noun, plural: ectoparasites
Parasitism is s form of symbiosis in which one organism (called parasite) benefits at the expense of another organism usually of different species (called host). This host-parasite association may eventuate to the injury of the host. Parasites may be grouped into ectoparasites and endoparasites. Parasites that live outside the host are called ectoparasites whereas those that live inside the host are called endoparasites. In this regard, the presence of ectoparasites on the host is called infestation rather than infection. The host infested with ectoparasites is not harmed as detrimentally as the other hosts infected with endoparasites. Nevertheless, some of these ectoparasites are vectors of pathogens. For instance, female Aedes mosquito is an ectoparasite of humans and may transmit dengue virus as it feeds on its host.
In humans, ectoparasites are comprised of two major animal groups: parasitic arachnids and parasitic insects. Parasitic arachnids include ticks and mites. As for the ectoparasitic insects, they are exemplified by mosquitoes, tsetse flies, fleas, and lice. In other animals, such as fish and crocodilians, they may be ectoparasitized by leechs. Some of these leeches, e.g. Piscicola geometria - a fish leech species, may transmit spring viraemia carp virus to a carp host.
Word origin: Latin parasitus from Greek parasitos (person who eats at the table of another).