Dog parks: Where pets, people, and parasites collide

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To evaluate the potential risk, a national survey of dog parks was initiated by veterinarians and other researchers at Elanco Animal Health, IDEXX Laboratories, and Oklahoma State University. Thirty metropolitan areas and 288 dog parks were visited during August and July of 2019, and fecal samples were collected from over 3,000 dogs whose owners provided demographic information as well as insight into heartworm/intestinal parasite control medication (HWCM) use.

Centrifugal fecal flotation and coproantigen testing revealed 85% of parks sampled had at least one infected dog and that one in five park-attending dogs across the United States is infected with gastrointestinal parasites. Giardia was the most commonly detected parasite, but hookworms, whipworms, or roundworms were found at almost half of the parks visited. Nematodes – especially hookworms – were most common in the South and Midwest, and Giardia was almost equally prevalent in all regions of the United States.

A majority (88%) of the dogs sampled were greater than one year of age and slightly more male dogs attend the dog park than female dogs, with the vast majority – 85% of males and 90% of females –neutered or spayed. Parasites, including nematodes and Giardia, were most commonly identified in younger dogs although parasites were seen in dogs of all ages. Owners reported using HWCM in 68.8% of park-attending dogs, and those dogs reportedly receiving HWCM were significantly less likely to be infected with nematodes. Additionally, dogs with a reported history of parasite infection were significantly more likely to be receiving a HWCM than dogs never before diagnosed with a parasite.

Parasites – if left uncontrolled – can have damaging effects on pet health. For example, feeding of hookworms in dogs results in blood loss and diarrhea while frank blood can be seen in feces of dogs infected with whipworms. Heavy infection with whipworms can lead to an electrolyte imbalance presenting as pseudohypoadrenocorticism. The findings in the DOGPARCS study demonstrate the continued need for parasite examinations and prevention of gastrointestinal parasites, including ones that create a zoonotic risk such as hookworms and roundworms. In fact, veterinary and public health organizations like AAHA, the Companion Animal Parasite Council (, and the Centers for Disease Control and Prevention ( recommend all dogs be tested for parasites at least once a year and routinely dewormed year-round for intestinal helminths due to the high risk for infection and disease. Additionally, limiting parasite infection can be achieved through careful management of dogs and a focus on containing dog waste.

Written by Kathryn Duncan, DVM (Resident in Parasitology, Oklahoma State University); EM-US-20-0063


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