Rarest porcine ectoparasite for a pig

The pig species possessing the rarest porcine ectoparasite is the pygmy hog Porcula salvania, which is categorized as Critically Endangered by the IUCN but is the only known host of an ectoparasitic sucking louse called the pygmy hog-sucking louse Haematopinus oliveri, which is therefore also categorized as Critically Endangered by the IUCN. Only around 150 pygmy hog specimens still exist, so these are the only available hosts for their species-specific louse parasite.

The pygmy hog-sucking louse was not formally described and named by scientists until 1978 and has never been found parasitising any other host species. So if the pygmy hog should die out, so too would this species, thus emphasising how specific some animal associations can be, and how vulnerable they are as a direct result of their specificity.

Precise numbers of this louse species currently still existing are unknown, but as noted by the IUCN: "Its host used to be found in northern West Bengal and northwestern Assam in India, but is now restricted to a few localities in and around Manas National Park in northwestern Assam."