Effect of temperature on development of the free-living stages of Ostertagia circumcincta.

Hatching of the eggs of Ostertagia circumcincta was studied by recovering them from faeces and incubating them in distilled water at temperatures of 4, 16, 25 and 35 degrees C. Hatching occurred at all the temperatures. The rate of hatching increased with the rise in temperature. Development of larvae to the infective third stage (L3) was studied in faecal cultures incubated at 4, 16, 25, 30, 35, 40 and 45 degrees C. Except at 4 degrees C, L3 developed at all temperatures, the optimum temperature being 16 degrees C. The rate of development of L3 increased with the rise in temperature. This resulted in a corresponding decrease in the percentage recovery of larvae.