Eimeria

Abstract

The protist phylum Apicomplexa Levine, 1970, comprises >4000 described species, all obligate parasites, that infect a wide range of vertebrates and invertebrates. Within the phylum, the genus Eimeria Schneider, 1875, (Family Eimeriidae) is the most speciose lineage (>1800 species) of intracellular parasites found in all classes of vertebrates and some invertebrates. All eimerians have direct life cycles that include both asexual (merogony) and sexual (gamogony) reproduction, the latter resulting in the production of resistant propagules, the oocysts, which are discharged into the environment by the infected host. Endogenous development usually occurs in epithelial or endothelial cells of the intestine or in related structures (e.g. gall bladder, bile ducts, renal tubular epithelium, esophageal epithelium, oviduct epithelium uterine wall epithelium, etc.). Some eimerian species are highly pathogenic, especially in domesticated animals, but some also in wild animal species. Key Concepts: Within the coccidia proper, the Family Eimeriidae comprises about 15 genera, including Eimeria ; all are obligate intracellular parasites known to infect every animal group which has been examined for them. Untapped Biodiversity: The genus Eimeria , with >1800 described forms, may be the most speciose group of parasites on Earth, but it has been little studied in the Earth's app. 62 150 vertebrate species. It can be estimated that 98.6% (or more) of the coccidian parasites of vertebrates are yet to be discovered, based on what we know through 2010. Our knowledge of the biodiversity of life on Earth is still badly incomplete, especially of the microbes that inhabit the seas, the soils and the bodies of ‘higher’ organisms that live in and on them. Parasitologists, and most other biologists in general, agree that parasites represent a large proportion of all living species and may, in fact, far exceed the total number of all ‘free‐living’ forms. As human population increases and agricultural development continues to shrink/fragment natural ecosystems, food webs will be disrupted and new and more virulent strains of coccidia may be expected, especially when exacerbated by environmental stressors (pollution), global climate change and invasion of new parasites from edge‐dwelling hosts.

Host specificity of turkey and chicken Eimeria: Controlled cross-transmission studies and a phylogenetic view

“…More than 1800 species of Eimeria have been described and it is estimated that most of the species (more than 98%) are still awaiting their discovery (Duszynski, 2011). Due to the significance of Eimeria as a causative agent of coccidiosis in livestock animals, major attention is paid to the species infecting these hosts, especially poultry.…”

Detection and quantification of house mouse Eimeria at the species level – challenges and solutions for the assessment of Coccidia in wildlife

“…Eimeria (Schneider, 1875) is with around 1700 species the most specious genus in the phylum Apicomplexa (Duszynski, 2011;Perkins et al, 2000). For economical reasons, the most studied parasites in this group are those infecting livestock (Shirley et al, 2005;Su et al, 2003).…”

Generalist Eimeria species in rodents: multilocus analyses indicate inadequate resolution of established markers

“…It is not clear, however, whether host specificity is the same for Eimeria species infecting hosts in different clades. Eimeria species of rodents show a degree of specificity (Ball and Lewis 1984;Duszynski 2011;De Vos 1970;Wilber et al 1998) but individual isolates can experimentally infect different species and even genera of rodents (Levine and Ivens 1988;Upton et al on phylogenetic analysis using established markers (nu 18S,mt COI and ap ORF470). We question in how far these markers are polymorphic enough to resolve between genetic clusters with different host usage (and whether a negative result for genetic differentiation therefore suggests generalism).…”