Toxocariasis is an infection caused by parasitic roundworms commonly found in the intestines of dogs and cats. The Center for Disease Control (CDC) estimates that almost 14 percent of the US population has antibodies to the parasite (Toxocara), meaning that tens of millions of people in the United States have been exposed to the disease. Worldwide, toxocariasis ranks as one of the most common infections.

Here are some of the most commonly asked questions about the diagnosis, treatment, and prevention of toxocariais in dogs, cats, and people:

1. How is toxocariasis spread?

Toxocariaisis is a zoonotic disease, meaning it can be transferred from animals to humans. Toxocara parasites are found in the intestines of dogs, cats, and foxes. Animals shed the parasite’s eggs through their feces, and the infection passes to other animals or people through the ingestion of dirt contaminated with parasitic eggs. More rarely, people can contract the disease by eating undercooked meat contaminated with Toxocara larvae. Puppies and kittens can also contract the disease in utero or through their mother’s milk. Toxocara larvae are only infectious after 2-5 weeks after being expelled in an animal’s feces. Thus, infection does not occur from contact with fresh feces. In addition, the disease cannot be spread through human-to-human contact.

2. What are the symptoms of toxocariasis in humans? What are the symptoms of toxocariasis in dogs and cats?

Many people infected with toxocariasis do not develop any symptoms at all. When symptoms do develop, they include mild cough, high fever, stomach pain, and headache. More severe symptoms can occur if the parasite infects the liver, lungs, eyes, or brain; these symptoms include fatigue, loss of appetite and subsequent weight loss, wheezing and difficulty breathing, blurred or cloudy vision, red and painful eyes, and seizures. Severe symptoms are most common in young children.

Symptoms of toxocariasis in dogs and cats include abdominal swelling and pain, diarrhea, loss of appetite and subsequent weight loss, anemia, fatigue, cough, nasal discharge, difficulty breathing, and the development of a rough coat. These symptoms, while serious, are rarely fatal; however, animals can sometimes develop intestinal blockages or perforation of the intestinal wall, resulting in death. This occurs most frequently in young puppies and kittens.

3. How is toxocariasis diagnosed?

In dogs and cats, toxocariasis is diagnosed by examining the animal’s feces to detect either adult worms or worm eggs. In humans, toxocariasis can more be difficult to diagnose with certainty. In most cases, if your doctor suspects toxocariasis infection, a blood sample will be taken to test for Toxocara antibodies. However, serologic tests may not always be accurate, since antibody responses will vary depending on the location and number of worms present in a person’s body. If toxocariasis is suspected and you are experiencing ocular symptoms, such as vision loss or headaches, an eye exam may also be used to detect the presence of parasites.

4. How is toxocariasis treated?

For mild symptoms, no treatment will be needed. However, for more severe infections that affect major organs (other than the eyes), an anthelmintic medication will be used in both humans and animals; this kills the parasite larvae, which are then expelled through the feces. This process is also known as deworming. For infections of the eye, steroids are used to reduce inflammation and prevent further damage; for severe eye infections, surgery may be required.

5. How can toxocariasis infection be prevented in dogs and cats? How can toxocariasis infection be prevented in humans?

Female dogs and cats should be dewormed regularly to prevent the transmission of toxocariasis larvae to offspring; in addition, puppies and kittens should be dewormed at 2, 4, 6, and 8 weeks of age. Animals’ environments, including dishes and bedding, should be cleaned regularly, and care should be taken to prevent animals from eating dirt. To prevent toxocariasis infection in yourself and your family, proper hygiene is key. Be sure to wash your hands thoroughly after playing with or handling pets, before handling food, and after any outdoor activity. Children should be taught proper handwashing techniques and should not be allowed to play in areas where animal feces may be present.

6. What are the different types of blood tests for toxocariasis?

As mentioned previously, serologic testing for toxocariasis can be difficult. Blood tests to detect Toxocara antibodies in response to toxocariasis infection include assays and enzyme-linked immunosorbent assays (ELISA) like the New Life Toxocara Microwell Serum ELISA. Research has shown that the latter tests are significantly more effective in reliably detecting Toxocara antibodies.


Center for Disease Control (CDC). “Toxocariasis: FAQs”. Available at

National Health Service (NHS). “Toxocariasis.” Available at

Paddock, Arliss. 2015. “Roundworms in Dogs: Symptoms, Treatment, and Prevention.” American Kennel Club. Available at

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