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Parasite control in livestock

Conventional parasite control measures are based on the use of curative (chemotherapy) and preventive (chemoprophylaxis) drugs.

Only three drugs are available - isometamidium chloride, diminazene aceturate and homidium (bromide and chloride). These compounds have been on the market for over 40 years. It is currently estimated that 35 million doses of these chemicals are used in Africa each year and that between 40 million and 60 million cattle are at risk. Although there is a consistent demand for trypanocides by African farmers and national veterinary/livestock services, the total value of the market (more than US$ 30 million) is not considered sufficiently financially important to justify investment by large pharmaceutical companies in the development and licensing of new trypanocides, the cost of which may exceed US$250 million for a single compound.

Perhaps the greatest risk to the future use of existing trypanocides is the development and spread of drug resistance in parasite populations to the point they become ineffective over large areas of Africa. Resistance to one or more of the trypanocidal drugs used in cattle has been reported in at least 13 countries of sub-Saharan Africa. Very few systematic surveys have been carried out and the occurrence of drug resistance was found to be greater in those regions where drug use was more intensive which led to the selection of resistant strains.

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