| Babesia microti | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Alveolata |
| Phylum: | Apicomplexa |
| Class: | Aconoidasida |
| Order: | Piroplasmida |
| Species: | B. microti |
| Binomial name | |
| Babesia microti (França, 1912) | |
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.
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]
| Piroplasmida phylogeny (mtDNA) [4] |
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]
The genome of Babesia microti has been sequenced and published. [8]
The mitochondrial genome is circular. [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]
The Apicomplexa are organisms of a large phylum of mainly parasitic alveolates. Most possess a unique form of organelle structure that comprises a type of (non-photosynthetic) plastid called an apicoplast—with an apical complex membrane. The organelle's apical shape is an adaptation that the apicomplexan applies in penetrating a host cell.
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 tick bite is most common in the Northeastern and Midwestern United States and parts of Europe, and sporadic throughout the rest of the world. It occurs in warm weather. People can get infected with Babesia parasites by the bite of an infected tick, by getting a blood transfusion from an infected donor of blood products, or by congenital transmission . Ticks transmit the human strain of babesiosis, so it often presents with other tick-borne illnesses such as Lyme disease. After trypanosomes, Babesia is thought to be the second-most common blood parasite of mammals. They can have major adverse effects on the health of domestic animals in areas without severe winters. In cattle, the disease is known as Texas cattle fever or redwater.
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. The economic impact of tick-borne diseases is considered to be substantial in humans, and tick-borne diseases are estimated to affect ~80 % of cattle worldwide. Most of these pathogens require passage through vertebrate hosts as part of their life cycle. Tick-borne infections in humans, farm animals, and companion animals are primarily associated with wildlife animal reservoirs. Many tick-borne infections in humans involve a complex cycle between wildlife animal reservoirs and tick vectors. The survival and transmission of these tick-borne viruses are closely linked to their interactions with tick vectors and host cells. These viruses are classified into different families, including Asfarviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, Bunyaviridae, and Flaviviridae.
George Henry Falkiner Nuttall FRS was an American-British bacteriologist who contributed much to the knowledge of parasites and of insect carriers of diseases. He made significant innovative discoveries in immunology, about life under aseptic conditions, in blood chemistry, and about diseases transmitted by arthropods, especially ticks. He carried out investigations into the distribution of Anopheline mosquitoes in England in relation to the previous prevalence of malaria there. With William Welch he identified the organism responsible for causing gas gangrene.
Babesia, also called Nuttallia, is an apicomplexan parasite that infects red blood cells and is transmitted by ticks. Originally discovered by the Romanian bacteriologist Victor Babeș in 1888, over 100 species of Babesia have since been identified.
A canine vector-borne disease (CVBD) is one of "a group of globally distributed and rapidly spreading illnesses that are caused by a range of pathogens transmitted by arthropods including ticks, fleas, mosquitoes and phlebotomine sandflies." CVBDs are important in the fields of veterinary medicine, animal welfare, and public health. Some CVBDs are of zoonotic concern.
Babesia divergens is an intraerythrocytic parasite, transmitted by the tick Ixodes ricinus. It is the most common cause of human babesiosis. It is the main agent of bovine babesiosis, or "redwater fever", in Europe. Young cattle are less susceptible. The current emphasis in Europe on sustainable agriculture and extensification is likely to lead to an increase in vector tick populations with increased risk of infection. B. divergens is also prevalent in cottontail rabbits on Nantucket Island, MA, USA.
Ixodes scapularis is commonly known as the deer tick or black-legged tick, and in some parts of the US as the bear tick. It was also named Ixodes dammini until it was shown to be the same species in 1993. It is a hard-bodied tick found in the eastern and northern Midwest of the United States as well as in southeastern Canada. It is a vector for several diseases of animals, including humans and is known as the deer tick owing to its habit of parasitizing the white-tailed deer. It is also known to parasitize mice, lizards, migratory birds, etc. especially while the tick is in the larval or nymphal stage.
Theileria is a genus of parasites that belongs to the phylum Apicomplexa, and is closely related to Plasmodium. Two Theileria species, T. annulata and T. parva, are important cattle parasites. T. annulata causes tropical theileriosis and T. parva causes East Coast fever. Theileria species are transmitted by ticks. The genomes of T. orientalis Shintoku, Theileria equi WA, Theileria annulata Ankara and Theileria parva Muguga have been sequenced and published.
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. They include the tick parasites Babesia and Theileria.
A transfusion transmitted infection (TTI) is a virus, parasite, or other potential pathogen that can be transmitted in donated blood through a transfusion to a recipient. The term is usually limited to known pathogens, but also sometimes includes agents such as simian foamy virus which are not known to cause disease.
Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium that is typically transmitted to humans by ticks of the Ixodes ricinus species complex, including Ixodes scapularis and Ixodes pacificus in North America. These ticks also transmit Lyme disease and other tick-borne diseases.
Hematozoa is a subclass of blood parasites of the Apicomplexa clade. Well known examples include the Plasmodium spp. which cause malaria in humans and Theileria which causes theileriosis in cattle. A large number of species are known to infect birds and are transmitted by insect vectors. The pattern in which Haematozoa infect a host cell depends on the genera of the blood parasite. Plasmodium and Leucozytozoon displace the nucleus of the host cell so that the parasite can take control of the cell where as Hemoproteus completely envelops the nucleus in a host cell.
Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is typified by a cellular variety with a distinct morphology and biochemistry.
Babesia bovis is an Apicomplexan single-celled parasite of cattle which occasionally infects humans. The disease it and other members of the genus Babesia cause is a hemolytic anemia known as babesiosis and colloquially called Texas cattle fever, redwater or piroplasmosis. It is transmitted by bites from infected larval ticks of the order Ixodida. It was eradicated from the United States by 1943, but is still present in Mexico and much of the world's tropics. The chief vector of Babesia species is the southern cattle fever tick Rhipicephalus microplus.
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.
Achromatorida is an order of non-pigmented intraerythrocytic parasitic alveolates belonging to the subclass Haemosporidiasina. The order was created by Jacques Euzéby in 1988.
Ticks of domestic animals directly cause poor health and loss of production to their hosts. Ticks also transmit numerous kinds of viruses, bacteria, and protozoa between domestic animals. These microbes cause diseases which can be severely debilitating or fatal to domestic animals, and may also affect humans. Ticks are especially important to domestic animals in tropical and subtropical countries, where the warm climate enables many species to flourish. Also, the large populations of wild animals in warm countries provide a reservoir of ticks and infective microbes that spread to domestic animals. Farmers of livestock animals use many methods to control ticks, and related treatments are used to reduce infestation of companion animals.
Babesia canis is a parasite that infects red blood cells and can lead to anemia. This is a species that falls under the overarching genus Babesia. It is transmitted by the brown dog tick and is one of the most common piroplasm infections. The brown dog tick is adapted to warmer climates and is found in both Europe and the United States, especially in shelters and greyhound kennels. In Europe, it is also transmitted by Dermacentor ticks with an increase in infections reported due to people traveling with their pets.
Babesia bigemina is a species of alveolates belonging to the phylum Apicomplexa and the family Babesiidae, a type of protozoan parasite. In cattle, it causes babesiosis, also called "Texas fever". Its length is 4–5 µm and its width is 2–3 µm. Usually, it has an oval shape. In blood cells, it is located midsagittally and can reach up to two-thirds of the diameter of the blood cell in size. It is transmitted by Boophilus ticks which are prevalent in the tropics. The genome for B. bigemina is incomplete and unassembled.