![]() ![]() This form of ecologically positioned agent is referred to as a ‘paratenic host.’ The act of passive transport and transmission by a paratenic host is referred to as ‘phoresis.’įor example, consider pine wilt disease, a serious disease affecting black and red pine trees. For instance, insectivorous rodents may acquire a nematode parasite that positions itself for the targeted end host: Cats which catch and consume the parasite-carrying rodents. Some vectors, known as paratenic hosts, are simply passive vehicles for their invisible infectious cargo.Īt times, the agent is positioned in space and time to merely facilitate ease of transport or transmission of the pathogen. More than 200 million people are infected with this disease each year, with over 700,000 dying yearly. falciparum and four closely related species of protozoal parasites transmitted by Anopheles cause malaria. falciparum multiplies and develops in the mosquito’s salivary glands, and is transmitted to hosts when the mosquito feeds. Anopheles frequently serves as a host for the protozoan pathogen, Plasmodium falciparum. Biologic vectors not only transmit such organisms, but serve as hosts during reproductive phases.Īn agent in or on which pathogen development occurs is a ‘biologic vector.’ A classic example of a biologic vector is the Anopheles genus of mosquitos, particularly Anopheles gambiae. The fungus is mechanically transmitted by the elm bark beetle (chiefly Hylurgopinus rufipes, but other species fall under the umbrella of the common name). If the vector merely serves as a passive agent of transport, and no development of the pathogen occurs on the agent, the vector is referred to as a ‘mechanical vector.’ For example, Dutch elm disease, an oftentimes lethal fungal disease of elm trees. However, many common diseases are transported actively through agents, which are referred to as ‘vectors.’ The formal definition of a vector is, “an organism or agent that transmits a pathogen.” (Image source: Pixabay, licensed via Pixabay license.) Mechanical vectors transmit disease-causing organisms, but don’t aid in their development. It is not known why in some cases the foetus escapes and in others it gets infected.Many pathogenic diseases-diseases caused by viruses, bacteria, spores, or other organisms-are initiated through ‘passive transmission.’ That is, the infective unit finds its way to a host via wind, water, and other passive means. Some diseases have been known to be carried tran placentally from infected mother to foetus in uterus e.g., syphilis, rubella, measles, toxoplasmosis. ![]() filarial parasite in culex mosquito and guinea worm embryo in Cyclops. The parasite undergoes a cycle of development without multiplication e.g. malaria parasite in mosquito, but increase its progeny, (iii) Cycle development. The disease agent multiplies and increases in the insect vector e.g plague bacilli in rat fleas, (ii) Cyclo propagative the parasite undergoes a cycle of development in the body of insect host with multiplication e.g. This may be of three types (i) Propagative. diarrhea, dysentery and typhoid fever by the housefly, and (b) Biological Transmission. ![]() The disease agent is carried mechanically on the legs or body of the insect, e.g. Vectors transmit disease in two ways (a) Mechanical Transmission. Given below is a list of the diseases that are caused by infected food and drinks: –Īccording to Park, Vectors are arthropods or other invertebrate hosts, which transmit infection by inoculation into the skin or mucosa by biting or by deposit of infective material on the skin or on food or other objects. Sometimes dust particles also discharge this function. Generally it is the fly that makes the drinks infected. At one hand it sits on the sputum of a patient and on the other hand it sits on the food. Cholera, typhoid fever and viral hepatitis are outstanding examples of diseases transmitted by vehicle transmission.įly is the strongest carrier of the infection. According to Park vehicle transmission implies transmission of the disease agent through the agency of water, ice, milk, food, serum, plasma or other biological products, of these, water is most important vehicle of transmission in many areas of the world because it is used by every one. ![]()
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