Hepatitis E virus: Cross-species infection and zoonotic risk

Hepatitis E virus (HEV), the causative agent of hepatitis E, is an important human pathogen responsible for a major proportion of enterically transmitted cases of acute viral hepatitis in many developing countries. Among the known hepatitis viruses, the high mortality rate of up to 25% observed in pregnant women is unique to HEV. Recent studies have shown that a significant proportion of healthy individuals in the United States and many other industrialized countries are positive for HEV antibodies, although acute hepatitis E occurs only sporadically in these countries. Increasing data have indicated that hepatitis E is a zoonotic disease, and that there exist animal reservoirs for HEV. Animal strains of HEV, antigenically and genetically related to human HEV, have been isolated and characterized from pigs (swine HEV) and chickens (avian HEV). Human HEV, swine HEV, and avian HEV have all been shown to infect across species. In addition to pigs and chickens, antibodies to HEV have also been detected in a number of other animal species, including rodents, chickens, dogs, cats, sheep, goats, cattle, and non-human primates; suggesting that these animal species have been exposed to HEV or a related agent. However, thus far, pigs are the only recognized potential animal reservoirs for HEV. It has been shown that pig handlers are at increased risk of zoonotic HEV infection. More recently, sporadic and cluster cases of acute hepatitis E have been linked to the consumption of raw or undercooked pig and deer meats, thus providing more direct evidence of zoonotic HEV transmission. This article briefly reviews the animal strains of HEV, their ability to infect across species, and potential zoonotic risks.