The US Department of Agriculture is testing several highly pathogenic avian influenza (HPAI) vaccines for effectiveness in hopes of preventing the spread of the largest outbreak of avian influenza in US history. So far, the virus has been reported in all except one state, Hawaii, and has killed about 60 million poultry.
While four vaccines are licensed for avian influenza (subtypes HA, H5N1, H5N3, and H5N9), none have been licensed for the most virulent strain, H5N1 clade 2.3.4.4b, which is responsible for the current outbreak. is found. This strain probably originated in wild birds, later found its way into commercial poultry operations, and then spread in Non-human mammals, including pumas, coyotes and bottlenose dolphins, that have ingested infected birds.
country officials Started testing four candidate vaccines this April, initiating the program with single-dose trials. Preliminary trial data is expected to be available in May. Researchers expect the two-dose vaccine study to be back with results in June.
If these trials are successful, the next step is to identify manufacturers interested in producing the vaccine. Once one or more manufacturers are identified, more than a dozen steps must be completed before the final vaccine can be supplied.
Officials said the typical time frame for animal vaccine development and approval is two-and-a-half to three years Manufacturers can speed up development in emergency situations Resulting in shorter license period.
Although vaccination can substantially reduce mortality and is supported by some sectors of the poultry industry, others They are concerned that vaccinated birds may still contract the disease and transmit it., effectively reducing the spread of the virus and hindering surveillance efforts. There is also concern about how quickly the virus can mutate, potentially reducing the effectiveness of a vaccine.
Given the many challenges to vaccine development and approval, the country’s government has said it is important that bird owners consider everything they can do to protect their animals immediately.
,Biosecurity is the best defense against bird flu And all bird owners should evaluate their biosecurity plans and develop a strategy to prevent exposure to wild birds or their droppings.
Differentiated vaccine
Another major problem with vaccination against avian influenza is the potential loss of export markets, commented Karen Grogan Professor of Avian Medicine at the University of Georgia College of Veterinary Medicine.
Historically, naturally infected birds could not be distinguished from vaccinated birds, so countries imposed trade restrictions rather than risk domestic poultry flocks.
“The way to preserve business is a vaccine that allows you to do what’s called the DIVA strategy, Isolate infected from vaccinated animals” One approach is to create a vaccine that uses a type of neuraminidase isolated from the circulating virus that can be tested serologically,” he explains.
Viral neuraminidase is a particle found on the surface of the influenza virus that allows the virus to be released from the host cell.
Grogan said an avian influenza vaccine could also be approved for specialized collections of birds, such as those displayed in zoos.
