Urban Rats as Vectors of Deadly Bacteria During Migration, New Research Reveals

A comprehensive six-year study conducted by researchers from Tufts University and collaborating institutions highlights the role of migrating urban rats in spreading dangerous bacteria, notably Leptospira spp., within city environments. The research focused on Boston and uncovered crucial insights into how rat populations move and transmit these pathogens. Leptospirosis, caused by bacteria present in rat urine, contaminates soil and water sources, posing a significant health risk to humans, dogs, and other animals. Although prevalent worldwide, the disease is particularly common in tropical climates, but changing global temperatures suggest its potential expansion into colder regions.

In Boston, the persistence and movement of leptospira strains among rat populations were investigated by tracking and sampling rats across the city from 2016 to 2022. A key breakthrough was the development of a novel method to culture leptospira from frozen rat kidneys, overcoming longstanding challenges in studying this fastidious organism. The research employed advanced genetic analysis to determine the relationships between various bacterial strains and rat populations, revealing distinct genetic clusters within the city. These findings indicated that rat migration occurs over distances of about 600 meters, with major roads acting as barriers, while greenways serve as conduits for movement.

One of the significant aspects of the study was the genetic analysis of a human leptospirosis case, which matched strains found in local rats, providing strong evidence that rats are a primary source of infection in humans. Human infections often go unrecognized due to mild symptoms or lack of testing, but severe cases involving multiple organ failure are life-threatening. Populations at higher risk include homeless individuals and those engaged in outdoor activities with frequent rat contact.

Understanding rat migration patterns and how they influence pathogen spread is critical for developing effective control strategies. Rosenbaum emphasizes that complete eradication of rats is unrealistic, but targeted pest management informed by genetic data can mitigate public health risks. The study underscores the importance of ongoing surveillance and advanced molecular techniques in addressing urban zoonotic diseases.

This research, published in PLOS Neglected Tropical Diseases, advances the understanding of how urban rat populations contribute to the transmission of leptospirosis and highlights the need for integrated urban planning and public health efforts to reduce the disease burden.

Source: https://medicalxpress.com/news/2025-05-urban-rats-deadly-bacteria-migrate.html