Otodectes cynotis (Acari: Psoroptidae): examination of survival off-the-host under natural and laboratory conditions

The biological and environmental factors affecting survival off-the-host of Otodectes cynotis (Acari: Psoroptidae) ear mites were investigated under natural and laboratory conditions. From November 2000 to November 2002 mites were collected monthly from cats and divided into four groups according to sex and stage. In laboratory conditions, the mites were placed in an incubator with a steady 95% relative humidity (r.h.), a 10 degrees C. All the plates were examined by stereomicroscopy every 24 h until all the mites had died. The data were analysed statistically by multiple linear regression and survival analysis. At 10 degrees C, the maximum survival time of mites was between 15 and 17 days, while at 34 degrees C, it was between 5 and 6 days. The maximum survival time of adult females was significantly longer than that of other stages. No differences were observed in maximum survival times of mites that had been offered food and those that had not, or in the time (in days) to reach 50% mortality (LT50). When exposed to environmental conditions, the maximum survival time (12 days) was observed at temperatures ranging from 12.3 to 14.2 degrees C and r.h.s between 57.6 and 82.9%. Multiple regression analysis showed that temperature alone influenced the maximum survival time and LT50 of mites, and that the rate of survival declined linearly with increasing mean temperature. This basic understanding of off-host survival suggests that, places which have been inhabited by infected animals may need to be disinfected or remain vacated for at least 12 days before occupancy by clean cats or dogs.