Parasites and Preventatives, Part 3:

June 2021

This article will conclude the topic of parasites with a discussion on preventatives and treatments for commonly seen worms that infect the GI tracts of cats and dogs. Intestinal parasites are very common, especially in puppies and kittens. The signs of these infections can be gastrointestinal problems, lack of weight gain, weakness due to anemia, or sometimes none at all. These infections are easily treated, and with the use of common preventatives, they are usually not a problem throughout a pet’s lifetime.

Hookworms are commonly seen intestinal parasites in cat and dogs throughout the United States. In dogs, they are commonly passed from pregnant mother to puppies either through the placenta or when puppies nurse. In both cats and dogs, oral ingestion or skin penetration by larvae can infect the animals. Adult hookworms attach inside of the small intestine and consume blood. A significant infection of these worms can cause an anemia due to blood loss, and potentially worse signs depending on the total worm burden. Prognosis is usually excellent after treatment. Additionally, hookworms are potentially zoonotic; they can cause a condition in people called cutaneous larval migrans, when the larva crawl under the skin of a person. It can be seen in young children that play in infected sandboxes or adults that come in contact with contaminated sand soil (e.g. beaches with free-roaming dogs).

Roundworms are another very commonly seen intestinal parasite in dogs and cats. They are almost exclusively seen in younger animals less than six months of age. Most of the time, they are incidental, and are causing no problems in the animal. However, there can be infections with multiple types of intestinal worms, and in extreme cases, intestinal obstructions or intussusception (intestine folding into itself) may occur. This is very rare. The larvae are ingested by animals in an environment where a host is passing the eggs through the stool. They are also potentially zoonotic; the larvae may lead to conditions in people (usually a child) called visceral larval migrans, or worse, ocular larval migrans. With these conditions, the larvae get into the organs in the body, causing illness or possibly blindness if seen the eye. Children that play in infected sandboxes are at risk.

Whipworms are intestinal worms that infect the cecum (appendix in people) in dogs, and rarely cats. They are passed by stools or an infected environment with eggs that prosper in that area. The eggs are extremely hardy and can survive up to 4-5 years, with weather having no effect. They are usually seen in puppies but they can affect older dogs that are in an infected environment. Clinical signs can range from none to having illness that mimics Addison’s disease (Hypoadrenocorticism). Most of the time, they are an incidental finding, causing no disease. Zoonotic disease is not a concern with this type of worm.

Diagnosing the intestinal worms is relatively easy. In most cases, a fecal exam that identifies the eggs of the worm (or worms if there is a co-infection) will be definitive. Sometimes, eggs may not be present in a fecal test due to the size of the sample or they are not being shed in the intestine at that time. There is a fecal antigen test that is more sensitive and can identify more mild infections of these worms. At St. Francis, we always test puppies and kittens for intestinal parasites until they have two negative tests consecutively. With adult animals, we recommend testing yearly for intestinal parasites, even if they are on preventatives because no preventative is perfect and clients often forget to give the medication consistently.

Treating and preventing these intestinal worms can be simple and effective. Roundworms and hookworms are usually treated at first with pyrantel or fenbendazole in puppies and kittens. Often, they are treated every 2 or 3 weeks when they are very young, as often the worms are passed from the mother to the neonates. Whipworms may need to be treated longer if there is a significant infection. The monthly preventatives treat and prevent most intestinal worms. Heartgard contains ivermectin and pyrantel, which is effective against heartworm larvae, hookworms, and roundworms. Trifexis contains Spinosad and milbemycin oxime, which is effective against fleas, hookworms, round worms, and whipworms. Sentinel Spectrum contains Lufeneron, milbemycin oxime, and praziquantel, is effective against fleas, hookworms, roundworms, whipworms, and tapeworms. Proheart, the injectable heartworm preventative, is effective against hookworms. For outdoor cats, Revolution, which contains selamectin, is effective against heartworms, hookworm, and roundworms. We recommend one of these preventatives for every dog and outdoor cats. We like to see our patients’ worm free!

If you have any questions, let us know at your next visit. Have a great Summer!

Dr. Jaime Kozelka
St. Francis Hospital for Animals