The parasitic ecology of the rodent mite, Myobia musculi. III. Lesions in certain host strains.

Mice (C57BL/6N) from a commercial production colony with ulcerative skin lesions were shown to have low level infestations with Myobia musculi. Lesions were abolished by exposure to dichlorvos-impregnated plastic strips. Experimental reinfestation with M musculi resulted in prompt exacerbation of lesions in previously healed mice. Exacerbated lesions were again abolished by subsequent dichlorvos treatments. The histopathology of such lesions was shown to be similar to those in cats allergic to Otodectes cynotis; and a morphologic basis for an allergic interpretation of the myobic lesions in the C57BL/6 mice was described. Other evidence supporting an allergic interpretation included the heritability of susceptibility to such lesions in certain strains, the paucity of mites required for extensive lesions, the chronic duration of infestation required prior to lesion development, and the apparent anamnesis to experimental reinfestation. A large commercial hybrid production colony requiring C57BL/6 females had an incidence of ulcerative lesions (in females) of 20% and depressed reproductive indices. Two 48 hour treatments at an interval of 14 days utilizing dichlorvos-impregnated strips (1 square inch per cage) abolished lesions and elevated production indices for a period of 5 months.