Rift Valley Fever- 2006 Rift Valley Fever Texas A&M University Texas A&M University College of Veterinary Medicine College of Veterinary Medicine Jeffrey

Rift Valley Fever- 2006Rift Valley Fever- 2006

Rift Valley Fever Rift Valley Fever

Texas A&M University Texas A&M University

College of Veterinary MedicineCollege of Veterinary Medicine

Jeffrey Musser, DVM, PhDJeffrey Musser, DVM, PhD

Suzanne Burnham, DVMSuzanne Burnham, DVM


Special thanks for materials Special thanks for materials borrowed with permission borrowed with permission

from presentations by:from presentations by:

Dr Linda Logan, “Rift Valley Fever” CSU Dr Linda Logan, “Rift Valley Fever” CSU Foreign Animal Disease Training Course, Foreign Animal Disease Training Course, College of Veterinary Medicine and Biomedical College of Veterinary Medicine and Biomedical Sciences, August 1-5, 2005. Sciences, August 1-5, 2005.

Professor JAW Coetzer, Professor JAW Coetzer, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, “Rift Valley Fever” presented at the FEAD course in Knoxville, Tenn. 2005.


Rift Valley FeverRift Valley FeverRift Valley Fever (RVF) is an Rift Valley Fever (RVF) is an arthropod-borne, acute, fever-arthropod-borne, acute, fever-causing viral disease of sheep, causing viral disease of sheep, goats, cattle and people. goats, cattle and people.

RVF causes abortions in sheep, RVF causes abortions in sheep, cattle and goats, high mortalities in cattle and goats, high mortalities in lambs and kids and generalized lambs and kids and generalized disease in man.disease in man.


Rift Valley FeverRift Valley Fever

RVF is reportable to the OIE. RVF is reportable to the OIE.

It is also on the USDA and It is also on the USDA and Department of Health and Human Department of Health and Human Services (HHS) High Consequence Services (HHS) High Consequence lists.lists.


Rift Valley FeverRift Valley FeverRVF was first observed when RVF was first observed when

European stocks of domestic European stocks of domestic animals, which are more severely animals, which are more severely affected than native stock, were affected than native stock, were introduced to Africa.introduced to Africa.

Rift ValleyRift ValleyRift ValleyRift Valley


Rift Valley Fever was first reported atRift Valley Fever was first reported at

Lake Naivasha in Kenya. Lake Naivasha in Kenya.

There were many sheep There were many sheep

abortions and young abortions and young

lambs were foundlambs were found

sick or dead.sick or dead.

Lake NaivashaLake Naivasha


Cyclic epidemicsCyclic epidemics

Periodic Pandemics occur near “Dambos” Periodic Pandemics occur near “Dambos” or Playa lakesor Playa lakes

These are depressions that accumulate These are depressions that accumulate water water

5-15 year cycles following heavy rainfall5-15 year cycles following heavy rainfall

Flooded Dambos allow the Flooded Dambos allow the Aedes Aedes mosquitoes infected with RVF to emergemosquitoes infected with RVF to emerge



A “Dambo” or

Playa Lake

Cattle near a “Dambo” in Kenya


Rift Valley FeverRift Valley Fever

Generally found in eastern and southern Generally found in eastern and southern Africa where sheep and cattle are raisedAfrica where sheep and cattle are raised

Most countries of sub-Saharan AfricaMost countries of sub-Saharan Africa

MadagascarMadagascar

September 2000 RVF outbreak in Saudi September 2000 RVF outbreak in Saudi Arabia and Yemen – first outbreak outside Arabia and Yemen – first outbreak outside of the African continentof the African continent


Possible modes of spreadPossible modes of spread

Infected mosquitoesInfected mosquitoes

Movement of viremic animalsMovement of viremic animals

Windborne movement of vectorsWindborne movement of vectors

Contaminated viscera and tissuesContaminated viscera and tissues



Kenya AfricaKenya Africa

Largest outbreak reported in sheep was in Largest outbreak reported in sheep was in 1950-19511950-1951

100,000 mortality in sheep 100,000 mortality in sheep

500,000 abortions in sheep500,000 abortions in sheep


Kenya 1997-1998Kenya 1997-1998

Largest outbreak recorded for human Largest outbreak recorded for human cases: 89,000 cases - 478 deaths.cases: 89,000 cases - 478 deaths.

Flooding near Flooding near

Garissa, KenyaGarissa, Kenya


RVF outbreak 1997-98RVF outbreak 1997-98

Nomadic Refugee Camp at Garissa, 1997Nomadic Refugee Camp at Garissa, 1997


Economic effectsEconomic effects

Disease in Disease in 89,000 89,000 farm farm

workers,workers, animal handlersanimal handlers veterinariansveterinarians

50% abortions in 50% abortions in ruminantsruminants


Economic effectsEconomic effects

Countries of the Countries of the Arabian peninsula Arabian peninsula ban trade of livestock ban trade of livestock from Africafrom Africa


Rift Valley FeverRift Valley Feverin the World in 2004, OIEin the World in 2004, OIE

http://www.oie.int/eng/info/en_presdistribgeo.htm

Disease reported present

Disease reported absent

Data unavailable or incomplete


EtiologyEtiology

Host rangeHost range

Incubation Incubation

Clinical signsClinical signs

TransmissionTransmission

Diagnosis Diagnosis

Differential DiagnosisDifferential Diagnosis

Rift Valley Fever


EtiologyEtiology

Family: Family:

BunyaviridaeBunyaviridae

Genus: Genus:

PhlebovirusPhlebovirus


EtiologyEtiology

RVF virus is serologically related to other RVF virus is serologically related to other phleboviruses, but can be differentiated by phleboviruses, but can be differentiated by serum neutralization tests. serum neutralization tests.

Enveloped RNA virusEnveloped RNA virus

There is only one serotype of RVF virusThere is only one serotype of RVF virus

However, there is different pathogenicity However, there is different pathogenicity among strains of RVF virusamong strains of RVF virus


Host Range - ZoonosisHost Range - Zoonosis

Mainly a disease of sheepMainly a disease of sheep

Goats are somewhat less susceptibleGoats are somewhat less susceptible

Native African cattle are less susceptible Native African cattle are less susceptible than the small ruminantsthan the small ruminants

Humans Humans


RVF is a Zoonotic Disease


Host RangeHost Range

Mainly SheepMainly Sheep Mortality in lambs Mortality in lambs

under 2 weeks of under 2 weeks of age reaches 100%age reaches 100%

Mortality in older sheep Mortality in older sheep reaches 30% with reaches 30% with

abortions at 100%abortions at 100%



GoatsGoats CattleCattle Buffalo Buffalo



Horses – have viremia but are resistantHorses – have viremia but are resistant



Domestic dogs and cats - SUSCEPTIBLEDomestic dogs and cats - SUSCEPTIBLE

Swine - resistantSwine - resistant

Birds - refractory, no virus isolationBirds - refractory, no virus isolation


Host rangeHost range

Cattle are less susceptible, some are Cattle are less susceptible, some are subclinical; mortality averages 5% with subclinical; mortality averages 5% with some abortionssome abortions


Host rangeHost range - wildlife - wildlife

SpringbokSpringbok

African Buffalo African Buffalo

Camels (in Egypt) Camels (in Egypt)

Water buffalo in EgyptWater buffalo in Egypt


Water buffalo - up to 50% abortion rateWater buffalo - up to 50% abortion rate


Camels (in Egypt) inapparent Camels (in Egypt) inapparent

disease except abortionsdisease except abortions


Incubation periodIncubation period

1-6 days1-6 days

12-36 hours in 12-36 hours in lambs; will be lambs; will be dead before they dead before they can acquire can acquire passive immunitypassive immunity



Clinical signs Clinical signs Sheep and GoatsSheep and Goats

Incubation period less Incubation period less than 3 daysthan 3 days

High rate of abortion High rate of abortion at any stage of at any stage of gestationgestation

Can be asymptomaticCan be asymptomatic


Clinical signs in sheepClinical signs in sheep

o Most severe in young Most severe in young lambs (mortality has lambs (mortality has high as 90%)high as 90%)

o Encrustation around Encrustation around the muzzlethe muzzle

o AnorexiaAnorexiao AbortionAbortiono JaundiceJaundiceo Weakness Weakness o Death within 36 hoursDeath within 36 hours



Clinical Signs in sheep and goatsClinical Signs in sheep and goats

Lambs, kids: Lambs, kids: – fever (40-42°C), fever (40-42°C), – anorexia, anorexia, – weakness, weakness, – death within 36 hours death within 36 hours – after inoculation. after inoculation.



Lambs: Lambs:

Mortality rate: for animals under 1 week of Mortality rate: for animals under 1 week of age - up to 90%; for animals over 1 week age - up to 90%; for animals over 1 week of age - up to 20%of age - up to 20%



Adults: fever (40-41°C), mucopurulent Adults: fever (40-41°C), mucopurulent nasal discharge, encrustation of nostrilsnasal discharge, encrustation of nostrils

Vomiting, foul diarrheaVomiting, foul diarrhea

Acute death may reach Acute death may reach

20-30% in adults20-30% in adults


In pregnant ewes, abortion may reach 100%In pregnant ewes, abortion may reach 100%


Clinical signs in cattleClinical signs in cattle

Anorexia

Weakness

Fetid diarrhea

Often only sign is a drop in calving rates

Add images



Calves: fever (40-41°C), depression. Mortality Calves: fever (40-41°C), depression. Mortality rate: 10-70%rate: 10-70%

Adults: fever (40-41°C), excessive salivation, Adults: fever (40-41°C), excessive salivation, anorexia, weakness, fetid diarrhea, fall in milk anorexia, weakness, fetid diarrhea, fall in milk yield. Abortion may reach 85% in the herd. yield. Abortion may reach 85% in the herd. Mortality rate is usually less than 10%Mortality rate is usually less than 10%



Disease most severe in young animalsDisease most severe in young animals

AbortionAbortion

Drop in milk productionDrop in milk production

Fever of 104-106 Fever of 104-106 °F°F

Excess salivationExcess salivation


Clinical signsClinical signs

Dogs: Abortions up to 100%, severe Dogs: Abortions up to 100%, severe disease and death in puppiesdisease and death in puppies

Death in kittensDeath in kittens


Relative susceptibilityRelative susceptibility

Newborn ruminants Newborn ruminants ++++++++

Pregnant ruminants Pregnant ruminants ++++++++

Sheep and young cattle Sheep and young cattle ++++++

Adult cattle, goats, sheepAdult cattle, goats, sheep ++++

HumansHumans ++++

Dogs, cats and camelsDogs, cats and camels ++

Pigs Pigs --



• RVF is primarily RVF is primarily transmitted from transmitted from animal to animal by a animal to animal by a mosquito mosquito

• Aedes, Culex, Aedes, Culex, Anopheles, Anopheles, Erehmapodites, Erehmapodites, MonsosmiaMonsosmia



Vertical transmission in Vertical transmission in mosquitoes is probably mosquitoes is probably important in maintaining RVF important in maintaining RVF in endemic areasin endemic areas

Trans-ovarial transmission is Trans-ovarial transmission is important in causing important in causing epidemics and maintaining the epidemics and maintaining the virusvirus



Other arthropods (Stomoxys, midges and Other arthropods (Stomoxys, midges and tabanids) are able to transmit RVF by tabanids) are able to transmit RVF by mechanical meansmechanical means


Transovarial TransmissionTransovarial Transmission

Mosquito eggs dormant in soil for long Mosquito eggs dormant in soil for long period of timeperiod of time

Hatch with heavy rainfallHatch with heavy rainfall


Aerosol TransmissionAerosol Transmission

RVF virus levels very high in body fluids RVF virus levels very high in body fluids during viremiaduring viremia

Virus aerosolized during butchering or Virus aerosolized during butchering or necropsy of infected animalsnecropsy of infected animals

Surgery, autopsy (humans)Surgery, autopsy (humans)

Laboratory workers riskLaboratory workers risk


Village butchers at riskVillage butchers at risk


Human TransmissionHuman Transmission

Direct contact most Direct contact most significant for humanssignificant for humans

Humans get RVF Humans get RVF from handling tissues, from handling tissues, blood, secretions and blood, secretions and excretions of infected excretions of infected animals.animals.



Milk contains virus: not known how important this is to transmission


Disease in humansDisease in humans

Incubation 2-6 daysIncubation 2-6 days

Inapparent, or flu-like symptomsInapparent, or flu-like symptoms

Fever, headache, myalgia, nauseaFever, headache, myalgia, nausea

Recovery 4-7 daysRecovery 4-7 days

Retinopathy, loss of visual acuity Retinopathy, loss of visual acuity

Mortality ~1%Mortality ~1%


Clinical Signs in humansClinical Signs in humans

RVF in humans can be a severe influenza-like RVF in humans can be a severe influenza-like disease.disease.

• Damage to retina (can lead to blindness)Damage to retina (can lead to blindness)• High fever (100-104 High fever (100-104 °F, °F, 37.8-40°C), 37.8-40°C), • Muscular painMuscular pain• WeaknessWeakness• NauseaNausea• Epigrastric discomfortEpigrastric discomfort• PhotophobiaPhotophobia• Hemorrhagic diathesisHemorrhagic diathesis


RetinopathyRetinopathy

Occurs in 1-10% of Occurs in 1-10% of affected humansaffected humans

ConjunctivitisConjunctivitis

PhotophobiaPhotophobia

Can lead to Can lead to permanent vision permanent vision lossloss

Al-Hazmi



Tentative diagnosisepidemiological, clinical and pathological features

Confirmation of diagnosis

Virus isolationliver, spleen and blood

Antigen capture ELISA

PCR

Serology•CF test•Virus neutralization•ELISA•other

Histopathology : Immunohistochemistry

Tentative diagnosisepidemiological, clinical and pathological features

Confirmation of diagnosis

Virus isolationliver, spleen and blood

Antigen capture ELISA

PCR

Serology•CF test•Virus neutralization•ELISA•other

Histopathology : Immunohistochemistry

DiagnosisDiagnosis


DiagnosisDiagnosis

Sample collection:Sample collection:

Heparinized bloodHeparinized blood

SpleenSpleen

LiverLiver

Acute and convalescent serum samplesAcute and convalescent serum samples


DiagnosisDiagnosis

Virus isolation in cell cultureVirus isolation in cell culture

Virus neutralizationVirus neutralization

Antigen detection by IF stainingAntigen detection by IF staining

ELISAELISA

Polymerase Chain Reaction (PCR)Polymerase Chain Reaction (PCR)


Clinical PathologyClinical Pathology

LeucopeniaLeucopenia

Increased liver enzymesIncreased liver enzymes

Prolonged clotting time, thrombocytopeniaProlonged clotting time, thrombocytopenia

Disseminated intravascular coagulopathyDisseminated intravascular coagulopathy


Necropsy findingsNecropsy findings

Massive hepatitis: hemorrhages, necrotic Massive hepatitis: hemorrhages, necrotic foci, marked enlargement, orange-brown, foci, marked enlargement, orange-brown, friable, edematous liver tissue friable, edematous liver tissue

(“If you open a newborn lamb, the liver jumps into your (“If you open a newborn lamb, the liver jumps into your face” Coetzer)face” Coetzer)

Chocolate-brown digested blood in Chocolate-brown digested blood in abomasum, hemorrhages in intestinal abomasum, hemorrhages in intestinal mucosa, free blood in lumenmucosa, free blood in lumen


Pathology SummaryPathology Summary

Focal or generalized Focal or generalized hepatic necrosis hepatic necrosis

Congestion, enlargement, Congestion, enlargement, and discoloration of liver and discoloration of liver with subcapsular with subcapsular hemorrhages hemorrhages

Brown-yellowish color of Brown-yellowish color of liver in aborted fetuses liver in aborted fetuses

Hemorrhagic enteritis Hemorrhagic enteritis

Icterus (low percentage) Icterus (low percentage)

Widespread cutaneous Widespread cutaneous hemorrhages, petechial hemorrhages, petechial to ecchymotic to ecchymotic hemorrhages on parietal hemorrhages on parietal and visceral serosal and visceral serosal membranes membranes

Enlargement, edema, Enlargement, edema, hemorrhages and hemorrhages and necrosis of lymph nodes necrosis of lymph nodes

Congestion and cortical Congestion and cortical hemorrhages of kidneys hemorrhages of kidneys and gallbladderand gallbladder


Necropsy : new-born lambsNecropsy : new-born lambs


Necropsy : new-born lambsNecropsy : new-born lambs


Necropsy : adult sheepNecropsy : adult sheep


Necropsy : adult sheepNecropsy : adult sheep

Gall bladder contains frank hemorrhage


Necropsy : sheep & cattleNecropsy : sheep & cattle

Abomasum is edematous similar to Heartwater


Necropsy : adult cattleNecropsy : adult cattle


Necropsy : adult cattleNecropsy : adult cattle


Necropsy : cattleNecropsy : cattle


Necropsy : other lesionsNecropsy : other lesions

Enlarged lymph nodes



Abortifacient agentsAbortifacient agents

Agents causing hepatitisAgents causing hepatitis

Agents that cause hemorrhagesAgents that cause hemorrhages



Bluetongue Bluetongue

Wesselsbron disease Wesselsbron disease

Enterotoxemia of sheep Enterotoxemia of sheep

Ephemeral fever Ephemeral fever

Brucellosis Brucellosis

Vibriosis Vibriosis

Trichomonosis Trichomonosis



Nairobi sheep disease Nairobi sheep disease

Heartwater Heartwater

Ovine enzootic abortion Ovine enzootic abortion

Toxic plants Toxic plants

Bacterial septicemias (Pasteurella, Bacterial septicemias (Pasteurella, Salmonella, Anthrax)Salmonella, Anthrax)

Rinderpest and Peste des petits ruminantsRinderpest and Peste des petits ruminants


Suspect Rift Valley Fever if:Suspect Rift Valley Fever if:

High mortalities in lambs, kids and calves following High mortalities in lambs, kids and calves following increase in mosquito populationsincrease in mosquito populations

Disease is milder in adults than in newbornsDisease is milder in adults than in newborns

Abortions in sheep, goats and cattleAbortions in sheep, goats and cattle

Extensive necrotic liver changesExtensive necrotic liver changes

Influenza symptoms in people working with sick animals Influenza symptoms in people working with sick animals or handling infected carcassesor handling infected carcasses


Rift Valley FeverRift Valley Fever - - BibliographyBibliography

1.1. Linda L Logan, DVM PhD, USDA APHIS AttachLinda L Logan, DVM PhD, USDA APHIS Attaché, é, North Africa, East Africa, Middle East, “Rift Valley North Africa, East Africa, Middle East, “Rift Valley Fever” CSU Foreign Animal Disease Training Fever” CSU Foreign Animal Disease Training Course, Aug 1-5, 2005.Course, Aug 1-5, 2005.

2.2. Professor Professor J A W Coetzer, Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, “Rift Valley Fever”

3. USAHA, Foreign Animal Diseases, 1992 Edition, p.311-317

4.4. W.A. Geering, A.J. Foreman and M.J. Nunn, W.A. Geering, A.J. Foreman and M.J. Nunn, Exotic Exotic Diseases of AnimalsDiseases of Animals, 1995 Australian Govt , 1995 Australian Govt Publishing Service, Canberra; p.218- 224. Publishing Service, Canberra; p.218- 224.


AcknowledgementsAcknowledgements

Special thanks to Special thanks to

Linda Logan, DVM PhD, Linda Logan, DVM PhD, USDAUSDA

Professor JAW CoetzerProfessor JAW Coetzer

Ken Waldrup, DVM, PhDKen Waldrup, DVM, PhD

Robin Sewell, DVM Robin Sewell, DVM

Kelsey Pohler- Research Assistant Kelsey Pohler- Research Assistant

Documents

Rift Valley Fever- 2006 Rift Valley Fever Texas A&M University Texas A&M University College of Veterinary Medicine College of Veterinary Medicine Jeffrey