Health Stream Literature Summary - Issue 53 - March 2009

Hepatitis E, Helicobacter pylori and peptic ulcers in workers exposed to sewage: A prospective cohort study.
Tschopp A, Joller H, Jeggli S, Widmeier S, Steffen R., Hilfiker S and Hotz P. (2009) Occupational and Environmental Medicine, 66(1); 45-50.

Hepatitis E is a viral infection with a low case fatality rate in the general population of about 1%, however mortality is significantly higher in pregnant women. This infection occurs in developing countries but is rare in developed nations. Helicobacter pylori is the major cause of peptic ulcers and stomach cancer. Both hepatitis E and Helicobacter pylori have been found in sewage. Workers exposed to sewage therefore may have an increased risk of infection by hepatitis E virus (HEV) and Helicobacter pylori. A follow-up study of a previous cross-sectional study in sewage workers was conducted. The original study found the prevalence of peptic ulcers and hepatitis E and the seroprevalence of H pylori and hepatitis E were not increased in workers exposed to waste water compared with non-exposed subjects.

Workers exposed to sewage in the Canton of Zurich, Switzerland, were invited to participate in this prospective cohort study. Potential control subjects were garbage collectors, gardeners, workers maintaining waterways, public transport works and forestry workers. In the baseline examination there were 355 workers from waste water plants and 423 from control plants. Exposure to sewage during the entire working life was assessed for each job separately. Ultimately there were 332 and 446 workers included for follow-up as currently exposed and non-exposed to waste water respectively. The study consisted of a baseline and four annual follow-up examinations. The baseline medical examination took place between June 2000 and July 2002 and the final examination between August 2004 and May 2006. Physicians examined both exposed and unexposed subjects. At each follow-up workers were asked whether their physician had diagnosed a liver or stomach disease since the last examination. At the final examination, workers were asked if they had received a blood transfusion (to account for any HEV transmission).

The presence of peptic ulcers and liver diseases was defined on the basis of clinical history and gastritis on the basis of biopsy data reported by the patient. At baseline, socioeconomic level, country of childhood, alcohol consumption, use of personal protective equipment and y-glutamyl transferase (GGT) activity were assessed. Smoking was assessed at baseline and in the final examination and travel to endemic areas was assessed yearly. Exposure was assessed individually at all five examinations with the same questionnaire and defined by four indicators: exposure to sewage during follow-up (yes/no), duration of exposure during follow-up (weeks), occurrence of splashes during follow-up, and exposure to raw sewage during follow-up. Analyses for immunological determinations included immunoglobulin G antibodies to H. pylori (H. pylori IgG) and immunoglobulin A antibodies to H. pylori (H. pylori IgA) determined with enzyme linked immunosorbent assays (ELISA). Antibodies (IgG/IgM) to HEV were determined with an ELISA using rDNA as an antigen.

There were 667 workers in total that were seronegative for hepatitis E at the beginning of follow-up and had at least one follow-up determination. During follow-up no cases of clinical hepatitis E were diagnosed. Seroconversion was found in 26 subjects, however incidence rates were identical in both exposed and non-exposed workers. Thirteen of the 26 workers with seroconversion had never been to an endemic area and there was no association found between seroconversion and travel to endemic areas (p greater than 0.6, x2 test). Survival (time before seroconversion) did not differ between sewage and control workers for any exposure indicator (p greater than or equal to 0.4). Wearing personal protective equipment had no statistically significant effect (p greater then 0.6).

There were no differences found for H. pylori with regard to clinical endpoints (incidence of hepatitis E and peptic ulcers and seroconversion rates). With regards to H. pylori IgG and IgA, valid follow-up data were available for 395 and 534 subjects, respectively who were seronegative at baseline and seroconversion occurred in 125 and 242 of these subjects, respectively. Incidence rates were found to be similar in control and exposed subjects. Analysis did not reveal any statistically significant effect of exposure to waste water (p greater than 0.2 for all four exposure indicators and both antibody classes). Shift work and person protective equipment had no statistically significant effect (p greater than 0.2) and no dose-response relationship was found. None of the sensitivity analyses examining informative censoring showed an increased seroconversion rate in sewage workers for any of the three serological outcomes.

A subgroup was drawn from the whole study population to calculate seroconversion rates in %/year. This subgroup included all subjects who had participated in the first and last examination with valid results, were seronegative at baseline and had a follow-up period longer than 4 years. This subgroup was followed for a median time of 4.5 years. The seroconversion rates were 6.8%/year and 10.8%/year for H. pylori IgG and IgA, respectively and decreased to 5.8%/year and 8.2%/year after excluding subjects with questionable seroconversion. For all four comparisons exposure to waste water had no effect on survival (p greater than or equal to 0.3).

This study found workers exposed to sewage do not have an increased incidence of clinical hepatitis E or peptic ulcers. Seroconversion rates due to contact with the hepatitis E virus or H. pylori were not increased in sewage workers. The results of this study may not be applicable to endemic areas or regions with poor sanitation as the Canton of Zurich is not an endemic area for hepatitis E and has good sanitation.

© Copyright Water Quality Research Australia Limited http://www.wqra.com.au/
Health Stream articles may be reproduced and communicated to third parties provided WQRA is acknowledged as the source. Literature summaries are derived in part from copyright material by a range of publishers. Original sources should be consulted and acknowledged.