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Reduced prevalence of genotype 3 HEV in Shanghai pig farms and hypothetical homeostasis of porcine HEV reservoir

Li, Zhen, Yu, Shuisheng, Dong, Shijuan, Zhu, Yumin, Si, Fusheng, Shen, Shiyuan, Jiang, Zhongqi, Yu, Ruisong, Zou, Sixiang
Veterinary microbiology 2009 v.137 no.1-2 pp. 184-189
viral hepatitis, Orthohepevirus A, livestock production, swine diseases, risk assessment, disease severity, genotype, homeostasis, mixed infection, epidemiological studies, sanitation, disease outbreaks, hygiene, swine, disease reservoirs, disease prevalence, longitudinal studies, genetic stability, disease incidence, China
A total of 493 fecal samples collected from local Shanghai pig farms were examined for Hepatitis E virus (HEV) after the introduction of stricter sanitary measures following outbreaks of a high fever-associated pig disease during 2006 and 2007. Our investigation revealed that, while the overall occurrence of HEV RNA positives decreased by only 3.7%, the incidence of HEV genotype 4 increased from 9.8% to 20.6% whereas the incidence of HEV genotype 3 decreased from 16.2% to 1.6%. As well as demonstrating that HEV genotype 3 was more sensitive than genotype 4 to the stricter sanitation procedures, our data also suggested that a homeostasis mechanism, whereby the overall incidence of HEV is maintained at a specific population level, might exist in the porcine HEV reservoir. Furthermore, in one case, we encountered the coexistence of HEV genotypes 3 and 4 within the same sample, indicating the possibility of future HEV infections of increased severity and even the occurrence of a HEV pandemic due to genetic recombination and species evolution.