August 15, 2006

 

 Protecting against avian influenza - August 15, 2006

 


posted August 1, 2006
 

The most recent outbreak of avian influenza in the United States, which occurred in 2004, was quickly contained and eradicated, thanks to the immediate and coordinated response of the government, industry, and veterinary leaders. Preparing for future outbreaks will also require a cooperative effort, and the role of veterinarians will be wide-ranging. From serving in an official capacity as state veterinary officials to responding to pet owner concerns as private practitioners, veterinarians will serve in a variety of ways to help educate and protect staff members, clients, and animal patients.

Dr. Leon H. Russell, president of the World Veterinary Association and a world-renowned expert on avian influenza, urges all veterinarians to take seriously the possibility that they could be the first line of defense against an outbreak in this country.

Because 95 percent of the chickens produced in the United States are raised under secure conditions, Dr. Russell believes poultry producers already are well-prepared against an outbreak. Where private practice veterinarians could make a real difference is with small hobby flocks and pet birds.

"Pet birds are sometimes smuggled into this country and show up at pet shops or at swap meets," Dr. Russell said. "Thousands of birds come into the country every day—and there are only 120 inspectors. If the virus should come to Latin America, it won't be long before we see it here in the United States in pet birds."

Dr. Russell pointed out that the 1971 outbreak of exotic Newcastle disease was first recognized by a private practitioner. The West Nile virus was first identified by a zoo veterinarian. An outbreak of monkeypox was identified by a Wisconsin veterinarian.

What are the odds of a veterinarian encountering a case of avian influenza in practice?

Dr. Y.M. Saif, a professor at The Ohio State University College of Veterinary Medicine and head of the Food Animal Health Research Program at the Ohio Agricultural Research and Development Center, said it is impossible to calculate such odds.

"I am very confident, should the virus ever get to the U.S., a prompt diagnosis will be made. The best-case scenario is to control the virus at the point where it first appears. We have a strong diagnostic lab system, well-equipped and staffed by veterinarians who can make that first diagnosis and supervise the control."

It is important to differentiate between the many subtypes of influenza viruses. Influenza viruses are classified on the basis of the relative numbers of hemagglutinin and neuraminidase antigens they have on their surfaces. Avian influenza is further defined by whether it is of high pathogenicity or low pathogenicity.

Low-pathogenic avian influenza has no effect or a mild effect on poultry and other birds. It is the highly pathogenic version that is of concern. The virus that has been making the news recently is a highly pathogenic version—the H5N1 strain. This is the virus affecting birds in Asia, Europe, the Middle East, and Africa. To date, there have been no cases of the H5N1 highly pathogenic avian influenza identified in the United States.

The chances of a U.S. veterinarian encountering a case of H5N1 or another highly pathogenic strain of avian influenza most likely will remain low. However, veterinarians should be prepared to advise clients as well as to take proper occupational safety precautions to protect themselves, co-workers, clients, and animal patients in case circumstances change.

Circumstances have changed in parts of Asia, Africa, and Europe, where the H5N1 virus has infected wild birds, as well as domestic poultry, pets, and farm animals. Eating the raw carcass of an infected bird poses a risk to animals and is the likely cause of the documented death earlier this year of a domestic cat in Germany.

In areas where a highly pathogenic strain of the avian influenza has been diagnosed or suspected in wild birds or poultry flocks, veterinarians should advise their clients of the small risk to their pets. Cats should be kept indoors. Dogs should be leashed when outdoors. Domestic birds must be kept away from wild birds, especially waterfowl. Animal owners should not allow their pets to have any access to wild or stray animals or the feces of those animals.

Dr. Saif reminds veterinarians that there is no evidence the virus moves from one pet to another. Dr. Russell confirmed that the H5N1 virus is different from the human influenza virus in that the avian influenza virus attaches deep in the lungs, making it harder to transmit.

As a precaution, however, Dr. Saif recommends that if a pet should contract a flulike illness, the causative agent should be confined. Typical precautions followed by veterinarians and staff members to prevent transmission of diseases from pet to pet, or pet to people, are also effective in preventing the spread of the avian influenza virus.

Frequent hand washing and disinfecting of examination tables and instruments will greatly reduce the risk of spreading the disease. The virus is inactivated by heat and by drying, and it is also sensitive to most disinfectants and detergents. It is critical to remove any organic material to allow proper decontamination of the area.

The WHO provides guidelines for veterinarians and laboratory animal workers who handle specimens suspected of containing avian influenza virus. Among its recommendations are the use of eye protection, disposable gowns, and gloves. The WHO cautions that procedures that could form aerosols or droplets should be avoided, and physical containment devices should be used for any manipulations that may cause splashes, droplets, or aerosols of infectious materials. Daily decontamination of work surfaces and equipment is also advised.

Veterinarians who handle sick or dead birds need to take similar precautions. In a bulletin published by the National Wildlife Health Center, individuals are cautioned to work in well-ventilated areas when indoors and to work upwind of animals outdoors to minimize the risk of inhaling dust, feathers, or dander. Recommended protective gear includes rubber or latex gloves, protective eye gear or face shields, coveralls, and rubber boots. Protective gear should be disposed of, disinfected, or both. Hands should be washed frequently, and work surfaces and instruments should be disinfected often.

"The virus can persist for a long time on surfaces," Dr. Russell said. "It can survive up to six weeks in chicken feces. The danger of dried feces is that it can become aerosolized."

The potential for infection through food or water sources is greatly mitigated in the United States. Thorough cooking of poultry and eggs kills the virus. Chlorination takes care of any potential spread of the virus from waterfowl into surface water—a large source of U.S. drinking water.

Veterinarians working in an area where a highly pathogenic strain of avian influenza has been detected, and who come into contact with diseased animals, need to monitor their own health carefully for clinical signs of influenza. A fever, flulike symptoms, or conjunctivitis should be immediately brought to the attention of a health care provider, who also needs to be told of the potential exposure to avian influenza.

Dr. Nina Marano, branch chief in the Geographic Medicine and Health Promotion Branch at the Centers for Disease Control and Prevention, said that no national veterinary guidelines for infection control exist. The good news is a consortium of public and private health care leaders have been working on such guidelines.

"There is a lot of debate on what type of personal protective equipment is necessary," Dr. Marano said. "The current guidelines are interim and continuously being updated."

At a minimum, Dr. Marano would recommend gloves and a face shield in the event a veterinarian was dealing with a suspicious case. She advises veterinarians to be alert to anything unusual and to pay attention to news coming from the media. She also urges all veterinarians to know who to call to report an incident.

"Call your state veterinarian," she advised. "And in 46 states, we also have a state public health veterinarian, who is assigned to the state health department. This individual, in addition to their veterinary training, has advanced training in public health, and will be able to help think through the human health issues."

Because of the safeguards being taken on a national level, the likelihood of an outbreak of avian influenza among U.S. birds or other animals has been greatly minimized. But staying aware of any breaking news and being prepared on the local level to protect staff and respond to pet owners is a task all veterinarians can undertake as part of their service.

"Brush up on your background of avian influenza," Dr. Saif said. "Keep current on the situation."

"Our poultry veterinarians are, of course, very alert," Dr. Russell added. "But I want to give private practitioners credit—they'll be out there as the first line of defense."