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"Rat Patrol": A Stable Hotspot of Dangerous Leptospirosis Found in Vietnam's Cities

Leptospirosis is one of the most common zoonotic infections in the tropics, claiming tens of thousands of lives every year. Yet, exactly which animals harbor the pathogen in nature and what the genetic structure of the causative agent looks like in Southern Vietnam has remained poorly understood.

Scientists from two Pasteur Institutes — in St. Petersburg and Ho Chi Minh City — conducted a large-scale, five-year study of synanthropic rodents and identified the main culprit: the brown rat. Its population stably circulates a highly virulent genovariant of Leptospira interrogans, ready to jump to humans at any moment.

Between 2016 and 2020, the team trapped 856 small mammals across three regions of Southern Vietnam. The overall infection rate was 7.8%, but among rats it reached 12.4%. Of the leptospires identified, the vast majority (77.6%) were L. interrogans, with the remaining 22.4% being L. borgpetersenii. This distinction matters, as L. interrogans is considered the most pathogenic for humans.

Unfortunately, the urban environment creates ideal conditions for the infection to persist — especially during the rainy season. Based on their findings, the researchers were able to formulate specific recommendations on how to reduce the risks and counter this threat.

It is worth noting that this is far from the first time Russian epidemiologists have assisted colleagues abroad — the Pasteur Research Institute has a great experience and a strong scientific tradition in this field.

The study was published in Microorganisms (IF = 4.2)

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