Mass depopulation isn’t the only way to stop the spread of avian influenza.
Dr. Leslie David Sims, a consultant for Asia Pacific Veterinary Information Service, Australia, said research collected since the first outbreaks of highly pathogenic avian influenza (HPAI) in the 1990s demonstrates successful application of vaccination can be effective in controlling and stopping the spread of HPAI.
During the Watt Global Media webinar, Vaccination as Part of an Avian Flu Eradication Plan, Sims presented information on how the use of vaccination has controlled and eliminated avian influenza viruses in nations other than the U.S. in the past.
Sims, who’s worked as a consultant for the Food and Agriculture Organization of the United Nations and the World Bank, has advised veterinary authorities in China, Thailand, Cambodia, North Korea, Mongolia, Indonesia and Vietnam. His presentation centered on lessons learned in almost two decades of fighting and studying the so-called “goose Quandong” strain of the HPAI virus in Southeast Asia.
Stamping out, culling of infected and susceptible flocks, has long been viewed as the only way to control the spread of HPAI. Sims said that’s not exactly true.
While this approach to stamping out does work if new cases are detected early and the response is rapid, it comes at a high cost. During the 2014-2015 HPAI outbreak in the U.S., he estimated 49 million birds were killed or culled. Sims said stamping out also depends on the density of poultry being low and is ineffective if the cull happens after the virus has already been transmitted to other flocks.
Vaccination, when used in combination with other biosecurity measures, can be just as effective in stopping the spread and eliminating the spread of HPAI. Sims noted that vaccination – without preemptive culling – was successful in stopping the spread of HPAI in Hong Kong in 2002. In 2003, vaccination, in combination with quarantine and depopulation of affected houses, was successful in stopping an outbreak that had already begun. More recently, Sims said, vaccination has been used successfully in Italy and with low pathogenic avian influenza in the U.S.
Vaccination works best when the vaccine’s antigen closely matches the genetic makeup of the pathogen, Sims said. An early response to an outbreak, as well as bio-secure administration by competent veterinary services is necessary to the success of an immunization program, too. Cooperation among government agencies and poultry industries and close monitoring of flocks are also needed.
“It’s great to have the vaccine and, hopefully, you won’t have to use it,” Sims said.
While empirical evidence demonstrates vaccination is successful, there is significant skepticism about the practice in the poultry industry. Sims said that likely comes from the inability to eliminate HPAI with vaccination in regions where it is endemic, concerns about the process of vaccination rather than the vaccine itself, concerns vaccines will be ineffective against new strains of HPAI, mistaken beliefs that only mass depopulation works and international trade concerns raised by wide-spread vaccination to prevent the spread of HPAI. Some countries, he said, will stop imports because of vaccination. However, China – where vaccination has been used for more than a decade – is still exporting poultry to Japan.
“They do this from areas where vaccine is not being used, but it shows it is possible for some countries to accept products from countries where vaccine is being used even though the product which is being exported is not subject to vaccination in those cases,” Sims said.