In a 2019 study by Dr. Susan Little, presented by Dr. Michael Dryden in a recent webinar, 50% of dog parks sampled in the United States found evidence of hookworm, whipworm, or roundworms. Ok, so you think, “well, I pick up after my dog!” which I’m sure is true but can you depend on others to adequately pick up after theirs? The worm parasites are passed in the feces via eggs and /or larvae and if even a little bit of feces remains on the ground, another pet is exposed. The eggs of these parasites, particularly whipworms, can winter over from 1-3 years so they can be very hardy in the environment. In the south where greyhound farms raised dogs for racing, hookworms have become resistant to most worming methods. All it takes is one of these rescue greyhounds to contaminate a dog park! I am by no means against rescuing greyhounds, in fact I donate my time and money to these groups but if a dog is not checked for intestinal parasites and treated, then this contamination of the park occurs. In fact, most younger dogs are commonly affected with intestinal parasites and those dogs on monthly heartworm preventative (not an intestinal parasite but one that is transmitted via mosquitos and causes heart blockage) actually have a lesser chance of gastrointestinal parasites.
Dog parks in the southern United States were the highest area of the country affected by intestinal parasites followed by the mid west, then northeast and finally, the western states. When individual cities were examined, Miami was the overall leader followed by Houston then lastly Oklahoma City.
Hookworms are probably the most worrisome to humans as they can cause larval migrans where the hookworm larva is absorbed across the skin and produces a creeping type of eruption. Dogs are commonly exposed via their skin as well where they have contact with the ground such as the belly and butt areas. It is not uncommon to be exposed in beach areas.
Another parasite that causes concern is the protozoa, Giardia. Giardia can be found in fecal samples as cysts. Giardia, according to Dr. Dryden is the most misdiagnosed, over diagnosed, and underdiagnosed parasite! Misdiagnosed because of failure to see the cysts in the stool sample or because the cysts are only shed periodically–meaning a dog can have Giardia but have a negative fecal sample because they didn’t pass cysts that day. Over diagnosed because veterinarians sometimes automatically think a dog with diarrhea may have Giardia not finding it in the stool sample and the dog responded to metronidazole which is commonly used to treat. Underdiagnosed because metronidazole is given to a dog with diarrhea and he/she responds yet no fecal sample was examined or cysts were not seen. Some dogs have Giardia and have no symptoms. Those dogs are usually not treated but it actually makes sense to treat them to reduce shedding of the cysts which another dog would be exposed to. A common myth is that humans can catch Giardia from dogs. There has not been one documented case of a human getting Giardia from a dog as a different “assemblage” of Giardia affects humans that is different from dogs. Not to say this couldn’t happen to an immunosuppressed human including babies!
And lastly, an emerging (or it may have always been around and we didn’t know it) parasite is Echinococcus multilocularis. 50% of coyotes are positive for this parasite and since coyotes are now more urban, this is gaining in importance for our domestic dogs as it can affect them. It looks the same as tapeworm (“grains of rice” found in the feces) but needs a laboratory test to tell the difference.
So before you go to the dog park, be sure your dog is on a monthly heartworm preventative such as Interceptor (which works well for whipworms), pick up after your dog while there, have yearly or every 6 months fecal exams done by your veterinarian or just stay in your own yard!!!