Nairobi sheep disease is a one of the most pathogenic diseases of small ruminants. In susceptible animals, this tick-borne viral infection results in a hemorrhagic gastroenteritis with very high morbidity and mortality rates. Until recently, the causative viruses were only known to exist in parts of Africa and on the Indian subcontinent. However, viral RNA was recently identified in ticks in China. There is no effective treatment, and eradication is generally not feasible once the virus has become established in ticks.