Detection and molecular identification of scrub typhus vectors and pathogens from rice field rats, a traditional food item of Mizo tribes in Mizoram, Northeast India.

Abstract

Background & objectives: Orientia tsutsugamushi, a bacterial pathogen of scrub typhus, is transmitted to humans through the bite of infected chigger mites, and rodents are the natural hosts of the disease vector. The traditional practices of the tribal ethnic groups (Mizo) of Mizoram state such as capturing and consumption of rat meat collected from the agricultural fields could be one source of vector-disease transmission route. The present study aimed to detect and identify the pathogen of scrub typhus from vectors collected from rice field rats which were captured by farmers for meat consumption purposes.

Methods: One hundred and fifty-six freshly captured rice field rats were examined for ectoparasites. Detection and genotyping of O. tsutsugamushi from ectoparasites were done by real-time PCR and conventional PCR using species-specific primers. Rodents and ectoparasites were identified down to the species level using morphological and molecular techniques.

Results: Rice field rats were identified as Rattus tanezumi and Rattus nitidus. A total of 7973 trombiculid mites collected from 156 rats were identified as Leptotrombidium deliense, Leptotrombidium fletcheri, and Leptotrombidium chiangraiensis. Of these, 26 pools of L. deliense and 15 pools of L. fletcheri tested positive for O. tsutsugamushi, and the O. tsutsugamushi detected belongs to Kato and Karp-related genotypes.

Interpretation & conclusion: The present study reported the presence of O. tsutsugamushi-infected chigger mites in the captured rats (R. tanezumi and R. nitidus). Direct contact with the rats as a result of rat-eating habits may correspond to the high incidence rate of scrub typhus cases in Mizoram. Preventive measures are crucial for the control of scrub typhus disease in Mizoram.