Exsheathment Characteristics and Infectivity of Revived Anhydrobiotic L3 of Haemonchus Contortus

This study was conducted to determine the effect of temperature and moisture stress on exsheathment process and infectivity of the infective larvae of the parasitic nematode Haemonchus contortus. Laboratory conditions were used in which infective (L3) of H. contortus were either subjected to gradually increasing temperatures, decreasing moisture or both. Post stress viability and exsheatment of L3 was determined prior to infection experiments. The viability of H. contortus after induction of anhydrobiosis declined significantly (p<0.05) from 85 to 60% in about 60 days. The results showed significant (p<0.05) delay in exsheathment in stressed larvae compared to unstressed larvae leading to low overall establishment (Infection). However, the proportion of the immature in relation to the mature parasites (hypobiosis) was significantly (p<0.05) higher in stressed compared to the unstressed L3. These results indicate that delayed exsheatment in stressed L3 contributes to low infectivity in ruminants.