Tick and tick-borne disease control in Ethiopia
Ticks and Tick-borne
Diseases Survey and Control, c/o FAO Office,
P.O. Box 5536, Addis Ababa, Ethiopia
Cattle are a prime resource for the people and Government of Ethiopia. The country has the largest cattle population in Africa, estimated at 27 million head. The majority of these cattle are indigenous Bos indicus breeds and are a vital component of the mixed farming system in the highlands, where they are used as draft animals for ploughing and for providing milk and meat. Cattle in the dry lowlands are part of the traditional nomadic life.
Government policy has recently been changed to give more encouragement to commercial farming. Local breeds are being upgraded through the introduction of pure-bred Bos taurus cattle and their crosses. There are already more than 70,000 improved cattle in the country. Although the introduction of Bos taurus dairy breeds may increase milk production, it may not in the absence of good management and adequate control measures against ticks and tick-borne diseases.
Ticks and tick-borne diseases control
The main tick genera found in Ethiopia are Amblyomma, Boophilus, Haemaphysalis, Hyalomma and Rhipicephalus. The most important and widespread tick species are A. variegatum (vector of Cowdria ruminantium and Theileria mutans) and B. decoloratus (vector of Anaplasma marginale and Babesia bigemina). There is no report of the presence of R. appendiculatus (vector of T. parva). The effects of ticks on indigenous cattle have been shown to be minimal.
Tick-borne diseases of cattle such as anaplasmosis, babesiosis, cowdriosis and theileriosis (T. mutans) are present in Ethiopia but their significance in terms of mortality and production loss and the degree of enzootic stability are not known. There are no clinical or serological reports of the presence of either bovine tropical theileriosis (T. annulata) or East Coast fever (T. parva). However, the relatively uncontrolled movement of livestock from Sudan, where these diseases and their vectors are found, suggests that there is a considerable risk of the diseases being introduced. In previous studies, B. bovis, T. orientalis and T. velifera were reported from western Ethiopia.
In a recent survey, 2434 blood smears and 242 serum samples were collected from 21 state and private dairy farms to determine the prevalence of tick-borne infections, mainly in dairy cattle. Over 90% of sera tested were positive for A. marginale, 60% were positive for B. bigemina and 30% were positive for T. mutans. Antibodies to A. marginale were very common in samples from state and private dairy farms; there were no significant differences in prevalence of antibodies to B. bigemina between these farms. More than 20% of the blood smear samples were positive for Anaplasma, Babesia and Theileria spp. This result did not correlate with the serological findings and this may have been due to technical reasons or because serologically positive cattle have very few or no detectable parasites. Taking this and the various results obtained into account, it can be concluded that enzootic stability exists for all tick-borne diseases present in indigenous and exotic cattle.
Serological diagnosis of tick-borne diseases using the indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) has been set up in the country. In December 1992 a consultant in tick-borne diseases trained project staff and laboratory technicians in serological diagnosis of tick-borne diseases under the FAO TCP/ETH/0053 bridging assistance in tick control project.
The conventional method of controlling tick infestations in Ethiopia is application of acaricide, either by hand spraying, by hand dressing or using spray races. Traditional tick control methods such as hand picking, burning with a hot iron or application of plant juice are also used in rural areas. The acaricides available in the country are:
Where they have been tested, Boophilus decoloratus ticks on dairy herds have been found to be resistant to camphechlor. For this reason, and for associated residue and public health reasons, the Ministry of Agriculture has banned the use of this chemical. At present, a field trial is being conducted to compare the cost effectiveness of chlorfenvinphos and deltamethrin on one state dairy farm.
In 1992 a tick-control consultant conducted in-service training and prepared a revised draft tick control and acaricide usage policy with particular reference to the dairy industry in Ethiopia. At present, the government has no direct control or registration requirements on the importation and use of acaricides. To address this problem the project has drafted a policy on acaricide registration, importation and utilisation, which has been submitted to the government for approval. It is a government responsibility to monitor the use of potentially dangerous chemicals and to conserve foreign exchange. The amount of foreign exchange involved is potentially very large; the economy of the nation cannot support such expenditure. Consequently, any measure taken to reduce the overall dependence on the use of chemicals for tick control should represent savings in foreign currency and should be cost effective. The strategy to be considered should be reduced tick control combined with immunisation of exotic and crossbred cattle, where reduced (strategic) acaricide application reduces costs significantly while immunisation ensures enzootic stability. Before importing vaccines we have to be sure that they are safe, potent and free from contamination with other infectious disease pathogens.