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Feature   |  Spring 2006

National defense

Bird flu one of many infectious diseases on scientists' watch

Suresh Mittal and a team of researchers developed a bird flu vaccine that has shown promising results during testing. (Photo by Tom Campbell)

From viruses to vaccines

Mittal and his colleagues at the Centers for Disease Control and Prevention (CDCP) and Harm HogenEsch, head of Purdue's Department of Veterinary Pathobiology, have developed a new type of human bird flu vaccine based on an adenovirus. In tests on mice, it has proved 100-percent effective in preventing illness and death from H5N1. The National Institute of Health's National Institute of Allergy and Infectious Diseases (NIAID) is funding the project with a $1.6-million grant.

An adenovirus is a harmless virus used to transport therapeutic drugs into cells. It cannot cause disease in people but grows well in a number of established cell lines. Mittal worked with viruses, including adenovirus, during graduate and post-graduate training. When he launched his own research, that interest continued.

“I was looking for a pathogen we could work against that would have a major effect on people and animals,” he says. “Knowing that flu causes a lot of problems worldwide in pigs, poultry and humans, it made sense to do something on influenza.”

Doctors and veterinarians in Mittal's native land of India deal with a number of zoonotic diseases, including rabies. Dogs are the primary carriers of rabies, which kills about 10,000 people in India each year. In contrast, rabies in the United States is transmitted mainly by wild animals, such as bats, skunks, coyotes and raccoons, depending on the region. Human cases are rare because domesticated animals are vaccinated.

Collaborations and challenges

Federal, state, and local agencies, universities and private organizations work together, using epidemiologic data and testing to track zoonotic diseases.

Last year, the Purdue-based ADDL tested 2,300 poultry samples for signs of various types of bird flu. Additionally, tests by Purdue-connected labs around the state brought the total number of tests to about 22,000. No bird flu was found, Thacker says.

ADDL is part of the National Animal Health Laboratory Network, composed of 55 laboratories in 42 states. It's designed to aid in early detection of foreign animal disease agents and newly emerging diseases to enhance response to animal health emergencies, including bioterrorist events. These testing facilities can provide approximately 18,000 tests daily for various strains of avian influenza and other diseases.

Other groups have joined the surveillance effort to identify early outbreak signs. Glickman works with Banfield, The Pet Hospital to monitor zoonotic illnesses through its National Companion Animal Surveillance System. The national chain of 500 veterinary clinics can add information within 90 seconds to a database about any dog or other pet that exhibits symptoms of influenza, tularemia and other diseases.

The fast emergence, mutation and spread of zoonoses are illustrated by lepto, now considered the most widespread zoonotic disease worldwide. Since 1990, many new lepto strains have appeared; about 200 are currently known. But experts don't know why lepto is reaching epidemic levels in animals. “Lepto used to be mainly in dogs and rats, but now it's in a lot a species,” says Glickman. “It might be because of wildlife ecology; we continue to move into their territory.”

People won't contract lepto from their pets unless they have direct contact with urine, mucus or raw tissue during an animal's infectious period. Bird flu H5N1 was identified in 1961, with the first human cases appearing in 1987. This year, the disease has been confirmed in people in Southeast Asia, China, Turkey and Iraq, with a number of cases being investigated in India. It has spread from poultry to migratory waterfowl. In February, 13 countries reported their first cases of the infection in birds. The area where bird flu has been found encompasses Southeast Asia, China, India, Egypt, Africa, and Eastern and Western Europe. U.S. agencies have expanded the number of migratory birds to be tested for H5N1.




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