Helminth parasites and hypobiosis of nematodes in N'Dama cattle during the dry season in The Gambia.

Three series of necropsies of cattle were performed, corresponding to early dry season, approximately 1 month after the last rains (November, n = 6), mid dry season (February, n = 6) and end dry season (April, n = 3). Eggs per gram of faeces (epg) were determined just before necropsy. Three trematodes (Fasciola gigantica, Schistosoma spp. and Paramphistomatids) and 11 nematodes were identified from cattle, with the prevalence rate varying from 6.7% to 100%. Haemonchus contortus was the most abundant nematode species, constituting from 81% (February) to 34.8% (April) of the total nematode burden. The proportion of L4 (indicating hypobiosis) of H. contortus was 85-99%. During the dry season, 44-67% of Oesophagostomum radiatum and 8-34% of Cooperia spp. population occurred as L4. There was no correlation between the number of worms found at necropsy and the epg. H. contortus survives almost exclusively as larvae in the abomasal mucosae, whereas Cooperia spp. and O. radiatum survive partly as larvae in the lumen, and also in nodules in the case of O. radiatum, and partly as hypometabolic adults with highly reduced fecundity. Trichostrongylus axei, T. colubriformis, Bunostomum phlebotomum, Strongyloides papillosus, Nematodirus spp. and Setaria labiatopapillosa occurred in small numbers.