| Popis: |
SUMMARY Investigations are described in which the molluscicide N-tritylmorpholine was used over the two seasons 1967 and 1968 to control L. truncatula, the intermediate snail host of F. hepatica in Northern Ireland. The efficiency of the molluscicide was measured by snail counts before and after treatment, and by the use of tracer lambs to estimate infection levels in treated and untreated snail habitats. Applications of the molluscicide in April and August were compared. The results indicated that a single application can result in the reduction of approximately 70 per cent in the snail population on a habitat, but that a significant repopulation of snails may occur in the spring following treatment in the previous season. Observations using tracer lambs showed that on a small, low density snail habitat, a reduction in the level of infection in the lambs, equivalent to previously observed reductions in snail numbers, resulted from treatment. When treatment was applied to a large, high density snail habitat, reductions in the number of snails were obtained following treatment, but levels of infections in lambs grazing treated pastures were dangerously high. The relative importance of techniques used to estimate snail populations, and infection level assessments by the use of tracer lambs in the interpretation and design of trials of this nature, are discussed. |
