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Transovarial Transmission
Transovarial or transovarian transmission (transmission from parent to offspring via the ovaries) occurs in certain arthropod vectors as they transmit pathogens from parent to offspring. This process, used by a wide variety of parasites, is also known as vertical transmission. For example, '' Rickettsia rickettsii'', carried within ticks, is passed on from parent to offspring tick by transovarial transmission. This is in contrast to parasites such as '' Rickettsia prowazekii,'' which are not passed on by transovarian transmission due to killing the vector that carries it (in this case, the human louse). Other examples of parasites that use this mechanism of transmission include the aedes mosquito vector of the yellow fever virus and in phlebotomine sandflies that transmit pappataci fever. Richard Dawkins in "The Extended Phenotype" notes that "bacterial endosymbionts of insects which are transmitted transovarially" share an interest in the "success of their host's gametes.....as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings. They are an extremely diverse group, with up to 10 million species. The haemocoel, an arthropod's internal cavity, through which its haemolymph – analogue of blood – circulates, accommodates its interior organs; it has an open circulatory system. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
Pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ''pathogen'' came into use in the 1880s. Typically, the term ''pathogen'' is used to describe an ''infectious'' microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them. There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rickettsia Rickettsii
''Rickettsia rickettsii'' (abbreviated as ''R. rickettsii'') is a Gram-negative bacteria, gram-negative, intracellular, coccobacillus bacterium that is around 0.8 to 2.0 μm long. ''R. rickettsii'' is the causative agent of Rocky Mountain spotted fever. ''R. rickettsii'' is one of the most pathogenic ''Rickettsia'' strains. It affects a large majority of the Western Hemisphere and small portions of the Eastern Hemisphere. History Rocky Mountain spotted fever (RMSF) first emerged in the Idaho Valley in 1896. At that time, not much information was known about the disease; it was originally called Black Measles because patients had a characteristic spotted rash appearance throughout their body. The first clinical description of Rocky Mountain Spotted Fever was reported in 1899 by Edward E. Maxey. Howard Ricketts (1871–1910), an associate professor of pathology at the University of Chicago in 1902, was the first to identify and study ''R. rickettsii''. At this time, the trademark ... [...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 addit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rickettsia Prowazekii
''Rickettsia prowazekii'' is a species of gram-negative, alphaproteobacteria, obligate intracellular parasitic, aerobic bacillus bacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the main reservoir for ''R. prowazekii'' is the flying squirrel. ''R. prowazekii'' is often surrounded by a protein microcapsular layer and slime layer; the natural life cycle of the bacterium generally involves a vertebrate and an invertebrate host, usually an arthropod, typically the human body louse. A form of ''R. prowazekii'' that exists in the feces of arthropods remains stably infective for months. ''R. prowazekii'' also appears to be the closest free-living relative of mitochondria, based on genome sequencing. History Discovery Henrique da Rocha Lima, a Brazilian doctor, discovered this bacterium in 1916. He named it after his colleague Stanislaus von Prowazek, who had died from typhus in 1915. Both Prowazek and Rocha Lima had been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aedes
''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: '' Aedes albopictus'', a particularly invasive species, was spread to the New World, including the United States, in the 1980s, by the used-tire trade. First described and named by German entomologist Johann Wilhelm Meigen in 1818, the generic name comes from the Ancient Greek ἀηδής, ''aēdēs'', meaning "unpleasant" or "odious". The type species for ''Aedes'' is '' Aedes cinereus''.. Systematics and phylogeny The genus was named by Johann Wilhelm Meigen in 1818. The generic name comes from the Ancient Greek ἀηδής, ''aēdēs'', meaning "unpleasant" or "odious". As historically defined, the genus contains over 700 species (see the list of ''Aedes'' species). The genus has been divided into several subgenera (''Aedes'', '' Diceromyia'', '' Finlaya'', ''Stegomyia'', et ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yellow Fever
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. In about 15% of people, within a day of improving the fever comes back, abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk of bleeding and kidney problems is increased. The disease is caused by the yellow fever virus and is spread by the bite of an infected mosquito. It infects humans, other primates, and several types of mosquitoes. In cities, it is spread primarily by ''Aedes aegypti'', a type of mosquito found throughout the tropics and subtropics. The virus is an RNA virus of the genus '' Flavivirus''. The disease may be difficult to tell apart from other illnesses, especially in the early stages. To confirm a suspected case, blood-sample testing with polymerase chain reaction is required. ... [...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] |
Pappataci Fever
Pappataci fever (also known as Phlebotomus fever and, somewhat confusingly, sandfly fever and three-day fever) is a vector-borne febrile arboviral infection caused by three serotypes of Phlebovirus. It occurs in subtropical regions of the Eastern Hemisphere. The name, pappataci fever, comes from the Italian word for sandfly; it is the union of the words ''pappa'' (usually this is used as a generic name for food, but in this case it is a ''verb'' meaning "eating") and ''taci'' (silent), distinguishing these insects from blood-feeding mosquitoes, which produce a typical noise while flying. Signs and symptoms A few days after the infective bite, a feeling of lassitude, abdominal distress and chills develop followed by fever of , severe frontal headaches, muscle and joint aches, flushing of the face and a fast heart rate. After two days the fever begins to subside and the temperature returns to normal. Fatigue, a slow heart rate and low blood pressure may persist from a few day ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transstadial Transmission
Transstadial transmission occurs when a pathogen remains with the vector from one life stage ("stadium") to the next. For example, the bacteria '' Borrelia burgdorferi'', the causative agent for Lyme disease, infects the tick vector as a larva, and the infection is maintained when it molts to a nymph and later develops as an adult. This type of transmission is seen in other parasites like viruses or ''Rickettsia''. In addition to ticks, mites are another common vector. Some sources consider transstadial transmission a type of horizontal transmission, whereas other sources consider it vertical or partial vertical transmission. Transstadial blockage could be considered the opposite of transstadial transmission, where the parasite cannot be carried over from one life stage to the next. For example, viruses that undergo transstadial blockage will have decreased infectivity in molting In biology, moulting (British English), or molting (American English), also known as sloughing, she ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
