Dogs and cats can become infected with a wide variety of parasites, both internal and external. Although most parasites can be treated, in general, prevention is the better way to go to avoid your pet suffering from these pests.
External parasites are ones that affect the skin. Examples include fleas, ticks, lice, ear mites, and mange mites. Fleas are by far the most common of these. They can make your pet miserable, in some cases literally scratching their skin open. The can cause secondary infections, allergic reactions, and can spread internal diseases and internal parasites, such as tapeworms. They multiply at an extremely rapid rate and will quickly spread within your house. We recommend Frontline Gold or Nexgard monthly for flea control - or Bravecto which lasts 3 months. Ticks also spread internal diseases like Lyme disease, Ehrlichiosis, Rocky Mountain Spotted Fever, and tick paralysis. If your pet gets infested, then we can also provide you with products to treat the house, in particular using insect growth regulating products. Just because you don't see fleas in the house doesn't mean that they aren't there! Some heartworm preventive products also work to prevent external parasites - call us for details. Because of less efficacy and greater side effects, we do not recommend using over-the-counter spot-on products, particularly on cats.
Heartworms are the most serious intestinal parasite that we see in dogs and cats (yes, cats get them too!). They are spread by mosquitoes so even indoor-only pets can become infected. Symptoms in dogs include coughing, fainting, shortness of breath, and a bloated abdomen from fluid retention. They can be treated; however, the treatment is very expensive and is somewhat risky in symptomatic pets. For that reason, we recommend annual blood tests to diagnose an infection early on, before symptoms arise, when treatment is not likely to cause significant side effects. Annual testing also prevents reactions to preventive medications. Symptoms in cats include coughing, vomiting, and sudden death. Unfortunately, cats cannot tolerate the medications that kill the adult worms so we can only treat symptoms. In both dogs and cats, year-round use of monthly preventive medications are strongly recommended --- relative to the cost of treatment, they are very inexpensive, and if you've ever seen a pet succumb to heartworm disease, you wouldn't consider going without. Many preventives also contain products that prevent intestinal worms and even some external parasites.
Intestinal parasites include worms like round, hook, whip, or tapeworms or protozoal infections like coccidia or giardia. The life cycle of these can vary from direct transmission from one pet to another while others, like tapeworms, require the pet to ingest an intermediate host like a rodent or a flea. In addition to infecting your pets, many of these have a zoonotic concern, meaning that they can spread from pet to people (so be sure to pick up all waste from the yard and litter box daily and teach children to wash hands after handling the pet, especially before eating). Most of these parasites are so tiny that they will never be seen in the pets stool. To diagnose these, we need to mix a stool sample with special chemicals that separate their eggs that can be then observed under the microscope (tapeworms often do not pass eggs so diagnosis is dependent on observing rice-like segments on the stools or on the hair around the rectum). Twice a year stool exams and quarterly de-wormings are recommended by the Center for Disease Control. Treatment varies with the type of worm; because nearly all puppies and kittens get infected from larvae in their mother's system, they should all be treated when they are a few weeks old. Most heartworm preventive products will help to prevent many of these worms too.
For detailed information on any specific parasite, click on "Links" at left then go the paragraph about parasites to be taken to the website of the Companion Animal Parasite Council and search for the parasite your pet has.