Brain Worm (Part 3)

 

Much has been learned about brain worm since it was shown to be the cause of “moose sickness” in 1964. However, there are still many important questions that need to be answered. Do infected gastropods behave differently than uninfected ones resulting in their being more likely to be ingested? Do infected moose no longer showing signs die from the parasite later? Does brain worm cause effects that are difficult for us to detect such as reproductive behavior and maternal care of calves?

I do have a small amount of information on this last question. I did examine a number of adult cow moose exhibiting classic signs of brain worm infection during time of year when they should/could be pregnant or be accompanied by calf/calves. Unfortunately, many of these were before Dr. Lankester was examining moose heads for me so not all were confirmed to be infected. Only 3 of 7 adult cows were pregnant, but this is far too small a sample to mean anything. However, of 14 adult cows that should have been accompanied by calf/calves, none were and one was just barely still slightly lactating. Were any calves born to them abandoned, or taken by predators due to lack of maternal instincts? These were moose that were exhibiting serious signs but tells us nothing about reproduction of infected moose that are not showing signs.

Another brain worm related item is that of potential woodland caribou reintroduction to northeastern Minnesota. In the early 1970’s and again a decade, or so, later there were serious discussions of such an undertaking. However, caribou are even more likely to die from a brain worm infection than are moose. No suitable location was identified where deer and wolves were low enough to consider the project, so the idea was abandoned. A few decades ago, Maine put some caribou on an offshore island. Things went well until deer swam to the island and brought brain worm with them. The caribou all died.

Brain worm is firmly established in nearly all states and provinces in the eastern half of the continent. Why has it not spread to the western half? We have always assumed that the prairie separating east from west to be a barrier for the parasite. But we do not know what makes it a barrier. There are white-tailed deer from coast to coast so the cause may have something to do with first stage larvae survival or gastropods.

The western states and provinces are very concerned about the possibility of brain worm becoming established there. As mentioned in Part 1, most of their big game species and some domestic animals also are susceptible to the debilitating neurologic effects, and possible death, from brain worm. Game farms are a major concern regarding brain worm. It is quite common for game farms to buy and sell animals to other game farms in order to prevent inbreeding of their herds. Sometimes the sales are of animals from far away and could involve animals that might be infected with brain worm. To address this possibility, a few decades ago Agriculture Canada developed a blood test that could detect if an animal was infected with (or had even been exposed to) brain worm. Unfortunately, not enough blood tests were purchased for it to be economically worth continuing production, so it was discontinued.

Brain worm is not the only parasite that can cause similar signs of infection. About 20 years ago I showed some videos of brain worm infected moose at a North American Moose Conference. A wildlife biologist from Montana said he had seen similar behavior in moose that were infected with carotid artery worm. When a number of these worms partially block the carotid artery, blood flow to the brain can be greatly reduced and result in abnormal behavior. The last I heard, the biggest problem area for this is western Wyoming.

A research biologist from Sweden said they see similar signs in moose infected with a retro virus. Both Norway and Sweden also have a couple of parasite species similar to brain worm, but of a different genus. They also cause deaths in moose and (if severe enough infection) reindeer. One of these species has become established on Newfoundland’s Avalon Peninsula thanks to some imported reindeer that were not checked closely enough. This and concern about brain worm becoming established in the western states and provinces are two examples why biologists and agencies are so concerned about wildlife and plant imports and transplants.

I mentioned the North American Moose Conference earlier. Few people realize how important professional conferences are for natural resource biologists, regardless of which species or field of biology is the focus. They provide an opportunity for in-person discussions on topics of mutual concern with other professionals from many different areas. These discussions often result in development of better management, or research, techniques. Sometimes direct assistance is given by working together on specific projects such as the brain worm studies with Dr. Lankester I mentioned earlier. Other times just providing information or biological samples is all that is needed. For example, a New Hampshire biologist mentioned they wanted to develop a moose hunter orientation program. We had recently developed one for northeast Minnesota, so I videoed it and sent it to them to show how we had approached the topic. Another time a research biologist wanted moose muscle samples from across the continent for a genetics study. Many of us each sent him dozens of samples. There are numerous other examples which did not involve me.

A few years ago, a number of Gary Gamble’s columns in this paper were based on information in the book “Ecology and Management of the North American Moose”. That book came about because of an informal discussion about the need for an updated moose book that took place during “Happy Hour” after a day of listening to research paper presentations at a North American Moose Conference.

The point is that likely none of the above (or many others) would have happened except that so many biologists met and had gotten to know each other at moose conferences. Other professional conferences probably have had similar results.