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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 ''Aedes'' (also known as the tiger mosquito) is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', ... mosquito vector of the yellow fever virus and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. 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. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...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 such as a parasite or microbe, to another living organism. Agents regarded as vectors are mostly blood-sucking (Hematophagy, hematophagous) arthropods such as mosquitoes. The first major discovery of a disease vector came from Ronald Ross in 1897, who discovered the malaria pathogen when he dissected the stomach tissue of a mosquito. Arthropods Arthropods form a major group of pathogen vectors with mosquitoes, Fly, flies, Sandfly, 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 and ticks 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pathogen
In biology, a pathogen (, "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 theory of disease, 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 Transmission (medicine), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rickettsia Rickettsii
''Rickettsia rickettsii'' is a Gram-negative, intracellular, cocco-bacillus bacterium that was first discovered in 1902. Having a reduced genome, the bacterium harvests nutrients from its host cell to carry out respiration, making it an organo-heterotroph. Maintenance of its genome is carried out through vertical gene transfer where specialization of the bacterium allows it to shuttle host sugars directly into its TCA cycle. Other characteristics of the bacteria include membrane proteins that are useful in the identification of ''R. rickettsii'' strains and useful in targeting from antibiotics. A capsule encircling the bacterium allows for attachment to host cells and additionally acts as a defense mechanism for resisting phagocytosis. Varying strains of ''R. rickettsii'' have different genotypes and phenotypes that alter the pathogenicity, virulence, and the appearance of the bacteria. ''R. rickettsii'' is the causative agent of Rocky Mountain Spotted Fever and is transferre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tick
Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. 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 around 100 million years old, and come from the Cretaceous period. 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 cephalotho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rickettsia Prowazekii
''Rickettsia prowazekii'' is a species of gram-negative, obligate intracellular parasitic, aerobic bacilliform bacteria of class Alphaproteobacteria 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 semi-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 Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aedes
''Aedes'' (also known as the tiger mosquito) is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', a particularly invasive species, was spread to the Americas, including the United States, in the 1980s, by the used-tire trade. It was first described and named by German entomologist Johann Wilhelm Meigen in 1818; the generic name comes from Ancient Greek (), 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 , , meaning 'unpleasant' or 'odious'. As historically defined, the genus contains more than 950 species (see the list of ''Aedes'' species). The genus has been divided into several subgenera (''Aedes'', '' Diceromyia'', '' Finlaya'', ''Stegomyia'', etc.), most ... [...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. Sandflies are small; a body size of about 3 mm in length is typical for many species, which aids them in escaping notice. Their bite is not always felt, but leaves a small, round, reddish bump that starts itching hours or days later. Use of insect repellent is recommended in areas where sandflies are present. Diet and reproduction Phlebotomine sandflies have a diet that includes both blood and plant-derived sugar meals. Phlebotomine females, and only females, suck blood from various mammals, reptiles, and birds, while both sexes consume sugary substances including nectar, honeydew, and phloem sap from plants. Some species are selective about their hosts, ... [...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 days ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transstadial Transmission
Transstadial transmission is the persistence of a symbiont or pathogen in an organism from one life stage ("stadium") to the next, such as larva to nymph to adult. This type of transmission is typically observed in insects. For example, the bacterium ''Borrelia burgdorferi'', the causative agent for Lyme disease, infects the tick vector as a larva, with the infection maintained as the tick molts to a nymph and later develops as an adult. Transstadial transmission is also seen with other microbes such as other bacteria, fungi, and viruses in numerous insects. In addition to ticks, mites are another common vector. Transstadial transmission is especially relevant to public health, as several threats to public health are maintained in insect populations by transstadial transmission. Some debate exists regarding the classification of transstadial transmission as vertical transmission versus horizontal transmission. Reasons for this stem from further debate regarding transovarial tra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
