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A Disease Cowboy Turns to Trout

November 12, 1995|RICHARD MANNING | Richard Manning is the author of three nonfiction books, the latest of which is "Grassland: The History, Biology, Politics, and Promise of the American Prairie." It was published by Viking in September

If anyone has earned a peaceful retirement, it is Karl Johnson, but this is not to be. Another disease has struck.

For 40 years, Johnson confronted the world's deadliest microbes and, in the process, twisted politics and grotesque poverty, work that led him to be called the "Disease Cowboy." He retired in 1987 to fly-fish in Montana--a supposed refuge from all of this--only to find the trout there sick and dying. The disease cowboy is back in the saddle.

The viral epidemiologist headed the team at the Centers for Disease Control and Prevention that named the Ebola virus. His microscope was the first to see the Hantaan virus, one strain of which killed about 30 people in the Southwest in 1993. In the early '60s, he cracked the case of Bolivian hemorrhagic fever, but not before he caught it. It nearly killed him, as it killed almost half the people it infected.

In 1976, a deadly strain of Ebola swept Zaire. Hundreds of victims bled to death internally in a matter of days. Johnson waded into the contagion to head the international commission that beat back the epidemic. He worked on Lassa fever in Sierra Leone. He chased hemorrhagic diseases throughout the former Soviet Union. Besides the CDC, his hat has hung at the National Institutes of Health and the Army's Medical Research Institute of Infectious Diseases.

With a full gray beard and gray hair, Johnson could be mistaken for a slimmed-up Santa in khakis, except that no one is likely to accuse him of being jolly. He deals in facts. Period. He is a snake charmer who has stared down the unseen world's most efficient killers, but all he really ever wanted to do, ever since he was a kid in New Jersey, was to fish.

"I always wanted to come here since I was 10 years old, fly rod in hand," he says from his new hometown in Bozeman, Mont. "I had to pay a lot of dues and lived a lot of places in the world so I could, and it was just--" (there is a long pause here to allow the shift to the subjunctive of dashed plans). "Well, this was going to be my first year of virtual retirement."

This interview was supposed to have taken place on a river where we were to fish, probably because it is Johnson's habit to suffer reporters while fishing; no sense in the day being a total waste. Richard Preston had fished on Montana's Bighorn River when he interviewed Johnson for the bestseller, "The Hot Zone," the account of a near outbreak of Ebola in the United States in 1989.

But Johnson canceled our fishing plans a few days before we were to go. Something about a schedule to keep and something about not having the heart to take a reporter to the Madison River, his home stream, one of Montana's finest, where the trout are dying of whirling disease.

For the past eight years, Johnson, 66, who was in semi-retirement, has lived mostly in Bozeman, set where the headwater streams of the Missouri River braid together from mountain meadows resting against the Great Divide, a fly-fisher's mecca. Late last year, though, state fisheries biologists realized a parasite that kills rainbow trout had spread into Montana.

Little was known about the disease, and its complexity is beyond the meager resources of most state fish departments. Enter Johnson, who volunteered his expertise, but his motivation probably has as much to do with the thrill of the chase as the love of the fish. Now he can read in this fish disease an all-too-familiar sign: tinkering with nature.

"Here's a situation where man is the culprit again. The things we have done to nature have given us something we have all enjoyed, but we poisoned our own well," he says. "Almost all of these things that come at us from nature are our responsibility."

Man's meddling is killing trout in Montana and at least 20 other states. It is caused by a protozoan, a microscopic jelly-blob of life that eats the flesh of trout. It enters young fish as a spore, develops, then attacks cartilage, mostly in the skull. This causes deformities--humped heads and twisted jaws--and a lack of coordination that makes the sick fish chase their tails, or whirl. It either kills the fish outright or leaves them vulnerable to predators. The disease, however, is harmless to humans even if they eat infected fish.

The parasite itself, Myxobolus cerebralis , was brought here by man, likely in a shipment of ground-up fish from Europe imported to feed hatchery fish in Pennsylvania in the mid-'50s. Because hatcheries stock sport fisheries, whirling disease spread.

Salmonids native to Europe, such as the brown trout, spent thousands of years negotiating a genetic truce with the parasite through co-evolution. Nature deals with disease through evolved immunity. Thus the browns that were imported to American streams do not suffer. Many trout native to this continent, however, are devastated.

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