Efforts to save endangered species may, paradoxically, lead to conservation-induced extinction of other species – a phenomenon summarized by a recent study. It mostly threatens the parasite and pathogen species that are highly host-specific to critically endangered hosts. When the last individuals of a host species are captured for the purpose of captive breeding and reintroduction programs, they typically undergo anti-parasitic treatments to increase survival and reproductive success. This practice may unintentionally result in the extinction of the species antagonistic to the target species, such as certain parasites. It has been proposed that the parasites should be reintroduced to the endangered population. A few cases of conservation-induced extinction are known to have occurred in parasitic lice.
Parasite: Colpocephalum californici – host: California condor
The parasite most probably became extinct when the last individuals of its only host species were captured for a captive-breeding program.
Parasite: Rallicola (Aptericola) pilgrimi – host: little spotted kiwi
The parasite most probably became extinct when the last individuals of its only host species were captured and, after routine veterinary antiparasitic treatments, re-introduced into predator-free islands.
Parasite: Rallicola (Rallicola) guami – host: Guam rail
The only known host species of this parasite exists exclusively in captivity and kept under veterinary control. No information about the fate of the parasite, likely extinct.
Parasite: Linognathus petasmatus – host: scimitar-horned oryx
The host specificity of this parasite is uncertain. Either it was specific to the scimitar-horned oryx and became extinct during captive breeding of the host, or – alternatively – it may be specific to the addax and possibly still surviving in the wild.
“The Trichodectid lice of the black-footed ferret” has been mentioned in the literature several times as a parasite that became extinct during the captive breeding program of the host. However, this parasite most probably never existed as a separate species.
Parasite species that are specific to a single host species are endangered whenever the host is to be saved by captive breeding programs. A current example is the louse Felicola isidoroi, a louse parasitizing the Iberian lynx.
The Iberian lynx and its unique louse
