Parâmetros imunoparasitológicos de cordeiros naturalmente infectados por Haemonchus spp., Teladorsagia spp. e Trichostrongylus spp.

Abstract

In the context of the current sheep-rearing, control of parasitic infection establishes a constant challenge to producers, because the gastrointestinal parasites have high prevalence in flocks, highly pathogenic and frequents resistance to anthelmintic products. The parasitic infections of sheep are characterized by simultaneously occur for several genera of nematodes, however, Haemonchus contortus is considered the major gastrointestinal parasites of sheep. In some situations, integrated methods of parasite control available become ineffective in the face of critical situation, aggravated by the parasite resistance to anthelmintics. Therefore, animal immune response became a central point in the dynamics and limiting the consequences related to parasitic infection. The systemic and local immune responses comprise a set of restrictive mechanisms or not characterized according to the animal's age, physiological condition, nutritional and management status. However, precepts of which the immune system works and how occurs is not fully understood, there are some factors to be revealed so that we can establish a secure and lasting immune protection against gastrointestinal parasites. In Chapter 1, shows the characteristics of the immune response of sheep naturally infected with gastrointestinal nematodes kept on native pasture. The study involved a set of immunological, parasitological and clinical techniques to characterize and establish the pathways of the immune response in resilient animals. In this study, was possible to establish a weak negative correlation between Eos and OPG in resilient Corriedale sheep. Interleukin-6, TNF-β, IFN-γ and In this study, a immunoglobulins (Ig) G, A and E had progressive increase during the study reflected in modulation and improves the immune response in sheep. In Chapter 2, demonstrated immune response of sheep naturally infected with Haemonchus spp. in different feeding levels, submitted in native pasture and cultivated pasture. The animals were allocated into native pasture for 42 days and then transferred to cultivated pasture until 84 days. Sheep feed with pasture cultivated of oats (Avena sativa) and ryegrass (Lolium multiflorum) had reduction in OPG and increased efficiency immune response. The improvement in nutritional support to animals induced a significant increase in the immune response of sheep, characterized by peripheral eosinophilia and increased serum concentrations of IgE, IgA, IgG, TNF-β, IFN-γ and IL-6.