Zoonotic and Foodborne Transmission of Hepatitis E Virus

Abstract

Hepatitis E, an important human disease, is characterized by explosive outbreaks of acute hepatitis in developing countries, and sporadic and cluster cases of hepatitis E in industrialized countries. 1,2 The causative agent, hepatitis E virus (HEV), has been genetically identified from humans and several other animal species including pig, chicken, deer, mongoose, rabbit, rat, ferret, and fish. [3][4][5] The host range and diversity of HEV have been significantly expanded in recent years. Hepatitis E is now a recognized zoonotic disease, and pigs and likely other animal species are reservoirs for HEV (►Fig.1). 5 Direct contact with infected animals and consumption of contaminated animal meat and meat products have been linked to sporadic and cluster cases of acute hepatitis E, thus raising concerns over zoonosis and food safety. 3 Recently, genotype 3 HEV-associated persistent infection has become a significant clinical problem in immunocompromised individuals, 6,7 which further underscores the clinical importance of these zoonotic genotypes 3 and 4 HEV strains. Here the natural history and emerging zoonotic risks of HEV are reviewed with emphases on the zoonotic and foodborne transmissions of the virus and potential strategies to prevent zoonosis and ensure food safety. Hepatitis E Virus NomenclatureHEV belongs to the family Hepeviridae, and according to the 9 th Report of the International Committee on the Taxonomy of Viruses (ICTV), 8 currently there is a single genus Hepevirus within the family along with a floating species of avian HEV. Keywords► hepatitis E virus ► HEV ► zoonosis ► foodborne transmission ► zoonotic transmission ► animal reservoirs AbstractHepatitis E is an important disease in many developing countries of Asia and Africa with large explosive outbreaks and is also endemic with sporadic or cluster cases of hepatitis in many industrialized countries. The causative agent, hepatitis E virus (HEV), is currently classified in the family Hepeviridae. Thus far, four putative genera of HEV representing mammalian, avian, and fish species have been identified and characterized worldwide. Within the mammalian HEV that infects humans, genotypes 1 and 2 are associated with epidemics and restricted to humans, whereas genotypes 3 and 4 are zoonotic and associated with sporadic and cluster cases of hepatitis E. As a fecal-orally transmitted disease, waterborne transmission is still an important route of HEV transmission especially for large outbreaks associated with genotypes 1 and 2. However, genetic identification of numerous animal strains of HEV and the demonstrated ability of crossspecies infection by these animal strains have significantly broadened the host range and diversity of HEV and raised public health concerns for zoonosis and food safety associated with genotypes 3 and 4 HEV infection. Pigs and likely other animal species serve as reservoirs for HEV. Direct contact with infected pigs and other animals and consumption of contaminated animal meat and meat products pose risks for HEV infection. ...

First Report of Hepatitis E Virus Circulation in Domestic Pigs in Nigeria

“…6,8 In addition to reports of large hepatitis E outbreaks in Africa, sporadic hepatitis E in Africa has been reported in Nigeria, Kenya, and Egypt. In these cases, routes of HEV transmission were not documented, and the extent of sporadic hepatitis E in Africa remains largely unknown.…”

“…The reaction was terminated after 15 min by adding 2.5 M sulphuric acid to each well and the plates were read at 450 nm using a spectrophotometer. Three internal controls, a positive control, a negative control, and a cut-off control, originating from pigs negative for HEV and pigs infected experimentally with HEV genotype 3 as described 8 were included on each plate. Cut-off controls were determined by means of a detailed receiver operating characteristic (ROC) curve analysis as described elsewhere.…”

“…Cut-off controls were determined by means of a detailed receiver operating characteristic (ROC) curve analysis as described elsewhere. 8 When the internal cut-off control value was within the expected range (0.50-0.54), the run was considered valid and the sample results were used. The results were calculated as "antibody index" (sample optical density [OD]/ cut-off serum mean OD) with results 0.9, 0.9-1.0, and 1.1 defined as negative, inconclusive, and positive, respectively.…”

“…7 Genotype 3 circulates worldwide and contains strains from sporadic, cluster, and chronic cases of hepatitis E in humans 6 and strains from pigs and wild boars, which are considered the most important reservoirs for HEV. 8 Genotype 4 circulates mainly in Asia; however, it has been reported recently in Europe 9 -11 and includes strains from sporadic and cluster cases of hepatitis E in humans and strains from pigs.…”

Hepatitis E: Epidemiology and Natural History

“…12 Further work prompted by these observations has led to a major change in our understanding about HEV and its epidemiology, including the routes of transmission and clinical outcomes. Thus, we now know that HEV has a fair degree of genomic heterogeneity, has a wide host range with frequent cross-species transmission, 13 circulates in most parts of the world, and causes persistent infection in some persons. 14 Despite the fact that HEV was discovered only in late 20th century, its origin appears to be fairly ancient.…”