title: Oseltamivir-resistant influenza A (H1N1) virus strain with an H274Y mutation in neuraminidase persists without drug pressure in infected mallards.
abstract: Influenza A virus (IAV) has its natural reservoir in wild waterfowl, and emerging human IAVs often contain gene segments from avian viruses. The active drug metabolite of oseltamivir (oseltamivir carboxylate [OC]), stockpiled as Tamiflu for influenza pandemic preparedness, is not removed by conventional sewage treatment and has been detected in river water. There, it may exert evolutionary pressure on avian IAV in waterfowl, resulting in the development of resistant viral variants. A resistant avian IAV can circulate among wild birds only if resistance does not restrict viral fitness and if the resistant virus can persist without continuous drug pressure. In this in vivo mallard (Anas platyrhynchos) study, we tested whether an OC-resistant avian IAV (H1N1) strain with an H274Y mutation in the neuraminidase (NA-H274Y) could retain resistance while drug pressure was gradually removed. Successively infected mallards were exposed to decreasing levels of OC, and fecal samples were analyzed for the neuraminidase sequence and phenotypic resistance. No reversion to wild-type virus was observed during the experiment, which included 17 days of viral transmission among 10 ducks exposed to OC concentrations below resistance induction levels. We conclude that resistance in avian IAV that is induced by exposure of the natural host to OC can persist in the absence of the drug. Thus, there is a risk that human-pathogenic IAVs that evolve from IAVs circulating among wild birds may contain resistance mutations. An oseltamivir-resistant pandemic IAV would pose a substantial public health threat. Therefore, our observations underscore the need for prudent oseltamivir use, upgraded sewage treatment, and surveillance for resistant IAVs in wild birds.
authors.affiliation: Section for Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden Zoonosis Science Centre, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden anna.gillman@medsci.uu.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Gillman
authors.affiliation: Zoonosis Science Centre, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Shaman
authors.initials: S
authors.lastname: Muradrasoli
authors.affiliation: Department of Chemistry, Umeå University, Umeå, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Söderström
authors.affiliation: Section for Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Holmberg
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
authors.forename: Neus
authors.initials: N
authors.lastname: Latorre-Margalef
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
authors.forename: Conny
authors.initials: C
authors.lastname: Tolf
authors.affiliation: Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Waldenström
authors.affiliation: Division of Natural Sciences, Kristianstad University, Kristianstad, Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Gunnarsson
authors.affiliation: Section for Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden Zoonosis Science Centre, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Olsen
authors.affiliation: Section for Infectious Diseases, Department of Medical Sciences, Uppsala University, Uppsala, Sweden Zoonosis Science Centre, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Josef D
authors.initials: JD
authors.lastname: Järhult
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D004372:Ducks; D005243:Feces / Q000821:virology; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000821:virology*; D050505:Mutant Proteins / Q000235:genetics; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics / Q000302:isolation & purification*; D053139:Oseltamivir / Q000494:pharmacology*; D012641:Selection, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D000998:Antiviral Agents; D050505:Mutant Proteins; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase