tetano
Editor, Senior Moderator
Published ahead of print 26 February 2014, doi: 10.1128/JVI.03689-13
Role of poultry in spread of novel H7N9 influenza virus in China
Mary J. Pantin-Jackwood1,
Patti J. Miller1,
Erica Spackman1,
David E. Swayne1,
Leonardo Susta1,
Mar Costa-Hurtado1 and
David L. Suarez1*
1Exotic and Emerging Avian Disease Research Unit, Southeast Poultry Research Laboratory, Agricultural Research Service, USDA, Athens, GA
ABSTRACT
The recent outbreak of H7N9 influenza in China has resulted in many human cases with a high fatality rate. Poultry are the likely source of infection for humans based on sequence analysis and virus isolations from live bird markets, but it?s not clear which species of birds are most likely to be infected and shedding sufficient levels of virus to infect humans. Intranasal inoculation of chickens, Japanese quail, pigeons, Pekin ducks, Mallard ducks, Muscovy ducks, and Embden geese with 106 EID50 of the A/Anhui/1/2013 virus resulted in infection but no clinical disease signs. Virus shedding in quail and chickens was much higher and prolonged than in the other species. Quail effectively transmitted the virus to direct contacts but pigeons and Pekin ducks did not. In all species, virus was detected at much higher titers from oropharyngeal swabs than cloacal swabs. The HA gene from samples collected from selected experimentally infected birds were sequenced and three amino acid differences were commonly observed when compared to A/Anhui/1/2013: N123D, N149D, and L217Q. Leucine at position 217 is highly conserved for avian isolates and is associated with α;2,6 sialic acid binding. Different amino acid combinations were observed suggesting that the inoculum had viral subpopulations that were selected after passage in birds. These experimental studies corroborate that certain poultry species are reservoirs of the H7N9 influenza virus, and that the virus is highly upper respiratorytropic so testing of bird species should preferentially be conducted with oropharyngeal swabs for best sensitivity.
IMPORTANCE The recent outbreak of H7N9 in China has resulted in a number of human infections with a high case fatality rate. The source of the viral outbreak is suspected to be from poultry, but definitive data for the source of the infection is not known. This study provides experimental data to show that quail and chickens are susceptible to infection and shed large amounts of virus and are likely important in the spread of the virus to humans. Other poultry species, including Muscovy ducks, can be infected and shed virus, but are less likely to play a role of transmitting the virus to humans. Pigeons were previously suggested as a possible source of virus because of isolation of virus from several pigeons in poultry markets in China, but experimental studies show they are generally resistant to infection and are unlikely to play a role in spread of the virus.
http://jvi.asm.org/content/early/20...id=1&usestrictdates=yes&resourcetype=HWCIT&ct
Role of poultry in spread of novel H7N9 influenza virus in China
Mary J. Pantin-Jackwood1,
Patti J. Miller1,
Erica Spackman1,
David E. Swayne1,
Leonardo Susta1,
Mar Costa-Hurtado1 and
David L. Suarez1*
1Exotic and Emerging Avian Disease Research Unit, Southeast Poultry Research Laboratory, Agricultural Research Service, USDA, Athens, GA
ABSTRACT
The recent outbreak of H7N9 influenza in China has resulted in many human cases with a high fatality rate. Poultry are the likely source of infection for humans based on sequence analysis and virus isolations from live bird markets, but it?s not clear which species of birds are most likely to be infected and shedding sufficient levels of virus to infect humans. Intranasal inoculation of chickens, Japanese quail, pigeons, Pekin ducks, Mallard ducks, Muscovy ducks, and Embden geese with 106 EID50 of the A/Anhui/1/2013 virus resulted in infection but no clinical disease signs. Virus shedding in quail and chickens was much higher and prolonged than in the other species. Quail effectively transmitted the virus to direct contacts but pigeons and Pekin ducks did not. In all species, virus was detected at much higher titers from oropharyngeal swabs than cloacal swabs. The HA gene from samples collected from selected experimentally infected birds were sequenced and three amino acid differences were commonly observed when compared to A/Anhui/1/2013: N123D, N149D, and L217Q. Leucine at position 217 is highly conserved for avian isolates and is associated with α;2,6 sialic acid binding. Different amino acid combinations were observed suggesting that the inoculum had viral subpopulations that were selected after passage in birds. These experimental studies corroborate that certain poultry species are reservoirs of the H7N9 influenza virus, and that the virus is highly upper respiratorytropic so testing of bird species should preferentially be conducted with oropharyngeal swabs for best sensitivity.
IMPORTANCE The recent outbreak of H7N9 in China has resulted in a number of human infections with a high case fatality rate. The source of the viral outbreak is suspected to be from poultry, but definitive data for the source of the infection is not known. This study provides experimental data to show that quail and chickens are susceptible to infection and shed large amounts of virus and are likely important in the spread of the virus to humans. Other poultry species, including Muscovy ducks, can be infected and shed virus, but are less likely to play a role of transmitting the virus to humans. Pigeons were previously suggested as a possible source of virus because of isolation of virus from several pigeons in poultry markets in China, but experimental studies show they are generally resistant to infection and are unlikely to play a role in spread of the virus.
http://jvi.asm.org/content/early/20...id=1&usestrictdates=yes&resourcetype=HWCIT&ct
