Host Species and Meteorological Influences on the Prevalence of Babesia microti (Aconoidasida: Piroplasmida) in Wild Rodents: Insights From a Meta-Analysis in Japan.

Rodents play a central role as reservoirs of zoonotic pathogens, yet the ecological and meteorological factors affecting pathogen prevalence remain unclear. In this study, a meta-analysis was used to evaluate the influence of host species and meteorological factors on the prevalence of Babesia microti in two common Japanese field mice, Apodemus speciosus and A. argenteus. The data were collected from seven published studies conducted across Japan. To examine the effects of total annual precipitation, average annual temperature, and host species, generalized linear mixed models were employed. The prevalence of the Hobetsu/Otsu-type B. microti was significantly higher in A. speciosus than in A. argenteus, indicating possible differences in reservoir competence and vector preference by Ixodes ovatus, which mainly infests terrestrial rodents. Conversely, the prevalence of the Kobe-type B. microti showed no significant differences between host species; however, it was negatively correlated with increasing precipitation. These findings suggest that meteorological factors may reflect a behavioral mismatch between the tick vectors, Haemaphysalis longicornis and Ixodes nipponensis, and their Apodemus hosts. One possible explanation for these results is that the vectors for Kobe-type B. microti, such as H. longicornis and I. nipponensis, primarily quest on vegetation, and the frequency of host-vector contact decreases when rodents remain in their burrows during heavy rain. This study provides the first quantitative evidence of host-environment interactions impacting rodent-borne babesiosis in Japan. It underscores the importance of considering meteorological and ecological perspectives when forecasting tick-borne disease risks in the context of climate change.