Parasites can pose serious health risks to your dog or cat, affecting the skin, digestive system, heart, and other organs. The types of parasites your pet is most at risk for depend on their lifestyle and environment.
For example, an indoor Persian cat in a city has fewer parasite concerns than an adventurous Labrador retriever in the southern U.S.
Because risks vary, it’s important to work with your veterinarian to create a parasite prevention plan tailored to your pet’s needs, your beliefs, and the risks specific to your region or travel destinations.
Ectoparasites: Fleas, Ticks, and Mosquitoes
Ectoparasites are external parasites that you can see, such as fleas, ticks, and mosquitoes. While they may cause discomfort from itching and irritation, they also carry dangerous diseases, including:
- Fleas: mycoplasma haemophilus
- Ticks: Lyme disease, Rocky Mountain spotted fever
- Mosquitoes: heartworm disease
Modern veterinary medicine offers effective monthly topical treatments that prevent infestations with minimal toxicity. However, some over-the-counter products, particularly those containing permethrins, can be highly toxic to cats. Always consult your veterinarian before choosing a product.
Although some owners worry about using “poisons,” these products are specifically toxic to parasites, not pets, and the benefit of preventing disease and discomfort often outweighs the risk of rare side effects.
Intestinal Parasites: Worms That Cause Internal Harm
Intestinal parasites, such as roundworms, hookworms, whipworms, and tapeworms, can cause:
- Diarrhea
- Weight loss
- Vomiting
- Loss of appetite
- Poor coat quality
Young pets are especially vulnerable, often picking up parasites from contaminated soil. Veterinarians typically recommend aggressive deworming for puppies and kittens — every two weeks from age 4 to 16 weeks. In some regions, lifelong monthly deworming is advised.
Human Health Risks (Zoonotic Concerns)
Many intestinal parasites are zoonotic, meaning they can be transmitted to humans. Children, the elderly, and immunocompromised individuals are especially at risk. For example, roundworm infections in infants can cause blindness.
The best defenses include:
- Maintaining a consistent deworming schedule for pets
- Practicing good hygiene, such as handwashing after contact with pets or their waste
Heartworm: A Serious, Life-Threatening Risk
Heartworm is spread by mosquitoes and can lead to heart failure and severe lung disease in both dogs and cats. Dogs are more commonly affected, but cats are not immune.
Preventive medications kill immature larvae before they develop into adult worms. Most preventives are given monthly (every 30 days), though their protection period extends up to 45 days. Consistent monthly dosing is easier for owners to remember.
Treatment vs. Prevention
While treatment for heartworm exists, it is expensive, risky, and not always available. Prevention remains the safest, most effective approach. Some preventives even combine protection against heartworm with intestinal deworming.
Testing for Heartworm
Veterinarians vary on whether yearly or biennial testing is best. Testing ensures pets are not already infected, as preventives are only effective against larvae, not adult worms. Testing and preventive use may also vary based on region:
- Southern U.S.: Year-round prevention is recommended
- Northern states: Seasonal prevention may suffice, except when traveling to warmer areas
Creating an Anti-Parasitic Plan
The best way to protect your pet is to develop an individualized parasite control plan with your veterinarian. This plan should take into account:
- Your pet’s lifestyle (indoor vs. outdoor, travel habits)
- The parasites common in your area
- Your personal preferences and comfort level with medications
With the right prevention strategy, you can protect your dog or cat from unnecessary illness, discomfort, and even life-threatening conditions.
