Simulation of Larval Populations of a Parasitic Nematode of Sheep

Abstract

This paper describes a mathematical model of part of the life-cycle of Haemonchus contortus, a parasitic worm of sheep and other ruminants. The model simulates the free- living stages of the life-cycle, beginning with eggs passing out in the faeces of the sheep, and predicts the con centration of infective larvae on the pasture that will develop from these eggs according to the prevailing climatic conditions. The output from the model has been compared over a three-year period with data from a real experiment; the agreement is good enough to indicate that the model is basically sound. The authors intend to combine this model with a model of the epidemiological and physiological responses of sheep to various levels of contamination of their forage by infective larvae of H. contortus. Such a model is expected to be useful in devising management strategies to control this parasite.