How Black Rats and Land Use Are Driving Hantavirus Risk in Madagascar

A new international study has revealed that black rats (Rattus rattus) are the sole carriers of hantavirus in rural Madagascar. These invasive rodents, which arrived from Asia between the 10th and 14th centuries, are not the only factor behind the virus’s spread — human activities like farming and deforestation are also significantly increasing the risk. The research, conducted near Marojejy National Park by scientists from UC Santa Barbara, Duke University, and University of Réunion, underscores the complex link between wildlife, land use, and emerging diseases.

Key Findings of the Study

• Black rats are the only animals found to carry hantavirus in the study area.
• Nearly 2,000 animals (rats, bats, etc.) were tested; only black rats tested positive.
• Bigger and older rats had a higher infection rate.
• Infected rats were primarily found in farming fields, not inside homes or rainforests.
• No infected rats were found in the rainforest, indicating a strong link to human-modified environments.
• The risk of infection is higher during outdoor agricultural work than while being indoors.
• The spread of hantavirus is tied not just to the presence of rats, but also to land use changes, like deforestation and agriculture.

Role of Human Land Use

• Farming and clearing forests increase rat activity and virus transmission.
• Human activity changes ecosystems, making them more favorable for disease spread.
• Proximity to farmlands raises human exposure to infected rats.
• The study emphasizes the eco-health connection between humans, animals, and the environment.

About the Research Project

• Published in: Ecology and Evolution

Institutions involved,

• UC Santa Barbara
• University of Réunion
• Duke University
• Location: Communities near Marojejy National Park, northeastern Madagascar
• Supported by: National Institutes of Health (NIH)
• Long-term goal: Understand how zoonotic viruses like hantavirus spread and how human activity affects this process.