There is only one species of louse that infects pigs, the hog louse, or Haematopinus suis. This one of the largest louse species, so they are easy to observe. Lice and mites can be treated via the same method, so lice infestations are uncommon in herds treated for mange.
Haematopinus suis are blood-sucking lice of roughly 6 mm length, with black markings on a grayish brown body. They are strictly host specific. Females are prolific egg layers and can lay about 5 eggs a day for thirty days. Eggs take 12 to 20 days to hatch and nymphs fully develop into adults within 23 to 30 days. Lice are spread by direct contact with infested pigs, but can survive for 2 to 3 days away from the pig, so contaminated environments can be a concern.
Lice are commonly found in hidden areas, such as the inside or behind the ear and in folds on the neck. Infested pigs will often display pruritus, and anemia can be observed in the most severely affected animals.
Slight irritation of the skin near louse bites are the only observable lesions.
Differential diagnosis of pruritus should always include lice, as well as mange, dry skin, nutritional deficiency, and allergies. Diagnosis can be confirmed by identifying lice on the body or eggs on the proximal portion of the hair shafts.
Differential diagnosis includes mange, and insect bites.
Treatment, Prevention and Control
Due to the fact that all life stages of this parasite are on the pig, easy spray-on, dusts, or pour-on treatments are available. Because eggs may not be affected, treatment should be repeated 2-3 weeks later to kill any hatched lice. Administering insecticides on the bedding can also assist with control.
What is the most important reason to retreat pigs 2-3 weeks after original treatment?
- Eggs are not affected by treatment
- Re-infestation from other pigs
- Re-infestation from the environment