Detection of Reservoir Species for Hepatitis E Virus in China

The research paper done by Xia et al published in 2015 addresses the prevalence of Hepatitis E virus (HEV) in animals in China. HEV is a single stranded, positive-sense RNA that is usually transmitted by the fecal-oral route. Four different genotypes of the virus has been isolated so far. Genotypes 1 and 2 occur in humans while genotypes 3 and 4 are present in both humans and animals. Anti-HEV antibodies have been discovered in an increasingly long list of animals leading scientists to label HEV as an emerging zoonotic disease. In order to identify the reservoir species of HEV, scientists collected fecal samples from 17 mammal species and 24 avian species and tested them for the presence of HEV RNA in them.

RT-nPCR tests were run on the 887 total fecal samples collected to extract and detect HEV RNA. Sequencing and phylogenetic analysis were then conducted to construct a phylogenetic tree to compare any HEV strains detected to those that already are already known. Twenty-nine (29) of forty-two (42) swine samples tested positive for HEV RNA and six (6) of four hundred ninety-two (492) rabbit samples also tested positive. None of the avian species or wild animal species tested positive for HEV RNA. Nucleotide sequencing revealed that swine HEV was 97.8% – 98.4% similar to genotype 4 while rabbit HEV was similar to genotype 3. From this, it was concluded that swine and rabbits population make up the animal reservoir for HEV in China. The higher rate of HEV presence in swine means that pigs are the primary reservoir. This supports the findings of HEV infection rates on swine farms throughout the world. It also confirmed the possibility of transmission of HEV from swine to humans.

 

HEV table
Table 1 shows the percent of fecal samples that were positive for HEV RNA testing from different species. The highlighted species are the only animals that had positive samples. Only rabbit and swine species tested positive.

 

The researchers go on to provide some recommendations to decrease the risk of HEV infection. The recommend that feces in the sties are cleaned immediately since they are the primary source of transmission. The sties should also be cleaned and disinfected regularly to provide a clean environment for the animals. Dirty sties will act as breeding grounds for a number of diseases including HEV. Finally, the water and food provided for pigs should be prevented from being contaminated with pig feces. Contamination will allow transmission of the virus within pigs regardless of how clean the sties are. If these three recommendations are practiced then the occurrence of HEV will decrease and thereby reduce the transmission of HEV from pigs to humans. Based on this, it is also hypothesized that the prevalence of HEV in rabbits is low because they are kept and fed separately from their feces. The natural environment of pig farms supports the spread of HEV.

This research was key to identifying the reservoir species for HEV and the transmission route. Farmers and animal handlers can be now made aware of the danger of transmission and the precautions they should take to avoid HEV. Knowledge of the exact strain of virus that can be transmitted from the different animals will help medical professionals administer the correct treatment rapidly. The next steps will be establish how exactly the transmission occurs and if the animals and humans can be vaccinated against the virus.

Work Cited:
Xia J, Zeng H, Liu L, Zhang Y, Liu P, Geng J, Wang L, Wang L, Zhuang H. 2015. Swine and rabbits are the main reservoirs of hepatitis E virus in China: detection of HEV RNA in feces of farmed and wild animals. Archives of Virology. [Internet]. Retrieved from http://link.springer.com.pitt.idm.oclc.org/article/10.1007%2Fs00705-015-2574-0#enumeration

 

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