Abstract

East Coast fever (theileriosis) is an animal disease in Africa caused by the protozoan parasite "Theileria parva". It excludes diseases caused by other "Theileria"

Introduction

East Coast fever or theileriosis is an animal disease in Africa caused by the protozoan parasite "Theileria parva".

It does not include tropical theileriosis (or Mediterranean theileriosis), a cattle disease caused by "T. annulata", nor human theileriosis, caused by "T. microti".

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.

Clinical signs and diagnosis

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.

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.

Treatment and control

One study using the medicinal plant "Peganum harmala" showed it to have a lifesaving effect on cattle infected with East Coast fever.

The classical treatment with tetracyclines (1970–1990) cannot provide efficiency more than 50%.

Since the early 1990s, buparvaquone is used in bovine theileriosis with remarkable results (90 to 98% recovery).

Other than the buparvaquones, other chemotherapeutic options are the parvaquones, e.g. Clexon. Halofuginone lactate has also been shown to have an 80.5% efficacy against "Theirelia parva parva" infections. The ultimate factor that causes death is pulmonary edema.

In May 2010, a vaccine to protect cattle against East Coast fever reportedly had been approved and registered by the governments of Kenya, Malawi and Tanzania. This consists of cryopreserved sporozoites from crushed ticks, but it is expensive and can cause disease.

Control of the disease relies on control of ticks of domestic animals, particularly disease-resistant ticks. This is a major concern in tropical countries with large livestock populations, especially in the endemic area. Pesticides (acaricides) are applied in dipping baths or spray races, and cattle breeds with good ability to acquire immune resistance to the vector ticks are used.