''Babesia microti'' is a parasitic blood-borne

piroplasm Piroplasmida is an order of parasites in the phylum Apicomplexa. They divide by binary fission and as sporozoan parasites they possess sexual and asexual phases (sexual reproduction occurs in the tick gut). They include the tick parasites ''B ...

transmitted by deer ticks. ''B. microti'' is responsible for the disease

babesiosis Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or '' Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via ...

, a

malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...

-like zoonosis which causes fever, hemolytic anemia caused by

hemolysis Hemolysis or haemolysis (), also known by #Nomenclature, several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may ...

, and enlarged spleen.

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. The parasite starts infecting red blood cells, where it digests hemoglobin for amino acids. After this, ''B. microti'' undergoes

asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...

and differentiation to male and female

gametocyte A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametids during gametogenesis. Male gametocytes are called ''spermatocytes'', and female gametocytes are called ''oocytes''. Development T ...

s. 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. ''B. microti's'' usual vertebrate hosts include domesticated animals, such as cattle, dogs, and rats, and wild animals. 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 United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

(the highest of any single organism). In 2018, the

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

approved an antibody-based screening test for blood and organ donors. An important difference from malaria is that ''B. microti'' does not infect liver cells or require haem iron for their metabolical processes. Additionally, the piroplasm is spread by tick bites (''

Ixodes scapularis ''Ixodes scapularis'' is a hard-bodied tick found in much of the eastern half of North America. It is commonly known as the deer tick, owing to its habit of parasitizing the white-tailed deer. It is also sometimes known as the black-legged tick ( ...

'', the same tick that spreads

Lyme disease Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of ''Borrelia'' bacteria, Disease vector, transmitted by blood-feeding ticks in the genus ''Ixodes''. It is the most common disease spread by ticks in th ...

), 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 The Maltese cross is a cross symbol, consisting of four " V" or arrowhead shaped concave quadrilaterals converging at a central vertex at right angles, two tips pointing outward symmetrically. It is a heraldic cross variant which develope ...

" or tetrad, in addition to intracellular "ring forms", which are also seen in the malaria parasite (''

Plasmodium ''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a Hematophagy, blood-feeding insect host (biology), host which then inj ...

'' spp.).

Taxonomy

Until 2006, ''B. microti'' was thought to belong to the genus ''

Babesia ''Babesia'', also called ''Nuttallia'', is an apicomplexan parasite that infects red blood cells and is transmitted by ticks. Originally discovered by Romanian bacteriologist Victor Babeș in 1888; over 100 species of ''Babesia'' have since ...

'', as ''Babesia microti'', until

ribosomal RNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...

comparisons placed it in the sister genus '' Theileria''. , the medical community still classified the parasite as ''B. microti'' though its genome showed it does not belong to either ''Babesia'' or ''Theileria''.

Genomics

The genome of ''Babesia microti'' has been sequenced and published. The mitochondrial genome is circular.

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. A vaccine to protect humans has yet to be approved.

References

External links

Babesia microti
Minnesota Department of Health {{Taxonbar, from=Q7777786 Piroplasmida Apicomplexa species