Dynamics of Infection with Strongylidae of the Przewalski Horse (Equus Przewalskii) Population in the Chernobyl Exclusion Zone

Dynamics of Infection with Strongylidae of the Przewalski Horse (Equus przewalskii) Population in the Chernobyl Exclusion Zone. Zvegintsova N. S., Zharkikh T. L., Yasynetska N. I. — In 1998 and in 1999, several Przewalski horses (PH) from the Reserve Askania Nova were transferred to the Chernobyl Exclusion Zone (CEZ), a free-roaming breeding population was therefore established. Parasitological monitoring of the population was carried out between 1998 and 2006. Before the transportation, PHs were dewormed with Albendazole. On arrival, the PHs were placed in large pasture enclosures for acclimatization, where they were kept between a few weeks and eight months before releasing into the wild. Besides PHs, some domestic working horses were kept in the enclosures. After transportation to CEZ, the level of infection with intestinal helminths in PHs increased. Probably, it was due to the following factors: 1) larvae of helminthes, which survived in intestines after deworming, developed, 2) the pasture in acclimatization enclosures was contaminated with parasites, as PHs shared the enclosures with domestic horses. Over the first three years, the prevalence of Strongylidae were 98.8%, the mean intensities varied from 248.0 ± 51.3 to 612.0 ± 278.2 eggs per gram faeces (epg). A mean intensity in bachelor males was higher than in members of harem groups, as the bachelors had closer contacts with domestic horses. After domestic horses had been transferred outside of CEZ in 2001, the overall intensity in PHs has progressively decreased. During 2004-2006, the mean intensity became stable with range 80.9 ± 25.5 to 138.9 ± 33.2 epg, with prevalence of 93.1%. In 3.5% of faecal samples, Parascaris equorum (Ascarididae) were found; a mean intensity was 29.0 ± 10.7 epg. A few eggs of Anoplocephala perfoliata (Anoplocephalidae) were found in three samples only. Due to negligible contamination of pastures excluded from farming industry long ago, there are comparatively low levels of infection in the free-roaming PHs. The present level of infection is considered harmless to the horses as clinical symptoms of helminthoses were never noticed.