Characterization of infestation and structure of horse helminth complexes in the provinces of the Altai Mountains

Abstract

The purpose of the study was to investigate the infestation and structural features of the helminth complexes of horses in the provinces of the Altai Mountains which differ significantly in natural, climatic and orographic conditions of the area. Fecal samples from spontaneously helminth-infested animals of the Central, Northern, Western and South-Eastern Altai Mountains were examined by ovolarvoscopic methods with the following calculation of occurrence indices (invasion intensity – II, level of invasion intensity – IIlevel), infestation intensity (abundance index – AI, level of abundance index – AIlevel) and parasitocomplex index (PI). The results of long-term studies (2019–2023) indicate that parasites of two classes are involved in the formation of the helminth complex of the digestive system of horses in the Altai Mountains: Nematoda (suborders Strongylata, Ascaridata, Rhabditata, and Ochycrata) and Cestoda (suborder Anoplocephalata). Strongylates dominate in the nosological profile of helminthoses in all provinces: the degree of their infestation among animals and their proportion in the helminth complexes (II = 68.6–93.1%, PI = 86.0–90.5) are significantly higher than the same indicators for the suborder Ascaridata (II = 6.2–16.5%, PI = 4.6–8.1) and for the cestodes of the suborder Anoplocephalata (II = 2.5–11.8%, PI = 2.1–5.8). Against the background of ubiquitous distribution of the main helminths of the gastrointestinal tract of horses in the conditions of physiographic provinces, differences in the structure of helminth complexes and intensity of helminth infestation of animals are observed. The level of infestation of horses in the Central Altai with strongyles is significantly higher relative to the infestation of the animals in the Northern and Western Altai. The infestation of ungulates of South-Eastern Altai with strongylates (II = 68.6%) and anoplocephalates (II = 2.5%, PI = 2.1) is minimal and, respectively, 1.5 and 2.8–4.7 times lower than in other provinces. However, there are significant intrazonal differences in the nematode infestation of horses – their infestation in the mountain-forest zone of the South-Eastern Altai is comparable to that in the Central Altai and is significantly higher than in the high-mountain steppe zone. At the same time, the IIlevel and AIlevel indices for horses of the high-mountain steppe zone of the South-Eastern Altai are statistically lower than in the animals of the Northern and Central Altai. It was found that the level of infection and the structure of helminth complexes of horses are mainly determined by the diversity of natural-climatic and orographic characteristics of mountainous territories.