Parasites 101

It is common for cat owners to think that their indoor only cat CANNOT get parasites. Parasites can be found both externally (on the body) and internally (inside the body) and are ABSOLUTLEY FOUND IN ‘INDOOR ONLY CATS’.

How can this be?

Parasites can be spread though any number of ways and all start from ‘environmental’ sources. Even though indoor only cats live inside- they are still exposed to outside environmental influences. Owners travel in and out of the home, windows and screen doors are opened, and items can be brought in from other places. Intestinal parasites often can lay dormant for years without any clinical symptoms. Mosquitoes, fleas and even ticks can travel into your home through windows, doors or even on clothing. Intestinal parasite eggs can also be brought in on the bottom of shoes.


Common Ectoparasites: Fleas and Ticks


Fleas are the most common (external) ectoparasite of the cat or dog. They are very prolific breeders and flea infestations can occur very quickly.

Life Cycle: Egg production begins within 20-24 hours of females taking their first blood meal and they can then lay 40-50 eggs PER DAY. Eggs are deposited onto the cat (host) and readily fall off into the environment. Larvae hatch from eggs and develop into pupae (cocoon like stage) in the environment. Pupae cocoons are also found in environment and adult fleas can emerge as anywhere from 8 days to 50 WEEKS.

Disease: Fleas are not only annoying to animals, they can cause extremely itchy skin conditions (Flea Allergy Dermatitis), can cause iron deficient anemia’s, transmit other parasites such as tapeworms and Mycoplasma and even the plague (Yersinia pestis).

Treatment: Due to the lifecycle of the flea and the fact that 3 out of the 4 stages of life cycle occur in the environment (ie- your home) both treatment of the environment and pet is highly recommended. Flea prevention should be purchased from the veterinary office. Safe products to treat the home can be recommended. For heavy infestations, adjunct treatments are often needed such as: deworming medications, vitamins or treatment for secondary anemia, and medications prescribed for skin infection/irritation.



Heartworm is spread though the mosquito. When an infected mosquito feeds on an unprotected cat, heartworm larva enters the cat through the bite. Larva can then migrate throughout the cat causing damage to the lungs and heart.

Disease: Ticks may cause localized irritation to the skin at the site of attachments. Tick-borne toxicoses can also develop- even to the extent of tick paralysis. Ticks spread many pathogens; Lyme disease being the most recognized. Other tick spread pathogens include: Ehrlichiosis, Rickettsios, Cytauxzoonosis, and Anaplasmosis.

Treatment: When only a few ticks are present, individual ticks can be manually removed. Removal of ticks should be done with caution or by your veterinarian to prevent damage to the tick or animal during removal. A topical prevention is recommended both as treatment and prevention of ticks. The tick can be sent in for testing of pathogens. Medical management and treatment of any secondary conditions from ticks are also recommended.

Common Internal Parasites

feline parasites


Heartworm is spread though the mosquito. When an infected mosquito feeds on an unprotected cat, heartworm larva enters the cat through the bite. Larva can then migrate throughout the cat causing damage to the lungs and heart.

Disease: Heartworm Associated Respiratory Disease (HARD) is the most common medical condition associated with feline heartworm. This disease is caused by the death of a developing juvenile worm(s). Cats can present with coughing or respiratory issues years after the initial infection.

If a heartworm matures in the feline patient, sudden death of the cat occurs 10-20% of the time.

Treatment: There is no treatment for cats with heartworm, though cats with HARD can be medically managed. Prevention of heartworm disease is the best choice for all feline patients. Studies have shown that 25-30% of heartworm infected cats were labeled as “indoor-only”.

feline roundworm


Cats (and dogs) become infected through ingestion of larvated eggs from contaminated environment, ingestion of other hosts that have consumed larvated eggs (hunting) and ingestion of larvae in the milk of an infected queen (mother cat).

Infective and larvated eggs of Roundworms are found in fecal-contaminated soil. It is possible to bring in infected soil on shoe soles. Roundworms eggs have also been found in potted plant soil.

Disease: Causes pot-bellied appearance in kittens. Roundworms cause irritation of the gastric mucosa (stomach) and vomiting. Cats are susceptible to infection of Roundworms throughout their life.

Treatment: De-worming agent prescribed by a veterinarian.

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