Horse infection with intestinal helminths in relation to age, sex, access to grass and farm system.

A 11-year survey on helminth intestinal infection of horses was done in seven provinces of southern Poland. 21,641 faecal samples were collected from horses of different age, sex, breed and management system originating from 84 farms. Age was the major factor influencing the cyathostome egg excretion, the maximum being observed in yearlings and second year horses. Parascaris was found mostly in foals and yearlings. The main factor for Anoplocephala was the access to pasture. The level of cyathostome egg shedding (EPG) could be related to sex (geldings had higher values of EPG), breed (Thoroughbred had higher EPG than other breeds), and type of farm (large farms had higher EPG than others). The change during the survey of anthelmintic treatment (from benzimidazole or pyrantel embonate to avermectins) was associated with lower cyathostome EPG, and this was probably due to partial resistance to benzimidazole. The seasonality of egg shedding (lowest from November to January included) was due to management (leaving the pasture to stable, anthelmintic treatment in October). The influence of climate on EPG was significant but small, annual rainfalls and average temperature being associated negatively and positively, respectively, with high cyathostome EPG.