Biology:Babesia microti

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Short description: Species of parasitic protist in the Apicomplexa phylum

Babesia microti
Scientific classification edit
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Apicomplexa
Class: Aconoidasida
Order: Piroplasmida
Family: Babesiidae
Genus: Babesia
Species:
B. microti
Binomial name
Babesia microti
(França, 1912)
Life cycle of B. microti, including human infection
Typically, B. microti is transmitted by the nymphal stage of Ixodes scapularis ticks (about the size of a poppy seed).

Babesia microti is a parasitic blood-borne piroplasm transmitted by deer ticks. B. microti is responsible for the disease babesiosis, a malaria-like zoonosis which causes fever, hemolytic anemia caused by hemolysis, and enlarged spleen.[1]

Lifecycle

The lifecycle of B. microti includes two hosts: a vertebrate and an arthropod, the deer tick. When the tick bites a vertebrate, B. microti can be transmitted as sporozoites into the vertebrate host.[1] The parasite starts infecting red blood cells, where it digests hemoglobin for amino acids. After this, B. microti undergoes asexual reproduction and differentiation to male and female gametocytes. These are then ingested by the arthropod host and B. microti gametes undergo a sporogonic cycle (sexual reproduction), where new sporozoites are made. The cycle begins again when the tick bites a new vertebrate host.[2]

B. microti's usual vertebrate hosts include domesticated animals, such as cattle, dogs, and rats, and wild animals.[1][2] Humans are accidental hosts of Babesia in general, but B. microti is an important transfusion-transmitted infectious organism in humans. Between 2010 and 2014, it caused four out of 15 (27%) fatalities associated with transfusion-transmitted microbial infections reported to the US FDA (the highest of any single organism).[3] In 2018, the FDA approved an antibody-based screening test for blood and organ donors.[4]

An important difference from malaria is that B. microti does not infect liver cells or require haem iron for their metabolical processes.[1] Additionally, the piroplasm is spread by tick bites (Ixodes scapularis, the same tick that spreads Lyme disease), while the malaria protozoans are spread by mosquitoes. Finally, under the microscope, the merozoite form of the B. microti lifecycle in red blood cells forms a cross-shaped structure, often referred to as a "Maltese cross" or tetrad, in addition to intracellular "ring forms", which are also seen in the malaria parasite (Plasmodium spp.).[5]

Taxonomy

Template:Piroplasmida Until 2006, B. microti was thought to belong to the genus Babesia, as Babesia microti, until ribosomal RNA comparisons placed it in the sister genus Theileria.[6][7] As of 2012, the medical community still classified the parasite as B. microti[8] though its genome showed it does not belong to either Babesia or Theileria.[9]

Genomics

The genome of Babesia microti has been sequenced and published.[9]

The mitochondrial genome is circular.[9]

Vaccine

In May 2010, a vaccine to protect cattle against East Coast fever reportedly had been approved and registered by the governments of Kenya, Malawi, and Tanzania.[10]

A vaccine to protect humans has yet to be approved.[11]

References

  1. ↑ 1.0 1.1 1.2 1.3 Si, Wenwen; Fang, Chuantao; Liu, Chuang; Yin, Meng; Xu, Wenyue; Li, Yanna; Yan, Xiaoli; Shen, Yujuan et al. (2023-06-08). "Why is Babesia not killed by artemisinin like Plasmodium?" (in en). Parasites & Vectors 16 (1): 193. doi:10.1186/s13071-023-05783-4. ISSN 1756-3305. PMID 37291657. 
  2. ↑ 2.0 2.1 Sojka, Daniel; Jalovecká, Marie; Perner, Jan (August 2022). "Babesia, Theileria, Plasmodium and Hemoglobin" (in en). Microorganisms 10 (8): 1651. doi:10.3390/microorganisms10081651. ISSN 2076-2607. PMID 36014069. 
  3. ↑ "Fatalities Reported to FDA Following Blood Collection and Transfusion: Annual Summary for Fiscal Year 2014". U.S. Food and Drug Administration. https://www.fda.gov/downloads/BiologicsBloodVaccines/SafetyAvailability/ReportaProblem/TransfusionDonationFatalities/UCM459461.pdf. 
  4. ↑ Approval Letter -Babesia microti AFIA/Babesia microti AFIA for Blood Donor Screening (Report). U.S. Food and Drug Administration. 6 March 2018. BLA/ STN#125589. https://www.fda.gov/downloads/BiologicsBloodVaccines/BloodBloodProducts/ApprovedProducts/LicensedProductsBLAs/BloodDonorScreening/InfectiousDisease/UCM601840.pdf. Retrieved 20 March 2018. 
  5. ↑ Clinical Microbiology made Ridiculously Simple (4th ed.). Medmaster. 2007. ISBN 978-0-940780-21-7. 
  6. ↑ "Polyphasic taxonomy". Annals of the New York Academy of Sciences 1081 (1): 492–497. October 2006. doi:10.1196/annals.1373.073. PMID 17135557. Bibcode: 2006NYASA1081..492U. 
  7. ↑ "Babesia--a historical overview". Veterinary Parasitology 138 (1–2): 3–10. May 2006. doi:10.1016/j.vetpar.2006.01.035. PMID 16513280. 
  8. ↑ "Human babesiosis". The New England Journal of Medicine 366 (25): 2397–2407. June 2012. doi:10.1056/NEJMra1202018. PMID 22716978. 
  9. ↑ 9.0 9.1 9.2 "Sequencing of the smallest Apicomplexan genome from the human pathogen Babesia microti". Nucleic Acids Research 40 (18): 9102–9114. October 2012. doi:10.1093/nar/gks700. PMID 22833609. 
  10. ↑ "Vaccines against bovine babesiosis: where we are now and possible roads ahead". Parasitology 141 (12): 1563–1592. July 2014. doi:10.1017/S0031182014000961. PMID 25068315. 
  11. ↑ "Babesia microti: Pathogen Genomics, Genetic Variability, Immunodominant Antigens, and Pathogenesis". Frontiers in Microbiology 12. 2021. doi:10.3389/fmicb.2021.697669. PMID 34539601. 

Wikidata ☰ Q7777786 entry



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