Abstract: Sporadic nontravel-related hepatitis E virus (HEY) infections have been reported in industrialized countries. These infections are caused by zoonotic BEV genotypes 3 and 4 that circulate in swine, wild boar, and deer. In The Netherlands, HEV RNA has been detected in >50% of the pig farms, and HEY-specific antibodies were detected in similar to 70% of the slaughter pigs. In the current study, HEY seroprevalences were investigated in pigs raised on conventional, free-range, and organic farms in The Netherlands. Differences in seroprevalence may indicate different exposure routes or transmission dynamics within pig herds for HEY. In 2004, serum samples of 846 fattening pigs were obtained from farms that applied conventional (265 pigs at 24 farms), organic (417 pigs at 42 farms), and free-range (164 pigs at 12 farms) farming. HEY-specific antibodies were detected in samples from all conventional and free-range pig farms and in 41 of 42 organic pig farms, indicating that the probability of introducing HEY on a farm appeared to be equal for the different farming types. The estimated average within-herd seroprevalence was significantly higher for pigs raised on organic farms (89%) than for pigs raised on conventional farms (72%, P = 0.04) and nearly significant for pigs raised on free-range farms (76%, P = 0.06). Six of ten organic farms were estimated to have a within-herd seroprevalence of >95%, compared with 1 of 10 and 4 of 10 of the free-range and conventional pig farms, respectively. This suggests a higher force of infection with HEY for pigs reared on organic farms compared with pigs reared on conventional or free-range farms. This may be due to repetitive exposure to HEY caused by farming system-specific housing conditions, such as a greater contact frequency between pigs and more exposure to pig manure, increasing the transmission rate.
Reference: Rutjes, S. A., et al. (2014). Seroprevalence of Hepatitis E Virus in Pigs from Different Farming Systems in the Netherlands. Journal of Food Protection 77(4): 640-642. Available online at http://dx.doi.org/10.4315/0362-028X.JFP-13-302