A cross sectional study on molecular prevalence of Orientia tsutsugamushi in household rat population of South India.

This study aimed to assess the molecular prevalence of mite-borne zoonotic pathogen O. tsutsugamushi in household rats of South India through nested polymerase chain reaction amplification of O. tsutsugamushi 47-kDa htrA gene and to determine the most suitable sample type for screening of O. tsutsugamushi in rats. Out of 85 rats trapped in Tamil Nadu, Karnataka, and Puducherry regions, 47 rats were found positive for the O. tsutsugamushi genome with prevalence of 55.29 %. Among different sample types screened, faecal samples exhibited the highest positivity rate, followed by liver, spleen, kidney, and blood samples. Agreement between faecal and spleen samples of rats for the presence of O. tsutsugamushi was the highest. Principal component analysis revealed a positive correlation between the spleen, liver, and faeces and a negative correlation between blood and faeces for the presence of O. tsutsugamushi genome. These findings underscore the varied distribution of O. tsutsugamushi among different samples and indicate that the faecal and liver samples of rats are an ideal choice of samples for epidemiological studies. This is the first study to report a high level of presence of O. tsutsugamushi in faecal samples of rats.