Many pet owners believe that parasites are only a problem in the summer months. But when it comes to the cold weather, parasites can still survive in stool left in the snow to "decompose." It is important for the health of our pets, each other and our children that everyone does their part and picks up after their pet in public areas.

Among the most common parasites infecting pets are the roundworm, hookworm, and the protozoan known as giardia. All of these parasites can be transmitted to humans either by ingestion of the parasite eggs or by migration through the skin. Children are most at risk since they are not as likely to practice proper hygiene after petting dogs, playing in sandboxes, or walking through contaminated soil barefoot. 

The most prevalent parasite in dogs and cats is the roundworm. The eggs of this parasite have a sturdy outer shell, which makes them able to survive in the environment for many months, and even extreme hot or cold conditions do not lessen their infective potential. For this reason, the roundworm continues to infect pets, and is most common in young puppies. While the parasite is easily detected in pets, it may take specialized procedures to diagnose the parasite in humans. Humans who ingest roundworm eggs through contact with contaminated soil or improper hygiene can suffer from visceral larva migrans or ocular larva migrans. In the former, the immature form of the roundworm can migrate through the liver, lungs, heart and even the brain. In the latter form, the parasite can migrate to the eye causing vision problems and even blindness. Fever, pain and permanent damage to tissues can result. In the worst-case scenario, central nervous system disorders can result from the parasite infecting the brain.

Hookworm is a parasite, which in dogs can cause blood loss due to the worms latching onto the intestines and feeding on the pet's blood. Hookworms migrate through the skin of the dog on their way to the intestine. In humans, hookworms do not usually find their way to the intestine, but can enter through exposed skin and cause an extremely itchy condition known as cutaneous larva migrans or "ground itch." Children playing in moist soil or sandboxes are most likely to be exposed. The parasite burrows into the skin leaving raised, reddened trails. The condition is treatable, but very painful. Because animals can reinfect themselves over the duration of treatment, it is very important to clean up all traces of stool.

Giardia is a common parasite seen in veterinary medicine and has sometimes made headlines for infecting the human population through contaminated water supplies. Although wild animals are often the cause of the contamination, they act as the reservoir for domestic pets that ingest wild animal droppings, and subsequently infect other pets and humans. Giardia may cause severe diarrhea and vomiting in both pets and humans. Children and people that are immune-suppressed (such as AIDS victims) are more susceptible to giardiasis infections. Prompt disposal of stool is the best way to ensure that the environment stays clean and people are not at risk of transmission.

Parasites can be easily treated and prevented by readily available and cost-effective medications year-round through your family veterinarian. Many of these products are easy to administer and are often combination flea, parasite and heartworm preventatives such as Advantage, Revolution and Sentinel. Veterinarians recommend that dogs be placed on these preventative products on a seasonal basis and have regular fecal tests to screen for parasites.

Prevention is key in protecting pets and humans from infection. Pet owners and their children should practice good hygiene after handling puppies or unknown dogs met in the park. Scooping and properly disposing of stool will not only prevent infection but will also help to keep our parks clean for the enjoyment of others.

Lori Williamson, RVT

Vaughan-Richmond Hill Veterinary Emergency Clinic