Parasites are a pervasive problem for all dogs and cats, regardless of their lifestyle or living situation. They have evolved alongside their hosts, finding creative and sneaky ways of reproducing and spreading. Internal and external parasites can affect your four-legged friend, but internal parasites are more difficult to identify, often flying under the radar for long periods. Left untreated, these pests can cause serious problems or death.

The Carolina Virginia Animal Hospital team recognizes the damage that parasites may cause and encourages all pet owners to take a proactive approach to keeping their furry pal parasite-free. Here is an overview of the most common internal parasites in dogs and cats and how you can protect your pet.

Intestinal parasites in pets

Intestinal parasites live inside your pet’s intestinal tract, where they feed on blood or steal some ingested nutrients. Common intestinal parasites include several species of macroscopic worms and a few species of microscopic single-celled protozoal organisms. All have one thing in common—they can cause diarrhea and other digestive problems in your pet. Additionally, severe infestations can lead to malnutrition or anemia in small or young dogs and cats. 

Nearly all pets are born with roundworms or hookworms, which are passed in utero or through the mother’s milk. This happens through a complex life cycle process that allows old, previously cleared infections to reactivate during the mother’s pregnancy. This is why all young puppies and kittens are dewormed several times during their first few months of life. Adults also can pick up intestinal parasites if they ingest the pests’ eggs, which can live in the environment for many months. 

Heartworm in dogs

Heartworms can grow up to a foot in length as adults. They live inside an infected pet’s heart, lungs, and associated large blood vessels, and their large size causes local inflammation, which damages the cardiovascular system over time. Untreated infections progress slowly at first, but as the population continues to breed and increase, heart failure and death can occur. 

Adult heartworms produce microscopic larvae that circulate in the bloodstream, where mosquitoes can ingest them. After a few weeks, the mosquito can bite another susceptible host and transmit the worms, starting the cycle over again. Because mosquito bites are the way heartworms are transmitted, all pets are at risk. 

Heartworm in cats

Cats are not a preferred host for heartworms, and their immune systems often destroy the immature larvae before they can migrate to the heart and cause problems. In some cats, a few of the larvae may evade the immune system and cause an adult heartworm infection. Cats have small hearts, and although they typically host fewer than six worms, this small number can prove deadly. Additionally, no safe heartworm treatments exist for cats, so the only option is to monitor closely, provide supportive care, and hope for the best until the worms die on their own.

Pet parasite diagnosis and treatment

Intestinal parasites can be diagnosed and treated relatively easily using routine tests performed on a stool sample to look for parasite eggs or genetic material. Many deworming and anti-protozoal medications are available to treat specific parasites, and most are highly effective. We recommend checking your pet’s stool sample at least once annually and more often if they are highly social or spend time in areas with a lot of wildlife.

Heartworms are more difficult to detect and treat because of their life cycle—a blood test can detect adult female worms but not until at least six to seven months after initial infection. Annual blood testing is recommended for all dogs, and additional tests may be required for rescue dogs with an unknown history to ensure infections aren’t missed because of timing. Cats are tested only when starting a preventive regimen or when infection is suspected. 

Heartworms are resistant to standard dewormers, so the treatment for them is more complex than for intestinal worms. Unfortunately for infected dogs, the recommended treatment by the American Heartworm Society is to give injections of a highly toxic substance that kills the worms, and they must remain on cage rest for several months between and after these injections. Antibiotics and steroids are also typically used to help prevent reactions to toxins and bacteria released as the heartworms die.

Pet parasite prevention

Heartworm treatments are no fun for dogs or their owners, but preventive medications can stop infections from developing in the first place. These products use low doses of safe medications and are highly cost-effective compared to the costs of treatment. Most heartworm preventives are given once monthly, and they work retroactively to kill immature larvae transmitted via mosquito bites in the previous month. Once larvae mature, the preventives can no longer kill them, so consistent administration is crucial. Nearly all heartworm preventives also are highly effective in preventing or treating hookworms and roundworms, providing pets with complete worm protection. We recommend year-round heartworm prevention for all dogs and cats.

Internal parasites don’t always cause obvious changes, but they can wreak havoc inside your pet’s body. Annual wellness examinations, routine parasite testing, and diligent preventive use will help keep your four-legged friend healthy and parasite-free. Contact our Carolina Virginia Animal Hospital team to schedule a wellness visit or to learn more about our parasite prevention products and services.