What Are Internal Parasites?

What people commonly refer to as “worms” are really internal parasites. Internal parasites are organisms that live within an animal, gaining their nutrition and protection at the expense of the host animal. Internal parasites live in the heart or intestinal tract, and many internal parasites can be life-threatening.

Dogs can pick up parasites outdoors from eating parasite-infested bark, leaves, soil and other natural matter (including raccoon feces, which is especially dangerous). In fact, some parasite eggs can last for more than a year in the soil. Pets can contract internal parasites from a variety of sources including:
• Contact with contaminated soil, food or water
• Mosquitoes
• Licking the ground
• Their mothers, before or after birth
• Fleas, birds, rodents
 

Some of the most common internal parasites include:
 

• Heartworms
Heartworms can be transmitted to pets by more than seventy species of mosquitoes. Adult heartworms live in the right side of the heart and pulmonary arteries where they restrict blood flow and cause organ damage. Blockage and injury caused by heartworms may lead to heart failure and liver and kidney damage. Symptoms include cough, exercise intolerance, enlarged liver and abnormal lung or heart sounds.
 

• Roundworms
 

Almost all puppies get roundworms from their mothers. Pets of all ages can pick up roundworms from the soil. Roundworm infections are usually accompanied by symptoms such as diarrhea, vomiting, stunted growth, rough coat and a bloated belly.
 

• Hookworms (A. caninum)
 

Hookworm eggs pass through the feces of an infected dog into the soil where they develop into larvae. The larvae are easily swallowed or can penetrate through your pet's feet. Hookworms attach to your pet's intestinal lining, creating bleeding internal wounds. Symptoms of a hookworm infection include blood loss, anemia and diarrhea.
 

• Whipworms
 

Whipworm eggs are passed in feces and can survive for years in the soil. Whipworm infections in pets are caused by ingestion of the eggs. Whipworm infections usually cause bloody diarrhea, anemia, dehydration and loss of appetite.

• Fleas
 

Fleas are another common parasite, though not an internal parasite, that can cause serious discomfort to your pets and spread more serious parasitic infections, like tapeworm. Adult fleas jump onto your pet when they sense a host is near. There, a female flea can lay up to fifty eggs each day. Eggs fall off your pet and develop into worm-like larvae, which hide in carpeting, furniture, bedding and other dark places. The larvae mature as they feed on fecal matter dropped by adult fleas and the cycle continues.

Adult fleas (typically the only fleas you can see, either on your pet or in your household) represent only 5% of any given flea population. The other 95% of any given flea population are pupae, larvae or eggs. Some interesting facts about fleas:
• Most fleas feed within seconds to minutes of landing on a new host.
• All fleas will bite practically any warm-blooded host they inhabit.
• No insecticide can stop a flea from biting.
• Once flea eggs are laid, they will usually hatch within 1 - 10 days, depending on temperature and humidity.
• Flea larvae mature inside a cocoon. And while the process of vacuuming effectively removes flea eggs and larvae from your household, it actually stimulates matured fleas to emerge from cocoons.
• Unlike mosquitoes, who eat once and then allow themselves to digest their meal, a flea will repeatedly bite its host long after its hunger is satisfied.

The key to controlling fleas is to consistently interrupt their life cycle at an immature stage so they do not develop into adult fleas.