Evaluating a Reduction in Treatment Duration of Ivermectin Diet for Fur Mite (Radfordia affinis) Eradication in Mice.

Murine fur mites are commonly excluded in modern research animal programs, yet infestations continue to persist due to challenges in detection and control. Because all diagnostic methods and treatment options have limitations, programs must make many operational decisions when trying to eradicate these ectoparasites. The primary aim of this study was to assess various durations of treatment time with an ivermectin-compounded diet in eliminating Radfordia affinis in mice as determined by PCR testing and pelt examination. A shorter treatment duration would be highly advantageous as compared with the current regimen of 8 wk as it would minimize cost and time for animal management programs, impediments to research, and ivermectin drug effects on infested animals. Five experimental groups of R. affinis-positive mice received dietary ivermectin for 0, 2, 4, 6, or 8 wk. A fur mite-negative, naïve mouse was added to each group every 8 wk to perpetuate the infestation and amplify any remaining populations of fur mites. At 16 wk after the respective treatment end, PCR testing was performed for all treated groups in conjunction with the positive control group (no treatment). Visual examination of pelts for mites and eggs via direct microscopy was also performed at each time point. All treated mice were free of R. affinis at 16 wk after the end of treatment as confirmed by both PCR testing and pelt examination. These findings indicate that a dietary ivermectin treatment duration of as little as 2 wk is effective in eliminating R. affinis, making successful eradication initiatives more achievable.