Merck Manual

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Professional Version

Lice in Pigs

By

Jennifer K. Ketzis

, PhD, Ross University School of Veterinary Medicine

Reviewed/Revised May 2023 | Modified Jun 2023

In swine, lice infestation can result in failure to gain weight and self-trauma due to itching. Treatment of entire herds and facilities have generally eliminated the problem in commercial operations. Individual animals can be successfully treated with various products applied topically, along with treatment of their housing.

Domestic pigs are infested with only one species of louse, Haematopinus suis, the hog louse. This very large sucking louse (5–6 mm) 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.

Pathogenesis and Disease Transmission of Lice in Pigs

The large louse H suis can cause severe anemia, especially in piglets, because of the amount of blood it imbibes. Extreme pruritus and subsequent self-trauma (alopecia, erythema, excoriations, and crusting) occur as hogs alleviate the irritation associated with the lice feeding.

Treatment of Lice in Pigs

  • Herd lice eradication programs

  • Prevention of introduction to a herd

Various compounds effectively control lice on swine, including synergized pyrethrins; pyrethroids; the organophosphates phosmet, coumaphos, and tetrachlorvinphos; and the macrocyclic lactones ivermectin, doramectin, and moxidectin.

Amitraz is no longer available for use on swine in the US. 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 problems should be addressed.

Lice can be eliminated from a production facility by combinations of dusts and injectable macrocyclic lactones and treatment of the environment. Elimination programs are similar to those for Sarcoptes(see Mite Infestations Mite Infestations in Animals Tightly adhered keratinous crusts along the ear margin in a case of sarcoptic mange. Sarcoptes scabiei is a common mange mite in pigs and dogs, and Notoedres cati (figure)is common... read more Mite Infestations in Animals ), employing avermectin. All animals and bedding on a premise should be treated.

To prevent the introduction of lice into a herd, new animals should be quarantined and treated at least twice before integration into the herd.

Key Points

  • Haematopinus suis can infest all ages of pigs and result in heavy production losses.

  • Preventing the introduction of lice to a facility should be the focus of control.

  • In the case of infestation, eradication using a combination of animal and facility treatments is possible.

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