Periparturient rise in faecal helminth egg counts of Udah sheep in the Zaria area of Nigeria

The trichostrongylid egg output in the faeces of seven lambing and seven barren Udah ewes was compared during the beginning of the rainy season in 1974. Both groups showed an increase in egg counts which reached a considerably higher level in the lambing ewes. The highest level, a mean count of 2 650 eggs/g, was reached 2 weeks after lambing.It is suggested that the increase was due to helminths, mainly Haemonchus sp., which had been inhibited during the dry season and resumed their development at the beginning of the rainy season.The rapid decline in egg counts recorded 5–6 weeks after lambing was considered to be due to self cure associated with high rainfall.