The effects of diurnal temperature variations on the development of free-living stages of Trichostrongylus colubriformis and Ostertagia circumcincta

Abstract

The effect of constant temperatures and diurnal temperature variations on the development of free-living stages of T. colubriformis and O. circumcincta was investigated. Both species were reared in faecal cultures and incubated at two changing temperature regimes which mimicked diurnal temperature variations that occurred within the faecal mass during summer and winter. In addition, the constant temperatures of 4°C, 15°C and 25°C were used.

Eggs of both species hatched at all temperatures; however, the eggs failed to reach the infective larval stage at 4°C and the summer temperature regime. At the winter temperature regime, the eggs of both species developed to infective stage (5.3% for T. colubriformis and 1.3% for O. circumcincta). At constant temperatures, the time needed for eggs to hatch was decreased as the temperature increased. The eggs developed to infective larvae in the shortest time and the highest numbers of infective larvae were recovered at 25°C. Under changing temperature conditions, more successful development of eggs was obtained than at relative constant temperatures.

These results suggest that changing temperatures may prevent the deleterious effects of lower and higher temperature extremes on the development of free-living stages. In addition, the eggs and larvae may survive at temperatures which are favourable for survival but insufficient for development and they could be able to develop subsequently as temperatures favourable for development prevailed.