The efficacy and safety of chlorpyrifos (Dursban) for control of Myobia musculi infestation in mice.

Mite infestation in laboratory mice is a common, but troublesome problem in animal facilities. Recommended treatment regimens are frequently ineffective because of the short period of exposure to the control agent. In an effort to develop a time-release approach, we have investigated the use of Dursban granules applied in animal bedding. Initial toxicity studies indicated that this pesticide can be added to shoebox cage litter at levels three times that used for outdoor application (6 g per 27 by 48 cm shoebox cage) without producing clinical signs of toxicity. Metabolism studies demonstrated that although individual mice showed decreased brain acetylcholinesterase activity following treatment, liver cytosolic glutathione-S-transferase, liver microsomal aminopyrine N-demethylase, or aryl hydrocarbon hydroxylase were not induced after 1 week of exposure. Parasitological studies indicated elimination of mites and itching in an experimental infestation, as well as reduction of itching in severely symptomatic, naturally infested mice, following treatment with the granules. These studies demonstrate the nontoxic efficacy of Dursban in the control of Myobia musculi.