Antiviral Drugs in Wildlife Patients

National Wildlife Rehabilitators Association

Veterinary Committee Statement

Regarding the Use of Human Antiviral Drugs in Wildlife Patients

Avian influenza and other emerging viruses are increasingly a significant threat to the health of wild birds, zoo species, poultry, and people around the world.  There are currently four approved antiviral drugs, in two classes, for the treatment or prevention of influenza A in humans. These are the adamantanes (amantadine and rimantadine) and the neuraminidase inhibitors (oseltamivir and zanamivir).  The drugs are not approved for use in the treatment or prevention of influenza or other viral infections in animals.

If and when a strain of highly pathogenic avian influenza (HPAI) capable of transmission to humans and adapted to human-to-human spread arrives in the United States, Tamiflu^® (oseltamivir phosphate, Roche Laboratories, Inc., Nutley, NJ) will be used as the first line of defense for preventing a catastrophic viral epidemic in humans.  Unfortunately, avian influenza viruses can mutate rapidly and the Asian strain HPAI H5N1 already has shown some resistance to these few anti-viral drugs available to treat the disease in people <http://www.who.int/csr/disease/influenza/H1N1ResistanceWeb20080505.pdf>.

Public health professionals whom we have consulted have recommended in very strong terms that these drugs NOT be used in wildlife.  When Tamiflu^® is used and then metabolized and excreted by people or other animals, it can persist in the environment for extended periods, potentially leading to avian influenza viruses acquiring drug resistance (Singer et al 2007).  Using the medication in wildlife for the prevention of other viral diseases (like parvovirus, distemper, etc.) might well lead to a highly resistant form of avian influenza and other viruses in the environment for which there would be no useful treatments should humans become sick.                                              

In 2005, the World Health Organization (WHO), Food and Agriculture Organization (FAO), and World Organization for Animal Health  (OIE) issued a joint statement urging “… not to use antiviral drugs in animals so that the efficacy of these drugs can be preserved for treatment of influenza infections in humans” and strongly requested Member States to ban the use of antiviral drugs in animals (WHO 2005).  On March 22, 2006, the FDA published a final rule prohibiting the extra-label use of adamantine and neuraminidase inhibitor classes of antiviral drugs in chickens, turkeys, and ducks (Regulations.gov, and FDA 21 CFR 530.41)

Given these regulatory prohibitions and the global concerns for the potential for a world-wide human health crisis surrounding influenza, the NWRA Veterinary Committee STRONGLY recommends that wildlife rehabilitators NOT use these drugs in our wildlife patients and that veterinarians NOT prescribe these drugs for extra-label use in animals.

FDA 21 CFR 530.4. Extra-label Drug Use in Animals. Last updated April 2007. Available at: <http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=530.41>

Regulations.gov. May 2008. New Animal Drugs; Adamantane and Neuraminidase Inhibitor Anti-influenza Drugs; Extralabel Animal Drug Use; Order of Prohibition. Available at: <http://www.regulations.gov/fdmspublic/component/main?main=DocketDetail&d=FDA-2006-N-0487>

Singer, A. C., M. A. Nunn, E. A. Gould, and A. C. Johnson. 2007. Potential Risks Associated with the Proposed Widespread Use of Tamiflu. Environmental Health Perspectives, Volume 115, Number 1.  

World Health Organization. 2005. Use of antiviral drugs in poultry, a threat to their effectiveness for the treatment of human avian influenza. Available at:

<http://www.who.int/foodsafety/micro/avian_antiviral/en/print.html>

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