Rats are arguably the most destructive invasive species on the planet, carrying pathogens that have been responsible some of the most devastating epidemics in human history. Through their close relationship with humans, rats have spread to every continent and can reach high numbers in densely populated urban areas, making them effective vectors for the spread of infectious disease. Hepatitis E virus (HEV) infections have been detected at a high frequency in humans from urban areas in the US, but the transmission pathways traditionally thought to be responsible for HEV spread (oral-fecal transmission or swine-human contact) are not present. Invasive rats have been shown to have high HEV infection rates in the U.S. (>40%) and are competent hosts of human HEV. In the proposed work, invasive rats collected from across the US will be examined for HEV infection to determine the infection rate and the rate with which rats are spreading HEV.

This research has important public health implications. The mortality rate of HEV infection ranges from 1-4% in the general public, but is as high as 20% in pregnant women. In addition, HEV is the only hepatitis virus known to have animal reservoirs. Yet no study has examined invasive rats as reservoirs for spreading HEV to humans. This project will provide the first data concerning the spread of HEV by rats, providing valuable information to manage the spread of HEV infections. Additionally, several undergraduates, including Native American students, will assist in the research.

Project Report

The hepatitis E virus has a 1% mortality rate in the general public, with mortality reaching 25% in pregnant women in their third trimester. Nonetheless, the sources of hepatitis E virus infection in urban areas of the U.S. are poorly understood. There is evidence for widespread infection in domestic pigs, but the relative lack of human-pig contact in large cities suggests an additional reservoir of infection. In these same urban environments, invasive rats can be extremely common and are routinely encountered by humans. In addition, invasive rats are common in agriculture settings, therefore frequently coming into contact with domesticated animals known to carry the hepatitis E virus. We examined over 400 individual rats from the U.S. and several international locations for the presence of hepatitis E virus RNA. We detected the hepatitis E virus in approximately 8% (35 out of 446) of individuals from localities across the United States, from Alaska to Florida. Also, we deteted the same strain of virus in multiple rat species, suggesting the hepatitis E virus is capable of being spread among these species. This work is the first to identify widespread infection of invasive rats with a zoonotic genotype of the hepatitis E virus. Furthermore, our results indicate invasive rats, in conjunction with domesticated animals, may play a role in the spread of the hepatitis E virus in the United States and warrant further study.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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George W. Gilchrist
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Oklahoma State University
United States
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