Seasonal changes and hypobiosis in Haemonchus contortus infection in the West African Dwarf sheep and goats in the Nigerian derived savanna.

A survey was conducted in the Nigerian derived savanna (from August 1987 to July 1988) on the seasonal fluctuations in the composition of Haemonchus contortus burden of naturally infected West African Dwarf sheep and goats. During this period 117 abomasa collected from locally slaughtered animals were processed. Male, female as well as immature worms were enumerated. The incidence of Haemonchus infection was high (77.8-100%) with no definite seasonal distinction. There was however, a clear seasonal trend in the worm burden of animals; higher burdens were evident during the rainy rather than the dry season. There was no significant hypobiosis; Haemonchus contortus survived in the host during the unfavourable dry season (November to March) as adults.