Dynamics and strategies for control of hepatitis E virus transmission in pig herds

Abstract

Hepatitis E virus (HEV) is an RNA virus that is globally the most common cause of acute liver inflammation in humans. The virus belongs to the family of Hepeviridae, species Paslahepevirus balayani, with eight genotypes identified so far, four of which are frequently found in humans. It has been estimated that one in eight people has experienced an HEV infection, although only 5% of them exhibit symptoms. In Europe, HEV genotype 3 is most prevalent in humans. This type is zoonotic, meaning it can be transmitted between animals and humans. Pigs and wild boars are known asymptomatic reservoirs of this genotype, and the consumption of raw or undercooked pork is likely the main source of human infection in Europe. People can also become infected by (in)direct contact with pigs, as infected pigs shed the virus in feces. Based on current knowledge, 'complete compartmentalization' would be the first step towards controlling HEV transmission between pigs. This includes all measures that can keep a compartment free from HEV, such as using cleaning boots and materials per compartment, effective cleaning and disinfection, pest control, and the all-in-all-out principle, where there is no mixing of animals from different groups. At present, controlling HEV does not seem to be a priority, given the low number of symptomatic human cases and the asymptomatic infection of pigs. On the other hand, the prevalence of HEV within farms can serve as a proxy for the overall internal biosecurity level of a farm. Before HEV control or surveillance programs are initiated, awareness among pig farmers about HEV and the importance of biosecurity should be increased. In conclusion, this research contributes to understanding the routes of transmission and infection dynamics of HEV within pig farms. Internal biosecurity measures may potentially reduce the number of HEV-infected pigs on pig farms and at slaughter, thereby reducing human exposure to HEV through various routes such as the environment, animal contact, and pork consumption.