Evaluation of Non-Invasive Sampling Methods for Detection of Hepatitis E Virus Infected Pigs in Pens

Abstract

Pigs are a reservoir of hepatitis E virus (HEV), which causes hepatitis in humans. To study the epidemiology of HEV in pig farms, sampling methods are currently used that cause discomfort to pigs, such as rectal sampling. In line with the 3Rs principle, we aimed to evaluate non-invasive methods to detect pens with HEV-shedding pigs. Twenty-eight pens of one farm were sampled cross-sectionally. Individual rectal swabs (IRS) were collected to determine prevalence within pens. Four pen-level samples were compared: a pool of IRS per pen (P), boot socks (BS), oral fluid (OF) and pooled faecal droppings (FD). Each sample was tested by RT-PCR and the sensitivity and specificity of each method was determined by Bayesian latent class analysis. According to IRS, 19/28 pens were HEV positive. BS had a sensitivity of 95% and detected HEV in pens with 10% of pigs shedding; however, specificity was below 30%. FD were comparably accurate to P, with a sensitivity and specificity of 94% and 86%, respectively. BS sampling is thus advised to detect early shedding of HEV or pen contamination, and FD to determine the duration of shedding. This study demonstrates that non-invasive sampling can replace rectal swabs in research on HEV in pigs.

Keywords: HEV; animal experiments; boot sock; oral fluid; pig farms; pooled faecal droppings; refinement; sensitivity; specificity; three Rs.

Figure 1

Location of sampled pens within farm compartments, per age group.

Figure 2

Within-pen prevalence according to IRS, for all combinations of positive tests for the four sample types. (N = number of, IRS = Individual Rectal Swabs, BS = Boot Sock, FD = Faecal Dropping, OF = Oral Fluid, P = Pooled Individual Rectal Swabs, ● = positive PCR test, ● = negative PCR test).