Heartworms & Other Parasites

Other Parasites That Can Make Your Pet Sick

1. Mosquitoes


Mosquitoes feed on nectar, but the female also needs blood to develop her eggs. And because of this blood-sucking habit, mosquitoes are by the far the most deadly vectors of disease known to man. Mosquitoes can carry disease-causing viruses and parasites from person to person without suffering from the disease themselves. Female mosquitoes suck blood from people and other animals as part of their eating and breeding habits. When a mosquito bites, she also injects saliva and anticlotting agents into the skin, which may contain disease-causing viruses or other parasites.

Dogs can be infected by the bites of mosquitoes. The most commonly known infection is heartworm disease. Luckily, a veterinarian can treat this infection if it is diagnosed in time. Ask your veterinarian about more information on this mosquito-borne disease of dogs, and how you can protect your dog from heartworm with preventive medication.

2. Hookworms


In dogs, hookworm infection occurs through ingestion or skin penetration of hookworm larvae found in the stools or soil contaminated by feces of an infected animal. The larvae then develop and migrate to the intestines, where they hook onto the intestinal wall and feast on the host's blood. The larvae of hookworms can penetrate the skin and infect humans through contact with soil or sand contaminated by feces of host dogs or cats. In a human host, the hookworm larvae do not migrate to the intestines and become blood-sucking adults as they do in pets. Instead, they move around under the skin and eventually die, causing an inflammatory skin reaction known as cutaneous larva migrans, or "creeping eruptions." It is important to keep your pet free of hookworms with good hygiene, preventive medication and regular veterinary checkups. Also, keep stray dogs and cats out of sandboxes and gardening areas.

3. Roundworms


Roundworms are parasitic worms that are round in shape, live in the dog's intestines and consume partially digested food. Unlike hookworms, they do not attach to the intestinal wall, but literally swim in their food. Adult worms resemble spaghetti and may come out in the feces or vomit of an infected dog. Transmission to dogs is through eggs in feces, eating a prey animal that is a host (usually rodents), mother's milk, or in utero. In dogs, roundworms cause diarrhea, vomiting and in extreme cases, pneumonia and intestinal obstruction.

In humans, roundworms can cause a serious condition known as visceral larva migrans. Most victims are children, who are infected when putting contaminated fingers into their mouths. Once ingested, the roundworm larvae, though not in its usual host, tries to complete its life cycle. The roundworm gets lost in the human body, usually in the eye, dies and generates an inflammatory reaction that can cause blindness. Proper hand washing can prevent infection. Pet deworming of puppies and preventive medication will reduce environmental contamination.

4. Tapeworms1


Tapeworms are long, flat worms with multiple parts, or segments, to their bodies—each segment with its own reproductive organs. Tapeworms attach themselves to your pet's intestines, and are usually diagnosed when you find segments of the worm around your pet's rear end, in your pet's feces, or where your pet sleeps. These segments appear as small white worms that resemble grains of rice.

Several species of tapeworms can infect your pet, each with a different "host," or carrier, of the tapeworm, that your pet has eaten to become infected. These include fleas, small rodents (like mice, rats, and squirrels), or larger animals such as deer or sheep.

Pets with tapeworm usually do not display any signs of illness. When animals rub their rear ends on the ground, it is usually related to illness other than tapeworm—for instance, skin or anal sac irritation around their tail.

5. Sand Flies2

Sand Flies

The Lutzomyia shannoni (or L. shannoni) species of sand fly can be found in southern states, from Florida to Louisiana, and in Arkansas, Tennessee, South Carolina and North Carolina. This species is also reported as far north as Maryland and Delaware.

L. shannoni can transmit a parasite that causes a disease called Leishmaniasis. Although this disease is not commonly found in North America, evidence suggests it may occur in Foxhounds and other breeds that have been infected with a strain of the parasite from southern Europe. The Spinone dog breed, in particular, which was imported directly from Italy, is also at risk of infection.

Infection with Leishmaniasis through sand flies in North America has not been confirmed. However, experts suspect that infection may be transmitted from dog to dog in blood and secretions caused from biting, licking, breeding, blood transfusions, etc.

Signs of Leishmaniasis in dogs are not always the same, and can appear many months after exposure. Some signs include weight loss, swollen lymph nodes (located on the neck, chest, and around leg joints), anemia, skin lesions, hair loss, appetite loss, fatigue and bleeding from the nose.


  1. Pets and Parasites. Tapeworms. http://www.petsandparasites.org/dog-owners/tapeworms/. Accessed March 18, 2014.
  2. University of Florida Institute of Food and Agricultural Sciences. Entomology & Nematology: Featured Creatures. http://entnemdept.ufl.edu/creatures/misc/flies/Lutzomyia_shannoni.htm. Accessed March 18, 2014.