become apparent 4 . Common clinical signs include fever and cough, although sore throat, joint pain, muscle pain, and shortness of breath have also been reported 18 . It is suspected that the virus’s dramatic effects are due to a combination of two factors. First, the virus induces apoptosis of airway epithelial cells. Second, avian influenza triggers high cytokine levels or a “cytokine storm,” further contributing to the inflammation caused by the virus itself 3 . In addition, there have been reports of patients who present with less common symptoms, including diarrheal and gastrointestinal disease and meningoencephalitis 3 . Human influenza testing can be performed using a number of methods, including viral culture, polymerase chain reaction (PCR), rapid antigen testing, and immunofluorescence using samples from either the upper or lower respiratory tract 3 . The identification of potential avian influenza strains, however, requires sending samples to an appropriate reference laboratory 3 . Treatment of avian influenza, like other human influenza infections, relies on antiviral medications and supportive care. The neuraminidase inhibitors (NIs), oseltamivir [Tamiflu ® ] and zanamivir [Relenza ® ], have been demonstrated to be more effective in cases of H5N1 HPAI. Some other strains of influenza respond well to M2 ion-channel inhibitors such as amantadine. Antiviral resistance can become a problem; therefore, the optimum drugs for treatment of an influenza strain are frequently changing 3 . A 2007 study indicated that veterinarians who work with birds are significantly more likely than the general public to have antibodies against the avian influenza strains H5, H6, and H719. It has also been documented that hunters and other individuals Avian influenza in other mammals Although the current strain of H5N8 HPAI has not been observed in other mammals, H5 strains of HPAI have previously been found to infect mammals and there is a concern that they could do so again. The incubation period of avian influenza in non- human mammals is short, often as little as 1 to 2 days 6 . Once infected, mammals can show varying degrees of respiratory and systemic signs, depending on the virus strain and the animal’s underlying health. Asian lineage H5N1 HPAI, a relative of the current H5N8 HPAI strain, has been associated with many disease presentations in mammals. Feline species appear to show some degree of
in contact with wild birds have higher seropositive rates than the general public 3 . Public health officials have been monitoring those individuals working with H5N8 HPAI within the United States, performing influenza testing to assess for the possibility of zoonotic disease. To date, there have been no human cases of H5N8. Still, given the zoonotic potential of some other avian influenza viruses, the CDC has recommended that H5N8 HPAI be view as a potentially zoonotic virus 17 . Individuals should use appropriate personal protective equipment (PPE) when working with sick, or potentially sick, birds. This PPE should include protective clothing, heavy gloves, boots, goggles, and masks and individuals should be provided with information on how to safely use the PPE 3 . Individuals who handle birds that may be infected with HPAI should also be monitored closely for upper respiratory signs for 10 days following exposure. There may also be a role for antiviral drugs in exposed individuals, especially those deemed high risk 17 . The decision of whether to provide prophylactic treatment to an exposed individual should be made by the individual’s doctor and based on their personal risk assessment. If antivirals are initiated, it is recommended to use oseltamivir [Tamiflu] and zanamivir [Relenza] at the twice-daily dosing usually recommended for treatment, instead of the once-daily dosing typically recommended for prophylaxis. This twice-daily dosing recommendation is based on avian influenza having been previously observed to require higher doses of antivirals for prophylaxis than other influenza strains, as well as a desire to avoid fostering viral resistance 20 . H5N1 susceptibility, with some infected housecats remaining asymptomatic and others developing respiratory signs, neurologic signs, and sudden death 4 . Cases of respiratory and neurologic disease associated with H5N1 HPAI have also been documented in tigers, leopards, dogs, and captive palm civets 4 . On necropsy, mammals infected with avian influenza can demonstrate both respiratory and systemic lesions. Pulmonary lesions may include pulmonary edema, lung consolidation, and pneumonia. Elsewhere in the body, findings such as internal organ hemorrhage, hepatic necrosis, hemorrhagic pancreatitis, and congestion of the brain, spleen, and kidneys may be noted 4 .
U.S. RESPONSE TO H5N8 HPAI
Many U.S. agencies are working together to coordinate the efforts to contain and eradicate avian influenza. Veterinarians should be aware of these agencies and their responsibilities for USDA Due to the financial implications of HPAI, as well as potential for public health effects, the USDA is heavily invested in controlling HPAI and is responsible for managing all detected outbreaks of this disease. The USDA has a number of stated goals related to avian influenza, each of which is related to controlling this virus and containing outbreaks. The USDA outlines two key strategies to be utilized to reduce future HPAI outbreaks, in addition to their quarantine/ depopulate approach: 1. First, the USDA has published materials designed to educate poultry producers about the importance of biosecurity and methods for keeping their flocks free of avian influenza. 2. Next, the USDA has developed a program for the surveillance of wild birds to detect HPAI that may be present within a given geographic area. As a collaboration between the USDA, the Department of Interior (DOI) U.S. Geological Survey (USGS), the DOI Fish and Wildlife Service, and state
controlling the response effort to provide appropriate guidance in case of suspected avian influenza infections.
departments of natural resources, this program involves sampling as many as 40,000 wild birds per year, looking for naturally occurring HPAI. Data from this surveillance will be shared with poultry producers and other involved parties, to encourage biosecurity and keep people aware of ongoing or changing risks in their particular geographic area 2 . The USDA is also working to enhance its ability to respond to HPAI outbreaks. Through collaboration with state departments and industry leaders, especially in those states with high poultry populations, the USDA is working to ensure that each state has a plan in place to deal with a possible HPAI outbreak. Additionally, the USDA has trained teams of professionals that can be deployed to HPAI outbreak sites to help with large-scale depopulation and disposal. The USDA has also created a task force charged with working with zoological parks and wildlife rehabilitation facilities to manage the intersection between agricultural/public health goals and conservation goals 2 .
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