Natural evolution of gastrointestinal nematodes in goats (Capra hircus) in the semi-arid ecosystem of the Paraíba backwoods, northeastern Brazil.

This study was conducted in Patos county, a semi-arid area with caatinga vegetation in Paraiba State, northeastern Brazil. Twenty-four male goats of mixed breeds were used. The animals were separated in age groups from 1-12 months, i. e., 1-2, 3-4, 5-6, 7-8, 9-10, 11-12 months, with four animals in each group. The animals were slaughtered and necropsied to recover and identify adult worms. The goats were exposed to nematode infection from the first month of life. The most prevalent nematodes in decreasing order were: Trichostrongylus colubriformis, Haemonchus contortus and Oesophagostomum columbianum. Age of the goats did not appear to be a factor in resistance to gastrointestinal nematode infection. Worm burdens of 11-12 month old animals were significantly (P<0.05) higher than in other age groups.