Autoinfective

Autoinfective is an adjective used in biology and medicine to describe organisms or life-cycle stages that can initiate infection within the same host without exposure to an external infectious source. In parasitology, autoinfective forms enable a parasite to complete its development and reinfect the host internally, allowing prolonged or lifelong infection with little or no environmental transmission.

A well-known example involves the parasitic nematode Strongyloides stercoralis. The parasite can produce autoinfective third-stage larvae that develop within the host. These autoinfective larvae can penetrate the intestinal mucosa or perianal skin and migrate to other tissues, effectively reinfecting the host without leaving the body. This internal cycle supports chronic infection that may persist for years or decades, particularly in the absence of treatment.

Clinical significance arises because autoinfection can be amplified in immunocompromised individuals. Hyperinfection syndrome, characterized by an increased larval burden and widespread dissemination, carries substantial morbidity and mortality. Diagnosis may require multiple stool examinations to detect larvae, serologic tests, or molecular methods, as chronic infections can be difficult to detect with a single test. Treatment typically involves antiparasitic medication such as ivermectin, with longer or combination therapy in severe cases, alongside management of the underlying immune status.

Beyond helminths, the term is occasionally used to describe pathogens or life stages capable of self-inoculation, though it is most closely associated with parasitology. In virology and bacteriology, autoinfective usage is far less common and context-specific. Overall, autoinfective describes self-sustaining infection within a single host without external exposure.