Cross-fostering in combination with ivermectin therapy: a method to eradicate murine fur mites.

A colony of mutant mice with sickle cell anemia was infested with the fur mites Myocoptes musculinus and Myobia musculi. Pups of sickle-cell phenotype obtained by cesarean section prior to natural birth were of such poor vigor that none survived the combined insults of delivery by hysterectomy and cross-fostering. Consequently, surgical rederivation, the most reliable means of mite eradication, was not an option. Because furless mice are not susceptible to mite infestation and because neonates putatively remain free of mites until 4 to 5 days after birth, pups born by natural delivery were cross-fostered within 0 to 36 h to outbred lactating females treated once with ivermectin (2 mg/kg topically) at the time of transfer and housed in filter-top cages. Cross-fostering in conjunction with topical ivermectin administered to weaned mice one or more times at approximate 9-day intervals beginning on the day of weaning was successful in reliably eradicating mites. In addition, the 58% postnatal survivability of pups cross-fostered to dams given ivermectin was equivalent to that of natural-born pups that were reared by their untreated biological mothers.