Parasites, oh my!
It's that time again when we (hopefully) can say goodbye to winter, and look forward to more time with our pets outside and in the sun. For us at the hospital, it’s also a reminder that we will be starting to see the emergence of parasites that tend to fall to back of mind during the snowy season.
Here are some interesting facts with respect to dog parasites of concern in our region:
Giardia, a microscopic organism causing intermittent to severe gastrointestinal signs, remains the most common internal parasite that we pick up on fecal tests with a positivity rate between 10 and 15%. Dogs can carry Giardia without clinical signs, but can still shed it into the environment, so routine fecal testing is important.
Roundworms, those disgusting spaghetti-like worms common in puppies, show up in about 3% of tested stool samples, while hookworms and whipworms are found in over 1% and 0.3% of samples respectively. These parasites can shed eggs in very large numbers into the environment, can also cause gastrointestinal signs, poor thriving, and even anemia.
We don’t see whipworms in cats but roundworms show up in 5% of samples, and hookworms in about 0.3%. Giardia is not as common in cats as dogs, but still shows up in 5% of samples.
The good news is that, other than Giardia, common preventive flea, tick and heartworm medications also prevent these intestinal parasites. If we find Giardia, however, it requires a more specific treatment.
Another parasite that can cause serious disease in dogs is Echinococcus, now found routinely in coyote poop and which infects dogs when they ingest the poop. We also carry preventive medication for those dogs at risk.
These internal parasites are best found on periodic fecal testing of your pet, at least once a year. For more information, the University of Saskatchewan has published annual data on parasites in companion animals. See: https://research-groups.usask.ca/cpep/parasitedata/ontario.php
Once the outside temperature goes above 4C, we see the emergence of ticks, which seem to be particularly prevalent in the Ottawa region and Eastern Ontario. Just ask me about my last walk with my dog at Foley Mountain Conservation Area last Fall!
While we are now well aware of the risk that ticks present in infecting dogs (and people!) with Lyme disease, we are seeing other emerging diseases spread by the same ticks, notably Anaplasmosis and Ehrlichiosis. Lyme disease in dogs occurs in about 10 to 15% of dogs who are bitten and produce antibodies to the organism, usually either as a lameness in one or more legs, or, more insidiously, as a kidney infection. Anaplasma and Ehrlichia can also cause similar symptoms but additionally target and damage blood cells in the body and can be life-threatening.
Testing for exposure involves a blood test (called a 4Dx) that should be considered annually with dogs at risk. The 4Dx tests for Lyme, Anaplasma and Ehrlichia, as well as for Heartworm disease. The following link from the Ontario Animal Health Network based out of the University of Guelph:
Prevention of tick infections starts with checking your pet carefully when coming in from outside, particularly when traveling to areas known to be problematic. However, our clients report finding ticks on their pets in urban Ottawa, as they drop off of migrating birds, so no place is without risk! The next level of prevention involves oral or topical flea and tick medications, of which there are a number of types available, differing only in the duration of activity and the number of other parasites they cover. We are always happy to discuss which product may be most suitable for your own pet.
Finally, an excellent vaccine for Lyme disease is available for dogs as a last line of defense, as no preventive medication can guarantee 100% prevention. Dogs routinely spending time in tick-infested places are excellent candidates for vaccination.
Our last topic in this newsletter is on Heartworm. When I started in practice (40 years ago this May!), heartworm did not exist in Ontario. Beginning in the early 1980’s it has developed into a resident disease, with hotspots throughout the province. Fortunately, most of the heartworm preventive medications have kept this from becoming as serious a disease as it still is in the more Southern US, but it still shows up with surprise and concern. Dr. Holzman, Sarah Baker and I spent a week on a reserve North of Kenora in North-western Ontario this past fall and learned that the region had just become a reservoir for the disease, with over 30% of the dogs testing positive! Spread by mosquitoes, it just takes one resident dog in a community to become the source for spread as mosquitoes go from dog to dog for blood meals.
Dr. Sparks recently had a dog booked in for surgery in our clinic and the owner serendipitously elected to test the dog for heartworm and tick diseases prior to the surgery, which came up positive for heartworm. Heartworm is also a spaghetti-like worm that grows into adults from the microscopic larvae injected by the mosquito, and which resides and breeds in the blood vessels exiting the heart and going to the lungs. Upon finding the positive test, we brought the dog to our ultrasound room and performed an examination of the dog’s heart.
Here's what we found…
While this is a confusing image to anyone not used to looking at ultrasounds, the blue arrow shows two parallel white lines that is a worm in the right pulmonary artery of the dog. We found three more in this location. When enough of these worms grow here, they block the blood vessels and can eventually cause respiratory disease and even heart failure. Fortunately, we caught this early enough to achieve a successful outcome.
This dog originally came from the Southern US and now resides in Ottawa. We’ve seen heartworm develop in regions in Ontario and Quebec from pets rescued or adopted from more southerly climes who are inadvertently carrying the parasite. We witnessed a large increase in the disease here after Hurricane Katrina due to the rehoming of dogs from Louisiana.
Enjoy the Spring and keep those parasites at bay!