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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 tropical theileriosis (also known as Mediterranean theileriosis), caused by T. annulata, and human theileriosis, caused by T. microti.
East Coast fever is among the most important livestock diseases in Africa,[1] causing an annual loss of 1.1 million cattle and $168 million, as of 1992.[2] It is found in Sudan, South Africa, the Democratic Republic of Congo,[1] Swaziland, Zimbabwe, Zambia, Tanzania, Kenya, and Uganda. The primary vector for T. parva is Rhipicephalus appendiculatus.[1]
T. parva was first described in 1902 in Zimbabwe, but was misdiagnosed as redwater (a disease caused by Babesia bigemina).
Theileria are the only eukaryotic organisms known to transform lymphocytes.[3] The intermediate hosts for T. parva are cattle. The definitive hosts are the ticks. Native cattle are often resistant to the parasite. This is not to say they do not suffer from the parasite; they do. They are hosts to the parasite, but do not suffer as severely as foreign cattle.[4][5]
Mortality can be up to 100%, with death occurring around 18–30 days after the initial attachment of infected ticks. This is 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 (aka meronts, or segmentors) can be found in infected lymphocytes. Pathology includes but is not limited to anorexia, dyspnea, corneal opacity, nasal discharge, frothy nasal discharge, diarrhea, pulmonary edema, leukopenia, and anemia. After this, endemic cattle that are given medication sometimes recover to varying degrees, or death follows due to blocked capillaries and parasites infecting the central nervous system.[6] Cattle that are endemic and manage to survive tend to be carriers.
A form of East Coast Fever called Corridor Disease is observed when the organism is transmitted from the African Buffalo to cattle.
Another form called January Disease only occurs over the Winter months in Zimbabwe due to the tick lifecycle.
For diagnosis, post-mortem findings are characteristic and mainly include damage to the lymphoid and respiratory systems.
One study using the medicinal plant Peganum harmala showed it to have a lifesaving effect on cattle infected with East Coast Fever.[7]
The classical treatment with tetracyclines (1970–1990) can not provide efficiency more than 50 %.
Since the early 1990s, buparvaquone is used in bovine theileriosis with remarquable results (90 to 98 % recovery).
Other than the Buparvaquones, another chemotherapeutic option are the Parvaquones e.g. Clexon.[8] Halofuginone Lactate[9] has also been shown to have an 80.5% efficacy against Theirelia parva parva infections.
In May 2010, it was reported that a vaccine to protect cattle against East Coast fever had been approved and registered by the governments of Kenya, Malawi and Tanzania.[10] This consists of cryopreserved sporozoites from crushed ticks but is expensive and can cause disease.
Control of the disease also relies on tick control and the development of resistant ticks to the disease.