Development and survival of Haemonchus contortus larvae on pastures in Ibadan.

The development and survival of the eggs of Haemonchus contortus on pasture at Ibadan were studied by spreading faeces containing eggs on grass plots from October 1973 to October 1974. Development of the eggs to the infective larvae took place within one week in May, June, July, September and October. Larvae were not recovered in the other months. Their survival times were 28, 42, 42, 35, 63 and 49 days respectively in October 1973. May, June, July, September and October 1974. Rainfall was the most important epizootiological factor which influenced the development and survival of the infective larvae. Development of the eggs to the infective larvae took place when the mean daily rainfall for the first 7 days was 3 mm or more. The survival time of the larvae appeared to be prolonged when rain fell evenly throughout the periods the larvae were on pasture.