Our cold climate does have its blessings: it keeps all sorts of pests and small critters at bay. Frigid conditions favour large mammals like grizzly bears and moose, while parasites do not flourish.

But that scenario could change in the future. Global warming could improve conditions for some parasites in the North, and that would be bad news for the larger animals on which they prey.

Not much is known about parasites of wildlife in the North, but a group of scientists has formed a research group on arctic parasitology, based at the University of Sasketchewan. One member, Susan Kutz, recently completed her doctoral thesis on a type of lungworm recently discovered in muskoxen.

Now a research associate at the Western College of Veterinary Medicine at the University of Saskatchewan, Kutz is now looking at the presence of parasites in muskoxen, Dall's sheep and caribou in the Northwest Territories.

Kutz says that her doctoral work on parasites in muskoxen really stirred her interest in the link between parasites and climate change. "In the arctic you really see how much the system is controlled by the environment.

"The big thing is that their life cycle is highly temperature dependent. Pretty much all parasites have a stage that is temperature dependent," she says.

Parasites must develop to a certain stage in their life cycle before they can infect another animal. Whether the parasites develop in host animals, such as slugs or snails, or out on their own, temperature plays a big role in this part of their life cycle.

Her work on musk oxen helped to demonstrate how much temperature controls the rate of development of parasites. For example, at 10 degrees Celsius lungworm will take more than 80 days to develop in slugs to the stage where they can infect other musk ox. But if the temperature doubles to 20 degrees, the parasites develop so rapidly that they can infect an animal in just 12 days.

Parasites can cause lung disease, anemia and lesions in the animals that they infect. Host animals also suffer reduced appetite and weight loss. During warm years, parasites may develop faster and may infect animals earlier in the season.

Parasites more common now in the south could also start to expand their range to the North. There are signs that this may be happening already, as in the NWT ticks are already being reported more frequently.

Kutz says that warmer temperatures could mean not only more types of parasites in the North, it could also mean increased numbers of them. A Norwegian study showed the toll that above- normal summer temperatures can take on reindeer.

In warm summers more reindeer suffered neurological diseases caused by an increase in one species of parasite. The parasites might have been present all the time, but in lower numbers that did not affect the reindeer as much.

Kutz points out that the Norwegian study is the only published one so far that has looked at the links between a changing environment and parasites, an area that she thinks has been neglected. "We're looking at many other aspects of climate change in the arctic, but no one is looking at disease processes in the wildlife.

"We do not know what parasites are in these animals. We know a lot about their biology, but we know very little about their parasites."

The first step in this process is establishing the types of parasites already present in the North. "Every time we turn around we find a new species, or an old species in a new host," she says. "These species have always been present, but we are just now looking for them."

Kutz is continuing to study muskoxen on Banks Island in the NWT. The animals are hunted every year as part of a commercial harvest, so it is easy for researchers to get samples from a large number of animals.

Among other things, the researchers want to look at whether animals of a certain age or sex are more prone to infection, and whether factors like climate and vegetation affect disease in the musk oxen.

In a study of Dall sheep on the NWT side of the Mackenzie Mountains, outfitters have been supplying the researchers with lung and fecal samples taken from the sheep. Kutz says that outfitters in the region have been very helpful with this project, and she hopes that the study can be expanded into the Yukon and Alaska as well.

Kutz says that the outfitters are understandably concerned about increased levels of disease in the sheep. So far there have not been any outbreaks of disease in populations of Dall sheep, but that is certainly not the case with Bighorn sheep, their southern cousins.

Much of the disease in these sheep comes from contact with domestic animals. While this is not much of an issue in the North at this time, Kutz points out that factors like increased exploration and tourism might also stress the sheep and affect their resistance to disease.

Also warmer conditions have been encouraging species such as mule deer and white-tailed deer to move north. These animals can carry parasites that might not bother them much, but could cause disease in northern animals.

With climate models predicting more warm weather ahead for the North, Kutz says that an increase in parasites is just one more change that might occur. "Just one hot year may have a profound effect," she says.

For more information on research on arctic parasites, contact Susan Kutz at susan.kutz@usask.ca.