Identification of an eimeriid parasite infection in camelids from Saudi Arabia: morphology and molecular studies

Abstract

Coccidiosis, an intestinal infection caused by protozoan parasites of the genus Eimeria, is a significant health concern in camelids, leading to economic losses in milk and meat production. Little is known about camelid coccidian parasites, with most relying on the prevalence of infection. This study aimed to describe and genetically characterize a camelid’s Eimeria species reported from the Dromedary camel. The taxonomic position of the recovered species was inferred using an analysis of sequences from the nuclear gene 18S rRNA and the mitochondrial gene COI with related taxa. A total of 80 fecal samples from Camelus dromedarius in the old camel market in Riyadh, Saudi Arabia, were collected between December 2023 to February 2024. Before these samples were sporulated in a 2.5% potassium dichromate solution, they were examined for the presence of Eimeria oocysts using the standard floatation technique. The rate of parasitic infections was ascertained. Eimerian oocysts were morphologically described and molecularly characterized using the recommended protocols. Of the 80 examined fecal samples, 18 (22.5%) were positive for Eimeria species. The identified parasite species, Eimeria sp., exhibited high morphometric similarity to Eimeria alpacae, which had a typical ellipsoidal oocyst shape with the presence of micropyle and the absence of oocyst polar granules and residual body. Moreover, sporocysts are elongated in shape and characterized by a distinct stieda body and a residuum within the sporocysts. DNA sequences generated from the 18S rRNA and COI gene regions showed high identity to sequences obtained from oocysts of Eimeria species of the family Columbidae. Phylogenetic analyses using neighbor-joining and maximum likelihood using both sequences from 18S rRNA and COI data consistently grouped the sequences obtained from Eimeria sp. of camel origin, reported in the present study, with DNA sequences in GenBank of domestic pigeon origin. This study highlighted the necessity of describing camel intestinal eimerian parasites using molecular methods rather than traditional morphology-based approaches to gain a better knowledge of their taxonomic status. Moreover, the presence of this eimerian species is considered the first record in Saudi Arabia. Future research studies are recommended to assess the impact of Eimeria infections on camel productivity and health, as well as investigate potential cross-species transmission between camels and other hosts, such as domestic pigeons.