Indoor-only cats can and do contract parasites

Q: Can cats that stay indoors get parasites? My veterinarian recommends that I apply a parasite preventive to my cat Seymour's skin every month, but I don't understand why it's necessary.

A: While cats that spend time outside are more likely to encounter parasites, even indoor-only cats can become infected. Three types are common.

The first is fleas. These pests catch a ride into our homes on our shoes and pant legs and sometimes on indoor-outdoor pets. Not only do they bite, drink blood and cause itchiness, but they also transmit tapeworms to cats and cause a variety of human illnesses, from cat scratch disease to the plague.

The second is intestinal parasites, such as roundworms and hookworms. Indoor cats "catch" these worms when they capture and eat a creature, such as a cockroach or mouse, that carries the immature parasites.

Moreover, roundworms, which are widespread in the environment, produce sticky, microscopic eggs that ride indoors on our shoes. The eggs are deposited on the carpet and transferred to the cat when he plays on the floor. When the cat grooms, he ingests the eggs, which mature into adult worms that produce more eggs.

Roundworms and hookworms cause stomach upset and diarrhea in cats. In humans who inadvertently ingest the microscopic eggs, these parasites cause blindness, seizures and organ damage.

The third parasite that infects indoor cats is heartworms, found in all 50 states. Heartworms are carried by mosquitoes, which easily enter homes. Research shows that 25% to 30% of heartworm-infected cats spend all their time indoors.

Heartworms cause heartworm-associated respiratory disease in cats. This condition is characterized by coughing, wheezing, labored breathing, lethargy, regurgitation, decreased appetite and death.

Fortunately, you can protect Seymour from all these parasites by applying a single product to his skin every month or two, according to the medication's directions.

Q: My 10-year-old golden retriever, Samson, developed golf-ball-size lumps under both jaws almost overnight. Otherwise, he is completely normal. Will they go away on their own, or should I make an appointment with his veterinarian?

A: By all means, take Samson to see his veterinarian, who should examine any unexpected change or abnormality that develops.

The lumps under his jaws may be enlarged submandibular lymph nodes. Lymph nodes grow large to fight infection or as a result of cancer.

Your veterinarian will check Samson's other easily accessible lymph nodes, particularly those behind his knees, in his groin, in front of his shoulders and in his armpits. If any of those are also enlarged, it's possible that Samson has a type of cancer called lymphoma or lymphosarcoma.

Although it can affect any organ of the body, lymphoma usually targets the lymph nodes in dogs. In addition to enlarged lymph nodes, dogs with lymphoma can experience lethargy, loss of appetite and other clinical signs related to the organ involved.

Lymphoma is most common in middle-aged to older dogs. The cause is unknown, though there is probably a genetic predisposition, since golden retrievers are 3.5 times more likely to develop the disease than most other breeds.

Additional risk factors include living in an industrial or polluted area, proximity to incinerators or radioactive waste, and exposure to professionally applied pesticide or herbicide lawn products, particularly 2,4-D.

The primary treatment is chemotherapy, which is highly effective and dosed to minimize side effects. Complete cures are rare, however, so the goal is to provide the longest possible time of high-quality life.

If Samson does have lymphoma, your veterinarian can refer you to a veterinary oncologist for treatment.

Lee Pickett, VMD, practices companion animal medicine in North Carolina. Contact her at