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Feature   |  Spring 2006

National defense

Bird flu one of many infectious diseases on scientists' watch
Larry Glickman's dog Indy survived leptosporosis, a disease that is reaching epidemic levels worldwide. Like avian influenza, lepto can be passed directly from animal to animal. Fully recovered, Indy is a familiar sight at Purdue's School of Veterinary Medicine, where Glickman is a professor. (Photo by Tom Campbell)

The big, black Labrador retriever with some gray around his muzzle spends most days curled up in a Purdue University School of Veterinary Medicine office or wandering the halls greeting visitors. Waggy-tailed 10-year-old Indy seems an unlikely victim of a near-fatal disease.

But when Indy was 5 years old, he returned from a run with his owner's son and collapsed. His eyes were bleeding, he had diarrhea and yelped in pain when he was picked up to be rushed to the emergency room.

“The examination showed that his retinas were hemorrhaging, his kidneys were failing and he had a high fever. We thought he was going to die right there,” says Indy's owner Larry Glickman, Purdue professor of epidemiology and public health.

Indy became one of the first dogs in the Midwest to be diagnosed with a strain of leptosporosis carried by raccoons, Glickman says. The illness, called “lepto,” can cause kidney damage, liver failure and even death in many mammals, including humans, dogs, pigs, horses and cattle. Glickman believes Indy contracted lepto by direct contact with a live or dead raccoon or with water contaminated by raccoon urine in the fenced one-acre yard where the dog plays.

Two years earlier, during a triathlon competition through Illinois and Wisconsin, the same disease sickened 73 athletes when they swam across a pond contaminated by urine from infected animals. Twenty-three were hospitalized.

With hydration, tetracycline and other antibiotics, Indy fully recovered. And the athletes' lepto symptoms of chills, headaches, diarrhea, eye pain and eye redness were successfully treated.

Pets and people susceptible

Lepto is a zoonotic disease, an illness to which both people and other animals are vulnerable. Most zoonoses, such as West Nile virus and Rocky Mountain spotted fever, are carried from an infected animal, a bird or deer, for example, and transmitted by a tick, mosquito or other pest. However, some diseases, including lepto, rabies and bird flu, can be passed directly from animal to animal, including humans.

Some zoonotic diseases, notably bird flu and West Nile virus, make big headlines; some, such as lepto, are little known. Others are feared because of their potential to cause catastrophic deaths, either from a pandemic or from use as biological weapons, as could be the case with plague and anthrax.

University researchers and others study and monitor zoonotic diseases to detect them earlier and to find new treatments in an effort to thwart the danger posed by natural illness progression or human aggression. “We don't live anywhere risk-free,” says Leon Thacker, Purdue veterinary pathobiology professor and head of the Purdue-based Indiana Animal Disease Diagnostic Laboratory (ADDL).

While speculation about the spread of bird flu often receives the most news coverage, Thacker says the public must also be aware of many more common zoonotic diseases, such as lepto, West Nile virus and Lyme disease, and take precautions to protect themselves and their animals.

Bird flu dominates headlines

Over the past year, a strain of bird flu, avian influenza virus H5N1, stole the headlines from West Nile virus and Eastern equine encephalitis, two mosquito-borne diseases that have plagued the United States in recent years. Scientists and health officials debate evolution of H5N1, but they all urge development of new vaccines and treatments against both new and resurrected diseases.

“If bird flu combines with a human virus or a pig virus and acquires the capability of spreading from human to human effectively, then it's a big problem,” says Purdue molecular virologist Suresh Mittal, who is refining a new type of flu vaccine. “In H5N1, at this stage, the human-to-human transmission is pretty weak. This is what is keeping us away from a pandemic.”



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