American Association of Swine Veterinarians position statement on pandemic (H1N1) 2009 influenza
AASV issues recommendations on A/H1N1 2009 pandemic influenza virus

The American Association of Swine Veterinarians (AASV) Board of Directors has approved the adoption of a series of position statements regarding the A/H1N1 2009 pandemic influenza virus. The document was developed by the AASV H1N1 Influenza Working Group chaired by Dr Joe Connor.

While pork continues to be safe to eat, concerns have arisen regarding the potential cross-species transmission of the novel virus. Recognizing the necessity to protect both animal and human health, the AASV Executive Committee created the working group, which it charged with examining the influenza issue and developing recommendations based on the best available current knowledge and pertinent published literature.

In response, the working group developed a series of recommendations to address concerns in four broad topic areas: protection of swine workers, vaccination of swine herds, vaccine development, and movement of animals from herds infected with the novel virus. The specific recommendations are outlined below. The complete document containing additional details is available online at

The emergence of the pandemic (H1N1) 2009 influenza virus has reminded us of the potential for cross-species transmission of influenza viruses. As veterinarians, we believe that protecting human health is of primary importance, and all reasonable measures should be taken to avoid any unnecessary risk to human health. The “One Health Initiative” of the American Veterinary Medical Association and the American Medical Association recognizes the impact that animals have on human health and vice versa.1 An essential component of protecting human health is providing a safe, high quality, and affordable food supply.

Influenza recommendations for pork-production staff, veterinarians, and harvest-plant workers

To protect both human health and the food supply, the AASV strongly advises that all personnel working in the pork-production industry be vaccinated against seasonal influenza annually and against any novel human influenza A viruses as they emerge.2-5 Vaccination enhances protection for personnel while minimizing the likelihood of viral transmission from personnel to pigs.

Therefore the AASV recommends that:

  • Swine owners continue to encourage, facilitate, and financially support employee vaccination against seasonal influenza viruses.
  • All personnel associated with pork production and harvest in North America be given high priority for vaccination against any novel influenza virus that emerges in the human population.
  • The Centers for Disease Control and Prevention, state departments of health, and local health departments work in close cooperation with, solicit input from, and collaborate in the decision-making process with USDA-APHIS, state animal health officials, and local veterinarians through the establishment of working groups and defined communication channels to facilitate the implementation of vaccination plans across North America.
  • All personnel associated with pork production and harvest intensify basic hygiene and biosecurity practices.

Influenza vaccination recommendations for swine

While humans have taken the approach of annual vaccine strain updates in attempts to minimize influenza illness and death, control of influenza in swine herds has been less flexible. Vaccination of swine with killed virus vaccines has been employed with varying degrees of success since the mid-1990s. As more strains of SIV emerged, biological companies have added contemporary strains to their existing, commercially licensed vaccines, resulting in bivalent and trivalent vaccines carefully balanced to induce immunity to all subtypes of SIV in the vaccine. Alternatively, autogenous killed influenza virus vaccines have gained in popularity to better match the antigenic and genetic differences of new SIV strains when compared to the commercial vaccine virus strains. A change in vaccine strain is generally recommended when issues such as antigenic correctness, timing, adjuvant, and co-infections have been properly addressed. More often, the decision to use an autogenous vaccine is driven by a need to more immediately respond with a specific and rapid solution to the problems unsolved by the use of commercial vaccines.

The AASV recommends:

  • Vaccination with currently approved vaccines for the control of swine influenza should continue to be used to control clinical signs of disease due to swine influenza virus as recommended on each product’s label.
  • Vaccination of swine against the pandemic (H1N1) 2009 influenza virus should be implemented if scientific evidence demonstrates that vaccination reduces virus shedding and the risk of transmission to pork-production personnel.
  • Increased funding and research on novel delivery methods and vaccines to rapidly develop and introduce safe, effective vaccines against novel influenza viruses that not only minimize the risk of transmission between species but also overcome maternal immunity.
  • Increased funding and research on the utilization of technologies, such as core matrix, that would enable the rapid updating of influenza vaccines to incorporate emerging strains, promote cross-protection against multiple influenza strains and facilitate the development of a differential vaccine.

Development of a national influenza vaccine strain selection system for swine

To protect both human health and the food supply, the AASV recognizes that minimizing the risk of cross-species transmission of influenza A viruses is critically important. Vaccination has been a useful tool for control of clinical disease due to influenza in humans. However, there is conflicting data regarding the use of currently available killed influenza vaccines in swine to control shedding or transmission of influenza between pigs. The AASV believes that it would be useful to have a vaccine strain selection system for swine production that is similar to the World Health Organization (WHO) system used for human vaccines. However, there are several barriers preventing implementation of this system in animals.6-16

Therefore, the AASV recommends:

  • The development of a system modeled on the WHO system for strain selection that facilitates the production of national or regional influenza vaccines for swine.
  • Increased government funding and infrastructure to support the surveillance of influenza strains of swine and the development of vaccine strategies that reduce influenza risk.
  • That the Center for Veterinary Biologics (CVB) promote new technology and streamlined vaccine approval methods to enable the timeliness of market entry, given the potential frequency of influenza antigenic drift and shift.
  • That universities, diagnostic laboratories, and commercial organizations release their rights to ownership of influenza genetic material for the purpose of production of a national influenza vaccination program for swine.

Swine movements in herds infected with novel type A influenza virus

To protect both human health and the food supply, the AASV recognizes that minimizing the risk of cross-species transmission of influenza A viruses is critically important. Slowing the rate at which swine herds are infected and the total number of herds infected with a novel type A influenza is an important “One World, One Health” control strategy. Historically, limiting movements between production sites early in an outbreak has been an accepted measure to contain a disease outbreak and minimize or stop introduction into new herds. Practically, these measures have been of limited value in situations where there is a high degree of mobility of potentially infected animals or people and where shedding of the organism occurs prior to significant clinical signs. This was the case in the recent introduction of the pandemic (H1N1) 2009 influenza infection in humans, where infection spread to multiple countries before it was detected and accurately diagnosed.

Therefore the AASV recommends that:

  • Pork producers cooperate fully and actively participate in the development and implementation of surveillance programs established by federal, state, and local governments to promote a full understanding of the extent of a novel virus spread in the US swine herd.
  • Producers consult with and implement the recommendations of their veterinarian to fully understand any potential new infections in their herds, and veterinarians use the best available information to make science-based decisions on appropriate control measures for those herds.
  • Movements of animals originating from infected herds are continued under the supervision of the herd veterinarian(s) in accordance with state and federal regulations (refer to USDA’s H1N1 Response Guidelines) and standard industry procedures.
  • The discovery of novel influenza strains in pork production systems be confidential regarding owner and location and that producers be protected by indemnity if quarantine or depopulation methodologies are employed by local, state, or national health control officials.


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