East Coast fever

East Coast fever (theileriosis) is a disease of cattle, sheep and goats caused by the protozoan parasite Theileria parva. The term excludes diseases caused by other Theileria, such as the cattle disease tropical theileriosis (also known as Mediterranean theileriosis), caused by T. annulata, and human theileriosis, caused by T. microti.

East Coast fever is probably the most important livestock diseases in Africa, causing an annual loss of 1.1 million cattle and $168 million in 1992. It is found in Sudan, South Africa, the Democratic Republic of Congo, Zimbabwe, Zambia, Tanzania, Kenya, Uganda, and Swaziland. The primary vector for T. parva is Rhipicephalus appendiculatus.

T. parva was first described in 1902 in Zimbabwe, but was misdiagnosed as redwater (a disease caused by Babesia bigemina).

Theileria species are the only eukaryotic organisms known to transform lymphocytes. The intermediate hosts for T. parva are cattle. The definitive hosts are the ticks. Native cattle are often resistant to the parasite, but not without symptoms. They are hosts to the parasite, but do not suffer as severely as foreign cattle.

Mortality can be up to 100%, with death occurring around 18–30 days after the initial attachment of infected ticks, because the incubation required is around 10–25 days, and the parasite spreads quickly and is rather aggressive.

Clinical signs for diagnosis include, but are not limited to, fever and enlarged lymph nodes near the tick bite(s). Smears and stains can also be done to check for the parasite. Schizonts (meronts, or segmentors) can be found in infected lymphocytes. Pathology includes anorexia, dyspnea, corneal opacity, nasal discharge, frothy nasal discharge, diarrhea, pulmonary edema, leukopenia, and anemia. Endemic cattle given medication sometimes recover to varying degrees, or death follows due to blocked capillaries and parasites infecting the central nervous system. Cattle that are endemic and manage to survive tend to be carriers.

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