Some observations on the epidemiology of Nematodirus battus in anglesey

A ten year study on ten fields on two sheep farms in Anglesey, North Wales (one lambing early and one late) naturally infected with Nematodirus battus is described. Double and single spring peaks of herbage infection were observed; their form and timing were satisfactorily correlated with temperatures in the period January to March. Some autumn hatching was also observed. The role of temperature and rainfall in influencing the population curves is discussed. The implication of these findings in relation to the treatment of lambs is reviewed.