Production losses and control of helminths in ruminants of tropical regions

The magnitude of production losses and the epidemiology and control of gastro-intestinal nematodes, fascioliasis and paramphistomiasis in sheep, goats and cattle and of Onchocerca gutturosa and Cysticercus bovis in cattle in tropical regions is reviewed in broad terms. The limited information available indicates tremendous losses caused by gastro-intestinal nematodes. Acute outbreaks are commonly seen in the wet season in animals grazing at moderate to high densities. Control is commonly by anthelmintic medication but is limited by the cost of treatment. Fascioliasis causes enormous losses; acute outbreaks are generally seen in the mid-dry season in West Africa. Anthelmintic medication is the major means of control but in most cases drugs are applied haphazardly. Intestinal paramphistomiasis is responsible for some losses; the epidemiology of the disease is essentially as described for fascioliasis, but attempts at control are negligible. Although Onchocerca gutturasa causes considerable losses in cattle, little is known about its epidemiology and control attempts are rare. Cysticercus bovis causes losses in cattle. The habit of eating grilled meat, lack of meat inspection facilities and reluctance of infected persons to seek treatment are responsible for the perpetuation of infection.