Heat shock, but not temperature, is a biological trigger for the exsheathment of third stage larvae of Haemonchus contortus

Gastro-intestinal nematodes are a major issue in ruminants, and resistance to current treatment methods is continuously increasing. Understanding the processes involved in the transition from the free living to the parasitic life stage of gastro-intestinal nematodes may aid in identifying new targets amenable to future intervention, either inside of the host or out on pastures. This transition to parasitism is initiated by exsheathment and is triggered by the sudden change in environment after ingestion by the host. We investigated the involvement of temperature and found that there are very specific requirements. The exsheathment response of Haemonchus contortus is highly dependent on the rate and magnitude of the temperature change. This greatly enhances our understanding of exsheathment and implicates rapid temperature change, but not temperature itself, as an important factor in triggering exsheathment.