Infectious Diseases: Terminology

• Parasite:A parasite is an organism that lives in or on another organism and draws its nourishment from it (from the Greek "para-sitos": beside food). Strictly speaking, it has no connotation of harmfulness or otherwise. Usually, however, the meaning is taken in a narrower sense and the term is used to refer to various worms, protozoa and arthropods which have another organism as their habitat. Parasites often have a complicated life-cycle with well-defined hosts and a specific mode of transmission.

• Paratenic host: a host in which a parasite lives and survives, but does not develop further.

• Vector: an intermediate host, which transports a parasite from the previous host to the subsequent one. E.g.: the tsetse fly is the vector of African sleeping sickness.

• Arthropod: Invertebrate animal with articulated legs. In medical practice the main arthropods belong to the group of insects and arachnids (including ticks and mites). Copepods are also arthropods and are vectors for a number of organisms.

• Epidemic: infection which fairly suddenly affects a large number of people at the same time. E.g. the plague epidemics in the Middle Ages in Europe, the meningitis epidemics in the Sahel.

• Pandemic: epidemic which spreads around the whole world. E.g.: Flu (influenza), AIDS pandemic

• Endemic: a disease is endemic if it is chronically present in a particular region. E.g.: in Africa there are foci of endemic malaria.

• Transmission: Transport of an organism can occur in various ways.

Category: Microbiology Notes