contortus infection, in comparison with sheep breeds of European origin also raised in Brazil ( Rocha et al., 2005, Bricarello

et al., 2005, Costa et al., 2007 and Amarante et al., 2009). CHIR-99021 in vivo However, Amarante et al. (2004) compared Santa Ines, Ile de France and Suffolk lambs that were naturally infected by gastrointestinal nematodes and observed a higher resistance to H. contortus and Oesophagostomum columbianum infections, but all three breeds had similar T. colubriformis worm burdens. Similar results were obtained in the comparison between Florida Native (resistant) with Rambouillet (susceptible) lambs ( Amarante et al., 1999), as well as in the comparison of Gulf Coast Native (resistant) with Suffolk (susceptible) lambs ( Bahirathan

et al., 1996). These results indicate that, in those “resistant breeds”, there are differences in the host–parasite interaction regarding the different nematode species, i.e., the immune response possibly acts with higher efficiency against Haemonchus spp. infection than against Trichostrongylus CH5424802 molecular weight spp. The losses generated by infection with T. colubriformis reinforce the importance of research involving this neglected nematode in South America, coupled with the lack of studies on this parasite in hair sheep was the motivation for the present experiment, which was carried out to evaluate the immune response and the impact of T. colubriformis artificial infections on the performance of Santa Ines growing lambs. Thirty lambs were raised indoors with their mothers since birth and were weaned at 60 days of age. After that they were transferred to individual pens with a concrete floor that was washed with water under pressure every two days. During an initial two week-period of adaptation, the animals only were vaccinated against clostridioses (Sintoxan Polivalente®–Merial S/A, Brazil) and fecal examinations

were carried out that showed that 15 lambs were shedding trichostrongylid eggs with a maximum of 200 eggs per gram (EPG). One of the animals also passed 200 EPG of Strongyloides spp. and Eimeria spp. oocysts were also sporadically observed in some animals, however, in small quantities. Larvae from Haemonchus spp. (78%), Trichostrongylus spp. (12%) and Cooperia spp. (10%) were found in fecal cultures from these lambs. For this reason, all lambs were orally treated with levamisole phosphate (Ripercol L 150 F® – Fort Dodge, Brazil) and albendazole (Valbazen 10 Cobalto® – Pfizer, Brazil) for three consecutive days. Subsequently, the animals also received trichlorfon (Neguvon® – Bayer, Brazil) for an additional three days. Seven days later, fecal examinations were repeated and three animals that were still shedding eggs in faeces were subjected to a new series of treatment with the same anthelmintics. Nematode trichostrongylid eggs were not detected in the fecal tests after this procedure.