Rodents as mechanical vectors for Ascaris suum in pig farms

Rodents are well-recognized agricultural pests, causing significant damage to crops and infrastructure, as well as posing health risks to both animals and humans by transmitting various infectious agents. On livestock farms, they can contribute to disease transmission dynamics, for example by acting as mechanical vectors that carry pathogens from one stable to another, forming a hidden transmission network. This study explored the potential role of commensal rodents as mechanical vectors for the roundworm Ascaris suum on pig farms in Belgium. While A. suum is a highly prevalent intestinal parasite in pigs worldwide, its potential spread by rodents on pig farms has not been thoroughly investigated. It addresses this gap by examining whether Mus musculus and Rattus norvegicus, two common rodent species found on farms, can carry and spread A. suum eggs between different areas of the farm. Rodents were trapped on two pig farms and their faecal samples were analysed microscopically for the presence of A. suum eggs. The results showed a low prevalence of eggs in the faecal samples, with 4.17% in M. musculus and 17.14% in R. norvegicus. Serological screening of pigs further confirmed prior exposure to A. suum in both farms. Despite the low prevalence, these findings suggest that rodents could act as mechanical vectors of A. suum eggs between stables, potentially leading to persistent environmental contamination. This highlights the potential need to include rodent control as part of broader biosafety strategies to limit A. suum transmission on pig farms, particularly by reducing the risk of reintroducing eggs into stables that have already been cleaned and disinfected.