Domestic pigs are infested with only one species of louse, Haematopinus suis, the hog louse. This very large (5–6 mm) sucking louse is common on domestic swine worldwide. Swine pediculosis is more common in smaller or backyard populations than in large, commercial operations. Nymphal lice are normally found on the inside of the ears (often in the ear canal), on the skin behind the ears, in the folds of the neck, and on the medial aspects of the legs. In severe infestations, H suis may be found elsewhere on the body.
H suis can cause severe anemia, especially in piglets, because of the amount of blood imbibed by this large louse species. Extreme pruritus and subsequent self-trauma (alopecia, erythema, excoriations, and crusting) can be seen as hogs alleviate the irritation associated with the lice feeding.
H suis is a vector of swine pox virus, and it has also been implicated as a vector of Eperythrozoon suis and E parvum, the causative agents of swine eperythrozoonosis and of African swine fever virus in regions where these agents are endemic. Except for swine pox virus, transmission of these agents by H suis is considered rare.
A variety of compounds effectively control lice on swine, including synergized pyrethrins; pyrethroids; the organophosphates phosmet, coumaphos, and tetrachlorvinphos; and the macrocyclic lactones ivermectin and doramectin.
Amitraz is no longer available for use on swine in the USA. Although eprinomectin is used in cattle, this compound should not be used in unapproved animal species, because severe adverse reactions, including fatalities, may result.
For severe infestations in swine, dust formulations can be used to treat bedding. Husbandry and underlying health issues should be addressed.