| 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 zoonosis which causes fever, hemolytic anemia caused by hemolysis, and enlarged spleen. [1]
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]
| Piroplasmida phylogeny (mtDNA) [6] |
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 . [7] [8] As of 2012 [update] , the medical community still classified the parasite as B. microti [9] though its genome showed it does not belong to either Babesia or Theileria. [10]
The genome of Babesia microti has been sequenced and published. [10]
The mitochondrial genome is circular. [10]
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. [11]
A vaccine to protect humans has yet to be approved. [12]
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.
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 blood-feeding insect host which then injects parasites into a vertebrate host during a blood meal. Parasites grow within a vertebrate body tissue before entering the bloodstream to infect red blood cells. The ensuing destruction of host red blood cells can result in malaria. During this infection, some parasites are picked up by a blood-feeding insect, continuing the life cycle.
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.
Plasmodium falciparum is a unicellular protozoan parasite of humans, and the deadliest species of Plasmodium that causes malaria in humans. The parasite is transmitted through the bite of a female Anopheles mosquito and causes the disease's most dangerous form, falciparum malaria. P. falciparum is therefore regarded as the deadliest parasite in humans. It is also associated with the development of blood cancer and is classified as a Group 2A (probable) carcinogen.
Plasmodium ovale is a species of parasitic protozoon that causes tertian malaria in humans. It is one of several species of Plasmodium parasites that infect humans, including Plasmodium falciparum and Plasmodium vivax which are responsible for most cases of malaria in the world. P. ovale is rare compared to these two parasites, and substantially less dangerous than P. falciparum.
Plasmodium knowlesi is a parasite that causes malaria in humans and other primates. It is found throughout Southeast Asia, and is the most common cause of human malaria in Malaysia. Like other Plasmodium species, P. knowlesi has a life cycle that requires infection of both a mosquito and a warm-blooded host. While the natural warm-blooded hosts of P. knowlesi are likely various Old World monkeys, humans can be infected by P. knowlesi if they are fed upon by infected mosquitoes. P. knowlesi is a eukaryote in the phylum Apicomplexa, genus Plasmodium, and subgenus Plasmodium. It is most closely related to the human parasite Plasmodium vivax as well as other Plasmodium species that infect non-human primates.
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 been identified.
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, Massachusetts, USA.
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.
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.
Sanaria is a biotechnology company founded to develop whole-parasite vaccines protective against malaria. Sanaria is also developing monoclonal antibodies protective against malaria, vaccines against diarrheal diseases, immunotherapeutics for disease of the liver, and related products for us in malaria research. Sanaria's vaccines are based on the use of the sporozoite (SPZ) stage of the malaria parasite, Plasmodium, as an immunogen, and as a carrier for immunomodulatory molecules.
Plasmodium cynomolgi is an apicomplexan parasite that infects mosquitoes and Asian Old World monkeys. In recent years, a number of natural infections of humans have also been documented. This species has been used as a model for human Plasmodium vivax because Plasmodium cynomolgi shares the same life cycle and some important biological features with P. vivax.