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Vector (epidemiology)
In epidemiology, a disease vector is any living agent that carries and transmits an infectious pathogen to another living organism; agents regarded as vectors are organisms, such as parasites or microbes. The first major discovery of a disease vector came from Ronald Ross in 1897, who discovered the malaria pathogen when he dissected a mosquito. Arthropods Arthropods form a major group of pathogen vectors with mosquitoes, flies, sand flies, lice, fleas, ticks, and mites transmitting a huge number of pathogens. Many such vectors are haematophagous, which feed on blood at some or all stages of their lives. When the insects feed on blood, the pathogen enters the blood stream of the host. This can happen in different ways. The '' Anopheles'' mosquito, a vector for malaria, filariasis, and various arthropod-borne-viruses ( arboviruses), inserts its delicate mouthpart under the skin and feeds on its host's blood. The parasites the mosquito carries are usually located in its sal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anopheles Stephensi
''Anopheles stephensi'' is a primary mosquito vector of malaria in urban India and is included in the same subgenus as '' Anopheles gambiae'', the primary malaria vector in Africa. ''A. gambiae'' consists of a complex of morphologically identical species of mosquitoes, along with all other major malaria vectors; however, ''A. stephensi'' has not yet been included in any of these complexes. Nevertheless, two races of ''A. stephensi'' exist based on differences in egg dimensions and the number of ridges on the eggs; ''A. s. stephensi'' ''sensu stricto'', the type form, is a competent malaria vector that takes place in urban areas, and ''A. s. mysorensis'', the variety form, exists in rural areas and exhibits considerable zoophilic behaviour, making it a poor malaria vector. However, ''A. s. mysorensis'' is a detrimental vector in Iran.Sinka, M.E., Bangs, M.J., Manguin, S., Chareonviriyaphap, T., Patil, A.P., Temperley, W.H., Gething, P. W., Elyazar, I.R.F., Kabaria, C.W., Harbach, R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tick
Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. The timing of the origin of ticks is uncertain, though the oldest known tick fossils are from the Cretaceous period, around 100 million years old. Ticks are widely distributed around the world, especially in warm, humid climates. Ticks belong to two major families, the Ixodidae or hard ticks, and the Argasidae, or soft ticks. '' Nuttalliella,'' a genus of tick from southern Africa is the only member of the family Nuttalliellidae, and represents the most primitive living lineage of ticks. Adults have ovoid/pear-shaped bodies (idiosomas) which become engorged with blood when they feed, and eight legs. Their cephalothorax and abdomen are completely fused. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onchocerca
Onchocerca is a genus of parasitic roundworm. It contains one human parasite – ''Onchocerca volvulus'' – which is responsible for the neglected disease Onchocerciasis, also known as "river blindness" because the infected humans tend to live near rivers where host black flies live. Over 40 million people are infected in Africa, Central America, and South America. , Indiana State University. Accessed 14 February 2008. Other species affect cattle, horses, etc. List of species *'' Onchocerca armillata'' *''[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leishmania
''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus ''Lutzomyia'' in the New World. At least 93 sandfly species are proven or probable vectors worldwide.WHO (2010) Annual report. Geneva Their primary hosts are vertebrates; ''Leishmania'' commonly infects hyraxes, canids, rodents, and humans. History Members of an ancient genus of the ''Leishmania'' parasite, '' Paleoleishmania'', have been detected in fossilized sand flies dating back to the early Cretaceous period. The first written reference to the conspicuous symptoms of cutaneous leishmaniasis surfaced in the Paleotropics within oriental texts dating back to the 7th century BC (allegedly transcribed from sources several hundred years older, between 1500 and 2000 BC). Due to its broad and persistent prevalence throughout antiquity as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onchocerciasis
Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm ''Onchocerca volvulus''. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindness due to infection, after trachoma. The parasite worm is spread by the bites of a black fly of the ''Simulium'' type. Usually, many bites are required before infection occurs. These flies live near rivers, hence the common name of the disease. Once inside a person, the worms create larvae that make their way out to the skin, where they can infect the next black fly that bites the person. There are a number of ways to make the diagnosis, including: placing a biopsy of the skin in normal saline and watching for the larva to come out; looking in the eye for larvae; and looking within the bumps under the skin for adult worms. A vaccine against the disease does not exist. Prevention is by avoiding being bitten by flies. This may include t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leishmaniasis
Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus '' Leishmania''. It is generally spread through the bite of phlebotomine sandflies, ''Phlebotomus'' and ''Lutzomyia'', and occurs most frequently in the tropics and sub-tropics of Africa, Asia, the Americas, and southern Europe. The disease can present in three main ways: cutaneous, mucocutaneous, or visceral. The cutaneous form presents with skin ulcers, while the mucocutaneous form presents with ulcers of the skin, mouth, and nose. The visceral form starts with skin ulcers and later presents with fever, low red blood cell count, and enlarged spleen and liver. Infections in humans are caused by more than 20 species of ''Leishmania''. Risk factors include poverty, malnutrition, deforestation, and urbanization. All three types can be diagnosed by seeing the parasites under microscopy. Additionally, visceral disease can be diagnosed by blood tests. Leishmaniasis can be par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Fly
A black fly or blackfly (sometimes called a buffalo gnat, turkey gnat, or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. It is related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. Over 2,200 species of black flies have been formally named, of which 15 are extinct. They are divided into two subfamilies: Parasimuliinae contains only one genus and four species; Simuliinae contains all the rest. Over 1,800 of the species belong to the genus '' Simulium''. Most black flies gain nourishment by feeding on the blood of mammals, including humans, although the males feed mainly on nectar. They are usually small, black or gray, with short legs, and antennae. They are a common nuisance for humans, and many U.S. states have programs to suppress the black fly population. They spread several diseases, including river blindness in Africa (''Simulium damnosum'' and ''S. neavei'') and the Americas (''S. callidum'' and ''S. metallicum'' in Cen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phlebotominae
The Phlebotominae are a subfamily of the family Psychodidae. In several countries, their common name is sandfly; but that name is also applied to other flies. The Phlebotominae include many genera of blood-feeding (hematophagous) flies, including the primary vectors of leishmaniasis, bartonellosis and pappataci fever. In the New World, leishmaniasis is spread by sand flies in the genus ''Lutzomyia'', which commonly live in caves, where their main hosts are bats. In the Old World, sand flies in the genus ''Phlebotomus'' spread leishmaniasis. Phlebotomine females, and only females, suck blood from various mammals, reptiles and birds. Some species are selective, whereas others bite any suitable host they find. Some species can produce one clutch of eggs before their first blood meal; such females are said to practise autogenous or partly autogenous reproduction. Other species need a blood meal before they can produce any eggs at all; they are said to practise anautogenous repro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salivary Gland
The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed). In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions, the main protein secreted is mucin, which acts as a lubricant. In humans, 1200 to 1500 ml of saliva are produced every day. The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine is the active neurotransmitter and binds to muscarinic receptors in the glands, leading to increased salivation. The fourth pair of salivary glands, the tubarial glands discovered in 2020, are named for their location, being positioned in front and over the torus tubarius. However, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arbovirus
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more specifically describe viruses transmitted by ticks, a superorder within the arthropods. Arboviruses can affect both animals (including humans) and plants. In humans, symptoms of arbovirus infection generally occur 3–15 days after exposure to the virus and last three or four days. The most common clinical features of infection are fever, headache, and malaise, but encephalitis and viral hemorrhagic fever may also occur. Signs and symptoms The incubation period – the time between when infection occurs and when symptoms appear – varies from virus to virus, but is usually limited between 2 and 15 days for arboviruses. The majority of infections, however, are asymptomatic. Among cases in which symptoms do appear, symptoms tend to be non-spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filariasis
Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. These are spread by blood-feeding insects such as black flies and mosquitoes. They belong to the group of diseases called helminthiases. These parasites exist in the wild in subtropical parts of southern Asia, Africa, the South Pacific, and parts of South America. One does not acquire them in temperate areas like Europe or the United States. Eight known filarial worms have humans as a definitive host. These are divided into three groups according to the part of the body they affect: * Lymphatic filariasis is caused by the worms ''Wuchereria bancrofti'', ''Brugia malayi'', and ''Brugia timori''. These worms occupy the lymphatic system, including the lymph nodes; in chronic cases, these worms lead to the syndrome of ''elephantiasis''. * Subcutaneous filariasis is caused by '' Loa loa'' (the eye worm), '' Mansonella streptocerca'', and ''Onchocerca volvulus''. These worms occupy th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anopheles
''Anopheles'' () is a genus of mosquito first described and named by J. W. Meigen in 1818. About 460 species are recognised; while over 100 can transmit human malaria, only 30–40 commonly transmit parasites of the genus ''Plasmodium'', which cause malaria in humans in endemic areas. ''Anopheles gambiae'' is one of the best known, because of its predominant role in the transmission of the most dangerous malaria parasite species (to humans) – ''Plasmodium falciparum''. The name comes from the Ancient Greek word 'useless', derived from , 'not', 'un-' and 'profit'. Mosquitoes in other genera ('' Aedes'', '' Culex'', '' Culiseta'', '' Haemagogus'', and '' Ochlerotatus'') can also serve as vectors of disease agents, but not human malaria. Evolution The ancestors of ''Drosophila'' and the mosquitoes diverged . The culicine and ''Anopheles'' clades of mosquitoes diverged between and . The Old and New World ''Anopheles'' species subsequently diverged between and . '' Anoph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
