Threadworms in Dogs

Threadworms are intestinal parasites that can infect dogs, cats and humans. Experts believe that different species of threadworms affect each different type of host; however, dog threadworms are contagious to humans, and humans can spread threadworms to dogs. Read on to learn what you should know about this parasitic intestinal worm. 

Life Cycle and Transmission of Dog Threadworms

The dog threadworm, Strongyloides stercoralis, lays eggs inside the intestines of its host animal. When these eggs hatch, the larvae escape from the intestine through the animal's feces. The larvae may not necessarily infect a new host, but if they do, they will do so by burrowing into the new host's skin. From there, they travel to the lungs and out of the windpipe, where they are swallowed and move to the digestive tract.

Sometimes, in female dogs, threadworms infect the mammary organs. A nursing mother can infect her puppies with threadworms through her milk. Infestations are most common in hot, humid temperatures.

Symptoms of Threadworms in Dogs

The severity of threadworm infestation symptoms can vary, depending on the severity of the infestation itself, and the age of the animal involved. Puppies often develop severe infestations when they catch threadworms through their mother's milk. In very young dogs, infestation can be deadly.

Often, however, the symptoms of threadworm infestation are quite mild. In most cases, symptoms consist of slight diarrhea.

In more severe cases, symptoms can include:

  • appetite loss
  • weight loss
  • dehydration
  • weakness
  • diarrhea

Dogs who have been newly infested with threadworms may display inflammation and skin irritation at the point where the threadworms entered the body. They may cough or experience difficulty breathing as the threadworms migrate through the lungs. 

Diagnosing and Treating Threadworms in Dogs

Your vet can diagnose threadworm infestation by examining a stool sample in the lab. Threadworm infestation be treated with orally administered drugs. Thiabendazole, ivermectin and fenbendazole are currently being prescribed for the treatment of threadworms in dogs.

Threadworm larvae can sometimes remain in other parts of your dog's body besides the intestines. Medication cannot remove these larvae from the body. If your dog has threadworm larvae encysted in other parts of his body, he may develop another intestinal infection and need treatment again in the future. 

Controlling Dog Threadworms

Threadworm larvae cannot tolerate cold or dry environments; they need heat and humidity to survive. Control threadworm infestations by keeping your dog in a cool, dry environment. Keep litter boxes and lawn areas free of feces. Since dog threadworms can spread to humans, use latex rubber gloves to protect yourself when handling your infected dog or his feces, and wash your hands thoroughly afterward.

Breeding females should be routinely tested for threadworm infestation, since they can spread the worms to their puppies in the womb, or during nursing. Threadworm infestation can easily be fatal for young puppies. Puppies of females known to have been infested with threadworms should be treated periodically during nursing, to prevent recurrent threadworm infestation.