Strategic control of gastrointestinal nematodes in dairy calves in Florestal, Minas Gerais, Brazil.

Following epidemiological studies of gastrointestinal helminthiasis in dairy cattle in Florestal County, Minas Gerais, 80 Swiss and crossbred Zebu x Holstein calves, 8-10-months old, were selected to test the efficacy of three treatment protocols using ivermectin for helminth control. The calves were treated in Brachiaria grass paddocks, naturally infected with Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus species, and then divided into four groups of 20 animals each: group 1 was treated with 200 microg/kg body weight ivermectin in April (at the end of the rainy season) and October (beginning of the rainy season); group 2 was treated in April, August (middle of the dry season) and October; group 3 was treated in April, August, October and December (middle of the rainy season); and group 4 was left untreated as a control. The treatments effectively eliminated the worm burden only in groups 2 and 3 (p < 0.05), although the calves continued to excrete Cooperia eggs after each treatment with ivermectin.

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.

Faecal water content and egg survival of goat gastro-intestinal strongyles under dry tropical conditions in Guadeloupe.

Faeces from naturally infected goats were deposited on a natural grassland during the dry season in Guadeloupe (French West Indies) at different times throughout the day. The grass was either 7 or 20-30 cm tall. After a period of between several hours and 7 days, the number of viable strongyle eggs and the faecal water content were measured. Faecal temperature was recorded continuously. Faecal temperature was greater than 40 degrees-45 degrees C at midday and dehydration was rapid between 8 a.m. and 2 p.m. Egg mortality was greater on short than on tall grass and higher in morning than in evening deposits. Minimal faecal water content during the first 36 h explained the 74%, 55% and 38% mortality rate for eggs of Oesophagostomum columbianum (OC), Haemonchus contortus (HC) and Trichostrongylus colubriformis (TC), respectively. In all, 5%-22% of the eggs of the latter species remained viable in a state of anhydrobiosis after 7 days on the ground. A delay of only 2 days between goat departure and irrigation would be sufficient to ensure that greater than 95% of O. columbianum and H. contortus eggs and 70% of T. colubriformis eggs are destroyed.