Moisture requirements for successful development of 'Haemonchus contortus' and 'Trichostrongylus colubriformis' to third stage infective larvae

Abstract

The overarching aim of the experiments conducted as part of this thesis was to determine the influence of moisture in the form of rainfall events (amount, timing and distribution) and soil moisture (SM) on faecal moisture (FM) and development of 'H. contortus' and 'T. colubriformis' to infective third stage larvae (L3). There are 4 experimental chapters reported in this thesis, (i.e. Chapters 4-7) which were written as a series of publications. ... In order to validate the results of the experiments conducted in controlled climate chambers (Chapters 4-6), a field experiment was conducted to investigate the effects of rainfall timing, rainfall amount and herbage height on translation success with grazing sheep. The results showed that initial SM of 20% alone was sufficient to support development and translation of both GIN species, as there was no effect of rainfall timing, rainfall amount and herbage height on the recovery of GIN species from grazing sheep. These results highlighted the importance of SM as a source of moisture for development of the nematode eggs in the faecal pellets. It also underlined the importance of taking soil moisture into account when predicting the likely effects of rainfall and herbage height on development to L3 and finally in predictive epidemiological models of sheep GIN parasites.