# Detection and phylogenetic analysis of Streptobacillus moniliformis, the causative agent of rat-bite fever and Haverhill fever, in free-living greater bandicoot rats in Northeastern India

## TL;DR

This study found evidence of a bacteria that causes rat-bite fever in wild rats in India, showing it could spread to humans.

## Contribution

First molecular detection of Streptobacillus moniliformis in bandicoots in India.

## Key findings

- S. moniliformis was detected in 3.3% of B. indica fecal samples.
- The isolate was genetically similar to global S. moniliformis and S. notomytis strains.
- The isolate clustered with human and rodent-derived strains, suggesting zoonotic transmission.

## Abstract

Streptobacillus moniliformis is the causative agent of zoonotic diseases such as rat-bite fever (RBF) and Haverhill fever (HF). While human infections are well-documented, limited studies have explored its presence in rodents in India. This study aimed to detect S. moniliformis in free-living bandicoots (Bandicota bengalensis and Bandicota indica) in Northeastern India and perform a phylogenetic analysis to assess its genetic relationship with global isolates.

A total of 106 bandicoots (B. bengalensis, n = 76; B. indica, n = 30) were captured from various environments in Meghalaya, India. Fecal and tissue samples were collected and subjected to DNA extraction. Molecular detection of S. moniliformis was conducted using species-specific polymerase chain reaction (PCR) targeting the 16S ribosomal RNA gene. Positive amplicons were sequenced, analyzed using Basic Local Alignment Search Tool, and subjected to phylogenetic analysis.

PCR-based detection revealed a fecal prevalence of 3.3% (1/30) in B. indica and 0% in B. bengalensis. No tissue samples tested positive for S. moniliformis. The detected isolate exhibited 100% sequence identity with previously reported S. moniliformis strains and 99.63% similarity to Streptobacillus notomytis. Phylogenetic analysis clustered the recovered isolate with human and rodent-derived S. moniliformis strains from multiple global regions, suggesting potential zoonotic transmission.

This study presents the first molecular detection of S. moniliformis in bandicoots from India, highlighting its zoonotic potential. Given its transmission risks through rodent bites and excreta contamination, public health surveillance is essential. Clinicians should consider RBF and HF in patients presenting with prolonged fever, particularly in rodent-endemic areas.