Intercontinental Movement of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4 Virus to the United States, 2021.

We detected Eurasian-origin highly pathogenic avian influenza A(H5N1) virus belonging to the Gs/GD lineage, clade 2.3.4.4b, in wild waterfowl in 2 Atlantic coastal states in the United States. Bird banding data showed widespread movement of waterfowl within the Atlantic Flyway and between neighboring flyways and northern breeding grounds.

Pathogen exposure in feral swine populations geographically associated with high densities of transitional swine premises and commercial swine production.

Surveys for evidence of exposure to pseudorabies virus (PRV), Brucella suis, swine influenza virus (SIV; human-like H1N1, reassortant type H1N1, H1N2-like H1N1 and H3N2), porcine circovirus 2 (PCV 2), and porcine respiratory and reproductive syndrome virus (PRRSV) in feral swine (Sus scrofa) were conducted in areas where feral swine were geographically associated with high densities of transitional swine premises in South Carolina and high densities of commercial swine production in North Carolina. In South Carolina, 10/50 (20.0%), 7/50 (14.0%), and 29/49 (59.2%) feral swine tested antibody positive for PRV, B. suis, and PCV-2, respectively. Antibodies to PRRSV (0/49) and SIV (0/49) were not detected. In North Carolina, antibodies to PRV and B. suis were not detected in serum samples from 120 feral swine; however, antibodies to PRRSV (1/120 [0.8%]), PCV-2 (86/120 [71.7%]; these included 80 positives plus six suspects), and SIV (108/119 [90.7%]) were present. The presence of PRV and B. suis in South Carolina may have been due to the introduction of infected feral swine into the area or to a previous association of feral swine with infected transitional swine. Their absence in the North Carolina populations may have been due to the absence of these disease agents in the feral swine originally introduced into the area and the lack of a potential for contact with infected commercial swine. Feral swine associated with commercial swine in North Carolina may have been exposed to SIV subtypes circulating in commercial swine via airborne spread of SIV from commercial swine facilities. Feral swine seropositive for PCV-2 were prevalent in both states, which may indicate efficient transmission from commercial swine and transitional swine, or that PCV-2 is widespread in feral swine. The low prevalence of animals with antibodies against PRRSV may indicate a less-than-efficient means of transmission from commercial to feral swine. Additional epidemiologic studies are needed to understand the risks and mechanisms of transmission of disease agents among commercial, transitional, and feral swine, and the role of feral swine as reservoirs of these disease agents.

Pseudorabies in feral swine in the United States, 2009-2012.

Although pseudorabies virus can affect a wide range of mammalian and avian hosts, swine are the only natural hosts of the virus. The US commercial swine industry obtained pseudorabies-free status in 2004, which was important because of the economic value of domestic swine production; however, feral swine remain competent hosts and represent a constant threat for reintroducing the virus into the commercial industry. To better assess feral swine infection status, we collected 8,498 serum samples from feral swine across the United States between 1 October 2009 and 30 September 2012. Of these, 18% were antibody positive in 25 of 35 states where samples were collected, indicating that transmission risk is widespread.

Antibodies to avian influenza viruses in Canada geese (Branta canadensis): a potential surveillance tool?

Traditionally, the epidemiology of avian influenza viruses (AIVs) in wild birds has been defined by detection of virus or viral RNA through virus isolation or reverse-transcription polymerase chain reaction. Our goals were to estimate AIV antibody prevalence in Canada geese (Branta canadensis) and measure effects of age and location on these estimates. We collected 3,205 samples from nine states during June and July 2008 and 2009: Georgia, Massachusetts, Minnesota, Mississippi, New Jersey, North Carolina, Pennsylvania, Washington, and West Virginia. Serum samples were tested for AIV antibodies with the use of a commercial blocking enzyme-linked immunosorbent assay. Overall, 483 (15%) Canada geese had detectable antibodies to AIV. Significantly higher prevalences were detected in geese collected from northeastern and upper midwestern states compared with southeastern states. This trend is consistent with results from virus isolation studies reporting AIV prevalence in North American dabbling ducks. Within Pennsylvania, significantly higher antibody prevalences were detected in goose flocks sampled in urban locations compared to flocks sampled in rural areas. Antibody prevalence was significantly higher in after-hatch-year geese compared to hatch-year geese. No significant differences in prevalence were detected from 10 locations sampled during both years. Results indicate that Canada geese are frequently exposed to AIVs and, with resident populations, may potentially be useful as sentinels to confirm regional AIV transmission within wild bird populations.