Density, location, and sampling of Sarcoptes scabiei (Acari: Sarcoptidae) on experimentally infested pigs

Forty-eight weaned pigs were inoculated with 0 (controls), 100 (low dose), and 1,000 (high dose) itch mites, Sarcoptes scabiei (De Geer), and allowed to develop infestations for up to 10 wk. Pigs were slaughtered in sequence during the experiment to sample hides and count mites through potassium hydroxide digestion. Incipient crusted lesions occurred in ears of 4 of 16 low-dose pigs and 7 of 16 high-dose pigs, averaged less than 3 cm2 in area, and contained 86% of all females and 87% of all other mite stages found on those pigs. Crusts aside, faces had the highest mite densities among six body regions in both infested groups. Overall, high-dose pigs had higher mite populations (269 compared with 39 mites on low-dose pigs), although values were not significantly different (P = 0.13). Mite populations did not grow significantly during the 10 wk, but variance increased among pigs in each dose group. A hide-sampling plan derived from these data indicates whole-body populations could be estimated by censusing only the crusts, if present. If absent, sampling mites from the face and dorsum should provide acceptable estimates of whole-body totals of females and other stages. A sample size of 13 hides from a herd will yield an estimate of mean whole-body total with a 90% CI less than or equal to 50% of the estimated mean.