Internal & External Parasites of Dogs and Cats
HEARTWORMS- See our page dedicated to heartworm disease
Dogs and cats can become hosts to many intestinal parasites and a few general statements apply to all parasitic infections:
- All deworming medicines are poisonous to some extent and should only be used as needed and under proper conditions.
- At this time there is no one dewormer that can eliminate all species of parasites. Consequently an accurate diagnosis is necessary to treat your pet properly.
- Diagnosis is usually made from a fresh stool sample (passed less than 12 hours) or, in the case of tapeworms, seeing the segments in the stool.
- Most puppies and kittens are infected before birth and, for this reason, will need deworming starting at 6 weeks of age. If hookworms are suspected, stools should be checked starting as early as 2-3 weeks.
- Occasionally, for a heavy parasitic infection, 3 or even 4 treatments may be necessary to eliminate the parasite.
The following is a brief description of the common intestinal parasites with their symptoms, diagnosis, treatment, prevention, and human transmission.
This is a common worm of puppies and kittens, but can be seen in any age dog or cat. Diagnosis is made from a microscopic examination of the feces or from a description of the worm if it is seen in the stool or vomit. Treatment is an oral medication given at 2-3 week intervals. Symptoms will vary from none to marked vomiting and diarrhea, and abdominal swelling. Transmission to adult dogs and cats occurs by infected feces contaminating the yard. As a result, prevention is accomplished by isolating your pet from infected feces of other animals. For both dogs and cats, the heartworm preventatives also prevent roundworm infection. Transmission to humans is rare; young children can develop "visceral larval migrans" by eating dirt contaminated with feces.
This is also a common worm of puppies and kittens, but is seen with equal frequency in adults. This parasite sucks your pet's blood and can cause a severe anemia. Diagnosis is made from a microscopic examination of your pet's stool. Treatment is either an oral medication or an injection or both. This is repeated 2 weeks later. Symptoms will vary from none to blood in the stool (dark tar-colored stool) with diarrhea. Severe cases may need a transfusion and hospitalization. Transmission to adults occurs by infected feces contaminating the grass or soil. Prevention, therefore, requires that the pet be kept away from contaminated areas. Two types of heartworm preventative can also prevent hookworm infections in dogs. Transmission to humans is uncommon and is usually in the form of skin lesions.
This worm affects dogs only. Diagnosis is also made from a microscopic exam of the feces. Eggs from this parasite pass intermittently, however, so it may be necessary to check multiple fecals before a diagnosis is made. Treatment is an oral medication given at 3 to 6 week intervals depending on the severity of the infection. Symptoms vary from none to a severe watery diarrhea, vomiting, and marked weight loss. Some dogs require hospitalization for treatment of dehydration, malnutrition, and infection. Prevention of this worm is now possible with the heartworm preventives Interceptor and Sentinel. There is no human transmission.
TAPEWORMS:This common worm affects both dogs and cats. Transmission occurs when your dog or cat bites and "eats" a flea. The intermediate form of the tapeworm is inside the flea's body and it then attaches to the intestine and begins to grow "segments". In about 3 weeks, these segments begin to pass in the stool. They are approximately ¼ to ½ inch long, flat, and white. After a short time in the air, they dry up to resemble a small yellow flat seed. Diagnosis is made from seeing these segments on the stool or on the pet's back end rather than a microscopic fecal exam. Treatment is either by oral tablets or by an injection. The tapeworm injection kills existing tapeworms but it does not prevent future infection. The only prevention is strict flea control. There is no direct transmission from dog or cat to a human.
This parasite is not a worm. It is a very tiny single-celled parasite that can live in the intestines of dogs, cats, and man. It is seen most commonly in dogs coming out of kennel-type situations (pet stores, shelters, dog pounds, etc.) but its incidence is increasing. Symptoms include intermittent or continuous diarrhea, weight loss, depression, and loss of appetite. Diagnosis is made from a very fresh fecal specimen that must be collected at the clinic for optimum results. A surprising number of affected animals are "occult"; that is, they are infected but are negative on these tests even with multiple examinations. As a result, this parasite is often treated without a confirming diagnosis. Treatment is an oral medication administered at home. Prevention involves careful disposal of all fecal material and cleaning contaminated areas. Humans can become infected with Giardia so special care must be taken to wash hands and utensils.
This is also a single-celled parasite. It is seen primarily in puppies and kittens, although debilitated adults can also be affected. Transmission occurs by eating the infective stage of the parasite. It then reproduces in the intestinal tract causing no symptoms in mild cases to bloody diarrhea in severely affected pets. Diagnosis is made from a fresh stool sample. Treatment varies greatly. Animals showing no signs of illness are often not treated because a mild case is often self-limiting. Pets with diarrhea are treated at home with an oral medication. Severely affected pets may need hospitalization. Prevention involves disposal of all stools and cleaning the pet's living area. Human transmission is uncommon but can occur.
- For environmental control, we recommend a professional exterminator. Current laws now prevent the over-the-counter sale of the most effective environmental flea control products.
- Vacuum the house thoroughly, at least once each week, to remove eggs, larva, and pupae.
- Fleas require a blood meal from a host to reproduce. In recent years, once monthly oral flea control has become the method of choice for controlling fleas in dogs. These products kill the fleas quickly (starting within 30 minutes of dosing) and last a full month. Trifexis (which also includes heartworm preventive), Comfortis, and Nexgard (which also kills ticks) are the most commonly recommended products. We recommend that you use one of these products every month, year-round, in Southeast Texas. These products are particularly effective at controlling Flea Allergy Dermatitis (FAD), a common cause of severe itching in many dogs in our area. We do not currently recommend any topical flea control products for dogs.
- For cats, we recommend Revolution, which is a topical product, since administering oral medications can be challenging in cats. It is effective against a wide range of internal and external parasites, including heartworms, intestinal worms, fleas, certain types of mange, and ear mites.
- All pets in the household must be treated at the same time.
Don't waste your money on over-the-counter products, flea shampoos, sprays, dips, and collars. They do not work nearly as well, and will only serve to frustrate you further.