Are Parasites in Dogs Contagious?

Some parasites in dogs can be contagious, both to other dogs and to people. Intestinal worms can be particularly problematic, but some external parasites can be passed between dogs and people, too. Let's look at some common canine parasites that can also pose health risks to dog owners.

Canine Intestinal Worms

Intestinal worms are a type of parasite that many dogs suffer from at some point in their lives. Some of them, including roundworms, tapeworms, whipworms and hookworms, are contagious between dogs, while others, such as roundworms and hookworms, can pass between dogs and people.

One of the most common intestinal parasites that affects both dogs and people is the roundworm. This parasite often infects puppies before they are born, and they can cause life-threatening intestinal blockages if they are not treated. Affected puppies usually appear pot-bellied, or they may lose weight and have diarrhea. A fecal examination can determine whether your dog has roundworms, and medications are available to treat the problem.

In people, roundworms do not commonly settle in the intestinal tract. Instead, they usually migrate into a person's brain, eyes or spinal cord. The infestation is called toxocariasis in humans, and it takes two main forms: ocular larval migrans, in which the worms settle in a person's eyes, and visceral larval migrans, in which the worms settle in other organs in a person's body. About 700 people a year suffer vision impairment due to roundworm infestations.

Hookworms are another common canine parasite. They are very contagious among dogs and can cause anemia and blood loss in affected animals. Signs of hookworm infestation include lethargy, weakness, bloody diarrhea and weight loss. Fecal screenings can detect these worms, which are readily treated with medications.

If they migrate into humans, hookworms can be responsible for intestinal problems or a condition called cutaneous larval migrans in which the worms leave itchy, red trails in the skin as they move under it.

Canine External Parasites

External parasites that affect your dog can also affect you and your family. Both dogs and people can be bothered by fleas, which can carry rickettsosis and bartonellosis , and ticks, which can harbor Lyme disease, Rocky Mountain spotted fever and tularemia.

Another external parasite that can pass between your dog and you is sarcoptic mange. This disease, which is transmitted by mange mites, usually causes only mild symptoms in people. In your dog, sarcoptic mange can cause extreme itching and hair loss, which can lead to crusty pustules and secondary skin infections.

In people, the same infection is usually referred to as scabies, and it can cause an itchy rash that commonly affects skin folds. The rash also becomes more problematic at night. Within the rash, trails left under the skin by burrowing mites can often be seen.

Medications are available to eradicate mange and scabies. While the mites can be killed quickly, the resulting skin irritation from their presence may take weeks or months to completely be resolved.