Molecular epidemiology and genome analysis of hepatitis E Virus in swine and blood donors

Abstract

Hepatitis E virus (HEV) infection affects approximately 20 million individuals and results in more than 50,000 deaths each year. The highest prevalence is in Asia where contaminated food and water are often the sources of infection. There was the difference among the genotype of human Hepatitis E virus which genotype 1 to 4 can infect human. HEV genotypes 1 and 2 are found only in humans and are responsible for viral hepatitis outbreaks, while genotypes 3 and 4 are zoonotic. The HEV infection in Thailand caused by HEV genotype 3f and usually found among adult males. However, the route of HEV transmission remains unclear. Swine is the main reservoir of HEV and economically important livestock, yet pork consumption and close contact with pigs are associated with the risk of hepatitis E virus infection. Thus, HEV infection in the general population may be acquired from the consumption of pork and variety meats. Furthermore, HEV infection of blood donors may concern with the food chain and transmitted to the patients via blood transfusion. To address these concerns, this study aimed to investigate the epidemiology of HEV in Thailand both in pork and variety meats, and in Thai blood donors. Moreover, this study provides the genetic variation and evolutionary of HEV as well. Polymerase chain reaction (PCR) was performed to investigate HEV RNA in samples. For the result of this study, the prevalence of HEV RNA in pork and variety meat from supermarket, bile and feces from slaughter house around 3,478 samples, was 1.58%. The HEV RNA was found in samples collected from fresh market around 0.23% while HEV RNA was found in slaughterhouse around 3.93%. The HEV genotype 3f was circulating in Thai swine from slaughterhouse and swine product from fresh market like in European and developed countries. Then, the screening of HEV in blood donors was performed which the detectable HEV RNA among healthy Thais blood donors at National blood centre, Thai Red Cross society, of 0.09%, or approximately 1 in 1,159 which was closely with China and most of positive samples were HEV genotype 3f. This result demonstrated that the prevalence and genotype of HEV in Thailand was closely with European and developed countries. In addition, HEV genotype 3f was intermixing between human and swine. Finally, the whole genome analysis of the complete genome sequencing isolated from Thailand showed that HEV genotype 3f was mostly predominating in Thailand. Moreover, the other subtype was also found in Thailand including HEV genotype 3a and 3c. The evolutionary analysis was estimated the mean time of the ancestor for HEV genotype 1 to 4 was 1,624 years ago (95% HPD: 1222.40-2110.48) and the substitution rate was 5.63x10-4 base substitution per site per year which was lower than the previous study. Moreover, HEV genotype 3 in Thailand was most probably originated in Thailand around 97-118 years ago and might be originated with swine infecting ancestor then intermix between human and swine. For the natural selection analysis, there are the positive selection in HEV genome sequence including ORF2 and ORF3 whereas ORF1 found only negative selection. Thus, HEV was the highly conserve in the functional domains. Furthermore, the mutation associated with the clinical manifestation was observed in complete genome sequences in this study. There were 4 mutation sites that were similar to those reported in other studies. However, the other mutation study should be performed in the future. This informative data provided the prevalence of HEV in Thailand. Including the evidence indicates that epidemiology and evolutionary may play a crucial role to help prevention of HEV infections in Thailand and useful for the further study of HEV infection.