jim6nez, R. Amanda Meza-Alvarez, Juan Cibrian-Tovar, Mario H. Rodriguez and Leopoldo Cruz-

L6pez

Centro de Investig,acidn de Paludismo, InstitutoNacional de Salud Prtbhca, Tapachula, Chiapas;

Instituto de Fitosanidad, Colegio dePostgraduados, Montecillos, Estado de Mdxico;Centro de Investigaciones sobre Enfermedades

Infecciosas, Instituto Nacional de Salud Piblica,Cuernavaca, Morelos; and El Colegio de la

Frontera, Tapachula, Chiapas, Mdxico

We studied whether the attraction that gravidAnopheles albimanus females have for water con-taining aquatic plants (Brachiaria mutica, Cynodondactylon, Jouvea straminea, Fimbristylis spadicea,or Ceratophyllum demersum) is related to chemi-cals (released substances from plants, water, orboth) or physical stimuli (shape or color). Gravidfemales were offered water bowls containing nat-ural plants (NP) in larval habitat water (LW) asoviposition substrates, or artificial plants (AP) indistilled water (DW); and NP in DW or AP in LWas oviposition substrates. Gravid An. albimanus fe-males deposited more eggs in bowls containing NPin LW than in bowls containing AP in DW. Also,gravid mosquitoes deposited more eggs in bowlscontaining NP in DW than in bowls containing APin LW. These results were confirmed in experimentsconducted in an olfactometer, indicating that femaleresponse was mediated by chemical cues fromplants. Gas chromatography and mass spectropho-tometry analysis of the organic extracts from all 5plants showed a mixture of terpenoid and alcoholcompounds, including guaiacol, phenol, isoeugenol,longifolene, caryophyllene, phenyl ethyl alcohol,and p-cresol. These results suggest that middle-range volatiles from plants function as chemical

t ]4 JOURNAL oF rHe AvremceN Mosqurro CoNrnol AssocrATroN Vor-. 17, No. 3

cues for the female An. albimanus oviposition re-sponse.

Advances in the characterization of insecticideresistance of the strain pattern "Chagas" of

Rhodnius prolixus (Hemiptera: Reduviidae) inVenezuela

Ana Soto Vivas and Darjaniva Molina

Instituto de Altos Estudios en Salud Piblica "Dr.

Arnoldo Gabaldon," Maracay, Venez.uela

In the detection of resistance to insecticides, anystudy should begin by evaluating a sensitive labo-ratory strain. In the case of the triatomines, a sen-sitive strain must have more than 5 generations inthe laboratory without the addition of field material.To determine the baseline of resistance to differentinsecticides, a laboratory (S) strain of Rhodniusprolixus was tested with organochlorine, organo-phosphate, carbamate, and pyrethroid insecticides.Topical applications of acetone solutions of insec-ticide were made to the dorsal abdomen of lst (0. Ipl) and 5th nymphal instars (0.5 p"l). Resultsshowed, for 1st-stage nymphs, median lethal doses(LD.us) of dieldrin, 243 ng/insect (i); fenitrothion,2 ng/i; methyl pyrimiphos, 13 ng/i; propoxur, 13ng/i; lambdacyhalothrin, 1.4 X 10 3 ng/i; delta-methrin, 5 X l0-4 ng/i; and cyfluthrin, 6 X lO 2 g/i. In nymphs, the LD.os were dieldrin,2,46O ng/i;fenitrothion, 100 ng/i; methyl pyrimiphos, 714 ng/i; propoxur, 69O ngli;' lambdacyhalothrin, 6.6 ng/i;deltamethrin, 18 ngli; and cyfluthrin, 380 ng/i.

Resistance of Aedes aegypti to pyrethroids inmunicipalities of the Aragua State, Venezuela

Enrique E. Pdrez and Darjaniva M. de Fern6ndez

Centro de Estudios de Enfermedades Enddmicas ySaneamiento Ambiental, Aretgua, Ve ne zuela

In 3 strains of Aedes aegypti from the munici-palities of Mario Bricefro Iragorri (MBI), Jos6 F6lixRivas (JFR), and Girardot of Aragua State (1981),we studied the resistance of 4th-stage larvae to thepyrethroids cyfluthrin, lambdacyhalothrin, and del-tamethrin, in comparison with the susceptibleRockefeller strain using the World Health Organi-zation method. Resistance to lambdacyhalothrinwas found in all strains; the MBI and Girardotstrains showed resistance to cyfluthrin and to del-tamethrin, respectively. Evaluating the synergist,piperonyl butoxide, and mixed-function oxidase(MFO) inhibitors in the strains where resistancewas detected, we found that resistance diminishedin all strains. For lambdacyhalothrin, the factor ofsynergism (FS) oscillated between 2X and 3X. TheMBI and Girardot strains had an FS : 25x forcyflutrin and 255X for deltamethrin, respectively.This involved the MFO system as a resistancemechanism in these strains to ovrethroids. The re-

sults indicate that insecticide resistance in Ae. ue-gypti is a problem of focal nature that should betreated independently.

Resistance mechanisms in Mexican Anophelesalbimanus using single insecticide, rotation, and

mosaic strategies

R. P Penilla, A. D. Rodriguez, J. Hemingway,A. D. L6pez and M. H. Rodrfguez

Centro de Investigacirin de EnfermedadesInfecciosas/Centro de Investigaci6n de la

Malaria, Instituto Nacional de Salud Piblica,Tapachula, Chiapas, My'xico; and School of

Biosciences, University of Wales, Cardiff Wales,United Kingdom

A large-scale,3-year field trial to evaluate insec-ticide resistance management and to investigate re-sistance gene frequencies of Anopheles albimanuspopulations was conducted in southern M6xico. Be-fore the intervention, a broad-spectrum resistanceto DDT, pyrethroids (PYRs), organophosphates,and carbamates was detected by World Health Or-ganization bioassays. Biochemical assays showedthat resistance was conferred by glutathione S-transferase (GST), elevated esterases, monooxygen-ases (mixed-function oxidases [MFOs]), and alteredacetylchol inesterase (AChE)-based mechanisms.Differences in resistance gene frequencies betweenvillages and collection methods suggested the pres-ence of subpopulations. During the 3-year study,significant variations in the enzymatic levels be-tween the different resistance management strate-gies were detected. Elevated esterases and MFOsdecreased in mosquitoes from villages under thecontinuous PYR pressure at the end of the inter-vention, indicating the presence of another resis-tance mechanism. The PYRs used in the rotationand mosaic strategies apparently selected for ele-vated esterase- and MFO-based mechanisms. TheGST activity and altered AChE gene frequenciesdecreased in villages under the PYRs and rotationstrategies by the 3rd year of intervention. Differ-ences in MFO and GST gene frequencies were as-sociated with sex; with females having higher lev-els of MFOs and males higher levels of GSTs.Resistant males with elevated esterases outnum-bered resistant females by 2 to l.

A 3-year field evaluation of resistancemanagement strategies in Mexican Anopheles

albimanus

A. D. Rodriguez, R. P. Penillal, J. Herningway,A. Trejol and M. H. Rodrfguez

Malaria Research Centre, National Institute ofPubLic Health, Tapachula, Chiapas, Mdxico; and

School of Biosciences, University of Wales,Cardffi Wales, United Kingdom

Since 1995, we have undertaken annual rotationsof unrelated insecticides (organophosphorus [OP],

SEPTEMBER 2001 Sylposruv oN MoseulTo Corvrnol rN L,crrN Aurnlca 175

pyrethroid tPYRl, and carbamate [CAR]), spatialmosaic spraying of 2 unrelated insecticides in thesame area (OP + PYR), and traditional spraying ofa single insecticide (DDT or a PYR) to comparethe efficacies of these strategies for resistance man-agement. High levels of DDT resistance and lowlevels of resistance to OP CAR. and PYR insecti-cides were detected before the intervention. TheDDT resistance did not change in any of the treat-ments after 3 years of intervention, whereas gluta-thione S-transferase levels remained constant onlyin the DDT-treated areas. Decreases in susceptibil-ity levels to the selected insecticide were detectedin the rotation but these reverted soon after the ap-plication of the subsequent insecticide. In the mo-saic, resistance to both insecticides increased andPYR resistance tended to stabilize by the 3rd yearof application. In the PYR-treated areas, PYR re-sistance increased constantly after the lst year ofintervention. Multiple resistance mechanisms werepresent and some resistance mechanisms declinedafter the lst intervention year; however, they fluc-tuated during successive sprayings. An altered ace-tylcholinesterase was the major resistance mecha-nism for OP and CAR, whereas monooxygenasesand esterases conferred PYR resistance.

POSTERS

Scorpions of Oaxaca, M6xico

Josefina C. Trujillo Garcia, Jorge P MartinezMuffoz, Gloria I. Flores Martfnez and Ram6n

Segura Arenas

Laboratorio Estatal de Salud Pilblica de Oaxacaand Servicios de Salud del Estado de Oaxaca.

Oaraca, Oaxaca, Mixico

In the state of Oaxaca, M6xico, a high index ofscorpion stings exists each year. Although they arenot always fatal, different symptoms do appear. Ourobjectives were to identify and to define the distri-bution of scorpions in the state. Biological materi-als were collected during entomological inspectionsmade by state health vector program personnelfrom July 1997 to July 2000. Scorpions were pre-served in TOVo ethyl alcohol and sent to the OaxacaState Public Health Laboratory for identification. Atotal of 3,725 scorptons including 4 families, 4 gen-era, and 12 species was identified from97 (l6.6Vo)of Oaxaca's municipalities. We identified species inthe family Buthidae: Centruroides infamatus infa-matus, C. limpidus limpidus, C. elegans, C. nigri-manus, C. nigrovariatus, C. fulvipes, C. gracilis,and C. nigricens; the family Vaejovidae: Vaeiovissp.; the family Diplocentridae (Diplocentrus sp.);and the family Iuridae (Hadrurus sp.). The mostdangerous species were C. infamatus infamatus, C.limpidus limpidus, and C. elegans. Centruroides in-famatus infamatus was the species with the highestdensity versus the rarely collected C. nigricens and

Hadrurus sp., with O.O2Vo of the collections. Thebroad distribution was of C. infamatus infamatus,which was found to be the most widely distributedon a monthly basis, coming from 64 municipalities.

Morphometric characterization of Anopheles(Nyssorhynchus) marajoara from Venezuela

Yasmin Rubio-Palis and Hern6n Guzm6n

Divisi6n de Investigaciones, Instituto de AltosEstudios en Salud Priblica "Dr. ArnoldoGabald6n," Maracay, Aragua, Venezuela

Anopheles (Nyssorhynchus) marajoara was orig-inally described in 1942, but later marajoara wasconsidered a synonym of albitarsis. Current molec-ular evidence suggests that An. albitarsis is a com-plex of at least 4 species: An. albitarsis sensu stric-to, An. deaneorum, An. marajoara, and a 4ttrspecies (species B), which has not been yet mor-phologically described. The available morphologi-cal keys for species identification of An. marajoaraare based on mixed specimens within the albitarsiscomplex. To clarify the taxonomic status of An. ma-rajoara in Venezuela and to determine diagnosticcharacters that can be used to update taxonomickeys, a morphometric study was carried out on pop-ulations of An. marajoara in Venezuela. To evalu-ate the diagnostic power of the characters identifiedamong the populations of marajoara, the other 3sympatric species belonging to the ArgyritarsisSection: An. argyritarsis, An. darlingi, and An. bra-ziliensis were included in the analysis. Selectedwing, leg, and head characters of adult femaleswere measured and analyzed on 195 females froml2 populations along the range of its distribution inVenezuela. The male genitalia of 5 populationswere dissected and all characters were measured.Adult females of An. marajoara can be identifiedby hindtarsomere 5 white; sternum I with a sub-medial stripe of white scales; caudolateral scaletufts well developed on abdominal segment III; pre-humeral dark spot on wing costa O.22-l.O lengthof humeral pale spot; and length of dark band onhindtarsomere II 0.37-0.60 length of tarsomere.Resulting measurements on male genitalia compo-nents were compared to those previously reportedfor marajoara and, albitarsis. In general, the rangeof variation for the characters measured are withinthe ranges previously reported for An. marajoara,except for the proportion length of gonocoxite di-vided by length of seta b, which showed a widerrange of variation for the Venezuelan populations.The proportional length of gonocoxite divided bythe width of gonocoxite for marajoara from Ven-ezuela was smaller than the reported vallue for al-bitarsis sensu Linthicum. The diagnostic charactersfor identifying adult populations of An. marajoarawill be useful for updating taxonomic keys to iden-tify Venezuelan anophelines.

1"76 Jour<N,q.l op rHe AnentceN MosQurro CoNrnol AssoctertoN Vol. 17, No. 3

Effectivity of Pirenona@ 3-30N against Muscadornestica larvae (Diptera: Muscidae)

F. GonzSlez-Jim6nez, K. M. Valdez-Delgado,K. L. Saavedra-Rodriguez, R. Hern6ndez-Cort6s,

Y. Gonzdlez-Robledo and Y. Grant-Huerta

Laboratorio de Entomoktgia, Facultad deCiencias Bioltigicas, Universidad Aut6noma deNuevo Le6n, San Nicokis de los Garz.a, Nuevo

Le6n, M4xico

The housefly, Musca dcsmestica, is a cosmopoli-tan insect, and frequently is found near humandwellings. Several methods have been used for itscontrol; however, housefly resistance to all majorgroups of insecticides has been increasing. The ob-jective of this study was to evaluate the toxicity ofPirenona@ 3-30N to M. domestica larvae. The testswere conducted with small pieces of filter paperthat were impregnated with 6 concentrations of Pi-renona. After the papers were introduced into asmall glass containers, ten 3rd-stage larvae wereintroduced in each test system and mortality wasregistered after I and 24 h of exposure. The datawere analyzed statistically with linear regression,correlation, and determination coefficients. Themortality after I h of exposure was represented byb: -0 .7671, r : O.4351 , and 12 = 0 .4039; mor -tality 24 h after application was represented by b: 1.9035, r : O.9545, ra = O.9079. The regressionand correlation coefficients were not significant (P< 0 .05) .

Operational program to control Chironomusplumosus (Diptera: Chironomidae) in a

wastewater plant

H. Quiroz-Martinez and V. A. Rodriguez Castro

Laboratorio de Entomologfa, Facuhad deCiencias Biol6gicas, Universidad Aut6noma deNuevo Le6n, San Nicolds de los Garzct, Nuevo

Le6n, Mdxico

After several years of suffering the presence oflarge swarms of Chironomus plumosas in thewastewater plant Agua Industrial de Monterrey,studies were carried out to identify the best toolsfor an operational control program. During 2000,no swarm of C. plumosas occurred, and no com-plaints were received at the water treatment facility.The best way to control these midges was to placean oviposition trap mesh to collect and eliminatethe egg masses. Midge control was possible at thebeginning of the life cycle. The operational pro-gram also included release and establishment ofbackswimmers, the use of light traps, and impreg-nation of surfaces to kill the adults.

Entomological risk in a potential zone ofecotourism

F. Gonzilez-Jirn1nez, H. Quiroz-Marrinez, J. l.Gonzdlez-Rojas, V. A. Rodriguez-Castro, V. A.

Gonz6lez-Robledo and A. S. Garcia-Garza

Laboratorio de Entomologia and Laboratorio deOrnitologia, Facukad de Ciencias Biol6gicas,

Universidad Aut6noma de Nuevo Le6n, SanNicolds de los Garza, Nuevo Le6n, Mdxico

It is important not to expose tourists to healthproblems. In this study, we identified the insectsthat could pose entomological risks to humanhealth in San Antonio Pefla Nevada, Zaragoza,Nuevo Le6n, M6xico, an ecotourism zone. Everymonth samples were taken from aquatic systemsand preserved in ethyl alcohol until identified in thelaboratory. Diptera was the most important order ofinsects collected and included 25 genera. The mostimportant species were Culiseta inornata, Cu. par-ticeps, Orthopodomyia alba, Culex restuans, Cx.quinquefasciatus, Cx. coronator, and Tabanus sty-glas. These could become public health problemsbecause they take blood. The 2nd most commonorder was Coleoptera with 7 species, followed byHemiptera with 3 species, and Odonata and Ephem-eroptera with 2 genera each, respectively.

Diversity of flies in solid material in awastewater plant

A. S. Garcia-Garza, H. Quiroz-Martinez,V. A. Rodriguez-Castro, F. Gonz6lez-Jim6nez,A. Escalera-Arredondo and J. C. Hernindez-

Reves

Laboratorio de Entomologia, Facultad deCiencias Biol6gicas, Universidad Aut6noma deNuevo Le6n, San Nicoltis de los Garza, Nuevo

Le6n, Mdxico

The 1st step in the treatment of wastewater is theseparation of solid material, which has high organiccontent and can become an ideal breeding site forflies. We studied solid material in 4 types: coarseparticulate organic matter (CPOM) at the beginningof the wastewater treatment, plastic, CPOM in adryer section, and material introduced in a contain-er. A l-kg sample was taken and all larvae wereseparated and preserved in ethyl alcohol. Muscadomestica was the dominant species (98Vo of thetotal) and other fly larvae were Fannia sp., Sar-cophaga sp., and Statiomyis sp. The highest den-sities were found in the material from the containerwith I ,182 larvae.

SpprrMsen 2001 Svupostuv os Moseutro Colrnor- t t Ler lN AMERTcA 1 7 7

Selectivity of oviposition sites of Aedes aegyptiunder laboratory conditions

E. G6mez-Ruiz, K. M. Valdez-Delgado, K. L.Saavedra-Rodriguez, V. A. Rodriguez-Castro,

A. E. Flores-Suiirez and E. A. Martinez-Yaldez

Laboratorio de Entomologia and lttboratorio deEntomologia Mddica, Facultad de Ciencias

Bioltigicas, Universidad Aut6noma de NuevoLedn, San Nicolds de los Garzq Nuevo Ledn,

Mdxico

Oviposition site selection by Aedes aegypti fe-males was evaluated in ovitraps baited with teme-phos (Abate@), Bacillus thuringiensis var israelen-sis (Bti) lOVo (Bactimos@), methoprene 47o(Altosido), poly (oxy-1,2-ethanediyl), a-isooctade-cyl-o-hydroxyl 1OO7o (Agnique@ MMF), 3Va chlo-ric acid (Cloralex@), and distilled water as the con-trol. The tests were carried out in a rearing cagewhere 20 gravid females were introduced; theywere bloodfed daily and every 3rd day the red ovi-position strips were separated and the collectedeggs were counted until the last female died. Anal-ysis of variance was used to find the significantdifference among treatments. The highest numberof eggs obtained was 914 in the control. Eggs inthe other treatments were 824, 433,341,316, and8 with Bti (824), methoprene (433), temephos(341), chloric acid (3 l6), and a monomolecular film(8). Analysis of variance showed a significant dif-ference among treatments (P : 0.05). The differ-ence was caused by Agnique MME

Susceptibility of Aedes aegypti larvae to thehistoric, most commonly used, and alternative

insecticides in Veracruz, M6xico

A. E. Flores, C. Bobadilla, M. H. Badii,I. Fern6ndez, M. L. Rodriguez and G. Ponce

Facultad de Ciencias Biol6gicas, UniversidadAut4noma de Nuevo Le6n, San Nicolds de los

Garza, Nuevo Le6n, Mixico

The insecticide resistance problem along with theabsence of a domestic hygiene program in VeracruzState, M6xico, have contributed to the high preva-lence of dengue cases. Peridomestic water contain-ers, such as 55-gal metal drums, cement tanks, anddiscarded tires, are the most important breedingsites for Aedes aegypti.'fhe discarded tires are re-sponsible for the build-up of this mosquito's pop-ulation. To date, no report has been made of insec-ticide susceptibility in Ae. aegypti larvalpopulations in Veracruz. The objective of this studywas to determine the level of susceptibility of Ae.aegypti to the historic, most commonly used, andalternative insecticides against this mosquito spe-cies. Egg samples from l0 ecological sites of Ve-racruz State were taken to determine the mortality-concentration lines for biphenthrin, cypermethrin,

malathion, temephos, and DDT. We used the WorldHealth Organization (WHO) bioassay methodolo-gy. The results were analyzed by probit analysesusing WHO and the maximum likelihood methods.

Comparison of developmental cycles of Aedesaegypti larvae exposed to sublethal

concentrations of 2 formulations of Bacillusthuringiensis var. israelensis

G. Ponce, A. E. Flores, M. H. Badii,M. L. Rodriguez, I. Fern6ndez and R. Torres

Facultad de Ciencias Bioligicas, UniversidadAut6noma de Nuevo Le6n, San Nicolds de los

Garza, Nuevo Le6n, Mdxico

Understanding the developmental cycle of mos-quitoes allows us to better manage control of theseinsects. In this research, the duration of the devel-opmental periods of larvae exposed to sublethalconcentrations of Bacillus thuringiensis var. israe-lensis using commercial formulations of VectobacG & AS was determined. Concentrations of 3O7olethal concentration (LC.o), LC.o, and LCr,, wereused under laboratory conditions of 12:12 h light:dark, 28'C mean ambient temperature, and 26"Cmean water temperature. Analysis of variance andTukey multiple range tests were used to analyze thedata. Developmental periods of 16.5, 15.5, 11.5,and 8.5 days were obtained for Vectobac G expo-sure for LC.., LC.o, LCrn, and control, respectively.A significant difference between control and LC.oand LC.o treatments was found. Exposure to LC.o,LC.n, and LCru of Vectobac AS resulted in a de-velopmental cycle of 7.5, 19.5, and 19.5 days, re-spectively, compared to 17.0 days for control. TheLC.n results differed significantly from the LC.,, andLCrn results and the control.

Larvicidal effects of Tagetes erecta andl T.luci.da (Compositae) against the dengue vector

Aedes aegypti

Gabril Martinez, Azucena Oranday, Adriana E.Flores Su6rez and L Fern6ndez-Salas

Inboratorio de Qufmica de Recursos Naturales,Facuhad de Ciencias Biol6gicas, UniversidadAut6noma de Nuevo Le6n, San Nicolds de los

Garza, Montercey, Mdxico

Research on plant-derived molecules with killingeffects on disease-carrying insects has intensified inrecent decades. Presence of resistance or the avoid-ance of environmental pollution are 2 bases for al-ternate control measures. Local plants used for in-dustries such as food sources, cosmetics, andtraditional medicine were investigated in this study.Tagetes erecta and T. lucida supplied organic ex-tracts with suspected larval mortality activity. Bio-assays using 3rd-stage Aedes aegypti larvae ex-posed to a methanol extract of T. erecta showed a

178 JounNer- or rnr AN,lsnrceN MosQurro CoNrnol AssoctlrloN Vor. 17, No. 3

median lethal dose (LD,n) of 75.5 ppm and a LD*of 185 ppm. On the other hand, a hexane extractof T. lucida demonstrated mortality ranges of 6.6-IOOVo for 90-130 ppm, respectively.

Diet effects on egg hatching, life cycle durafion,and gender ratio of Aedes aegypti and Aedes

albopictus in Nuevo Le6n, M6xico

Mireya Martinez, Ma. L. Rodriguez-Tovar, A. E.Flores- Su6rez, M. B adli-Zabeh, I. Fern6ndez- S alas

and A. Gonz6lez

Laboratorio de Entomologfa, Facultad deCiencias Biol6gicas, Universidad Aut6rutma de

Nuevo Le6n, Monterrey, Mdxico

Body size and longevity are responsible for pro-ducing highly efficient dengue virus vectors. Aedesaegypti and Ae. albopictus populations prevail innorthwestern M6xico, where dengue fever occurs.Eggs from paper strips collected in ovitraps wereused and, therefore, the 2 species were mixed. Theywere hatched and reared on an optimal or suboptimaldry liver powder diet. The effect of both diets onthe following biological parameters was assessed:hatching rate, life cycle duration, species proportion,and gender ratio. Emerged adults were fed with hu-man blood and dissected to measure oogenesis.From a group of 3,605 eggs collected betweenMarch and July 2000, about 676 adults emerged.Aedes albopiclrzs comprised 62.87o of the adults andAe. aegypti comprised 37.ZVo of the adults.

Age structure of Aedes aegypti ^ndl Aedesalbopictus in Nuevo Le6n, Mdxico

Romana de L. Moreno, Ma. L. Rodrfguez-Tovar,M. H. Badii, Adriana E. Flores-Sudrez and

I. Fern6ndez-Salas

Laboratorio de Entomologia Mddica, Facuhad deCiencias Biol6gicas, Universidad Aut6noma deNuevo Le6n, San Nicolds de los Garza, Nuevo

Le6n, Mdxico

Aedes albopictus was found in Nuevo Le6n Statein 1998. However, its role as an effective flavivirusvector is unknown in northeastern M6xico. On theother hand, Aedes aegypti is a common dengue vec-tor in this endemic area. To better understand andto prevent risks of dengue fever transmission by Ae.aegypti, studies focused on vectorial capacity var-iables in the field. We studied the age structure bydetermination of the blood digestion stage andovarian development. The study site was AllendeCity, where 50 dwellings were selected to conducthuman landing collections. Concurrently, femalemosquitoes were aspirated indoors and outdoors toassess postfeeding resting behavior. Studies wereconducted in September and October 2000. Humanlanding collections produced 86.47o Ae. aegypti and13.57o Ae. albopictus. Ase structure determinations

using abdominal appearance and ovarian develop-ment of both species resulted in following catego-ries: 847o unfed and nulliparous, 8.2Vo parots, andO.97o gravid.

Mapping Ochlerotatus albifasciatus abundancein central Argentina with AVHRR/NOAA

imagery

Raquel M. Gleiser and David E. Gorla

Centro Regional de Investigaciones Cientificas yTransferencia Tecnol6gica de La Rioja, La Rioja.

Argentina

Ochlerotatus albifosciatus is a Neotropical flood-water mosquito developing over short periods intemporary ground pools. In the Mar Chiquita de-pression, the adult mosquito population increasesduring the rainy season, and females irritate live-stock and thus affect dairy production. Previousstudies showed that higher densities were recordedin areas that periodically flood, where more larvalsites are available. Normalized Difference Vegeta-tion Index (NDVI) images calculated from Ad-vanced Very High Resolution Radiometer(AVHRR) products were used to map areas withhigh probability of adequate Oc. albifasciatusbreeding sites. Training sites for high, medium, orlow abundance were defined as 3.3 X 3.3-km poly-gons over mosquito sampling sites, and were usedon a supervised classification of National Oceano-graphic and Atmospheric Administration (NOAA)/AVHRR imagery. The flrst 3 components of a stan-dardized principal components analysis on a NDVItime series represent statistical abstractions of theinherent variability of the original image set, andwere used as bands in the classification. A maxi-mum-likelihood classification resulted in a 78.6Voprobability of predicting areas with potential foryielding high mosquito densities. Results suggestthat NOAA images were useful to identify thoseareas potentially more important for mosquito de-velopment or activity and where increases in theadult density could affect daily production.

Abundance of adult Ochlerotatus albifosciatusin relation to habitat features

Raquel M. Gleiser, David E. Gorla andGabriel Schelotto

Centro Regional de Investigaciones Cientificas yTransferencia Tecnol6gica de La Rioja, La Rioja,

Argentina

An extensive area of central Argentina is peri-odically flooded by rainfall and river overflow, pro-viding breeding sites for mosquitoes. Adult popu-lation explosions of Ochlerotatus albifosciatusirritate livestock, affecting milk and beef produc-tion. Although the species is a known vector ofwestern equine encephalomyelitis virus, its popu-

SsprrMsrn 2001 Svuposruv oN Mosqurto CoNrnol lN LarrN Auenrcl 179

lation dynamics on a regional scale is poorlyknown. This work studied factors affecting the spa-tial pattern of mosquito abundance. Adult mosqui-toes were collected with light traps baited with CO,in 28 sampling sites in a 14 X l4-km study areasouth of Mar Chiquita Lake. Each site was definedaccording to its vegetation cover, terrain slope, cat-tle density, and distance to potential breeding sites.The spatial and temporal patterns of abundancesuggested that this species preferred prairies andnatural grasslands subject to periodic flooding vs.woodlands and agroecosystems. A discriminantfunction based on the proximity to Salicornia sp.and Sesuvium sp. prairies, distance to woodland,and land slope correctly classified 957o of the datahaving an average high (>500) or low (<500) mos-quito abundance, and was validated using 6 siteslocated away from the study area. Using the dis-criminant function, a map of abundance distributionwas created with the aid of a geographic informa-tion system.

Levels of insecticide resistance toorganophoshates in field strains of Aedes

aegypti from Venezuela

Darjaniva Molina de Fern6ndez, M. M. Rodrfguezand Juan Bisset

Instituto de Altos Estudios en Salud Prtbhca,Ministerio de Salud y Desarrollo Social,

Maracay, Venezuela; and Instituto de MedicinaTropical "Pedro Kouri," La Habana, Cuba

As part of an insecticidal resistance surveillanceprogram, resistance to several organophosphates(temephos, malathion, fenitrothion, and methyl pi-rimiphos) was investigated in 8 field strains of Ae-des aegypti collected in 1997 and 1999 from Ven-ezuela. The larvae were bioassayed using the WorldHealth Organization standard procedure. All strainsshowed high susceptibility to temephos (<4-fold),fenitrothion (<3-fold), and methyl pyrimiphos (<9-fbld), but were resistant to malathion (>36-fold).Malathion and temephos have been used extensive-ly in Venezuela for Ae. aegypti control. Tests ofadults revealed resistance to malathion in allstrains. Biochemical studies of the synergists dieth-yl triphosphate and piperonyl butoxide suggestedthat malathion resistance was associated with theesterases and mixed-function oxidase mechanisms.Continuous monitoring of the insecticide resistancein these populations is fundamental for rationalmosquito control and insecticide application pro-grarns.

Field evaluation of effectivity of Bacillussphaericus against Anopheles aquasalis larvae

in Venezuela

Jesris Berti, Xiomara Ramfrez, Jlulio Gonztlez,Melfran Herrera and Frances Osborn

Instituto de Altos Estudios de Salud Priblica "Dr.

Arnr.tldo Gabald6n," Maracay, Aragua,Venezuela; and Universidad de Oriente, Cumarui,

Venezuela

Anopheles aquasalis is the main vector of ma-laria in northeastern Venezuela. A study of its bi-ological control was carried out in Sucre State. Theobjective of this study was to evaluate the impactof the introduction of Bacillus sphaericus on larvalpopulations of An. aquasalis. Aquatic breedingsites were a priori classified into 2 habitat catego-ries: seasonal brackish mangrove with vegetation(Avicennia germinans), and semipermanent fresh-water wetlands with herbaceous emergent vegeta-tion (Eleocharis mutata). In field trials, 3 commer-cial concentrations (2, 3, and 4 glm2) of a granularformulation (Vectolex@ CG 7.5qo) of B. sphaericuswere evaluated in the 2 typical breeding sites ofAn. aquasalis. The 3 doses had the same effectagainst An. aquasalis larvae in breeding sites ex-posed to sunlight, low salinity, and with herbaceousemergent vegetation, producing a larval reductiongreater than 9OVo during 14 days after treatment. Inbrackish mangrove breeding sites with A. germi-nans, the same concentrations were very effectivein producing a larval reduction equal to or greaterthan 9OVo during 28 days after treatment.

Introduction to LECO hand-held dual modeULV and thermal fogging machine for

application of an adulticide with residual effectin dengue control

Empatrice Lugo and William Jany

Ministry of Health of Nicaragua, Managua,Nicaragua; and Clarke Mosquito Control, Inc.

Roselle, IL

An introduction to the new LECO hand-helddual-purpose ultra-low-volume (ULV) and thermalfogging machine and its use with an aqueous-basedresidual adulticide was presented. The purpose ofthis system is to provide immediate knock-downand kill of adult mosquito populations. The ma-chine is also designed to extend residual protectionwithin dwellings for a prolonged period of time tornaintain Aedes aegypti mosquito density at reducedlevels. The presentation outlined the concepts be-hind the system and gave results of recent field tri-als conducted in Nicaragua.

180 JOURNAL oF THE AMERTCAN Moseuno CoNTRoL AssocrlrtoN VoL. 17, No. 3

Habitat characterization, dispersion andassociation of Aedes albopictus Sktse

(Diptera: Culicidae) with otherCulicids in Cuba

M. C. Marquetti, V. Vald6s, E. Contreras,L. Aguilera, M. Leyva and A. Navarro

Instituto de Medicina Tropical "Pedro Kouri,"Unidad Municipal de Higiene y Epidemiologia del

Municipio Boyeros, y Unidad Municipal deHigiene y Epidemiologfa del Municipio La Lisa,

Ciudad de La Habana, Cuba

Aecles albopictas was first found in Cuba in 1995in the municipality of Lisa within the province ofHavana. Since then, this species has dispersed toother cities within the province. This paper dis-cusses the distribution and dispersion of this speciesin the municipalities of Lisa and Boyeros. Most ofthe containers infested with Ae. albopictus werefound outdoors and larvitraps (ll4 of automobiletire), which are widely used in Cuba's national Ae-des agypti surveillance program, were the "con-

tainers" most commonly infested. Artificial con-tainers, including discarded tires and tin cans, werethe next most commonly infested group of contain-ers. These results suggest a possible competition foroviposition in larvitraps between Ae. albopictus andAe. aegypti. Although Ae. albopictas was foundbreeding in association with Aedes mediovittatusand Culex quinquefasciatus, the dominant speciesin Lisa and Boyeros, an increase in the number ofcontainers infested by this species alone was ob-

served. These results may reflect interspecific com-

petition between the recently introduced Ae. albo-

pictus and long-established species, including Ae.

aegypti.

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