Abstract

Background: Several species of amphibians in agricultural areas are often infected with ranaviruses; however, the biological or ecological factors that cause this infection are not well understood. In this study, we investigated whether local tadpole density, Gosner de velopmental stage, and weather conditions affected ranavirus infection in Dryophytes ja ponicus tadpoles in rice paddies over three months. Results: During the study, eight samplings were undertaken between June 6 and August 21, 2022. No die-off of tadpoles occurred, but 20 of 110 tadpoles (18.8%) were found to be infected with ranavirus. The tadpole density at the sampling site and Gosner stage of the sampled tadpoles were not related to the daily ranavirus infection rate. The mean daily highest temperature during the two weeks prior to the sampling date and the mean daily lowest and highest temperatures during the week prior to the sampling date were nega tively related to the daily infection rate. Conclusions: Our results suggest that low and extreme temperatures caused by flood ing and draining of paddy fields or climate change in summer could be a significant risk factor for ranavirus infection in summer-breeding frogs in agricultural areas.