Thermotolerance of L3 Ostertagia (Teladorsagia) circumcincta and some of its enzymes

Parasitic nematodes of ruminants can be expected to experience temperatures in excess of 40 °C in faeces on pasture and, perhaps, in the host. L3 Ostertagia (Teladorsagia) circumcincta survived for at least 90 min at 45 °C in vitro in water, but the larvae were inactivated rapidly by only slightly higher temperatures. The glycolytic enzymes hexokinase and pyruvate kinase were inactivated in a similar temperature range, whereas malate dehydrogenase maintained its activity at temperatures in excess of 50 °C. These data imply that the loss of glycolytic activity might explain the loss of larval motility at temperatures between 45 °C and 50 °C.