B158 - NAIROBI SHEEP DISEASE

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B158 - NAIROBI SHEEP DISEASE

Nature of the disease
Nairobi sheep disease is a tick born disease caused by a Nairovirus of the family Bunyaviridae. It causes severe disease with fever and gastroenteritis. 
Classification
OIE, List B disease
Susceptible species
Sheep and goats. Man is also susceptible.
Distribution
Africa only
Clinical signs
After 1-3 days of incubation
  • Fever
  • Depression, anorexia,
  • Muco-purulent nasal discharge,
  • Severe diarrhoea
  • Collapse
  • High mortality rate (up to 90%)
Post-mortem findings
  • Haemorrhagic gastro-enteritis
  • Enlargement of lymph nodes and spleen,
  • Petechiae on gall bladder and heart
Differential diagnosis
Specimens required for diagnosis 
Blood on EDTA with antibiotics from live animals, and mesenteric lymph nodes and spleen from dead animals. Diagnosis can be made from direct immunofluorescence, agar gel immunodiffusion test , complement-fixing or ELISA

Serum can also be submitted for indirect diagnostic, methods include indirect fluorescent antibody test, complement fixation and indirect haemagglutination tests.

Transmission
Nairobi sheep disease is exclusively transmitted by ticks and is not a contagious disease. The virus is principally transmitted by the tick Rhipicephalus appendiculatus where the virus is transmitted vertically (transtadial and transovarial). Other ticks can transmit the disease (several species of the genus Rhipicephalus and Amblyomma variegatum).
Risk of introduction
Risk is mainly through the introduction of infected ticks as infected animals would exhibit signs of the disease. 
Control / vaccines
There is no treatment. There is a killed vaccine. The control relies on tick destruction.
References
  • GEERING WA, FORMAN AJ, NUNN MJ, Nairobi Sheep Disease In Exotic Diseases of Animals, Aust Gov Publishing Service, Canberra, 1995, p 159-172
  • Office International des Epizooties, 2002
  • Nairobi Sheep Disease, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 536-537