Page 10 The Sun Bay Paper March 21, 2026 Tiny Parasites Can Cause Big Problems for Dogs By David Lewis Q: Why are parasites such a danger to dogs? Dr. Rossman: Parasites can cause dangerous health issues including anemia, gastrointestinal upset, extreme weight loss, and blindness. Parasites are typically transmitted when a dog unknowingly ingests parasite eggs or spores in contaminated food, animal feces, water, or soil. Q. What are the most common internal parasites that affect dogs? How do dogs contract these parasites? Dr. Rossman: Roundworms and hookworms are the most common types of internal parasites. Roundworms are primarily transmitted through the fecal oral route, meaning they are transmitted through ingestion of fecal material. Hookworms are transmitted to puppies in their mother’s milk. Hookworms can also be transmitted through an infected environment or contact with fecal material. Both these parasites can cause serious side effects. Anemia, blindness and death are potential outcomes of parasitic infestation. Q: What are the most common external parasites that affect dogs? How do dogs contract these parasites? Dr. Rossman: Ticks and fleas are the most common external parasites in dogs. Dogs can become infected with ticks in heavily wooded areas, areas with tall grass, or areas populated with deer. Dogs can obtain fleas through concurrent infections with tapeworms, from other affected animals, or environments that have a heavy flea burden. Ticks can be extremely dangerous as they often carry tick-borne diseases including Lyme disease and ehrlichiosis. Flea infestation can cause anemia and severe dermatitis. Q: What are some symptoms of both internal and external parasites in dogs? What should pet owners watch for? Dr. Rossman: Visually inspect and then run your fingers through your pet’s hair after going outside to be certain ticks have not attached to your dog. If your dog has diarrhea lasting more than 36 hours, is coughing, experiences weight loss or lethargy, or is just not behaving normally, immediately consult your veterinarian. Q: What are the most common treatments for parasites in dogs? Dr. Rossman: There is not one dewormer or antibiotic that works for all parasites. Dewormers should always be purchased through a veterinarian, so the dog owner knows they are using the correct product for their specific pet. This is especially important. Q: Do you have any advice to help dog owners protect their pets from fleas? Dr. Rossman: A monthly flea and tick preventative helps to control external parasites. This can be in the form of an oral chew, topical application, or a collar. Seresto is currently the only collar that I believe is effective, and it requires a prescription. Bravecto Quantum has recently been released as the first-of-its-kind, FDA-approved injectable flea and tick preventative that lasts for 12 months. Canine patients who are six months and older can be given this product. However, I recommend it not be given until 12 months of age since puppies are still growing at six months. It is very important to have your veterinarian evaluate the dog’s stool sample 1-2 times per calendar year. And heartworm testing should be done on a yearly basis. It is always best to diagnose a parasitic infection early before it has begun to cause clinical signs. Dr. Ashley Rossman, DVM is a licensed veterinarian and co-owner of Glen Oak Dog and Cat Hospital in Glenview, Illinois. The advice contained within this column is for informational purposes only. Pet owners are advised to consult with their own veterinarian to evaluate their pet’s behavior, illness or medical condition. David Lewis is a publicist and writer based in Morton Grove, Illinois.
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