Detection of the Hepatitis A virus in marine coastal waters

Very often waterborne illnesses are due to viruses of human faecal origin. One such virus, and the topic of this paper, is the Hepatitis A virus (HAV), which is commonly present in raw sewage and the cause of acute hepatitis worldwide. Its primary transmission is through the faecal-oral route where outbreaks occur from contaminated food or water. Studies have shown that HAV is capable of surviving outside of a host and can stay infectious for at least nine months in an aquatic environment – so it is important to understand as much as possible about it.

Despite frequent incidence worldwide, little literature is available on HAV levels in marine waters because detection of HAV is very challenging and time-consuming, due to the poor growth of wild-types in vitro. The aims of the authors were to i) develop a sensitive and rapid HAV detection method to monitor possible sources of contamination during sporadic HAV infection outbreaks and ii) identify the major HAV genotype present in Hong Kong coastal waters.

Seawater samples were collected from seven sewage-polluted sites in Hong Kong. The authors developed a sensitive and quantitative TaqMan-based PCR method (which targeted the 5’-noncoding region of HAV), this quantified the HAV particles present in the samples. Of the seven sites, HAV was detected in four; the levels detected ranged from 416 – 1028 HAV particles/L. Total Escherichia coli counts for each sample were also enumerated on TBX medium. The E. coli densities observed showed no correlation of any significance between HAV and E. coli counts. For example, at the Kwun Tong Pier, there was a high count of 118,800 E. coli/100mL, but HAV particles were barely detectable.

Use of phylogenetic analysis of 10 PCR clones from each of the HAV-positive sites indicated that the human HAV genotype IB is the most widely distributed type in Hong Kong waters.

In conclusion the stand alone use of total E. coli counts as a faecal indicator needs to be addressed. However, HAV quantification together with the use of total E. coli counts may serve as a tool to assess water quality.

This paper is short and to the point, the only problem I had with reading it was the lack of sections (introduction, methods, discussion etc.). I felt I was getting bogged down in a lot of the small details, which I would have preferred to read at the end. The conclusions from this paper are the complete opposite to another paper (Gersberg et al., 2006), which suggests E. coli can be used to indicate the presence of HAV; I feel more research needs to be done to understand why such different results were obtained. But on the whole this is a paper that will lead to further research on the matter of faecal contamination indicators.


A review of:

Yang, N., Ling Ho Chu, D., Man Lai Wong, M., Qi, H., Shui Sun Wu, R. and Yuen Chong Kong, R. (2011) Major human Hepatitis A virus genotype in Hong Kong marine waters and detection by real-time PCR. Marine Pollution Bulletin 62 2654-2658.