Ascariasis in foals

A Survey of Seasonal Gastrointestinal Parasitic Infections in Donkeys from a Semiarid Sub-Saharan Region, Sudan

Out of 92 donkeys examined for gastrointestinal parasites, 90 animals were found infected by one or more gastrointestinal parasites with an overall prevalence rate of 97.78%. The distributions of the recovered parasites in the different parts of the body were as follows: stomach, 92.4%, small intestine, 19.6%, caecum, 88%, colon, 80.4%, rectum, 73.9%, and cranial mesenteric artery, 64.1%. A significant difference was found between mean parasite counts and seasons. Hot wet season had higher mean parasites count (5411.5 ± 1694.4) in comparison with hot dry (1795.9 ± 399.6) and cool dry (1719.9 ± 522.4) seasons. Although there was no significant difference between age and mean parasite count, animals more than four years old had high mean count (3361.3 ± 921.8) in comparison with 2330 ± 744.3 and 2030.2 ± 873.1 for young and adults animals, respectively. No significant positive or negative correlation was found between total parasite counts of infected animals and any of the climatic factors. The parasites identified were Habronema spp. (40.2%), Trichostrongylus axei (30.4%), Parascaris equorum (18.5%), Anoplocephala perfoliata (4.35%), Gastrodiscus aegyptiacus (8.7%), large strongyles (84%), small strongyles (72%), and Oxyuris equi (1.1%).

Climatic influences on development and survival of free-living stages of equine strongyles: implications for worm control strategies and managing anthelmintic resistance

Development of resistance to anthelmintic drugs by horse strongyles constitutes a growing threat to equine health because it is unknown when new drug classes can be expected on the market. Consequently, parasite control strategies should attempt to maintain drug efficacy for as long as possible. The proportion of a parasite population that is not exposed to anthelmintic treatment is described as being "in refugia" and although many factors affect the rate at which resistance develops, levels of refugia are considered the most important as these parasites are not selected by treatment and so provide a pool of sensitive genes in the population. Accordingly, treatment should be avoided when pasture refugia are small because such treatments will place significant selection pressure for resistance on worm populations. Given this new paradigm for parasite control, it has become important to identify seasons and circumstances wherein refugia are diminished. Free-living stages of equine strongyles are highly dependent on climatic influences, and this review summarises studies of strongyle development and survival under laboratory and field conditions in Northern (cool) temperate, Southern (warm) temperate and subtropical/tropical climates. In Northern temperate climates, refugia are smallest during the winter. In contrast, refugia are lowest during the summer in warm temperate and subtropical/tropical climates. Although adverse seasonal changes clearly have significant effects on the ability of free living stages of strongyle nematode parasites to survive and develop, available data suggest that climatic influences cannot effectively "clean" pastures from one grazing season to the next.

Transmission of some species of internal parasites in horses born in 1993, 1994, and 1995 on the same pasture on a farm in central Kentucky

Data are presented on the last 3 years of a 7-year study (1989-1995) on transmission of natural infections of internal parasites in horse foals (n = 27) born in 1993, 1994, and 1995 on the same pasture on a farm in central Kentucky. The foals were in a closed breeding herd of horses. Research on the first 4 years (1989-1992) of the study was published earlier (Lyons et al., 1991, 1994). Thirty-five species of endoparasites were identified, including 24 species of small strongyles. Monthly, seasonal, and host-age transmission patterns were elucidated for the parasites. Comparison of data between the first 4 years and last 3 years of the study indicates similarities, but also differences, including an increase in prevalence and numbers of Thelazia lacrymalis and Anoplocephala perfoliata.