NATURALLY-OCCURRING TRYPANOSOMA-GRANULOSUM INFECTIONS IN THE EUROPEANEEL, ANGUILLA-ANGUILLA L. FROM COUNTY MAYO, WESTERN IRELAND

Eels were sampled from three lake and two stream sites in the Burrisho ole catchment, western Ireland, at bimonthly intervals; the eels were bled and released. Prevalence of Trypanosoma granulosum was determined using a haematocrit centrifuge technique and parasitaemia was estimat ed by counting trypanosomes in 30 fields (10 ocular x 10 objective) on Giemsa-stained smears. Prevalence was consistently high in eels from the lake sites, but lower and more variable in the two stream sites. P arasitaemia was generally low and the distribution highly skewed. Indi vidual eels carrying medium and high infections were most common in la te summer and autumn. The size distribution of trypanosomes found in t he blood was bimodal. Seasonal changes in trypanosome morph sizes indi cated that parasitaemia did not increase immediately after infection, but was delayed until water temperatures increased during the summer m onths.