Effect of Oseltamivir Carboxylate Consumption on Emergence of Drug-Resistant H5N2 Avian Influenza Virus in Mallard Ducks

Abstract

Oseltamivir carboxylate (OC) has been detected in environmental waters at various levels during recent influenza seasons in humans, reflecting levels of usage and stability of this drug. In consideration of the role of waterfowl as hosts for influenza viruses that may contribute to human infections, we evaluated the effect of consumption of low doses of OC on development of oseltamivir-resistant influenza virus mutants in mallard ducks (Anas platyrhynchos) infected with two different low-pathogenic (LP) H5N2 avian influenza viruses (AIV). We detected development of virus variants carrying a known molecular marker of oseltamivir resistance (neuraminidase E119V) in 4 out of 6 mallards infected with A/Mallard/Minnesota/182742/1998 (H5N2) and exposed to 1,000 ng/liter OC. The mutation first appeared as a minor population on days 5 to 6 and was the dominant genotype on days 6 to 8. Oseltamivir-resistant mutations were not detected in virus from ducks not exposed to the drug or in ducks infected with a second strain of virus and similarly exposed to OC. Virus isolates carrying the E119V mutation displayed in vitro replication kinetics similar to those of the wild-type virus, but in vivo, the E119V virus rapidly reverted back to wild type in the absence of OC, and only the wild-type parental strain was transmitted to contact ducks. These results indicate that consumption by wild waterfowl of OC in drinking water may promote selection of the E119V resistance mutation in some strains of H5N2 AIV that could contribute to viruses infecting human populations.

Influenza A/H4N2 mallard infection experiments further indicate zanamivir as less prone to induce environmental resistance development than oseltamivir

“…Previous in vivo experiments using a mallard model have demonstrated that NA substitutions affecting drug susceptibility emerge in response to the exposure of mallards infected with LPAIV to OC and ZA through their water source [13–17]. In a scenario where such substitutions are incorporated via reassortment into pandemic IAVs infecting humans or an avian IAV carrying these substitutions is directly transmitted to humans, the treatment of humans and pandemic preparedness planning may be at risk of failure.…”

Oseltamivir-Resistant Influenza A (H1N1) Virus Strain with an H274Y Mutation in Neuraminidase Persists without Drug Pressure in Infected Mallards

“…In vivo experiments have demonstrated that OC resistance evolves in avian IAVs of both the N1 and N2 neuraminidase groups when infected mallards (Anas platyrhynchos) are exposed to 0.95 to 12 g/liter OC in their water (23)(24)(25). However, a fundamental question for the persistence of NAI resistance in the environment is whether a resistance mutation is retained without continuous selective drug pressure.…”

Characterization of Novel Reassortant Influenza A (H5N2) Viruses Isolated from Poultry in Eastern China, 2015

“…Previous studies predicted lower viability among resistant mutant viruses compared with sensitive strains (Aoki et al, 2007; Zaraket et al, 2010; Achenbach and Bowen, 2013). Neither of these substitutions was observed in the NA of the H5N2 AIVs.…”