Swine Ectoparasites: Hog Louse
Description and Biology
The hog louse is one of the largest members of the suborder Anoplura, a group of bloodsucking insects infesting swine (Figure 3). Restricted to the skin surface, hog lice take several bloodmeals each day. The louse is equipped with large claws to grasp the hair allowing these insects to move about the host. Each active life stage resembles the adult except that they are smaller in size. Gravid females glue their eggs to the base of the hair shaft (Figure 3). The eggs hatch into nymphs after incubating about 10 to 14 days. In cool weather hatching may be extended up to 20 days. Nymphs have the same feeding habits as adult lice. After undergoing 3 molts over a 10 to 14 days period, the nymph develops into an adult. Although growth and development is temperature dependent under optimal conditions the entire life cycle from egg to adult can be completed in about 3 weeks.
Hog lice tend to feed in clusters during their development. Infestations generally start around the ears before expanding to lower body regions. Predilection sites include the ears, neck, skin folds, and the inside surface of the legs. Hog lice spend their entire life cycle on the animal. Dislodged lice can survive for several days in warm bedding, but the primary method of transmission is direct contact with infested hogs. Hog lice are relatively rare in the US but in a recent examination of German swine farms, approximately 14% had hog louse infestations (Damriyasa et al. 2004).
Damriyasa, I.M., Failing, K., Volmer, R., Zahner, H. and Bauer, C., 2004. Prevalence, risk factors and economic importance of infestations with Sarcoptes scabiei and Haematopinus suis in sows of pig breeding farms in Hesse, Germany. Medical and Veterinary Entomology, 18, 361–367.