Seasonal occurrence of Rhipicephalus sanguineus in Okayama Prefecture, Japan and effect of temperature on development of the tick

The seasonal occurrence of Rhipicephalus sanguineus on dogs was examined at a kennel in Okayama Prefecture, Japan. The number of ticks suddenly decreased after treatment with an acaricide in late August. Small numbers of adults and nymphs were detected in September and October, then ticks were not seen on the dogs early in November, when the mean temperature was below 15 degrees C. Then 3 dogs were found to be infested by some adult ticks toward the end of March, when the mean temperature was above 11 degrees C. The effects of temperature on the oviposition and the development of the tick were examined under laboratory conditions. The larval and nymphal post parasitic period, the pre-oviposition period and the oviposition period were prolonged when the temperature was decreased from 37 to 23 degrees C. The oviposition period was extremely long at 14 degrees C, but the tick could not develop below 14 degrees C. No eggs hatched below 14 degrees C. The ability to attach and engorge of adult ticks was examined under cold conditions. Unengorged adult ticks could attach to rabbits on the ear which were kept in an outdoor kennel in October, November and March, however they could not engorge completely in November. They could not attach on rabbits from December to February. The longevity of the tick was also examined under low temperatures. Unengorged adults could attach and engorge on rabbits after kept at 12 degrees C with 50% relative humidity (RH) for 140 days or 12 degrees C with 50% RH for 40 days followed by 4 degrees C with 50% RH for 100 days. These findings suggest that R. sanguineus could be established in Okayama Prefecture under optimum condition.