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 92% 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 unicellular organisms 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. Some trypanosomatida are intracellular parasites, with the important exception of Trypanosoma brucei.
Tsetse are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus Glossina, which are placed in their own family, Glossinidae. The tsetse is an obligate parasite, which lives by feeding on the blood of vertebrate animals. Tsetse has been extensively studied because of their role in transmitting disease. They have a pronounced economic impact in sub-Saharan Africa as the biological vectors of trypanosomes, causing human and animal trypanosomiasis.
Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans this includes African trypanosomiasis and Chagas disease. A number of other diseases occur in other animals.
Trypanosoma is a genus of kinetoplastids, a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Euglenozoa. 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. Trypanosoma equiperdum is spread between horses and other equine species by sexual contact. They are generally found in the intestine of their invertebrate host, but normally occupy the bloodstream or an intracellular environment in the vertebrate host.
Trypanosoma brucei is a species of parasitic kinetoplastid belonging to the genus Trypanosoma that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extracellular and inhabits the blood plasma and body fluids. It causes deadly vector-borne diseases: African trypanosomiasis or sleeping sickness in humans, and animal trypanosomiasis or nagana in cattle and horses. It is a species complex grouped into three subspecies: T. b. brucei, T. b. gambiense and T. b. rhodesiense. The first is a parasite of non-human mammals and causes nagana, while the latter two are zoonotic infecting both humans and animals and cause African trypanosomiasis.
Trypanosoma evansi is a parasitic species of excavate trypanosome in the genus Trypanosoma that is one cause of surra in animals. Discovered by Griffith Evans in 1880 at Dera Ismail Khan, it is the first known trypanosome that causes infection. It is a common parasite in India and Iran and causes acute disease in camels and horses, and chronic disease in cattle and buffalo. In Pakistan, it has been found to be the most prevalent trypanosome species in donkeys. It is now established to infect other mammals, including humans.
Surra is a disease of vertebrate animals. The disease is caused by protozoan trypanosomes, specifically Trypanosoma evansi, of several species which infect the blood of the vertebrate host, causing fever, weakness, and lethargy which lead to weight loss and anemia. In some animals the disease is fatal unless treated.
Major-General Sir David Bruce was a Scottish pathologist and microbiologist who made some of the key contributions in tropical medicine. In 1887, he discovered a bacterium, now called Brucella, that caused what was known as Malta fever. In 1894, he discovered a protozoan parasite, named Trypanosoma brucei, as the causative pathogen of nagana.
Trypanosoma suis is a species of excavate trypanosome in the genus Trypanosoma that causes one form of the surra disease in animals. It infects pigs. It does not infect humans.
Paratransgenesis is a technique that attempts to eliminate a pathogen from vector populations through transgenesis of a symbiont of the vector. The goal of this technique is to control vector-borne diseases. The first step is to identify proteins that prevent the vector species from transmitting the pathogen. The genes coding for these proteins are then introduced into the symbiont, so that they can be expressed in the vector. The final step in the strategy is to introduce these transgenic symbionts into vector populations in the wild. One use of this technique is to prevent mortality for humans from insect-borne diseases. Preventive methods and current controls against vector-borne diseases depend on insecticides, even though some mosquito breeds may be resistant to them. There are other ways to fully eliminate them. “Paratransgenesis focuses on utilizing genetically modified insect symbionts to express molecules within the vector that are deleterious to pathogens they transmit.” The acidic bacteria Asaia symbionts are beneficial in the normal development of mosquito larvae; however, it is unknown what Asais symbionts do to adult mosquitoes.
Trypanosoma congolense is a species of trypanosomes and is the major pathogen responsible for the disease nagana in cattle and other animals including sheep, pigs, goats, horses and camels, dogs, as well as laboratory mice. It is the most common cause of nagana in east Africa, but is also a major cause of nagana in west Africa. This parasite is spread by tsetse flies. In its mammalian host, Trypanosoma congolense only lives in blood vessels, and causes in particular anaemia.
A Trypanosomiasis vaccine is a vaccine against trypanosomiasis. No effective vaccine currently exists, but development of a vaccine is the subject of current research.
Wendy Gibson is Professor of Protozoology at University of Bristol, specialising in trypanosomes and molecular parasitology.
Trypanosoma vivax is a parasite species in the genus Trypanosoma. It causes the disease nagana, affecting cattle or wild mammals. It is mainly occurs in West Africa, although it has spread to South America.
Many species of flies of the two-winged type, Order Diptera, such as mosquitoes, horse-flies, blow-flies and warble-flies, cause direct parasitic disease to domestic animals, and transmit organisms that cause diseases. These infestations and infections cause distress to companion animals, and in livestock industry the financial costs of these diseases are high. These problems occur wherever domestic animals are reared. This article provides an overview of parasitic flies from a veterinary perspective, with emphasis on the disease-causing relationships between these flies and their host animals. The article is organized following the taxonomic hierarchy of these flies in the phylum Arthropoda, order Insecta. Families and genera of dipteran flies are emphasized rather than many individual species. Disease caused by the feeding activity of the flies is described here under parasitic disease. Disease caused by small pathogenic organisms that pass from the flies to domestic animals is described here under transmitted organisms; prominent examples are provided from the many species.
Glossina fuscipes is a riverine fly species in the genus Glossina, which are commonly known as tsetse flies. Typically found in sub-Saharan Africa but with a small Arabian range, G. fuscipes is a regional vector of African trypanosomiasis, commonly known as sleeping sickness, that causes significant rates of morbidity and mortality among humans and livestock. Consequently, the species is among several being targeted by researchers for population control as a method for controlling the disease.
A trypanotolerant organism is one which is relatively less affected by trypanosome infestation.
Glossina morsitans is a species of tsetse fly in the genus Glossina. It is one of the major vectors of Trypanosoma brucei rhodesiense in African savannas.
The Sleeping Sickness Commission was a medical project established by the British Royal Society to investigate the outbreak of African sleeping sickness or African trypanosomiasis in Africa at the turn of the 20th century. The outbreak of the disease started in 1900 in Uganda, which was at the time a protectorate of the British Empire. The initial team in 1902 consisted of Aldo Castellani and George Carmichael Low, both from the London School of Hygiene and Tropical Medicine, and Cuthbert Christy, a medical officer on duty in Bombay, India. From 1903, David Bruce of the Royal Army Medical Corps and David Nunes Nabarro of the University College Hospital took over the leadership. The commission established that species of blood protozoan called Trypanosoma brucei, named after Bruce, was the causative parasite of sleeping sickness.
