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CORVALLIS - The eternal gloom of a rainy, overcast Oregon winter, long known to cause seasonal affective disorder, or "SAD" symptoms in its human population, has now officially claimed more victims - llamas and alpacas.

They probably don't get depressed and lethargic like the people do.

But according to recent research findings at Oregon State University, the problem can be even worse for some llama babies - the northern latitudes and often overcast conditions during winter months can cause a vitamin D deficiency in llamas that leads to rickets, a crippling bone disease.

OSU veterinary researchers have already solved this riddle, developed a successful treatment regimen and are continuing research in the area.

While the jury was still out, though, it was no laughing matter - Oregon has the largest llama and alpaca herds in the nation with a market value that exceeds $50 million, and the level of this disease syndrome was already bad and getting worse.

"Llamas and alpacas are native to the Andes Mountains of South America," said Brad Smith, an associate professor in the OSU College of Veterinary Medicine. "The sun is very intense near the equator, they often live at high altitudes and are exposed to very intense ultraviolet light all their lives."

The result, Smith said, is that in their native habitat llamas got lots of sun, even in winter, which helps llamas and other mammals - including humans - naturally synthesize vitamin D in their skin. Otherwise, this vitamin essential to normal bone growth can be in short supply.

In recent years an increasing incidence of rickets was being observed in llamas and alpacas, Smith said, and concerned ranchers turned to OSU for help. The university has the largest llama research program in North America - and two OSU scientists, in collaboration with a local veterinary practitioner, recently published a new book on llama and alpaca neonatal care.

Several things are known to cause rickets, which can cause permanent, crippling injury to animals and stunted growth if not treated and prevented.

"The first tipoff that Dr. Bob Van Saun and I had that vitamin D was the problem was the incidence of rickets seemed to be much worse in the winter months and among the babies, which are at a stage where their bones are growing most rapidly," Smith said.

"Some of these babies were barely half the size they should have been, they had tender joints, knock knees and other problems," he said.

Blood analysis and other tests confirmed that vitamin D was the root of the problem, Smith said, and supplement regimens were developed to cure it. The treatments are making a huge difference in the health of affected llamas, Smith said, and vitamin supplementation in food - similar to the Vitamin D fortified milk that humans consume - may provide a permanent solution.

"The work we've done has shown that the ability of llamas to synthesize vitamin D is pretty limited during the winter," Smith said. "Some animals had blood levels of the vitamin 20 times higher in late summer than during the winter. And at its worst, their vitamin D blood level was 10 percent of what it should have been to be healthy."

In their efforts to create from scratch a largely new program of medical care for llamas and alpacas, OSU researchers are continually identifying unsuspected differences such as this in these woolly pets and companion animals.

Llamas and alpacas were largely on their own in South America since they split off from camels on the evolutionary path millions of years ago. And for veterinary doctors trained with cattle, horses and sheep, the same types of therapy and care don't always work.

One other oddity being studied at OSU is a nasal defect in llamas called choanal atresia, which can make breathing difficult and nursing nearly impossible - many llama babies with the problem inhale milk into their lungs, get pneumonia and die.

OSU scientists developed surgical techniques to manage this condition and are now trying to trace what they believe are its genetic roots. Oddly enough, the other animal known to suffer from the problem is humans - and some day llamas may form a useful model to study the syndrome.

OSU's work on these and other problems should help nurture the llama breeding industry in Oregon, which is continuing to expand, Smith said.