Infectivity and antigenicity reduction rates of human rotavirus strain Wa in fresh waters

Abstract

The rates of inactivation of human rotavirus type 2 (strain Wa) (HRV-Wa) and poliovirus type 1 (strain CHAT) were compared in polluted waters (creek water and secondary effluent before chlorination) and nonpolluted waters (lake water, groundwater, and chlorinated tap water). Viral infectivity titers were determined by plaque assays, while HRV-Wa antigenicity also was monitored by an enzyme-linked immunosorbent assay. Both viruses persisted longest in lake water and shortest in tap water. The actual inactivation times (i.e., times required for two-log10 reductions of initial viral titers) for the two viruses were significantly different in all waters except tap water. With the exception of the groundwater and secondary effluent results, the HRV-Wa inactivation times in the fresh waters tested were significantly different. Owing perhaps to aggregation, HRV-Wa appeared less susceptible to the effects of chlorine than previously reported for this virus and for the simian rotavirus SA11. HRV-Wa displayed prolonged survival in lake water and groundwater exceeding that previously reported for the SA11 virus. The HRV-Wa infectivity reduction rate (ki) was significantly correlated with the water pH (i.e., as pH increased, ki increased). The water pH may have influenced viral aggregation and thereby HRV-Wa susceptibility to other virucidal factors in the water. Enzyme-linked immunosorbent assay results showed similar inactivation patterns with the most significant reduction in HRV-Wa antigenicity occurring in polluted waters and tap water. In all waters, particularly tap water, infectivity declined at a faster rate than antigenicity. It is proposed that HRV-Wa can be used as a model for future studies of rotaviral persistence in the aquatic environment.