Eimeria is a genus of apicomplexan parasites that includes various species capable of causing .. mice (M. musculus) Eimeria weybridgensis – sheep (O. aries) Eimeria wobati – southern hairy-nosed wombat (L. latifrons) Eimeria zuernii – cattle (B. taurus). Eimeria zuernii is a species of the parasite Eimeria that causes diarrheic disease known as eimeriosis in cattle (Bos taurus), and mainly affects younger animals. Coccidiosis is usually an acute invasion and destruction of intestinal mucosa by protozoa of the genera Eimeria or Isospora. Clinical signs include diarrhea.
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Taxonomic ranks under review cf. Illustrated Guide to Protozoa, Protista unicellular eukaryotes Apicomplexa cells with cluster of organelles known as apical complex Coccidea gamonts small and intracellular, form small resistant spores called oocysts Eimeriida gametes develop independently without syzygy; known as coccidian parasites Family: Eimeriidae These protozoa are known as the enteric coccidia; monoxenous one-host parasites in the digestive tracts of herbivores or carnivores causing diarrhoeal disease known as coccidiosis.
Parasites form environmentally-resistant oocysts which undergo faecal-oral transmission between hosts. There are three sequential stages in the parasite life-cycle: Many genera are recognized on the basis of oocyst configuration the number of sporocysts per oocyst, and the number of sporozoites per sporocyst.
Eimeria zuernii – Wikipedia
Coccidian parasites form three developmental ekmeria Schizonts range in size depending on parasite species, location in the host and stage of maturity. They begin as small basophilic rounded cells mother meronts located intracellularly within host cells. The meronts form numerous daughter merozoites by endogenous division of the nucleus followed by cytokinesis. Mature schizonts appear as membrane-bound clusters of small basophilic bodies similar to bunches of grapes.
Developing oocysts contain numerous eosinophilic wall-forming bodies which give rise to the tough outer oocyst walls. Unsporulated oocysts contain a developing sporoblast which eventually undergoes sporulation forming sporocysts which contain the infective sporozoites. Eimeria oocysts exhibit a characteristic 1: Infections have been recorded throughout the world in most vertebrate species, including eutherian and metatherian mammals, birds, reptiles and fish.
Most coccidian species are considered to be highly host-specific and only parasitize single host species oioxenousalthough some species in birds and reptiles may parasitize closely-related hosts stenoxenous and a few eeimeria in fish may parasitize unrelated hosts emieria.
Many hosts also harbour multiple species of coccidia which may vary considerably in morphology, developmental cycle, site of infection and pathogenicity. In general, the small rapidly-developing species are generally the zuermii pathogenic. They generally exhibit rigid tissue tropism, infecting host cells in particular locations. The parasites undergo eimegia cycles of schizogony culminating in the lysis of host cells eimeris release merozoites.
Ultimately, gamonts are formed which mature to produce micro- and macro-gametes that undergo fertilization forming a non-motile zygote oocyst which is excreted with host faeces.
Most species are not significant pathogens and cause little or no disease. Certain species, however, are highly pathogenic and cause catarrhalic or haemorrhagic enteritis by severe erosion of the mucosal membranes through cell lysis resulting in profuse watery-to-bloody diarrhoea.
Clinical disease is not usually manifest until cumulative tissue damage associated with second or third generation schizogony. Zurrnii animals may show progressive signs such as poor weight gain or weight loss, weakness and emaciation, while severely-affected individuals may die soon after the appearance of disease.
Pathogenicity depends on many factors; such as parasite species, viability, infectivity, virulence, tropism, host age, nutritional status, immunological competence, as well as prevailing environmental conditions temperature, moisture and management practices.
Young animals are most susceptible to clinical disease, although survivors develop strong specific protective immunity against subsequent infection and disease.
Oocysts excreted with host faeces contaminate the external environment, but they must undergo internal sporulation sporozoite formation before they become infective. New hosts are infected when they ingest sporulated oocysts contaminating food or water supplies faecal-oral transmission. Following ingestion, oocysts and sporocysts excyst in the intestines releasing their contained sporozoites which invade host cells to begin merogony. Excystation stimuli include appropriate post-gastric physico-chemical conditions, such as oxygen levels, pH, bile salts, pancreatic enzymes, etc.
Infections are usually diagnosed by the coprological examination of host faeces for coccidial oocysts concentrated using various sedimentation-flotation techniques.
The pathogenesis of the lesions produced by Eimeria zuernii in calves.
Unstained oocysts are best observed by light microscopy using suboptimal transmitted illumination condenser wound down to introduce diffractionphase-contrast or interference-contrast optics.
Researchers have recently used a range of molecular techniques to characterize genetic variation between and within parasite species, but few techniques are suitable for routine diagnostic use. Disease progression is usually so rapid that any therapeutic curative treatment may simply be too late.
For this reason, continuous in-food or in-water medication is often used for prophylactic preventative treatment in many intensive animal industries.
A wide range of drugs are available, including those with coccidio-static reversible suppressive activity or coccidio-cidal irreversible lethal activity. The main drug groups include sulfonamides sulfanilamide, trimethoprim, ethopabatepyridinoles clopidol, decoquinatenitrobenzamides zoaleneorganic arsenicals roxarsonenitrofurans furazolidone, amproliumquinazolinones halofuginonepolyether ionophorous antibiotics monensin, laslocid, salinomycin, narasinasymmetric diclazuril and symmetric toltrazuril triazines.
Regrettably, there are mounting problems being encountered with drug resistance amongst many coccidian species, especially that against synthetic drugs which tends to persist within parasite populations.
Many industries recommend periodic rotation between different drug groups and the use of combination cocktail drugs to minimize the occurrence of resistance. Most coccidial infections stimulate the development of strong protective immune responses, albeit transient unless premunitive short-lived unless parasites persist.
There has been considerable success with control through immunoprophylaxis using attenuated or precocious strains of parasites, particularly in the poultry industry. Researchers are now attempting to develop recombinant subcellular vaccines.
Production of bovine coccidiosis with Eimeria zuernii.
Outbreaks can generally be controlled by management practices based around improving hygiene, reducing crowding, removing contaminated litter and isolating infected individuals. Chemical disinfection is usually impractical as the oocysts are resistant to many conventional disinfectants.
Allen Press Protista unicellular eukaryotes Apicomplexa cells with cluster of organelles known as apical complex Coccidea gamonts small and intracellular, form small resistant spores called oocysts Eimeriida gametes develop independently without syzygy; known as coccidian parasites Family: