Transmission of H6N2 wild bird-origin influenza A virus among multiple bird species in a stacked-cage setting

Abstract

Live bird markets are common in certain regions of the U.S. and in other regions of the world. We experimentally tested the ability of a wild bird influenza A virus to transmit from index animals to naïve animals at varying animal densities in stacked cages in a simulated live bird market. Two and six mallards, five and twelve quail, and six and nine pheasants were used in the low-density and high-density stacks of cages, respectively. Transmission did not occur in the high-density stack of cages likely due to the short duration and relatively low levels of shedding, a dominance of oral shedding, and the lack of transmission to other mallards in the index cage. In the low-density stack of cages, transmission occurred among all species tested, but not among all birds present. Oral and cloacal shedding was detected in waterfowl but only oral shedding was identified in the gallinaceous birds tested. Overall, transmission was patchy among the stacked cages, thereby suggesting that chance was involved in the deposition of shed virus in key locations (e.g., food or water bowls), which facilitated transmission to some birds.

A Comparison of Host Responses to Infection with Wild-Type Avian Influenza Viruses in Chickens and Tufted Ducks

“…Notably, H6N2 was detected at the highest virus loads both in oropharyngeal swabs and in tissue samples from both chickens and tufted ducks. This is perhaps not surprising as this virus subtype is very common in wild mallards ( 38 , 45 , 46 ) and has been demonstrated to infect gallinaceous birds, including pheasants and quails ( 47 ) as well as chickens ( 19 ). Our findings are corroborated by previous studies, similarly illustrating that when wild bird origin AIV is inoculated into chickens, the outcome of infection varies based on virus subtype, but there can also be great variations in virus titers in, e.g., oropharyngeal swabs within a group infected with the same virus ( 6 , 48 ).…”

Strength in numbers: Avian influenza A virus transmission to poultry from a flocking passerine

“…Nonetheless, in a previous study associated with the interspecific transmission of an IAV, some quail ( Coturnix sp.) showed evidence of shedding viral RNA but did not seroconvert by the end of the study period (Root et al., 2017). Furthermore, one quail in the study mentioned above showed no evidence of exposure even though both quail that it was co‐caged with shed viral RNA or shed viral RNA and seroconverted (Root et al., 2017).…”

“…Bobwhite quail ( Colinus virginianus ; hereinafter referred to as ‘quail’) were purchased from a commercial vendor. Generically speaking, quail have been previously shown to be a well‐suited recipient species in IAV transmission studies (Bosco‐Lauth et al., 2016; Root et al., 2017). Additionally, the transmission scenario we mimicked could be informative to both poultry and wild game bird settings.…”

Revealing interspecies transmission barriers of avian influenza A viruses

“…Notably, H6N2 was shed at high loads both in oropharyngeal swabs and in tissue samples from both bird species. This virus subtype is very common in wild mallards 41, 50, 51 and has been demonstrated to infect gallinaceous birds including pheasants and quails 52 as well as chickens 53 . On the other hand, the unsuccessful infection in chickens with the H9N2 subtype was unexpected as LPAIV H9N2 is endemic in chickens in many countries 54 .…”