Parasite Carrier State

the condition in which the causative agent of a disease is harbored within the host’s body without producing pronounced symptoms of the disease. The causative agent can be a virus, bacterium, worm, or protozoan. The term “parasite carrier state” is sometimes used in a more narrow sense to refer only to those conditions that are caused by animal parasites. In general, the condition can be viewed as a special case of symbiosis in which both parasite and host adapt to each other.

The duration of the parasite carrier state can be long, as in quartan malaria, or short, as in relapsing fever. Several types of carriers are distinguished. The casual carrier is asymptomatically infested with the parasite, usually an amoeba or Giardia lamblia. The incubatory carrier, found with such diseases as leprosy, is infested with the parasite but does not yet exhibit symptoms of the disease. Another type of incubatory carrier is the chronic carrier, who is infested with the causative agent of a disease that has a chronic course, for example, malaria; like other incubatory carriers, the chronic carrier does not manifest symptoms of the disease. The convalescent carrier has already had at least one clinical attack of the disease. (SeeCARRIER OF INFECTION.)