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Pets, Parasites, and People

A veterinarian gently holds and examines a small Yorkshire Terrier dog, focusing on its eyes, in a bright, clinical setting.

It is common for a dog or cat to become infected with an internal or external parasite at some point in their life. Parasites can affect your pet in a variety of ways, ranging from simple irritation to life-threatening conditions if left untreated. Some parasites are also zoonotic which means they can be transmitted from animals to humans.

Who is at risk?
Any person in contact with an infected animal or disease vector (a disease carrier that spreads the disease from an infected animal to an uninfected human) is considered at risk. Individuals with compromised or immature immune systems or those with poor hygiene are generally at higher risk, such as infants and small children, pregnant women, and the elderly.

What can I do to reduce the risk of parasites for my family and pets?

  1. Practice good personal hygiene.

  2. Clean up pet feces regularly.

  3. Use an effective flea and tick preventative year-round.

  4. Use an effective internal parasite preventative administered monthly year-round.

  5. Visit your veterinarian for annual testing and physical examination.

What kind of internal parasites or worms can infect my cat or dog?
Intestinal Worms: There are a number of intestinal worms that can infect dogs and cats. The most common intestinal parasites in dogs and cats include roundworms, hookworms, whipworms and tapeworms, and they are very prolific. Roundworms are the most common intestinal parasites of pets and the most likely to be transmitted to humans. Humans can become infected with roundworms by accidentally ingesting infective worm eggs that are found in soil or sand contaminated with feces. In humans, larvae hatch from the eggs and can travel to various tissues in the body, including the liver, lung, and brain, potentially causing serious conditions.

Giardia: Giardia is another common internal parasite which can infect humans, dogs, and cats. Giardia can be contracted by:

  • Drinking contaminated water,

  • Rolling and playing in contaminated soil,

  • Eating feces, or

  • Coming into contact with contaminated fur of another dog or cat.

Once giardia is contracted, the parasite will live in the intestines of the host. It is passed along from host to host through feces, and may survive for long periods of time in the environment, especially in water or areas with high moisture content (for example, a dirty kennel run).

Young puppies and kittens are more vulnerable to infection and are therefore at greater risk. Dogs and cats infected with giardia have a higher risk of illness than older dogs and cats. Symptoms of giardia include diarrhea, vomiting, weight loss, and an overall poor condition. Many dogs and cats can also be infected and not show any signs or symptoms of illness.

Heartworm: Heartworm is a very serious parasitic concern for both dogs and cats. Heartworm is transmitted via mosquitoes, as mosquitoes are the vector and intermediate host for the parasite. Heartworms can kill or seriously debilitate pets that are infected with them. The adult worms live in the bloodstream, lungs and heart, causing blood vessel obstruction, restricted blood flow, and decreased organ function. A year-round preventive program is most effective to keep pets free of heartworms.

Do fleas and ticks on my pet present a health risk to my family?
Yes. Fleas and ticks can carry and either directly or indirectly transmit several potential illnesses of humans. For example, rickettsiosis can be transmitted directly by ticks. Bartonellosis is transmitted between cats through fleas and then may spread to people. Fleas and ticks are an important risk for transmission, which can infect both pets and humans. A year-round preventive program is most effective to keep pets free of fleas and ticks.

Additional Resources: www.petsandparasites.org

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