In this study, the protozoan E. leuckarti was observed in two cases of the studied horses from north Iran. Ahmadi et al. have reported four E. leuckarti-infected samples in Shahrekord district horses (Karimi ghahfarrokhi et al., 2014). According to the results of this study and the study conducted in the Shahrekord region, it can be concluded that E. leuckarti exists in Iranian horses with a low prevalence. There have been reports of E. Leuckarti parasites on horses in North America and other parts of the world, but they are ubiquitous protozoal parasites (Attia et al., 2018; Jenkins et al., 2020; Jota Baptista et al., 2021). As a result of a survey conducted on Kentucky horse farms, 41% of foals examined were found to have an oocyst, and 85% of farms had foals with an oocyst, according to the survey (Lyons & Tolliver, 2004; Lyons et al., 2006). Studzinska et al. reported 9.18% E. leuckarti in Poland (Studzińska et al., 2008), and Gulgen et al. reported 2.9% E. leuckarti in Turkey (Gülegen et al., 2016). Also, a species of E. uninugulata was observed in one sample (0.29%) of horses from the north region, which was reported for the first time from horses in Iran. This species has already been reported in the Soviet Union, Tajikistan, Uzbekistan, and Turkey (Dubey & Bauer, 2018).
The protozoan parasites of the genus Eimeria multiply in the intestinal tract and cause tissue damage, with resulting interruption of feeding and digestive processes or nutrient absorption; dehydration; blood loss; and increased susceptibility to other disease agents (Blake et al., 2020; Gajadhar et al., 2015; Gutiérrez-Expósito et al., 2017). The disease may be mild, resulting from the ingestion of a few oocysts, and may escape notice, or it may be severe as a result of the ingestion of millions of oocysts (Kompi et al., 2021). Like many parasitic diseases, coccidiosis is largely a disease of young animals because immunity quickly develops after exposure and gives protection against later disease outbreaks (Abbas et al., 2019).
Despite the lower prevalence of coccidian disease in horses, sporadic clinical cases and deaths are still possible, especially in young foals starting to wean (Mulwa et al., 2020). Compared to other animals, it is much less common for horses to be affected by clinical leuckarti than in other species. However, clinical cases and deaths occur from time to time, especially in foals just recently weaned from their mothers (Kalef, 2015). Regardless of which type of facility the horses are kept in, coccidiosis can strike any type of horses (dos Santos et al., 2014). Despite the fact that there is some doubt about the pathogenicity of E. leuckarti in horses, it has been described in foals and young horses to exhibit diarrhea lasting several days and to develop an acute massive intestinal hemorrhage leading to rapid death from the disease (Kornaś et al., 2011; Marinković et al., 2013).
Based on the results of the present study, it can be concluded that some examined horses in northern Iran are suffering from subclinical coccidiosis and are infected with different Eimeria species. While none of the horses had clinical signs of coccidiosis, there was evidence of subclinical contamination with coccidiosis in the herd. Thus, more research needs to be carried out on this subject in local rural areas in Iran, and pay greater attention to the molecular identification and characterization of the species of Eimeria found there. Based on these results, Iran can develop a strategy to control the disease based on relevant data that will provide a solid foundation.