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How Do Pets Get Roundworm?

Causes of Roundworm Infections in Dogs and Cats

By Kat Sherbo. November 05, 2012 | See Comments

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    PetCareRx Staff Veterinarian

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How Do Pets Get Roundworm?

Dogs and catS can become infected with roundworms in a few different ways. Read about the causes of roundworm infections in pets.

Roundworms are parasites that can infect a dog or cat’s intestinal tract or other bodily tissues, ultimately causing malnourishment, as the parasites consume the pet’s food and block the intestines.

Areas with humid climates, such as the southeastern United States, are more conducive to roundworm growth, and so the risk of infection can be higher.

Different types of roundworms can infect dogs and cats. Toxocara cati infects cats, Toxocara canis infects dogs, and Toxascaris leonina can infect either animal. Toxocara cati and Toxocara canis have similar lifecycles, while the Toxascaris leonina lifecycle has fewer steps. 

The Roundworm’s Life Cycle

Roundworm infections begin whenever a roundworm egg enters the body of a dog or cat. This can happen when an animal eats the feces of an infected animal, or ingests soil that was in contact with infected feces. Eating another animal that’s infected, such as a rodent, will also spread the infection. Roundworms can also infect a puppy or kitten in utero or through an infected mother’s nursing milk.

Worm eggs hatch in the intestines after being eaten, and if the worms are Toxascaris leonina, they reach their adult stage here. If the worms are Toxocara cati or Toxocara canis, then the worms migrate from the digestive tract to other bodily tissues, like the liver, usually eventually ending up in the animal’s lungs. If the animal is pregnant, instead of entering the lungs, the worms will make their way to the uterus and infect the unborn puppies or kittens.

From the lungs the parasites are coughed up by the dog or cat, swallowed, and then make their way to the pet’s small intestine again. If enough worms are in the animal’s lungs and throat, pneumonia may develop. The adult roundworm will then remain in the intestine, consuming the pet’s food and laying more eggs. 

Those eggs are released in the pet’s feces, starting the cycle over. The eggs remain in their hard shell for one week to a month, and only then do they become infectious again. The worms can survive in their egg stage in the soil for up to several years, but can be safely disposed of before they become infectious.

Implications for Humans, Too

Some parasites that infect pets can travel to humans, too. Roundworms can infect humans, often with no resulting symptoms. However, in severe cases, roundworms can cause a disease called visceral larval migrans in humans, which can lead to ocular (eye) diseases.

More on Causes of Parasite Infections

How Do Dogs and Cats Get Whipworm?
Hookworm Infections in Pets

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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