Report No FR0083

Apr 1990

I OBJECTIVES

To establish a survival curve for human rotavirus in marine water under controlled conditions of light and temperature which simulate field conditions, and to calculate associated T₉₀ values.

II REASONS

Rotavirus is recognised as a major cause of severe infantile diarrhoea and can also cause gastroenteritis in adults. Sea outfalls are currently designed to meet bacterial, rather than viral, standards. In order to improve the effectiveness of sewage treatment and disposal, more information is needed on the fate and inactivation of viruses in the sea, and the effectiveness of different means of sewage treatment in removing viruses.

III CONCLUSIONS

1. Human rotavirus in seawater was significantly inactivated by exposure to light under laboratory conditions. After the initial 24.5 hours of constant exposure to artificial light, when a T₉₀ of 25.4 hours was indicated, the rate of inactivation decreased with an increased T₉₀ of 33.5 hours being calculated for the period 0 to 72 hours.
   
2. The rate of rotavirus inactivation in the dark was slower: over the first 24 hours of the experiment a T₉₀ of 13 days was indicated.
   
3. The rate of inactivation of rotavirus was considered to be artificially high under the enclosed conditions of the experiment and consequently the survival characteristics of the rotavirus may be significantly different under conditions which more accurately represent the marine situation

IV RECOMMENDATIONS

A more accurate assessment of the survival of human rotavirus in saline waters could be obtained from in situ studies. However, this type of study has many inherent difficulties and so the following recommendations were made to improve the enclosed system used to assess rotavirus survival:

1. Filtration of the sewage and rotavirus faecal extract to remove coarse particulates and so reduce the amount of nutrients.
   
2. Treatment of the sewage and rotavirus control with broad spectrum antibodies to reduce the numbers of indigenous bacteria-
   
3. Continuous monitoring of the pH of the seawater to detect any changes which may subsequently affect virus survival.

V RESUME OF CONTENTS

This report reviews the literature concerning factors affecting the viability of human virus in the marine environment. Little data appear to exist on the survival of human rotaviruses in the marine environment. Because of the apparently ubiquitous nature of rotaviruses, together with their pathogenic properties, it is important that their survival characteristics in the marine environment are established.

Laboratory-based experiments in which non-cultivatable human rotavirus was exposed to artificial light in seawater are described. From the results tentative T₉₀ values for human rotavirus in seawater, both when exposed to artificial light and in the dark were calculated. The limitations of laboratory measurements are discussed and recommendations made as to how the experimental design might be improved.

Copies of the report are available from FWR, price £15.00, less 20% to FWR Members.