Life cycle of B. microti, including human infectionTypically 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 disease which also causes fever and
hemolysis.
Life cycle
The life cycle of B. microti includes human
red blood cells and is an important transfusion-transmitted infectious organism. Between 2010 and 2014 it caused four out of fifteen (27%) fatalities associated with transfusion-transmitted microbial infections reported to the
US FDA (the highest of any single organism).[1] In 2018, the
FDA approved an antibody-based screening test for blood and organ donors.[2]
An important difference from malaria is that B. 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 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.).[3]
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.[5][6] As of 2012[update], the medical community still classified the parasite as Babesia microti[7] though its genome showed it does not belong to either Babesia or Theileria.[8]
Genomics
The genome of Babesia microti has been sequenced and published.[8]
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.[9]
A vaccine to protect humans has yet to be approved.[10]
^Vannier E, Krause PJ (June 2012). "Human babesiosis". The New England Journal of Medicine. 366 (25): 2397–2407.
doi:
10.1056/NEJMra1202018.
PMID22716978.
^Florin-Christensen M, Suarez CE, Rodriguez AE, Flores DA, Schnittger L (July 2014). "Vaccines against bovine babesiosis: where we are now and possible roads ahead". Parasitology. 141 (12): 1563–1592.
doi:
10.1017/S0031182014000961.
hdl:11336/35696.
PMID25068315.
S2CID34025694.