Theileria parva
| Theileria parva | |
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| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | SAR |
| (unranked): | Alveolata |
| Phylum: | Apicomplexa |
| Class: | Aconoidasida |
| Order: | Piroplasmida |
| Family: | Theileriidae |
| Genus: | Theileria |
| Species: | T. parva |
| Binomial name | |
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Theileria parva |
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Theileria parva is a species of parasites, named in honour of Arnold Theiler, that causes East Coast fever (theileriosis) in cattle, a costly disease in Africa. The main vector for T. parva is the tick Rhipicephalus appendiculatus. Theiler found that East Coast fever was not the same as redwater, but caused by a different protozoan.
Sporozoites from the tick secrete into the feeding site of the animal. Sporozoites enter lymphoblasts to form a schizont. There is a clonal expansion of schizonts and then multiply by merging to form merozoites. The merozoites go into erythrocytes and invade the cells and are now in the piroplasm stage. When a tick ingests the piroplasms, the parasites undergo syngamy in the gut and can move to hemolymph. The motile kinetes can infect the salivary glands. From this, sporogony occurs to create sporozoites to continue the life cycle.
Theileria parva causes East Coast fever which results from infected lymphocytes. East Coast fever has symptoms of anorexia, fever, enlarged lymph nodes which can cause lymphadenopathy. Less common symptoms include diarrhea and nasal discharge. A disorder called "turning sickness" can occur and is when the parasites in cells block the blood vessels in the brain and causes brain damage. This disease usually results in death but is very uncommon.
Xenodiagnosis can be used to confirm the tick vectors but is not used routinely. Blood smears can be performed to detect Theileria but can be hard to differentiate from other species. Serological assays, including indirect fluorescent antibody test, IFAT, and enzyme-linked immunosorbent assays, ELISA, are being used in research. For IFAT test, schizont or piroplasms are used from infected animals to identify transforming parasites. This method is economically friendly but is hard to differentiate between Theileria parva and other close species. ELISA is able to detect more specific antigens. Molecular assays such as PCR are continuing on the rise to be used but require more specialized equipment.
Parvaquone and buparvaquone are used for the early stages of the disease and are very effective. As the disease progress, treatment is much harder to control and parvaquone and buparvaquone are less effective. Immunization for Theileria parva is available and consist of strains of Theileria from infected ticks with oxytetracycline, a type of antibiotic. This inhibits the parasite to develop. It is recommended to immunize cattle approximately 3-4 weeks before turning cattle out on to infected pasture.
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Wikipedia