Once infected birds have been cleared from the facility, thorough cleaning is necessary to ensure the facility is virus-free before restocking. There are many methods available to disinfect affected areas, but the USDA recommends a dry cleaning of the facility and then heating the facility to 100°F to 120°F for 7 days, with at least 3 of those days being consecutive, as these temperatures are sufficient to kill the virus 2 . After this disinfection process, the facility must remain empty for an additional 21 days prior to reintroducing birds. During this time, the USDA will take samples to ensure the virus has been eliminated from the environment prior to authorizing restocking 9 . There has been some discussion about the possible role of vaccination in the control of HPAI. The USDA does not currently recommend vaccinating against HPAI, because there is not a vaccine that protects against the H5N8 virus strain. However, on August 17, 2015, the USDA published a Request for Proposals (RFP) that would enable the USDA to purchase avian influenza vaccines to be stockpiled or used during outbreaks. This action was designed to encourage the private sector to develop a vaccine effective against H5N8, which could help control HPAI outbreaks. While the focus would still be on eradication of the virus through quarantine and depopulation, vaccines could be used to provide some protection to poultry in high-risk areas 2 . Vaccination would be recommended in a number of situations, including high- genetic-value birds located in an outbreak area, areas with a high density of poultry, and areas with a high density of infected wild birds 12 . All vaccine use would be authorized and Avian influenza in wild birds In wild birds, LPAI often does not produce any significant clinical signs, which contributes to the virus being so effectively spread by wild migrating birds. There have been isolated reports of severe clinical signs in flocks of game birds (e.g., quail, pheasants), but these cases are uncommon and most game birds show no clinical signs of disease 4 . The effects of HPAI on wild birds are also variable. While waterfowl are typically resistant, other wild bird species can be affected by the virus in many ways. Asian lineage H5N1 HPAI has been associated with diarrhea, respiratory distress, neurologic signs, and outbreaks of high mortality in affected wilds birds, however H5N8 HPAI has not yet been observed to have such severe, widespread effects 4 . HPAI H5N8 was endemic in wild birds in the United States during the summer of 2015. Virus transmission typically increases in the fall because there are high concentrations of birds at migration staging areas, naïve young birds join the general population at these staging areas, and migration leads to geographic travel 14 . Therefore, there is a concern that an increased number of cases in wild birds will be seen. A study conducted in Korea in 2014 was one of the first to examine the effects of avian influenza on wild birds. Necropsies of 771 wild bird carcasses revealed that 22% of the tested birds were positive for H5N8 HPAI. Some of these wild birds, including waterfowl, demonstrated gross and histologic lesions in their lungs, pancreas, brains, and kidneys. Other infected Avian influenza in humans While there are currently no reports of human infection with HPAI H5N8, it is not uncommon for avian influenza viruses to demonstrate zoonotic potential. Historically, a number of avian influenza viruses have been noted to cause sporadic human infections, including H2, H7, and H9 influenza viruses 16 . These zoonotic infections have often been associated with LPAI 17 , but Asian lineage H5N1 HPAI was more recently noted to infect large numbers of exposed individuals with high mortality rates 16 . Low-pathogenicity H7N9 avian influenza has also been associated with a number of cases of zoonotic disease in China. Since 2013, over 600 humans have been diagnosed with H7N9 influenza. The mortality rate in these cases is approximately 36% and infection has been linked to exposure to infected poultry 17 .
managed by the USDA and state veterinarians to provide the most benefit. Experimental studies have demonstrated that strain-specific vaccination against avian influenza offers a decrease in clinical signs, decrease in mortality, reduced virus shedding, and resistance against viral infection. Vaccination does not confer sterilizing immunity. Vaccinated birds are still capable of spreading this infection; therefore, vaccination is not considered an effective method for the control of HPAI and is instead intended as an adjunct to other methods of virus control 6 . Vaccinated poultry would be monitored routinely to ensure that vaccination was offering benefits, and movement of these birds would be carefully controlled by government authorities 12 . Avian influenza vaccines currently under development are injectable vaccines. These vaccines can be administered to hatching eggs or day-old chicks, and confer immunity within approximately 21 days. The need for booster doses would be dependent on the bird’s lifespans; turkeys and laying hens are anticipated to need one to two booster doses over their lifespan 13 . If vaccinations have been used in a given flock, there are tests that can distinguish between exposure and vaccination. These DIVA tests (Differentiating Infected from Vaccinated Animals) can be used for surveillance in areas where vaccination is being utilized as a control strategy 4 . birds, however, were noted to have died of other causes (e.g., gunshot) with no visible H5N8 lesions, supporting the idea that asymptomatic waterfowl are a frequent occurrence and a major carrier of this virus 15 . In the United States, HPAI H5N8 has been documented to cause neurologic signs among Canadian geese. These signs can include muscle tremors, twisted necks, and circling 14 . Additionally, a group of captive falcons fed meat from HPAI- infected waterfowl developed illness and rapid death, thus raising concern about H5N8’s potential impact on raptor populations. HPAI has been detected in red-tailed hawks ( Buteo jamaicensis ), Cooper’s hawks ( Accipiter cooperii ), captive gyrfalcons ( Falco rusticolus ), peregrine falcons ( F. peregrinus ), captive great-horned owls ( Bubo virginianus ), snowy owls ( B. scandiacus ), and bald eagles ( Haliaeetus leucocephalus ). Testing in these raptors confirmed that HPAI infection caused or contributed to their deaths. However, it is not yet known whether HPAI-infected raptors have a high disease mortality rate or if these particular birds were more susceptible because of other factors 14 . Due to possible effects on raptors, there is concern among many that this virus may have significant effects on some already- threatened raptor populations, such as the California Condor ( Gymnogyps californianus ), which may prey on or scavenge infected birds 1 . Human infections with Asian lineage H5N1 HPAI were first documented in 1997, in Hong Kong poultry workers; these individuals were exposed by touching contaminated poultry or poultry parts and butchering poultry 17 . To date, over 800 individuals in Asia, Africa, and Europe have been infected with H5N1 HPAI, with a case fatality rate of approximately 60%17. Most H5N1-affected individuals report exposure to infected poultry at live bird markets or in backyard farms. Additionally, people who perform such activities as feeding live chickens or cleaning their enclosures were also noted to have high levels of H5N1 antibodies in their blood 17 . The incubation period for Asian lineage H5N1 HPAI is typically 5 to 8 days, though some cases may take up to 2 weeks to
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