Detection of hepatitis E virus (rabbit genotype) in farmed rabbits entering the food chain

Abstract

Hepatitis E virus (HEV) infects humans and many animal species. The rabbit HEV has been found in farmed, wild and pet rabbits as well as in human patients suggesting zoonotic transmission. Although the routes of human infection with rabbit strains are unclear a foodborne transmission is suggested especially when asymptomatically infected animals could enter the food chain. The aims of the study were an evaluation of the prevalence of HEV infections in slaughtered rabbits, identification of the virus genotype(s) and assessment of their genetic relatedness to other zoonotic HEV strains. A pair of blood and liver samples (n = 482) were collected from meat rabbits of different breeds slaughtered at the age of 2.8 to 6 months. The animals originated from 20 small-scale and 4 large-scale commercial farms operating in Poland. The presence of anti-HEV antibodies in animals was detected by the use of a recomWell HEV IgG (human) ELISA kit (Mikrogen Diagnostik) adapted to rabbit sera. The isolation of HEV and sample process control virus (feline calicivirus) RNA from homogenates of liver destined for food and virus-positive sera was performed using a QIAamp® Viral RNA Mini Kit (Qiagen). A one-step real-time reverse transcription PCR method containing a target-specific internal amplification control was used for detection of HEV. The (sub)genotype of detected rabbit HEV strains was identified based on sequence analysis of the ORF2 and ORF2/3 virus genome fragments. Anti-HEV antibodies were detected in 29 (6%) out of 482 rabbit sera samples collected from animals raised only on the small-scale rabbit farms. Four sera were also positive for HEV RNA. Viral RNA was detected in 72 (14.9%) animal livers. Analysing ELISA and PCR results using Student's t-test, there were significant differences observed in the frequency of HEV infections between rabbits from small-scale and commercial farms (t = 2.675, p = 0.015 < 0.05 for ELISA and t = 2.705, p = 0.014 < 0.05 for PCR). All detected virus strains were identified as HEV gt3 ra subtype. The results of this study provide data on the occurrence of HEV infections in rabbits entering the food chain, suggesting that a risk of foodborne HEV infection due to consumption of contaminated meat and liver exists. In this light, the presence of rabbit HEV in food animals is pertinent as an issue of food safety and the surveillance of these animals for emerging or re-emerging viruses.

Keywords: Detection; Farmed rabbits; Food chain; Hepatitis E virus; Meat.