Trypanosoma lewisi is a globally distributed parasite of Rattus species and other rodents such as mice, and of kangaroo rats in America. Among these host species were two endemic species of rats: Rattus macleari and Rattus nativitatis . Both are now believed to be extinct. It is not very clear whether or not the same parasite infected both species. However, both parasites are very similar. The northern rat flea ( Nosopsyllus fasciatus ) acts as the vector for the parasite, harboring the epimastigote stage in its midgut.The trypomastigote is the stage that is present in the main host, the rodent. The epimastigote form attaches itself to the rectum of the insect using its flagella to burrow through the rectal walls. The parasites also appear in the flea's feces. Ingestion of either the flea or its feces during grooming infects the host rodent with the parasites. T. lewisi is normally non-pathogenic but is known to have produced fatal infections in rats.
Trypanosomes in the blood of rats were first noted and described by Timothy Richards Lewis from Calcutta and the species was named after him.In the 1900s, a parasitologist noticed that Rattus macleari , a species of rat endemic to Christmas Island, were becoming sick. The suspected cause was a species of trypanosomes. There was no proof that this was actually correct until scientists from the American Museum of Natural History deposited some rats that had been collected from Christmas Island as specimens into museums. Scientists argue that Trypanosoma lewisi is partially or wholly responsible for the subsequent extinction of Rattus macleari. The parasites were transmitted from fleas infesting the then recently introduced black rats ( Rattus rattus ).
T. lewisi can be cultured in various media including in vivo in rat serumand in vitro in mammalian cell culture media. The parasite can also be grown in mice if the host is supplemented with a controlled diet and intraperitoneal injection of rat serum. Ablastin, an antibody that arises during an infection in the host’s body, prevents the parasite from reproducing although they remain in adult form.
A research paper suggests that the data on the aftermath of introduction of a Trypanosoma lewisi to immunologically naïve murine hosts on Christmas Island around 1900 matches reports of complete extinction within the range of 1–9 years. This gives some more information on the first pathogen introduction to a species to have caused species extinction.
Although rare, there were also many cases in which human beings and primates were infected with Trypanosoma lewisi. In a recent study comparing Brazilian isolates in rats and primates, it was found the DNA sequences were the same when considering Trypanosoma lewisi. This further proves the potential of Trypanosoma lewisi's ability to infect human beings, despite being rare in most cases.
A flea bites an infected rodent and ingests its blood. Within six hours, the parasites migrate and reproduce in the epithelial cells of their host flea's stomach. They then go further into the lumen of the stomach and finally move into the insect's rectum. days postinfection. After a few weeks, the trypanosomes stop growing and disappear from the bloodstream. The rat then develops immunity against re-infection.The parasite's metacyclic trypomastigote infects a rat after it eats the host flea or the flea's feces. Once inside the rat's body, the parasite will then begin reproducing epimastigotes in the blood capillaries of the host. After about five days, trypanosomes will begin appearing in the peripheral blood of the host, with the appearance of thick worms. These parasites are usually attacked by ablastin, a trypanocidal IgG antibody produced by their host's immune system beginning 2–4
African trypanosomiasis, also known as African sleeping sickness or simply sleeping sickness, is an insect-borne parasitic infection of humans and other animals. It is caused by the species Trypanosoma brucei. Humans are infected by two types, Trypanosoma brucei gambiense (TbG) and Trypanosoma brucei rhodesiense (TbR). TbG causes over 98% of reported cases. Both are usually transmitted by the bite of an infected tsetse fly and are most common in rural areas.
Trypanosomatida is a group of kinetoplastid excavates distinguished by having only a single flagellum. The name is derived from the Greek trypano (borer) and soma (body) because of the corkscrew-like motion of some trypanosomatid species. All members are exclusively parasitic, found primarily in insects. A few genera have life-cycles involving a secondary host, which may be a vertebrate, invertebrate or plant. These include several species that cause major diseases in humans. Trypanosomatida are intracellular parasites.
Trypanosoma is a genus of kinetoplastids, a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek trypano- (borer) and soma (body) because of their corkscrew-like motion. Most trypanosomes are heteroxenous and most are transmitted via a vector. The majority of species are transmitted by blood-feeding invertebrates, but there are different mechanisms among the varying species. Some, such as Trypanosoma equiperdum, are spread by direct contact. In an invertebrate host they are generally found in the intestine, but normally occupy the bloodstream or an intracellular environment in the vertebrate host.
Maclear's rat is an extinct large rat endemic to Christmas Island in the Indian Ocean. It was one of two species of rat native to Christmas Island, alongside the bulldog rat. Abundant, unfamiliar with and seemingly unafraid of humans, large numbers of the creatures emerged and foraged in all directions at night. Making querulous squeaks, the rats entered the Challenger Expedition's tents and shelters in 1886, ran over sleepers, and upset everything in the search and fight for food. Maclear's rat might have been responsible for keeping the population of the Christmas Island red crab in check, as recent numbers of the crab are greater than in the past. It is thought that black rats inadvertently introduced by the expedition infected the Maclear's rats with a disease, which in turn could have contributed to the species' decline. The last recorded sighting was in 1903, although it is possible that Maclear's rats hybridized with black rats. A hard tick, described as an ectoparasite of Maclear's rat, is also thought to be extinct.
Echinococcus multilocularis is a small cyclophyllid tapeworm found extensively in the northern hemisphere. E. multilocularis, along with other members of the Echinococcus genus, produce diseases known as echinococcosis. Unlike E. granulosus,E. multilocularis produces many small cysts that spread throughout the internal organs of the infected animal. The resultant disease is called Alveolar echinococcosis, and is caused by ingesting the eggs of E. multilocularis.
Tunga penetrans is a parasitic insect found in most tropical and sub-tropical climates. Jiggers are often confused with chiggers - a type of mite. Jiggers are native to Central and South America, and have been inadvertently introduced by humans to sub-Saharan Africa.
Schistosoma malayensis is a schistosome parasite. It was first described in 1988 in Peninsular Malaysia and appears to be a zooenotic infection. The species is named after the country of Malaysia. The natural vertebrate host is van Müller's rat. The intermediate hosts are aquatic snails, Robertsiella kaporenisis. Among Robertsiella kaporenisis are two other Roberstiella species.
Trypanosoma brucei is a species of parasitic kinetoplastid belonging to the genus Trypanosoma. This parasite is the cause of vector-borne diseases of vertebrate animals, including humans, carried by species of tsetse fly in sub-Saharan Africa. In humans T. brucei causes African trypanosomiasis, or sleeping sickness. In animals it causes animal trypanosomiasis, also called nagana in cattle and horses. T. brucei has traditionally been grouped into three subspecies: T. b. brucei, T. b. gambiense and T. b. rhodesiense. The first is a parasite of non-human vertebrates, while the latter two are known to be parasites of humans. Only rarely can the T. b. brucei infect a human.
Trypanosoma cruzi is a species of parasitic euglenoids. Amongst the protozoa, the trypanosomes characteristically bore tissue in another organism and feed on blood (primarily) and also lymph. This behaviour causes disease or the likelihood of disease that varies with the organism: Chagas disease in humans, dourine and surra in horses, and a brucellosis-like disease in cattle. Parasites need a host body and the haematophagous insect triatomine is the major vector in accord with a mechanism of infection. The triatomine likes the nests of vertebrate animals for shelter, where it bites and sucks blood for food. Individual triatomines infected with protozoa from other contact with animals transmit trypanosomes when the triatomine deposits its faeces on the host's skin surface and then bites. Penetration of the infected faeces is further facilitated by the scratching of the bite area by the human or animal host.
Pneumocystis jirovecii is a yeast-like fungus of the genus Pneumocystis. The causative organism of Pneumocystis pneumonia, it is an important human pathogen, particularly among immunocompromised hosts. Prior to its discovery as a human-specific pathogen, P. jirovecii was known as P. carinii.
Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. Toxascaris leonina, or T. leonina, is an ascarid nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts of T. leonina include canids and felines (cats), while the intermediate hosts are usually rodents, such as mice or rats. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.
Trypanosoma rangeli is a species of hemoflagellate excavate parasites of the genus Trypanosoma. Although infecting a variety of mammalian species in a wide geographical area in Central and South America, this parasite is considered non-pathogenic to these hosts. T. rangeli is transmitted by bite of infected triatomine bugs of the Reduviidae family, commonly known as barbeiro, winchuka(vinchuca), chinche, pito ou chupão.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii. R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus. This bacterium is recognized as a biocontainment level 2/3 organism. R. typhi is a flea-borne disease that is best known to be the causative agent for the disease murine typhus, which is an endemic typhus in humans that is distributed worldwide. As with all rickettsial organisms, R. typhi is a zoonotic agent that causes the disease murine typhus, displaying non-specific mild symptoms of fevers, headaches, pains and rashes. There are two cycles of R. typhi transmission from animal reservoirs containing R. typhi to humans: a classic rat-flea-rat cycle that is most well studied and common, and a secondary periodomestic cycle that could involve cats, dogs, opossums, sheep, and their fleas.
Capillaria hepatica is a parasitic nematode which causes hepatic capillariasis in rodents and numerous other mammal species, including humans. The life cycle of C. hepatica may be completed in a single host species. However, the eggs, which are laid in the liver, must mature outside of the host body prior to infecting a new host. So the death of the host in which the adults reach sexual maturity, either by being eaten or dying and decomposing, is necessary for completion of the life cycle.
Trichostrongylus species are nematodes, which are ubiquitous among herbivores worldwide, including cattle, sheep, donkeys, goats, deer, and rabbits. At least 10 Trichostrongylus species have been associated with human infections. Infections occur via ingestion of infective larvae from contaminated vegetables or water. Epidemiological studies indicate a worldwide distribution of Trichostrongylus infections in humans, with the highest prevalence rates observed in individuals from regions with poor sanitary conditions, in rural areas, or who are farmers / herders. Human infections are most prevalent in the Middle East and Asia, with a worldwide estimated prevalence of 5.5 million people.
Nosopsyllus fasciatus, the northern rat flea, is a species of flea found on domestic rats and house mice. Northern rat fleas are external parasites, living by hematophagy off the blood of rodents. It is the most widely spread of its genus, having originated in Europe, but has been transported to temperate regions all over the world.
Trypanosoma irwini is a blood parasite of koalas. First discovered in 2009 by Linda M. McInnes and her peers, it was named in honor of Steve Irwin, "The Crocodile Hunter". The study done by McInnes et al. was the first to describe a Trypanosoma species from koalas.
Variant surface glycoprotein (VSG) is a ~60kDa protein which densely packs the cell surface of protozoan parasites belonging to the genus Trypanosoma. This genus is notable for their cell surface proteins. They were first isolated from Trypanosoma brucei in 1975 by George Cross. VSG allows the trypanosomatid parasites to evade the mammalian host's immune system by extensive antigenic variation. They form a 12–15 nm surface coat. VSG dimers, ~90% of all cell surface protein. It also makes up ~10% of total cell protein. For this reason, these proteins are highly immunogenic and an immune response raised against a specific VSG coat will rapidly kill trypanosomes expressing this variant. However, with each cell division there is a possibility that the progeny will switch expression to change the VSG that is being expressed. VSG has no prescribed biochemical activity.
Trypanosoma tungarae is a species of giant trypanosome, a protozoal parasite, which infects the túngara frog and is thought to be transmitted by members of the midge genus Corethrella. It was discovered in 2016.
Lucy Engel Graves Taliaferro was an American parasitologist and professor, notable for her research in parasitology and immunology. She and her husband, William Hay Taliaferro, worked together as research partners from 1919 to 1973. She worked as a researcher in her husband's parasitology laboratory for over 30 years at the University of Chicago, where she co-taught a parasitology course with William and achieved the rank of Assistant Professor, although she was never paid. After retiring from the University of Chicago in 1960, the Talioferros researched the effects of ionizing radiation on the immune response at Argonne National Laboratory and coauthored Radiation and Immune Mechanisms (1964).