Comprehensive diagnosis of parasites in sheep kept under different zootechnical management in a region temperate in Mexico.

Parasites cause losses in animal production. Parasite infection in ruminants has been estimated to be a major problem causing more than 3 billion USD per year, from which 60% corresponds to the sheep industry. Treatment is based on the use of synthetic anthelmintics; however, repeated application or under dosage have resulted in the selection of nematodes resistant to anthelmintics. The objective of the present work was to perform a diagnosis of gastrointestinal parasites in sheep kept under different zootechnical management. Ninety female sheep were used, most of them pregnant. Sampling was performed monthly from December 2015 to June 2016 (flock 5 until April). Fecal samples were collected from the rectum; the McMaster technique was performed, morphological characteristics were observed, oocysts and eggs were counted per gram of feces (opg and epg), frequency and intensity were obtained. Faecal culture was performed for feces that had a positive result, infective larvae were obtained and taxonomically identified. At the end of the study, a dewormer (fenbendazole) was administered and its effect was measured. The frequency of gastrointestinal parasites was 100%. The highest opg was 3,600 (flock 3, March, 2016), the epg for cestodes was 2800 (flock 1, January, 2016) and for gastrointestinal nematodes (GIN) was 25,000 (flock 1, May, 2016); the intensity was variable and it was increased by peripartum. Protists (Eimeria spp), cestodes (Moniezia) and nematodes (Haemonchus, Trichostrongylus, Cooperia, Chabertia ovina. Teladorsagia, Oesophagostomum, Nematodirus and Trichuris ovis) were identified. No previous diagnosis is performed in flocks, and sometimes dewormers are administered, even though resistance to ivermectin and benzimidazole is suspected. Flock management, its feeding system and its conditions were determinant for the observed results; therefore, it is necessary to count with a diagnosis that provides information about the parasitic population and its dynamic, in order to carry out a selective and comprehensive control that has an impact on the animal, human and environmental health.

Gastrointestinal nematodes in rotationally grazing ewes in the mountainous region of central Mexico.

The aims of this study were to determine the frequency of egg shedding (percentage of egg-positive faecal samples) and faecal egg counts (FEC) over 13 months in two different breeds of ewes, both pregnant and non-pregnant, in a mountainous region of central Mexico. Additionally, the effect of ivermectin and albendazole treatments on FEC reduction was recorded. The study also aimed to relate temperature and rainfall to FEC. The gastrointestinal nematode (GIN) third-stage larvae genera recovered from both faeces and grassland pastures in a temperate region were also assessed. Faecal samples were collected from ewes at monthly intervals for 13 months to investigate the FEC population of GIN larvae, their concentration and genera in grass samples collected from grazed and rested pastures. Egg-shedding frequency ranged from 0 to 92% and FEC from 0 to 12,000 eggs per g faeces (epg), with counts in Suffolk higher than in Dorset ewes. The identified genera were Haemonchus, Trichostrongylus, Teladorsagia, Cooperia, Oesophagostomum, Bunostomum, Nematodirus and Strongyloides. Haemonchus and Trichostrongylus were the most common genera. The number of L3 was higher in grazing lands than in those at rest. The highest FEC were recorded in the dry season due to peripartum, but the highest L3 counts were recorded in the rainy season. The coexistence of species of different geographical distributions at this site may be because there is a confluence of Nearctic and Neotropical geographic regions; thus, despite the temperate climate, tropical species can be found. Additionally, this study suggests that increasing temperatures could favour the presence of different tropical GIN species together with typical temperate-zone GIN species.