A review of Eimeria infections in horses and other equids

Authors: Dubey, Jitender; BAUER, CHRISTIAN - Justus-Liebig University

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2018
Publication Date: 6/1/2018
Citation: Dubey, J.P., Bauer, C. 2018. A review of Eimeria infections in horses and other equids. Veterinary Parasitology. 251:1-2. https://doi.org/10.1016/j.vetpar.2018.04.010

Interpretive Summary: Toxoplasma, Neospora, Sarcocystis, Eimeria, and Cystoisopora are related coccidian parasites that cause severe illness in livestock. Oocyst is the environmentally resistant stage passed in feces of the definitive hosts. While Toxoplasma and Neospora have wide host range, Eimeria are generally host specific. Coccidiosis due to Eimeria is an important cause of diarrhea in livestock worldwide. There is considerable confusion concerning species of Eimeria in horses, and most of the literature is in obscure journals. Dubey and Bauer have summarized information on history, validity of Eimeria species, life cycle, pathogenicity, prevalence, epidemiology, diagnosis and control of coccidiosis in horses. These results will be of interest to parasitologists and veterinarians in diagnosis of coccidiosis in horses.

Technical Abstract: There is considerable confusion concerning validity of Eimeria species in equids, and endogenous developmental stages and pathogenicity of equid Eimeria. This paper summarizes worldwide information on history, structure, life cycle, pathogenicity, prevalence, epidemiology, and diagnosis of Eimeria infections in equids. The following conclusions were drawn. Although 3 species of Eimeria, E. solipedum, E. uninugulata, and E. leuckarti were named from horses, only E. leuckarti is a valid species infecting equids, including horses, donkeys and zebra. We consider E. solipedum, E. uninugulata and Isospora sp.as spurious/contaminants with coccidia from other hosts, particularly rodents and avian feces. Eimeria leuckarti oocysts are distinctive, dark brown and up to 94 µm long and up to 79 µm wide. Its gametogonic stages and oocysts are located in the lamina propria of small intestine. In equids naturally infected with E. leuckarti asexual stages are unknown; microgamonts are up to 300 µm in diameter. In most of the approximately 50 cases of histologically diagnosed cases of E. leuckarti infection, this infection was considered coincidental. However, in some cases E. leuckarti was considered pathogenic, causing diarrhea and enteritis. The prepatent is long, 30 days or more in experimentally infected equids. Natural infections have been found in 28 days old foals, indicating that foals can become infected on the day of birth. The number of oocysts excreted is not correlated with clinical signs.