Theileria microti

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Theileria microti
Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Alveolata
Phylum: Apicomplexa
Class: Aconoidasida
Order: Haemosporida
(unranked): Piroplasmida
Family: Theileriidae
Genus: Theileria
Species: Theileria microti
  • Babesia microti
Life cycle of T. microti, including human infection

Theileria microti is a parasitic blood-borne piroplasm transmitted by deer ticks. It was previously in the taxonomic genus Babesia, as Babesia microti, until ribosomal RNA comparisons placed it in the sister genus Theileria.[1][2] T. microti is responsible for the disease human theileriosis, similar to babesiosis, a malaria-like disease which also causes fever and hemolysis.

Within the medical community, as of 2012, this parasitic agent is still classified as Babesia microti.[3]


The genome of Theileria microti (aka Babesia microti) has been sequenced. The sequence shows that this species does not belong to the either of the established genera - Babesia and Theileria - but instead belongs to a separate genus.[4]

The mitochondrial genome is linear.[4]

Life cycle[edit]

An important difference from malaria is that T. microti does not infect liver cells. Additionally, the piroplasm is spread by tick bites (Ixodes scapularis, the same tick that spreads Lyme disease), while the malaria protozoans are spread via mosquito. Finally, under the microscope, the merozoite form of the T. microti lifecycle in red blood cells forms a cross-shaped structure, often referred to as a "Maltese cross", whereas malaria forms more of a diamond ring structure in red blood cells.[5] Living in red blood cells, T. microti is an important transfusion-transmitted infectious organism. Between 2010 and 2014 it causing four out of fifteen (27%) of transfusion-transmitted microbial infections (the highest of any single organism).[6]


In May 2010, it was reported that a vaccine to protect cattle against East Coast fever had been approved and registered by the governments of Kenya, Malawi and Tanzania.[7]

A vaccine to protect humans has yet to be approved.[citation needed]


  1. ^ UILENBERG,G. & GOFF,W.L. (2006). "Polyphasic Taxonomy". Annals of the New York Academy of Sciences. 1081: 495. doi:10.1196/annals.1373.073. PMID 17135557.  [1]
  2. ^ Uilenberg, G (May 2006). "Babesia--a historical overview". Veterinary Parasitology. 138 (1–2): 3–10. doi:10.1016/j.vetpar.2006.01.035. PMID 16513280. 
  3. ^ Vannier, Edouard; Krause, Peter J. (21 June 2012). "Human Babesiosis". New England Journal of Medicine. 366 (25): 2397–2407. doi:10.1056/NEJMra1202018. PMID 22716978. 
  4. ^ a b Cornillot, E.; Hadj-Kaddour, K.; Dassouli, A.; Noel, B.; Ranwez, V.; Vacherie, B.; Augagneur, Y.; Bres, V.; Duclos, A.; Randazzo, S.; Carcy, B.; Debierre-Grockiego, F.; Delbecq, S.; Moubri-Menage, K.; Shams-Eldin, H.; Usmani-Brown, S.; Bringaud, F.; Wincker, P.; Vivares, C. P.; Schwarz, R. T.; Schetters, T. P.; Krause, P. J.; Gorenflot, A.; Berry, V.; Barbe, V.; Ben Mamoun, C. (2012). "Sequencing of the smallest Apicomplexan genome from the human pathogen Babesia microti". Nucleic Acids Research. 40 (18): 9102–14. doi:10.1093/nar/gks700. PMC 3467087Freely accessible. PMID 22833609. 
  5. ^ Goldberg, Stephen (2007). Clinical Microbiology made Ridiculously Simple (4th ed.). Medmaster. ISBN 978-0-940780-21-7. 
  6. ^ "Fatalities Reported to FDA Following Blood Collection and Transfusion" (PDF). 
  7. ^ Florin-Christensen, Monica; Suarez, Carlos E.; Rodriguez, Anabel E.; Flores, Daniela A.; Schnittger, Leonhard (October 2014). "Vaccines against bovine babesiosis: where we are now and possible roads ahead". PARASITOLOGY. 141 (12): 1563–1592. doi:10.1017/S0031182014000961. 

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