Life cycle[ edit ] The Eimeria life cycle has an exogenous phase, during which the oocysts are excreted into the environment, and an endogenous phase, where parasite development occurs in the host intestine. During the endogenous phase, several rounds of asexual reproduction , or schizogony take place, after which the sexual differentiation of gametes and fertilisation occurs. Parasite transmission occurs via the oral-fecal route. Infections are common in farming environments where many animals are confined in a small space. An infected host releases oocysts into the environment in their unsporulated form. These contain a multi-layered cell wall making them highly resistant to environmental pressures.
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Life cycle[ edit ] The Eimeria life cycle has an exogenous phase, during which the oocysts are excreted into the environment, and an endogenous phase, where parasite development occurs in the host intestine. During the endogenous phase, several rounds of asexual reproduction , or schizogony take place, after which the sexual differentiation of gametes and fertilisation occurs.
Parasite transmission occurs via the oral-fecal route. Infections are common in farming environments where many animals are confined in a small space.
An infected host releases oocysts into the environment in their unsporulated form. These contain a multi-layered cell wall making them highly resistant to environmental pressures. In the case of E. Invasion is mediated through specialised membrane-bound structures on the surface of the parasite that release secretions.
This results in the recognition of, and attachment to host cell receptors. This process is known as gliding motility , which is conserved across all species of Apicomplexa. Membrane glyconjugates have been proposed as potential host cell receptors for Eimeria species. This results in many nuclei developing within the schizont. Each nucleus develops into a merozoite. Merozoites[ edit ] When schizonts rupture, merozoites are released, which either go on to re-infect more enterocytes or develop into either male or female gametes via the process of gametogenesis.
These gametes fuse to form an oocyst, which is then released in its non-infectious, unsporulated form through the faeces of the host. Merozoite invasion also requires the formation of a moving junction, however the proteins involved in this process differs from those on sporozoites.
There is also a greater diversity of variant surface antigens found on the surface of merozoites. It is hypothesised that this may be due to the fact that merozoites are short-lived and a greater antigen repertoire would permit faster binding and invasion. The classification of eimeriid coccidian was largely based on morphological and life cycle details.
This new genus retains the majority of the species. This genus contains about 20 species. This genus contains a single species, Crystallospora cristalloides Epieimeria : The species in this genus are tetrasporocystic, dizoic, possess Stieda bodies, and undergo merogony and gametogony on the lumenal surface of the intestinal tract.
Three species are in this genus. Out of these, comparing oocyst structures was the most commonly used method. Since , the sequencing and annotation of a further six avian Eimeria species genomes is in progress.
A combination of these factors may result in poor growth and death of the animal, particularly amongst young. The severity of the disease is directly dependent on the number of infective Eimeria oocysts that are ingested. However, in heavy infections, it may only take two weeks for many intestinal epithelial cells to be infected with either Eimeria meronts or gametocytes.
These cause the epithelial cells to burst, which causes significant damage to the intestine epithelial layer, resulting in the release of blood, fluid, and electrolytes into the intestine. However, it is often more effective to prevent this disease in cattle, which can be aided by the products lasalocid , decoquinate , and monensin. As a result, other avenues of control are being explored, particularly vaccine development, although several live attenuated vaccines have been in use since the s.
Infection with Eimeria results in life-long immunity to that particular parasite species, but does not give cross protection against other species. For these reasons, vaccines for control seem promising, of which live attenuated vaccines are most effective. However, the search for highly immunogenic antigens and overcoming antigenic variation of the parasites remains a challenge. Immunity to the parasite varies depending on parasite and host species, as well as the site of invasion.
Eimeria species in long life-cycle birds: focus on Eimeria tenella
Advantages of combined transmembrane topology and signal peptide prediction—the Phobius web server. Sign In or Create an Account. Table S05 Click here to view. Coccidia, metabolism, invasion, Apicomplexa.
Description[ edit ] This species has a monoxeous life cycle with the only definitive host as chickens ; it is extremely host-specific. Acquired via fecal contamination of food and water oral-fecal route , it undergoes endogenous merogony in the crypts of Lieberkuhn intestinal ceca of chicken and gametogony in epithelial cells of the small intestines. Fusion of microgamete and macrogamete forms results in unsporulated zygotes , which are released with feces of chicken. The zygote sporulates after one to five days, and becomes infective. Diagnosis is based on finding oocysts in feces. While no effective treatment exists, the rate of infection can be reduced via prophylates , anticoccidial drugs and vaccination of baby chicks. Life cycle[ edit ] Eimeria tenella has a monogenetic life cycle, that is, the life cycle involves a single host.