FILARIASIS - NUTRITIONAL INTERACTIONS IN HUMAN AND ANIMAL HOSTS

Vector-borne nematodes of the Order Filarioidea produce chronic, debil itating human infections which are usually nonfatal but are associated with a high degree of severe morbidity. Weight loss often accompanies infection and is probably a consequence of the increased energy cost associated with filarial fever, lymphangitis and lymphadenitis. In onc hocerciasis, weight loss is associated with heavy worm loads as assess ed by abundant nodules and large numbers of skin microfilariae. Experi mental infections using rodent filariae have confirmed these observati ons and have also shown that low protein diets render hosts more susce ptible to infection; nevertheless, parasite growth and embryogenesis i s retarded in stunted female worms from protein deficient animals. In the absence of appropriate evidence, studies of experimental filariasi s suggest that human protein-energy malnutrition may delay the develop ment of stage-specific acquired immunity with a corresponding prolonga tion of patency. Epidemiological and experimental evidence shows that filarial nematodes acquire certain nutrients directly from their hosts . Of major importance in this respect is vitamin A which is taken up p referentially by human and rodent filariae; in humans, symptoms of hyp ovitaminosis A often accompany infection and could be an aggravating f actor in onchocerciasis. Filariae also appear to require other specifi c nutrients such as iodine, thiamine and pyridoxine; dietary levels of these nutrients affect the host-parasite relationships in filariasis and pyridoxine seems to be of particular importance in this respect. F ilarial parasites obviously compete with their hosts for available nut rients and, in the real world, human filariasis is often associated wi th a deterioration in the plane of nutrition of infected individuals.