INVESTIGATING THE HOST¿PARASITE INTERACTION: INTRASPECIFIC DIFFERENCES IN A GOAT MODEL

Gastrointestinal nematodes (GIN) infect small ruminants throughout the world and are an important cause of disease and production loss. Our research focused on the nematode–host interactions in the goat and the work was developed through different approaches. In particular we studied the effects of GIN infection on milk yield and quality; the trends of FEC under natural and experimental infection comparing the egg emission between a local goat breed (Nera di Verzasca) and a more selected one (Alpine); the levels of parasite-specific circulating antibodies to investigate if the differing susceptibilities to nematode infection found in the two goat breeds were due to differences in the humoral immune response. The studies showed that the milk production in goats was affected by the parasite burden and that this effect could be stronger in the first lactation and decreased in the following lactations. This resilience was also found to be different among goat breeds, with the local breed showing fewer effects on production than the more selected breeds. Testing the effect of different classes of infection on milk yield and quality, our study showed a high significance of the interaction of the class of infection with breed and days in milk, giving evidence that high levels of GIN infection can lead to production losses and that the level of EPG necessary to cause the loss in production may be different among breeds. Comparing the EPG emission under natural infection for a whole year between goats of Verzasca and goats of Alpine breed reared together, we found resistance to nematodes in the Nera di Verzasca goats. This breed confirmed its resistance also under experimental infection, after a single challenge with mixed GIN infective larvae. Finally, investigating the specific antibody response against Teladorsagia circumcincta L3, our research confirmed the role of IgE in the protection against gastrointestinal nematodes in goats.