Dynamics of Lymnacea viator infection with Fasciola hepatica under natural conditions in Uruguay

Abstract

Infection dynamics of 6450 Lymnaea viator collected during 10 years ar different farms in Uruguay. A Fasciola hepatica infection prevalence of 2,60% was found. From the 51 samples with 40 or more snails examined (maximum nomber: 303), 33 samples (64,7%) were positive to the infection of the parasite. The infection median was 2,41 ± 0.38% (range: 0 - 10,45%). The proportion of positive samples and percentage of mature infections (with cercaria ready to emerge) were greater in snails collected in permanent environments with running water than those collected in temporary environment and stationary waters. Infection levels were also higher in L. viator intermediate density of colonies than in very low or very high density. The bigger the snail the higher the percentage of infection and proportion of mature infections. The higher levels of infection were observed in the three last bimesters of the year, mainly September-October. The lower values were observed at the beginning of winter (May-June). The recent infection (redias containing only germinal masses) pattern followed a similar pattern, even thou the pick was higher in September-October. Mature infections followed a binomial pattern, with the picks in March-April and September-October, decreasing dramatically in winter (May-June and July-August). The significance of the result in epidemiology of fasciolasis in Uruguay is discussed.