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Rift Valley Fever Symptoms. Texas A&M University University of Pretoria College of Veterinary Medicine Department of

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Rift Valley FeverSymptoms

Texas A&M University University of Pretoria

College of Veterinary Medicine Department of

Veterinary Tropical Diseases

Jeffrey Musser, DVM, PhD Professor J.A.W. Coetzer

Suzanne Burnham, DVM

Rift Valley Fever- 2006


Special thanks for materials borrowed with permission from presentations by l.jpg
Special thanks for materials borrowed with permission from presentations by:

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

  • 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 Fever- 2006


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Rift Valley Fever

In this presentation the authors especially drew from the first hand experience of their colleagues in South Africa. Personal interviews as well as standard research sources provide the insights we bring you for the recognition of this exotic disease.

JAW Coetzer

Jeffrey Musser

Suzanne Burnham

Rift Valley Fever- 2006


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Rift Valley Fever

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

Rift Valley Fever- 2006


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Rift Valley fever in Africa causes abortions in sheep, cattle and goats high mortalities in lambs and kids and generalized disease in man.

Rift Valley Fever- 2006


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Rift Valley Fever cattle and goats high mortalities in lambs and kids and generalized disease in man.

RVF was first observed when European stocks of domestic animals were introduced to Africa. These species are more severely affected than native African stock.

Rift Valley Fever- 2006


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Host Range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Mainly a disease of sheep

Rift Valley Fever- 2006


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Host Range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • In Sheep

    Mortality in lambs under 2 weeks of age approaches 100%

    Mortality in older sheep reaches 30%

    with abortions

    approaching 100%

Rift Valley Fever- 2006


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Host range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Cattle are less susceptible than sheep, some are subclinical; mortality averages 5% with some abortions

Rift Valley Fever- 2006


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Host Range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Goats

  • Buffalo

Rift Valley Fever- 2006


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Host Range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Domestic dogs and cats – susceptible but usually only have asymptomatic viremia

  • Swine - resistant

  • Birds - refractory, no virus isolation

Rift Valley Fever- 2006


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Host Range cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Horses – have viremia but are resistant

Rift Valley Fever- 2006


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Host range - wildlife cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Springbok

  • African Buffalo

  • Camels (in Egypt)

  • Water buffalo in Egypt

Rift Valley Fever- 2006


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Host range - wildlife cattle and goats high mortalities in lambs and kids and generalized disease in man.

Water buffalo - up to 50% abortion rate

Rift Valley Fever- 2006


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Host range - wildlife cattle and goats high mortalities in lambs and kids and generalized disease in man.

Camels (in Egypt) - inapparent disease except abortions

Rift Valley Fever- 2006


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Humans cattle and goats high mortalities in lambs and kids and generalized disease in man.

Rift Valley Fever- 2006


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Incubation period cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • 1-6 days

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

Rift Valley Fever- 2006


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Incubation period less than 3 days cattle and goats high mortalities in lambs and kids and generalized disease in man.

High rate of abortion at any stage of gestation

Some show no symptoms

Clinical signs Sheep and Goats

Rift Valley Fever- 2006


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In pregnant ewes, abortion may approach 100% cattle and goats high mortalities in lambs and kids and generalized disease in man.

Aborted fetus is usually autolyzed.

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

  • Abortion rate in sheep from 40 – 100%

  • Ewe may also retain the placenta

  • Endometritis is another complication after aborting the fetus

USDA

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

Early signs

  • Fever 40-41°C

  • Loss of appetite

  • Jaundice

  • Weakness

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

  • Encrustation around the muzzle from bloody nasal discharge

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

  • Some develop diarrhea

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

  • Acute death may occur

    in 20-30% of adults

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.Sheep and Goats

Heavy sheep losses

occur

during epidemic

Rift Valley Fever- 2006


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Clinical Signs in lambs and kids cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Newborn Lambs, Kids: Most severe in

    young lambs under 2wks old

    (mortality has high as 90%)

    • fever (40-42°C),

    • anorexia,

    • weakness,

Rift Valley Fever- 2006


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Clinical Signs in lambs and kids cattle and goats high mortalities in lambs and kids and generalized disease in man.

Lambs seem reluctant to move;

they have signs of abdominal pain,

rapid respiration and listlessness.

Rift Valley Fever- 2006


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Clinical Signs in lambs and kids cattle and goats high mortalities in lambs and kids and generalized disease in man.

Death may occur within 24 to 36 hours

after the first signs appear. Death is due to severe liver necrosis and vascular collapse.

Rift Valley Fever- 2006


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Clinical signs in cattle cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Anorexia

  • Weakness

  • Fetid diarrhea

  • Often only sign is a drop in calving rates

Add images

Rift Valley Fever- 2006


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Clinical signs in cattle cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Calves: fever (40-41°C), depression. Mortality rate: 10-70% Death occurs about 2-8 days after the first signs appear.

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

Rift Valley Fever- 2006


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Clinical signs in cattle cattle and goats high mortalities in lambs and kids and generalized disease in man.

Rift Valley Fever- 2006


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Clinical signs in cattle cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Disease most severe signs are seen in young animals

  • Symptoms may be prolonged and will include jaundice in some calves

  • Aborted calves are moderately autolyzed.

Rift Valley Fever- 2006


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Clinical signs cattle and goats high mortalities in lambs and kids and generalized disease in man.

  • Dogs: Abortions may occur in adult dogs; severe disease and death usually only in puppies

  • Cats: Death in kittens

Rift Valley Fever- 2006


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Relative susceptibility cattle and goats high mortalities in lambs and kids and generalized disease in man.

Newborn ruminants ++++

Pregnant ruminants ++++

Sheep and young cattle +++

Adult cattle, goats, sheep ++

Humans ++

Dogs, cats and camels +

Pigs -

Rift Valley Fever- 2006


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RVF is primarily transmitted from animal to animal by a mosquito

Aedes, Culex, Anopheles, Erehmapodites, Monsosmia

Transmission

Rift Valley Fever- 2006


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Necropsy findings mosquito

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

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

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

Rift Valley Fever- 2006


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Focal or generalized hepatic necrosis mosquito

Congestion, enlargement, and discoloration of liver with subcapsular hemorrhages

Brown-yellowish color of liver in aborted fetuses

Hemorrhagic enteritis

Icterus (low percentage)

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

Enlargement, edema, hemorrhages and necrosis of lymph nodes

Congestion and cortical hemorrhages of kidneys and gallbladder

Pathology Summary

Rift Valley Fever- 2006


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Necropsy : new-born lambs mosquito

Liver massively enlarged; hemorrhages; orange-brown color;

small areas of necrosis. The liver is very friable.

Rift Valley Fever- 2006


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Necropsy : new-born lambs mosquito

Gall bladder hemorrhage; Abomasum diffuse hemorrhage,

serosa has petechial hemorrhage

Rift Valley Fever- 2006


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Necropsy : new-born lambs mosquito

Abomasum shows diffuse chocolate brown hemorrhages,

serosa has petechial hemorrhages, necrotic foci, and D. I. C.

Rift Valley Fever- 2006


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Necropsy : adult sheep mosquito

May look like plant poisoning

Rift Valley Fever- 2006


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Necropsy : adult sheep mosquito

Gall bladder contains frank hemorrhage

Rift Valley Fever- 2006


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Necropsy : sheep & cattle mosquito

Abomasum is edematous similar to Heartwater

Rift Valley Fever- 2006


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Necropsy : adult cattle mosquito

Close up of gall bladders

Rift Valley Fever- 2006


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Necropsy : adult cattle mosquito

Petechia

Rift Valley Fever- 2006


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Necropsy : cattle mosquito

Spleen with many hemorrhages

Rift Valley Fever- 2006


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Necropsy : other lesions mosquito

Enlarged

lymph nodes

Rift Valley Fever- 2006


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Differential Diagnosis mosquito

  • Abortifacient agents

  • Agents causing hepatitis

  • Agents that cause hemorrhages

Rift Valley Fever- 2006


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Differential Diagnosis mosquito

  • Bluetongue

  • Wesselsbron disease

  • Enterotoxemia of sheep

  • Ephemeral fever

  • Brucellosis

  • Vibriosis

  • Trichomonosis

Rift Valley Fever- 2006


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Differential Diagnosis mosquito

  • Nairobi sheep disease

  • Heartwater

  • Ovine enzootic abortion

  • Toxic plants

  • Bacterial septicemias (Pasteurella, Salmonella, Anthrax)

  • Rinderpest and Peste des petits ruminants

Rift Valley Fever- 2006


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Suspect Rift Valley Fever if: mosquito

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

  • Disease is milder in adults than in newborns

  • Abortions in sheep, goats and cattle

  • Extensive necrotic liver changes

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

Rift Valley Fever- 2006


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Rift Valley Fever mosquito - Bibliography

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

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

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

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

Rift Valley Fever- 2006


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An excellent video about Rift Valley Fever is available from:

http://www.up.ac.za/academic/veterinary/depts_vtd_teach/index.htm

Rift Valley Fever- 2006


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Image Watermark from:

  • “KAW” images by Dr. Ken A. Waldrup

  • “Coetzer” images used with permission by Dr. Koos Coetzer

  • “LLogan” images by Dr. Linda Logan

  • “Suz” images by Dr Suzanne Burnham

  • “MFitilodze” images by Dr. M. W. (Bill) Mfitilodze Bunda College of Agriculture, University of Malawi

Rift Valley Fever- 2006


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Acknowledgements from:

Special thanks to

Professor JAW Coetzer

Linda Logan, DVM PhD, USDA

Ken Waldrup, DVM, PhD

Robin Sewell, DVM

Kelsey Pohler- Research Assistant

Rift Valley Fever- 2006


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