Nairobi sheep disease (NSD), is a serious tick-borne viral disease of sheep and
goats. The RNA virus belongs to the family Bunyaviridae, in the genus Nairovirus.
Nairobi sheep disease is characterized by fatal hemorrhagic gastroenteritis,
starting with high fever, depression, respiration problems, myocarditis and
tubular nephritis, often pulmonary edema, and very high mortality rate up to 30–
90%. The principal vector for NSDV in Africa is the brown ear tick (Rhipicephalus
appendiculatus), in which the virus can survive up to 800 days. Transovarial
and transstadial transmission occurs via this vector. Affected animals may die
within a few days, and pregnant ewes abort. Subclinical infections also occur,
and recovered animals are immune. Nairobi sheep disease virus is shed in urine
and feces; however, the disease is not transmitted directly between animals.
Indirect fluorescent antibody tests are recommended for detecting antibodies in
the infected and recovered animals. Immunodiffusion, hemagglutination, ELISA,
and complement fixation tests may also be used. RT-PCR for virus detection
is applied. There is no commercial vaccine for NSD. However, in endemic
countries, experimental vaccines have been developed for use in naïve animals
entering enzootic areas, or to protect animals when tick vectors expand their
geographical range.