Delve Deeper Into Understanding Intestinal Parasites


Author: Dr. Clarissa G. Noureddine, DVM, MS, MS

As you may have heard, our ‘Paws to Protect’ topic for this month is Intestinal Parasites. On some levels, this is a pretty easy topic to educate owners about because most people think intestinal parasites are “gross” and would never want their pets to have them. So, if a pet is diagnosed with an intestinal parasite infection, it’s an easy choice to treat the problem. But it’s important to delve a little deeper into the world of intestinal parasites so that we can try and stay “ahead of the game” and better protect our pets (and our families).

How do pets become infected with intestinal parasites?
From a scientific viewpoint, this is a question that has some interesting answers. Intestinal parasites have developed a variety of ways to infect potential hosts.

  • An obvious route of infection is fecal-oral transmission. This means your pet ingests the infective form of the parasite from feces (or from items that have been previously contaminated with feces). Perhaps some pets will directly eat feces (anyone out there have a dog that likes to frequent the litter box for snacks?), but they could also just ingest something off the ground that has been previously contaminated with feces containing the infective form of the parasite.
  • Some intestinal parasites are transmitted when an animal ingests another organism that is infected with a parasite. Some parasites will reside in muscle tissue, so when a predator feeds on prey containing a parasite encysted in the muscle, the parasite can become active and create an infection in the predator. Toxoplasma gondii, the parasite that causes Toxoplasmosis can do this – for example, when a cat feeds on an infected mouse.
  • Certain parasites can also have transplacental and transmammary transmission – important routes of transmission for young and vulnerable puppies and kittens.
  • In the case of hookworms, in addition to fecal-oral transmission, the larval form of this parasite can actually penetrate the skin and infect the animal (or human).
  • There is another important component of the life cycles of some intestinal parasites that pet owners need to understand: Somatic infection. When an animal is infected with certain intestinal parasites (e.g., hookworms, roundworms), the parasitic larvae will migrate through the somatic tissue to reach the final destination (intestines). Some larvae will actually arrest the migration in the somatic tissue. Then, at a later point in the pet’s life, these larvae can reactivate and cause active infection. Unfortunately, the dewormers we have available are not effective against the larvae arrested in somatic tissue.

How long can intestinal parasites last in the environment?
While you would have to explore the life cycle of each individual parasite to fully answer this question, it’s actually helpful to take a couple of the common intestinal parasites and talk about the ability to persist in the environment. For example, hookworm eggs will hatch and develop into infective larvae within about 2 to 9 days. The larvae cannot last for years, but may last for months in the environment (depending on hookworm species). On the other hand, roundworm eggs can take one to several weeks to become infective, but then the infective eggs can persist in the environment for years.

What symptoms will a dog or cat display when they have intestinal parasites?
Symptoms will certainly depend on the type of intestinal parasite causing the infection. Importantly, some animals may not display any symptoms at all. Others may show vague symptoms such as appetite changes, weight loss, or lethargy. Of course, since intestinal parasites reside in the intestinal tract, pets can display gastrointestinal signs such as vomiting and diarrhea (with or without blood). Parasites that feed on the blood of the host can cause anemia from blood loss. This is particularly concerning (and possibly life-threatening) in young puppies and kittens.

How do I find out if my pet has intestinal parasites?
Sometimes owners will see worms in the pet’s vomitus or in the stool, but this is not always the case. Testing at the veterinary clinic can identify several parasites, and there are more sensitive and specific tests available for some of the more uncommon parasites. Lawndale Veterinary hospital recommends that all pets have a fecal test performed at least annually. You can learn more about our annual fecal testing here.

How do I protect my pet against intestinal parasites?
Lawndale Veterinary Hospital recommends year-round intestinal parasite protection through the use of preventive medications. While these preventive medications won’t cover all intestinal parasites, they do help protect against some of the most common ones. For example, Revolution for cats protects against roundworms and hookworms. Sentinel for dogs protects against roundworms, hookworms, and whipworms.

Are intestinal parasites dangerous to humans?
It depends on the species, but there are many intestinal parasites that are zoonotic – which means they can be transmitted between animals and humans. All pet owners should be aware of this risk and take basic preventive measures to help protect themselves and their family. The Centers for Disease Control and Prevention (CDC) has some great resources on zoonotic infections here. Some of the more common zoonotic intestinal parasites found in pets can include roundworms, hookworms, Toxoplasma gondii, Cryptosporidium, Giardia, and Tapeworms.

What steps should pet owners take to minimize the risk of intestinal parasite transmission?

  • Scoop your litterbox daily and pick up fecal waste immediately from the yard (before eggs have a chance to develop into the infective stage).
  • Cover outdoor sandboxes so wildlife and feral cats don’t use the sand as a “litter box”.
  • Wear gloves when gardening.
  • Cook meat to the recommended temperatures prior to eating.
  • Wash your hands after handling pet waste and before eating.

Where Can I learn More About Intestinal Parasites in Pets?

Visit this great website: PetsandParasites