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Malaria Epidemiology,
Surveillance and Prevention Guided by
Dr. S. B. Bansal
Dr. Amit Gharia
Group 22
Sunil Chawrasia
Sushila Chouhan
Susheel Soni Shoubhik Banerjee
Surrendra Singh
Sunil Desai
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INTRODUCTION
A protozoal disease.
Caused by infection of parasite of genus plasmodium
Transmitted to man by certain species of infected
Anopheles Mosquito
Typical attack- cold stagehot stage
sweating stage
Clinical Feature depends on-sp. Of parasite
-pt. state of immunity
-intensity of infection
-presence of concomitant condition
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BURDEN OF MALARIA IN INDIA
YEAR CASES(million)
Deaths
2005 1.82 963
2006 1.76 1703
2007 (up toNovember)
1.29 996
STATES/UTs POPULATION % MALARIA % Pf % Death %
N.E State 3.79 12.55 18.31 55.08
Jharkhand 2.60 11.36 6.23 0.27
Chhattisgarh 2.16 6.59 10.29 0.13
Orissa 3.61 22.52 43.34 17.01
TOTAL 12.16 53.02 78.60 72.49
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PREVALENT MAJOR
EPIDEMOLOGICAL TYPES OFMALARIA
Tribal malaria
Rural malaria
Urban malaria
Malaria in projected areas
Border malaria
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TRIBAL MALARIA
In tribal areas of Andhra Pradesh, MadhyaPradesh, Chhattisgarh, Gujarat, Maharashtra,Bihar, Jharkhand, Rajasthan & North eastern states
Contributes to about 50% cases of P.falciparum High risk to infants, young children ,pregnant
women
Factor responsible:-Limited health infrastructureLack of drugs at village level
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RURAL MALARIA
Irrigated areas of arid and semiarid areas ofHaryana, Punjab, West U.P, parts of M.P &Rajasthan, plains of Orissa, Andhra Pradesh, Tamil
Nadu Malaria is moderate to low endemicity
An.culicifacies is the main vector
P.vivax is predominant during lean period &P.falciparum during periodic exacerbation
In this areas health infrastructure is moderatelydeveloped
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URBAN MALARIA
In major cities:-Delhi ,Mumbai ,Chennai, Kolkata,Hyderabad, Bangalore
, Ahmadabad, Bhopal, Jaipur, Lucknow, Chandigarh,Kanpur.
An.stephansi is main vector
P.vivax is predominant &P.falciparum in focal
transmission
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MALARIA IN PROJECTED AREAS
Areas where construction & development activities aretaken up and temporary aggregation of labourers takeplace.
This bring different strains of malaria parasite in thenon immune population.
More than one vector is usually involved
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BORDER MALARIA
These are high malaria transmission belts along theinternational and national border.
Problem in regard to malaria control due to mixing ofpopulation and poor administrative control.
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EPIDEMIOLOGICAL DETERMINANTS1. AGENT FACTOR
2. HOST FACTOR
3. ENVIROMENTAL FACTORa. Climate
b. Vector
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1. Agent
2. Reservoir of infection
3. Period of communicability
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AGENT
4 species of plasmodiumP.vivax :-70% cases in India
P.falciparum :-25-30% cases
P.malariae :-< 1% cases
P.ovale :- very rare (Tumkur & Hassan districtin Karnataka
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LIFE CYCLE OF AGENT
2 developmental cycles1. Human cycle (asexual phase)
2. Mosquito cycle (sexual phase)
-Definitive host :- Mosquito
-Intermediate host :- Man
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ASEXUAL CYCLE
/ENDOGENOUS/SCHIZOGNY
Infective stage to man :--sporozoite
4 phases;-1. Pre-erythrocytic phase
2. Erythrocytic phase
3. Gamatogony
4. Exo-erythocyic phase
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PRE-ERYTHROCYTIC PHASE
Sporozoite infect liver cell forms hepatic schizonts
In P.falciparum-1 sporozoite-40,000 merozoiteOthers -1 sporozoite -2,000-15,000 merozoite
merozoite
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Merozoite specific receptors of RBC Ringtropozoite
schizonts immature schizonts maturetropozoite
Cycle is repeated again and again.
Duration of erythrocytic cycle
P .malariae- 72.hours
others- 48 hours
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-In all species of malaria some of erythrocytic formsdo not divide but forms male & female gamatocyte.
-This are sexual form of parasite.
-They are infective form to mosquito.
Ring tropozoite microgamatocyte infective to
macrogamatocyte mosquito
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Infective form gametocyte stage
Microgametocyte exflagellation 4-8microgamete
Macrogametocyte macrogamete
zygote
ookinete
oocyst
sporozoite
-Time period from gametocyte to sporozoite formation
10-20 days(Extrinsic incubation period)
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Resemble Pre-erythrocytic cycle.
Some sporozoite does not undergo multiplication but
enter a stage of resting (dormant) phase.These resting parasite are called HYPNOZOITE.
After a period they get activated and releasemerozoite.
Cause relapse of fever.
Not found in P .falciparum , so no relapse infalciparum malaria.
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RESERVIOR OF INFECTION
Animal reservoir ;- chimpanzees in tropicalAfrica
Human reservoir ;- one who harbours thesexual form of parasite
Condition for reservoir
1. Person must harbour both sex of gametocyte in blood.
2. Gametocyte must be mature
3. Gametocyte must be viable4. Gametocyte must be present in sufficient density to
infect mosquito at least ;-12 /cu.mm of blood
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PERIOD OF COMMUNICABILTY
Malaria is communicable as long as mature viablegametocyte exist in circulating blood in sufficientdensity to infect mosquito.
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RELAPSE
In P.vivax & P.ovale infection the parasite may survivefor long periods in dormant exo-erythrocytic stage ashypnozoites in liver cells.
Reactivation of hypnozoites leads to initiation of fresherythrocytic cycle and new attack of fever.
Usually from 24 weeks to 5 years after the primaryattack .
P vivax & ovale - 2-3 years
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RECRUDESCENCE
After a number of paroxyms the primary attacksubsides due to partial immunity.
The parasite however is not eliminated but persistin some erythrocyte though the level ofparasitaemia is below the threshold level.
Erythrocytic schizogony continues in body at lowlevel and gradually the number of parasite buildup to cross threshold level
This causes new attack after a period of latency.
Occurs in P.falciparum & P.malariae
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HOST FACTORS
1. Age2. Sex3. Race4. Pregnancy5. Socio-economic development6. Housing
7. Population mobility8. Occupation9. Human habits10. Immunity
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1. AGEAffects all age group
New born infants have considerable resistanceto infection with falciparum due to highconcentration of foetal Hb during few months oflife
2. SEX
Male > Female
Males are more exposed to out door activityFemales in India are better clothed
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3. RACE
Sickle cell trait ;- mild illness with falciparumDuffy negative ;-resistant to vivax infection
4. PREGNANCY
Increase the risk of malaria
May cause intrauterine death of foetusCause premature labour or abortion
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5. POPULATION MOBILITY
Labours connected with engineering ,irrigation
,agricultural & other project and migration ofnomads may import malaria parasite in theirblood & reintroduce malaria in areas wheremalaria have been controlled or eliminated.
6.OCCUPATION
Malaria is predominantly a rural disease and is
closely related to agriculture practices
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7. SOCIO ECONOMIC DEVELOPMENT
A disease of low socio economic areas
Malaria disappeared from developed country as a resultof socio economic development.
8. HOUSING
The ill ventilated and ill-lighted houses provide ideal indoor resting place for mosquito
So, proper housing is major control measure
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9. HUMAN HABITSSleeping outside doors.
Nomadism.Refusal to accept spraying of housing.Replastering of walls after spraying .Not using measures of personal protection.
All the above factors increase the risk of malaria.
10. IMMUNITYImmunity is accquired after repeated exposure for several years.
In endemic areas a state of collective immunity is established slowly. So, infants and travellers from non-endemic areas are main suffers. Immune mother transfer IgG antibody that infants for 3-5 months. Active immunity is species specific. Immunity usually declines after leaving endemic areas.
Both humoral &cellular factors play a role in protection
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ENVIRONMENTAL FACTORS It is divided into parts:-
a. Climate
b. Vector
A. Climate :- This include
1. Season2. Temperature
3. Humidity
4. Rainfall5. Altitude
6. Man made malaria
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3.Humidity:
-Direct effect on the life of the mosquito.
-It has no effect on the parasite.-A relative humidity of 60% is necessary formosquitoes to live their normal lifespan.
-When the relative humidity is high, mosquitoes aremore active & feed more voraciously.
-If the humidity is low mosquitoes do not live long.
4.Rainfall:-
-It provides opportunities for the breeding ofmosquitoes and may give rise to epidemics ofmalaria.
-It also increases humidity which is necessary for thesurvival of mosquitoes.
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5.Altitude:-
High altitudes unfavourable for mosquitoes.
6.Man Made Malaria:-
These are:-
-Burrow Pits
-Garden Pools
-Irrigation Channels
-Engineering Projects
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VECTOROut of 51 species of Anopheles only 9 causes malaria
-An. Culicifacies:- rural areas
-An. Stephensi:- urban areas
-An. Fluvitalis:- Hills & Foot hills areas
-An. Minimus:- Hills & Foot hills areas-An. Philippinensis:- Planes of West Bengal &
North East India
-An. Sundaic:- Eastern costal areas
-An. Annularis:- Andman & Nicobar-An. Varuna:- Hills & Foot hills of eastern ghat
-An. B balabacensis:- Forest area of North East India
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IMPORTANT VECTOR FACTORS
1.Density
2.Life span
3.Breeding habits
4.Resting habits5.Resistant to insecticide
6.Choice of host
7.Biting time
8.Vectoral capacity
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1.Density-
- Critical density:- density below which the effectivetransmission not occur.
-It is vary from species to species.
-High density required- An. culicifacies
- Low density required- An. fluviatilis
2.Life Span-
It is the key factor in the transmission of malaria.
-The vector mosquitoes must live at least 10-12daysafter an infective blood meal.
-The strategy in malaria eradication is to shorten thelife span of mosquitoes to
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3.Breeding habits:-
It varies from species to species.
-Moving water An. Fluvitalis-Brackish water - An.Sundaicus
-Wells & overhead tanks-An.stephensi
It is required for conducting anti-larval operation.
4.Resting habits:-
Endophily-those mosquito resting indoor.
Exophily- those mosquito resting outdoor.
These forms the basis the of Anti-adult measures.
R i t t i ti id
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5.Resistance to insecticides:-It is necessary for the choice of insecticide to beused.
6.Choice of host:-Some mosquitoes prefer human blood, some animal blood &
some show great variation in their feeding habits.
7.Biting time:-Majority of Indian mosquitoes bite after eveningthroughout the night.
8.Vectoral capacity:-
It refers to the combine effect of :--Density of vector population-Susceptibility to infection-Probability to feed on man
-Life span
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MODE OF TRANSMISSION
Two types-A)VectoralB)Non-Vectoral
A. Vectoral Transmission-
Malaria is transmitted by certain infected species ofAn.mosquitoes.
Important factors for transmission are--Adequate life span-Preference to human host
-Tendency to reside around human population-Should be in sufficient density to maketransmission chain-Environmental factors like temp., humidity, rainfall
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B) Non-Vectoral Transmission-
-Blood transfusion
-Sharing infected needles
-Transplacental or vertical
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INCUBATION PERIOD
This is the length of time between the infective mosquito
bite and the first appearance of clinical sign of whichfever is most common.
P.Falciparum-9-14 days
P.Vivax- 12-17 days
P.Ovale- 16-18 daysP.Malariae- 18-40 days
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PRE-PATENT INCUBATION PERIOD:-
It is the time between the inoculation of parasiteinto human being & appearance of 1st parasite in blood .
PROTRACTED INCUBATION PERIOD:-In some strains of P.vivax a period of latencyis observed when incubation period isprolonged to 8 -10 months
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CLINICAL FEATURES
-The primary fever corresponds to the development ofparasites in the RBC.
-The peaks of fever coincide with the release ofmerozoites into the blood stream.
The typical attacks comprises three stages-
1.Cold stage-
-The onset with lassitude, headache, nausea, chillysensation associated with rigors.-This stage lasts for about an hour.
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2.Hot stage-
Patient feels burning hot & casts off his clothes.The skin is hot and dry to touch.
Headache is intense but nausea diminishes.
This stage lasts for 2-6 hours.
3.Sweating stage-
Fever comes down with profuse sweating.
Temp. drops rapidly to normal & skin become cool & moist.This stage lasts for 2-4 hours.
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COMPLICATIONS
1.P.Falciparum--Cerebral malaria-Acute renal failure
-Liver damage-GIT symptoms
2.P.Vivex, Ovale & Malariae--Anaemia
-Splenomegaly-Herpes
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WHAT IS SURVEILLANCE ?
Surveillance means to watch over with greatattention ,authority & often with suspicion.
DEFINITION
The surveillance can be defined as continuousscrutiny of the factor that determine the occurrence
and distribution of disease and other condition ofill health.
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OBJECTIVE OF SURVEILLANCE
1. To provide information regarding new andchanging trends in the health status of apopulation.
2. To provide feedback regarding on going controlprogram.
3. To provide timely warning of health disaster.
The ultimate objective of surveillance isprevention.
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WHY NEED SURVEILANCE
The surveillance is needed for :-
1.Effective control and prevention.
2.For collection, analysis, interpretation
& distribution of relevant data foraction.
The main purpose of surveillance is to detectchanges in trends and distribution in order toinitiate investigative and control measure.
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SURVEILLANCE OF MALARIA- IN
MPO The Modified plan of operation (MPO) under the
NMEP came into force from 1st April 1977. Surveillance is an integral part of MPO.
For better control and stabilise the malariasituation in the country, endemic area arereclassified again according to API.
- area with API >2
-area with API 10 or
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SURVEILLANCE IN MALARIA
Surveillance of malaria is aimed at case detectionthrough laboratory services and providing facilities forproper treatment.
Collection and examination of blood smear is a key
element in MPO.
If all the detected cases are given radical treatment, itwill lead to depletion of the human reservoir.
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TYPES OF MALARIA SURVEILLANCE
It is of two types
Active surveillance
Passive surveillance
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ACTIVE SURVEILLANCE Carried by-surveillance workers (or MPW )
Norms -
-For normal area10,000 population / 2000 houses
-1 surv.worker /MPW
For 4 surv. Worker/MPW -1surv.Inspecter (health assistant)
-For terrain area8000 population-1 surv. Worker/MPW
For 4 surv.workers /MPW -1surv.Inspecter(health assistant)
FORTNIGHTLY DOMICILIARY
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FORTNIGHTLY DOMICILIARYVISITS
The surv.worker/MPW will visit each house in his area once a fortnight& enquire whether-
1.there is a fever case in house .2.there was a fever case in the house between his previous visit
and present visit.
If the answer to either of these question is yes
-MPW collects a blood film (thick & thin) on same slide &
presumptive treatment .-Make entries in house card about his visit.
-Dispatch the blood slides at least twice a week to the unit
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-Dispatch the blood slides at least twice a week to the unitlaboratory (PHC) for microscopic examination.
-He also collects blood slide from the sub-centre and FTD &send to laboratory (PHC)
-Take report from laboratory (at least twice aweek).
-If report is positive for malaria parasite .
-MPWreturns to patientand administer a full course ofradical treatment for malaria.
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PASSIVE SURVEILLANCE
The search for malaria cases by local agencies such as PHC ,sub-centre ,hospitals , dispensaries and local medical practioners.
In this patients voluntary report to the health agencies.
Those cases that escape by active search (MPW) are caught by theseagencies.
They collect blood smear from all fever cases and also from those withhistory of recent fever and give presumptive dose of malaria.
These collected slides are ,collected by MPW and send to unitlaboratory (PHC).
In next turn to laboratory the MPW collects report, if the report ispositive ,he goes to patient and give radical treatment.
PARAMETERS FOR MALARIA
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PARAMETERS FOR MALARIASURVEILLANCE
By definition surveillance also implys thecontinuing scrutiny of all aspects of occurrenceand spread of disease that are pertinent to effective
control .
So ,in these also include the systematic collectionof data and evaluation of field investigations etc.
For epidemiological surveillance of malaria thefollowing parameters are used -
IN PRE ERADICATION ERA
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IN PRE-ERADICATION ERA
1. Spleen rate-
- defined as %of children between 2-10 year ofage showing enlarged spleen.-it is a measure of endemicity of malaria in acommunity.
2. Infant parasite rate-
-% of infant showing malarial parasite in theirblood film.
-Most sensitive index of recent transmission ofmalaria in locality.
3.Parasite rate
-% of children between 2-10 years showingmalaria parasite in their blood films
4.Average enlarged spleen5.Proportional case rate
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ERADICATION ERA
1.Annual parasite incidence (API)API= confirmed cases during 1 year 1000
population under surveillance
-It is based on active & passive surveillance.
-It measure malaria incidence in acommunity
2. Annual blood examination rate (ABER)
ABER- No. of slides examined 100population
-It is an index of operational efficiency.3.Annual falciparum incidence (AFI)
4.Slide positivity rate (SPR)
5.Slide falciparum rate (SFR)
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Reduce vector mosquito population
Repel the vector mosquitoes
Form a barrier between vector andpotential host (personal protection)
Reduce the lifespan of vector mosquitoes
Reduce the lifespan ofpotentially infectedvector mosquitoes
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Epidemiological situation and risk factors Appropriate for controlling the specificvector species, given its breeding , flight and
resting, behavior Simple to understand and apply Affordable and based on locally availableresources (equipment , consumable supplies,
and technical skills) Acceptable and compatible with localcustoms and practices (postemergency phase) Safe for the user and the environment
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VECTOR CONTROL
CHALLENGES
Resources and infrastructure
Insecticide resistance
Inadequate surveillance
Mosquito species complexes
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ANTI-LARVALMEASURES
oSOURCE REDUCTIONoCHEMICAL CONTROLBIOLOGICAL CONTROL
ANTI -ADULT MEASURES
oRESIDUAL SPRAYSoSPACE SPRAYS
oGENETIC CONTROL
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PROTECTION AGAINST MOSQUITOBITES
oMOSQUITO NET
oSCREENING
oREPELLENTS
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SOURCE REDUCTION :-COMPRISES
FILLING DITCHES, AREAS, PITS, LOW LYING AREAS,
STREAMLINING,
CHANNELISING,DESILTING,
DEWEEDING,
TRIMMING OF DRAINS,
WATER DISPOSAL AND SANITATION,EMPTY WATER CONTAINER ONCE IN A WEEK, ETC.
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CHEMICAL CONTROL :-COMMONLY USED LARVICIDES ARE
I. Mineral oils
II. Paris green
III. Synthetic insecticides
Toxicants employed as larvicides
Toxicant Doses (g/ha)
Abate 56-112
Malathion 224-672
Fenthion 22-112
Chloropyrifos 11-16
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Biological Control :-
Bilogical control of mosquito breeding through biologicalagents specially larvivorous fish and by larvicides.
The best known are:-
GAMBUSIA AFFINIS
LEBISTER RETICULATUS
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2.ANTI-ADULT MEASURES
INDOOR RESIDUAL SPRAYING:-
Residual spraying with DDT was a major reason
for successes in malaria control of 1950s & 60s
Malaria eradicated or nearly eradicated from
many parts of the world at that timeHouse spraying remains a valuable tool for
malaria control under the right circumstances
However, large-scale ongoing application of
insecticides in this manner is not sustainable
due to financial and operational constraints and
development of insecticide resistance
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INDOOR RESIDUAL SPRAYING ISAPPROPRIATE
WHEN...
A high percentage of structures in an operational
area have adequate sprayable surfaces, and can be
expected to be well sprayed The majority of the vector population in endophilic,
i.e. rests indoors
The vector is susceptible to the insecticide in use
In a given area, residual spraying can be targeted at
selected houses where the risk of transmission is
highest, e.g. those near important breeding sites
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FACTORS TO CONSIDER IN SELECTION
OF RESIDUAL INSECTICIDES Residual effectiveness
Safety (LD50, environmental persistence,
bioaccumulation)
Vector susceptibility/Management of resistance Impact on disease
Excito-repellency
Costs
Acceptance (odor, visibility)
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AEROSOL SPACE SPRAY :-
Space spraying of Pyrethrum extract(2%) in 50 houses inand around every malaria positive case to kill the infectivemosquitoes.
Involve the application of pesticides in the form of fog ormist using special equipment:-
ULV SPR YER THERM L FOG SPR YER
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GENETIC CONTROL:-
GENETIC METHODS SUCH AS
STERILE MALE TECHNIQUE CYTOPLASMIC INCOMPATIBILITY
CHROMOSOMAL TRANSLOCATION
SEX DISTORTION
GENE REPLACEMENT
BEING CHEAPER AND POTENTIALLY MORE
EFFICIENT THAN CHEMICAL METHODS .
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Many types of potential vaccine for controlling malariaare under are development.
TYPES OF MALARIA VACCINES
1)PRE-ERYTHROCYTIC VACCINES
2)ASEXUAL BLOOD STAGES VACCINES3)SEXUAL STAGES VACCINES
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1. PRE-ERYTHROCYTIC VACCINE
They are developed to prevent infection and
impact of disease
2. ASEXUAL BLOOD STAGE VACCINE
-Based on antigens derived from the bloodstages of P.falciparum present in man
o -Designed to reduce severe and complicated
manifestation of disease
o
-They could lower morbidity and mortality,aparticularly high risk group
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3. SEXUAL STAGE /TRANSMISSION BLOCKINGVACCINE
oThus Designed to arrest the development of the
parasite in mosquito.
oReduce or eliminate transmission of the disease
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Stage ofPlasmodium Antigens Salient features
Pre-erythnocytic Circum Sporozoite Protein (CSP)
, Liver stage Antigens -1 (LSA-1)
-Stage/species specific;-antibody blocks infection of
liver;
- large immunising dose required;can abort an infection
Merozoite andErythrocytes
Erythrocyte Binding Antigen,Merozoite Surface Antigen 1&2 (MSA-
1&2);Ring Infected Erythrocyte Surfacentigen (RESA)
Serine Repeat Antigen (SERA) ApicalMembrane Antigen-1 (APM-1)
-Specific for species and stage; --
Cannot abort an infection;Prevents invasion of erythrocytes,-thus reducing severity oinfection
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Gametocytes & gametesPfs 25,,Pfs 230
-Prevents infection ofmosquitoes;
-antibody to this antigenprevents either fertilizationor maturation ofgametocytes,zygotes orookinetes-antibody blockstransmission cycle
Combined vaccine (cocktail)
SPf 66 (based on pre-
erythrocytic and asexual bloodstage proteins of Pf)
-Based on incorporation ofantigens from different stagesinto one vaccine to produce an
immune response,- blocking all stages of theparasite development
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Recombinant Vaccine:
Against P. vivaxblood stage infection .Combination of malarial antigens with immune boostingadjuvant and hepatitis B surface antigens have been reported.
Gamete Vaccine:When the antibodies are taken up by the mosquitoes, gametesescaping the RBCs will be neutralized, thus preventingfertilization and reducing transmission.
DNA Vaccine:Based on a synthetic gene, made by adding 21 epitopes of 9different antigens present in P. faciparum.Example - Pf 155/RESA (Ring Infected Erythrocyte Surface
Antigen).
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Problems in vaccine production including not beingable to grow the parasite in large quantities.
Difficulty of evaluation.
Complexity of conducting clinical and field trials.
Mutation of the parasites.
Multiple antigens, specific to species and stage.
CONCLUSION
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CONCLUSION-Sporozoite vaccines generated by recombinantDNA technology, combined with potent T-cellepitopes for higher immunogenecity seem toinhibit early liver-stages of the parasite .
Blood stage antigens combined with Freund's adjuvant or
other immunoboosters may generate effects resemblingchloroquine chemoprophylaxis.
Merozoite vaccines get longer time to interact with theirtarget than the transiently appearing sporozoites in case
of sporozoite vaccines.
Gamete vaccines hold promise for future where in antibodieswhen taken up by the mosquitoes will neutralise the gametes
escaping RBCs, thus preventing fertilization.
.
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Can be motivated at 2 levels
1. Individual /Family level2.Community level
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INDIVIDUAL PROTECTION AGAINSTMOSQUITO BITES:-
By preventive measures such as the use of-
Repllents
Protective clothing
Bed nets
Mosquito coils
Screening of house
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1. HEALTH EDUCATION-Educate the people to wear full sleave cloths.
-Avoid outdoor sleeping.
-Do not allow water to collect in the
sourroundings eg. In tyresin coconut shells
2.COMMUNITY PARTICIPATION
- There is no standing wastewater around water pointsor elsewhere in the settlement.
- Promotion for insecticidal spray in community.
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Thank You