January 5, 2007

UK study finds widespread Tamiflu use in humans could build resistance in birds

Widespread use of the antiviral Tamiflu to fight pandemic avian flu in humans could lead to the development of drug-resistant strains of the virus in wild birds, according to British researchers at the Centre for Ecology and Hydrology in Oxford.

The findings, released in the January 2007 issue of Environmental Health Perspectives (EHP) demonstrate how Tamiflu's persistence in wastewater and river water could affect the waterfowl that drink from those water sources.

Tamiflu, which minimises flu symptoms and duration, inhibits the movement of the influenza virus from the cells it infects, and also helps uninfected people avoid contracting the flu.

However, Tamiflu's active agent, the metabolite oseltamivir carboxylate (OC) would be excreted into sewers for several weeks during a pandemic and is expected to withstand biodegradation. According to the researchers in the current study, once birds drink OC-laced water from catchments receiving treated wastewater, they could produce Tamiflu-resistant strains and pass them on to other birds who share the same waters.

The study looked at waterway catchments in the United States and England to determine the potential biodegradability of OC. They also measured wastewater discharges into the catchments.

The study called for more detailed water contamination modeling, especially in high-risk areas of the world such as Southeast Asian countries, where there is more frequent human-to-waterfowl contact and where future use of Tamiflu would be significant.

They also recommend development of methods to minimise the release of OC into wastewater systems, such as biological and chemical pretreatment in the toilet.