Nairobi sheep disease virus (NSDV) infects sheep and goats and is transmitted by ticks.The virus causes Nairobi sheep disease, which is one of the most pathogenic diseases affecting these animals.
The primary vector is the tick Rhipicephalus appendiculatus, but it can be transmitted through other vectors such as R. pulchellus, R. simus, and Amblyomma variegatum. Infected adult ticks can transmit the NSDV for over two years.
NSD is found in East and Central Africa and the disease may also be present in Botswana and Mozambique. A variant of NSD (Ganjam virus) has been reported from parts of Asia including India and Sri Lanka.
Clinical signs
High morbidity and mortality are seen in both sheep and goats, although goats tend to have less severe clinical signs than sheep.
Clinical Signs:
- Fever
- Reduction in white blood cells
- Rapid respiration
- Anorexia
- Profound depression
- Diarrhoea
- Drop in body temperature
- Pregnant animals frequently abort
- Death - in some cases within 12 hours of the onset of the fever
Virology
The virus belongs to the family Bunyaviridae, in the genus Nairovirus. NSDV has a single-stranded RNA genome, that is surrounded by a capsid and an envelope.
Pirbright's research on Nairobi sheep disease virus
Research at the Institute is ongoing to discover how NSDV causes disease in the host and investigating the species specificity of disease by comparing host responses to the virus in sheep and cattle. Effort is also going into determining how NSDV interferes with host defences and using the information to create a weakened virus that may be useful as a vaccine in the field.