Many organisms live inside our dogs. Most of them cause no problems, and some can even produce benefits for the host. Your dog's digestive tract contains bacteria that help break down food. That bacteria is an example of a mutually beneficial relationship. However, internal parasites or endoparasites can also live inside your dog and can sometimes be detrimental since they will draw nutrients away from their host.
When it comes to dogs, the most common internal parasites are worms. Dogs’ worms are divided into two broad categories: nematodes and cestodes.
Nematodes are cylindrical cream-colored worms which include intestines-living roundworms, hookworms, whipworms, thread worms and some other worms that live in the heart, lungs or other organs.
Cestodes or tapeworms are flattened worms that live exclusively in the intestines. These internal parasites can cause severe diseases if they consistently take away the dog's essential nutrients, block the intestinal tract, or damage its walls.
Hookworms are tiny parasites that latch onto the lining of their host's intestines and suck blood. The most recognized hookworm species in dogs is the Ancylostoma caninum.
The dog gets infected by ingestion of parasite eggs or by direct contact with parasite larvae in a contaminated environment, like a rodent. Hookworms can also be spread through the dog mother's milk and placenta.
Most common signs of hookworm infection are diarrhea, which can sometimes contain blood, reduced appetite, pale gums, diminished overall health and coat quality.
Owners should be aware that some dogs may not show any of this signs. But if left untreated, the disease progresses and leads to intestinal inflammation, acute weight loss and ultimately severe anemia (low red blood cell count).
To prevent this, be sure to keep your dog out of dumpsters and don't let them eat small prey like rodents.
The hookworm larvae live in the soil and can also penetrate the human skin. They can cause itchy and bumpy skin lesions known as creeping eruptions or cutaneous larva migrans.
Roundworms or ascarids are the most common worms in dogs. The most recognized species is Toxocara canis. Just like hookworms, the dog can get infected by ingesting parasite eggs or by being in direct contact with parasite larvae.
Most common signs of roundworm infection are mild vomiting and diarrhea, pot-bellied appearance, poor coat quality, and cough. Occasionally, infected dogs may pass spaghetti-looking worms in their stool.
If left untreated, the disease progresses into intestinal inflammation, weight loss, severe abdominal pain, and dehydration.
If a person accidentally ingests a Toxocara canis egg from contaminated soil, the egg will evolve into larva and will cause a condition known as visceral larva migrans.
Because of the parasite-host incompatibility, the larva will fail to complete its natural life cycle but will migrate to the lungs, liver or eyes, where it forms cysts and provokes an inflammatory response. If left untreated, the disease will worsen and will lead to chronic bloody diarrhea, dehydration, weight loss and anemia.
Whipworms are thread-like blood sucking parasites that inhabit both the colon and the small intestines. The dog gets infected by ingestion of the parasite eggs.
Most common signs of whipworm infection are intermittent diarrhea and loose stool with blood presence.
To help your dog prevent them, keep him away from contaminated environments like dumpsters.
Tapeworms spend part of their life cycle in another host. The most recognized dog tapeworm, the Dipylidium caninum, uses fleas and lice as the intermediate hosts.
The dog gets infected with tapeworm if she has a heavy flea infestation (Dipylidium caninum) or hunts and scavenges wildlife (Taenia species, Diphyllobothrium latum, Echinococcus granulosus and Echinococcus multilocularis).
Some tapeworm species use humans as intermediate hosts and can cause infections to us as well.
The best diagnosis method is testing a stool sample for parasite presence (eggs, worms, antigens). The treatment of choice is applying deworming medications, which have an excellent prognosis. There are no vaccines available for preventing these conditions. Using a monthly parasite control product, available and approved by your veterinarian, is the best prevention method.
Dirofilaria immitis spreads via mosquito bites and will reside in the dog's heart and pulmonary arteries.
Most common signs of heartworm infection are mild, persistent cough, reluctance to move, tiredness after moderate exercise, reduced appetite and weight loss. If left untreated, it can lead to heart failure and sudden death.
Dogs get infected with lung worms if they eat earthworms containing infectious larvae (Capillaria aerophila); through their mother's saliva (Filaroides osleri) or by eating contaminated crayfish (Paragonimus kellicotti).
Among the most common rare worms are the Spirocerca lupi, which creates nodules in the dog's esophagus and impairs swallowing, and the Dioctophyma renale, which is a giant kidney worm that causes kidney deterioration and can only be treated by removing the affected kidney.
Diagnosing these worms requires a special blood test. The treatment of choice is to start a proper deworming protocol. There are no vaccines available for preventing these conditions, although using a monthly parasite control product, available and directed by your veterinarian, is the best prevention method.
Preventing worm infections, in both you and your pet, is a crucial step. The best way to avoid infection is to follow these simple steps:
1. Pick up your dog's feces, especially in places where both children and animals play.2. Wash your hands thoroughly after picking up after your dog, or after being exposed to soil, sandboxes and raw meat.
3. Cover sandboxes and play areas to prevent wildlife from contaminating the area.
4. Have your dog tested for intestinal parasites and parasitic infections at least once a year.
5. Ask your veterinarian about parasite infection risks in your area and your options for an effective year-round prevention.
It can be concluded that the majority of dogs’ internal parasites live in the intestinal tract, where they have a ready source of nutrients and can escape the host's immune defenses.
The internal parasites produce eggs that are passed in the dog's feces. Those eggs can survive in the environment for a long time and can be swallowed by another dog to cause a new infection.
It is also possible for your dog to be infected and show few or no signs of illness. Therefore, you should pay close attention to any subtle changes in your dog's behavior. Early intervention is essential for a lifetime of good health.