Pathogenicity and Transmissibility of North American H7 Low Pathogenic Avian Influenza Viruses in Chickens and Turkeys.

Low pathogenic avian influenza (LPAI) viruses can silently circulate in poultry and wild aquatic birds and potentially mutate into highly pathogenic avian influenza (HPAI) viruses. In the U.S., recent emergence and spread of H7N8 and H7N9 HPAI viruses not only caused devastating losses to domestic poultry but also underscored the capability of LPAI viruses to mutate into HPAI viruses. Therefore, in this study, we evaluated pathogenicity and transmissibility of H7N8 and H7N9 LPAI viruses (the progenitors of HPAI viruses) in chickens and turkeys. We also included H7N2 isolated from an outbreak of LPAI in commercial chickens. H7 viruses replicated more efficiently in the respiratory tract than in the gastrointestinal tract, suggesting that their replication is restricted to the upper respiratory tract. Specifically, H7N2 replicated most efficiently in two-week-old chickens and turkeys. In contrast, H7N8 replicated least efficiently in those birds. Further, replication of H7N2 and H7N9 was restricted in the upper respiratory tract of four-week-old specific-pathogen-free (SPF) and broiler chickens. Despite their restricted replication, the two viruses efficiently transmitted from infected to naïve birds by direct contact, leading to seroconversion of contacted chickens. Our findings suggest the importance of continuous monitoring and surveillance of LPAI viruses in the fields.

A Novel A(H7N2) Influenza Virus Isolated from a Veterinarian Caring for Cats in a New York City Animal Shelter Causes Mild Disease and Transmits Poorly in the Ferret Model.

In December 2016, a low-pathogenic avian influenza (LPAI) A(H7N2) virus was identified to be the causative source of an outbreak in a cat shelter in New York City, which subsequently spread to multiple shelters in the states of New York and Pennsylvania. One person with occupational exposure to infected cats became infected with the virus, representing the first LPAI H7N2 virus infection in a human in North America since 2003. Considering the close contact that frequently occurs between companion animals and humans, it was critical to assess the relative risk of this novel virus to public health. The virus isolated from the human case, A/New York/108/2016 (NY/108), caused mild and transient illness in ferrets and mice but did not transmit to naive cohoused ferrets following traditional or aerosol-based inoculation methods. The environmental persistence of NY/108 virus was generally comparable to that of other LPAI H7N2 viruses. However, NY/108 virus replicated in human bronchial epithelial cells with an increased efficiency compared with that of previously isolated H7N2 viruses. Furthermore, the novel H7N2 virus was found to utilize a relatively lower pH for hemagglutinin activation, similar to human influenza viruses. Our data suggest that the LPAI H7N2 virus requires further adaptation before representing a substantial threat to public health. However, the reemergence of an LPAI H7N2 virus in the northeastern United States underscores the need for continuous surveillance of emerging zoonotic influenza viruses inclusive of mammalian species, such as domestic felines, that are not commonly considered intermediate hosts for avian influenza viruses.IMPORTANCE Avian influenza viruses are capable of crossing the species barrier to infect mammals, an event of public health concern due to the potential acquisition of a pandemic phenotype. In December 2016, an H7N2 virus caused an outbreak in cats in multiple animal shelters in New York State. This was the first detection of this virus in the northeastern United States in over a decade and the first documented infection of a felid with an H7N2 virus. A veterinarian became infected following occupational exposure to H7N2 virus-infected cats, necessitating the evaluation of this virus for its capacity to cause disease in mammals. While the H7N2 virus was associated with mild illness in mice and ferrets and did not spread well between ferrets, it nonetheless possessed several markers of virulence for mammals. These data highlight the promiscuity of influenza viruses and the need for diligent surveillance across multiple species to quickly identify an emerging strain with pandemic potential.

Pathobiology and transmission of highly and low pathogenic avian influenza viruses in European quail (Coturnix c. coturnix).

European quail (Coturnix c. coturnix) may share with Japanese quail (Coturnix c. japonica) its potential as an intermediate host and reservoir of avian influenza viruses (AIV). To elucidate this question, European quail were experimentally challenged with two highly pathogenic AIV (HPAIV) (H7N1/HP and H5N1/HP) and one low pathogenic AIV (LPAIV) (H7N2/LP). Contact animals were also used to assess the viral transmission among birds. Severe neurological signs and mortality rates of 67% (H7N1/HP) and 92% (H5N1/HP) were observed. Although histopathological findings were present in both HPAIV-infected groups, H5N1/HP-quail displayed a broader viral antigen distribution and extent of microscopic lesions. Neither clinical nor pathological involvement was observed in LPAIV-infected quail. Consistent long-term viral shedding and effective transmission to naive quail was demonstrated for the three studied AIV. Drinking water arose as a possible transmission route and feathers as a potential origin of HPAIV dissemination. The present study demonstrates that European quail may play a major role in AI epidemiology, highlighting the need to further understand its putative role as an intermediate host for avian/mammalian reassortant viruses.

Optimal specimen collection and transport methods for the detection of avian influenza virus and Newcastle disease virus.

BACKGROUND: Active and passive surveillance for avian influenza virus (AIV) and Newcastle disease virus (NDV) is widespread in commercial poultry worldwide, therefore optimization of sample collection and transport would be valuable to achieve the best sensitivity and specificity possible, and to develop the most accurate and efficient testing programs. A H7N2 low pathogenicity (LP) AIV strain was selected and used as an indicator virus because it is present in lower concentrations in swabbings and thus requires greater sensitivity for detection compared to highly pathogenic (HP) AIV. For similar reasons a mesogenic strain of NDV was selected. Using oro-pharyngeal and cloacal swabs collected from chickens experimentally exposed to the viruses we evaluated the effects of numerous aspects of sample collection and transport: 1) swab construction material (flocked nylon, non-flocked Dacron, or urethane foam), 2) transport media (brain heart infusion broth [BHI] or phosphate buffered saline [PBS]), 3) media volume (2 ml or 3.5 ml), 4) transporting the swab wet in the vial or removing the swab prior to transport, or transporting the swab dry with no media, and 5) single swabs versus pooling 5 or 11 swabs per vial. RESULTS: Using real-time RT-PCR (rRT-PCR), virus isolation (VI) and commercial antigen detection immunoassays for AIV we observed statistically significant differences and consistent trends with some elements of sample collection and transport; media, dry transport and swab construction. Conversely, the number of swabs pooled (1, 5 or 11) and whether the swab was removed prior to transport did not impact virus detection. Similarly, with NDV detection by both VI and rRT-PCR was not affected by the numbers of swabs collected in a single vial (1, 5 or 11). CONCLUSIONS: We observed that flocked and foam swabs were superior to non-flocked swabs, BHI media was better than PBS, and transporting swabs wet was better for virus recovery and detection than transporting them dry. There was no observable difference in detection whether the swab was removed prior to transport or left in the vial. Also, with both AIV and NDV, there was no observed difference in virus detection between pools of 1, 5 or 11 swabs.