Moisture and temperature requirements in faeces for the development of free-living stages of gastrointestinal nematodes of sheep, cattle and deer.

Isolates from eight gastrointestinal nematode species parasitic in sheep, cattle and deer were maintained in sheep, to provide eggs in similar faecal environments and to compare temperature and moisture requirements for their development. Faecal cultures were processed at different temperatures (for four species) and moisture contents (for the eight species). At 60% of faecal moisture content (FMC), maximal rates of development (expressed as L3/100 hatchable eggs estimated by an extraction technique from the faeces) were observed at 20, 23 and 28 degrees C respectively for Ostertagia leptospicularis, O. ostertagi, Teladorsagia circumcincta and Trichostrongylus colubriformis. For the eight species, the curves of development rates as functions of FMC were Gaussian, without modification between 18 and 28 degrees C. Optimal developments were when the FMC ranged from 57 to 68%; low developments of 1L3/100eggs were observed when the FMC ranged from 85 to 95% and from 25 to 55%. The main differences between species were in the ability of the eggs of Teladorsagia circumcincta, Trichostrongylus colubriformis, T. vitrinus and Chabertia ovina to develop at lower FMC than Haemonchus contortus, O. ostertagi, O. leptospicularis and Cooperia oncophora.