This Twice Yearly Test Could Help Save Both Your and Pet's Health

pet parasites

Story at-a-glance -

  • Intestinal parasites can be one of the less pleasant realities of pet ownership
  • Intestinal parasites invade your dog’s or cat’s gastrointestinal tract, often causing digestive issues like diarrhea
  • Common GI trespassers include microscopic organisms such as giardia, and a variety of parasitic worms
  • Because there is not one “universal” dewormer for all GI parasites, automatically deworming your pet on an annual basis is a poor choice

By Dr. Becker

Today I want to talk about a subject near and dear to every pet parent’s heart (not really) — intestinal parasites.

These are the quite disgusting little creatures that can take up residence inside your dog’s or cat’s gastrointestinal (GI) tract (and in some cases they’re zoonoses, meaning you can get them as well), and cause all sorts of digestive and other issues.

Common invaders of the digestive tract include parasites such as giardia, coccidium and cryptosporidium, and worms (whipworms, tapeworms and hookworms).


How infection occurs. Your pet can acquire giardia by ingesting an infected cyst contained in another animal's poop. Contamination can occur directly or indirectly through contact with infected cysts. The most common route of transmission is through feces-contaminated water.

Once inside a dog's or cat's small intestine, the cyst opens and releases the active form of the parasite. These forms are able to move around and attach themselves to the walls of the intestine, where they reproduce by dividing in two.

Eventually, the active forms of giardia encyst (build cysts around themselves) and are passed from the animal's body in feces. Those feces then contaminate water sources, grass, soil and other surfaces.

Also, if a dog is giardia-positive, licks his backside and then licks another dog, cat or human, there's potential for transmission to occur.

Common symptoms. The majority of pets with giardia show no obvious signs of infection. For those pets who do experience symptoms, the most common is diarrhea that can be acute, chronic or on-and-off.

What happens with a lot of pet parents is, about the time they’re ready to call the vet about their dog’s or cat’s loose stools, the situation seems to correct itself.

Diarrhea caused by a giardia infection can come and go, which causes many people to write off the occasional loose stool as the result of indiscriminate eating or a random food sensitivity.

This is exactly why so many cases of giardia go undiagnosed — sometimes for months or even years. Eventually, a pet with a long-standing giardia infection can suffer a severe, debilitating episode of bloody diarrhea that causes dehydration.

Most of these pets don’t lose their appetite, but they often do lose a noticeable amount of weight. This is because the parasitic infection in the GI tract is interfering with digestion and absorption of nutrients from the food they eat.

Preventing infection. Don’t kennel your pet in close quarters with other animals. Clean up your pet’s poop outdoors, and don’t walk your dog or cat in areas where other animals relieve themselves. Don’t allow your pet to drink from outdoor water sources.

Drop off a fecal sample (that includes a fecal smear) with your vet twice a year for testing. This will help identify the presence of a parasitic infection before digestive function is compromised.

Giardia infections can easily be missed with traditional fecal flotation techniques, so if you suspect your dog may have a giardia infection, ask your veterinarian for a PCR test to know for sure.


How infection occurs. Immature coccidian, called oocysts, are passed in the poop of an infected dog or cat. The oocysts are resistant and can live for quite some time in the environment.

Coccidia infections typically spread from one dog or cat to another through contact with infected feces. Coccidiosis is most commonly found in puppies or kittens that have contracted the parasite from an adult dog’s feces.

The infection is especially dangerous for young pets with underdeveloped immune systems, and adult pets who are immunocompromised.

Common symptoms. The hallmark symptom of coccidiosis is watery diarrhea that contains mucous. Left untreated, the infection can eventually cause bloody, explosive diarrhea, weakness and lethargy.

Preventing infection. Don’t let your pet sample the poop of other animals. Keep infected animals isolated, and clean and disinfect areas where pets have been ill or had diarrhea. It’s a good idea to test the feces of pregnant dogs or cats and those that have just given birth, along with newly acquired pets.


How infection occurs. Infected animals shed the parasite in their feces. In damp environments, the organism can survive for up to six months. It can be transmitted when an animal ingests contaminated food or water, or licks or comes in contact with a contaminated object or surface.

Rarely, transmission can occur by inhaling the organism. Cryptosporidiosis can be a primary disease as well as a secondary disorder in pets with compromised immune systems.

Crowding and unsanitary conditions increase the risk of exposure, and young animals are more susceptible to infection.

Common symptoms. In pets with healthy immune systems, the disease is self-limiting, and many infected dogs and cats show no symptoms. In symptomatic pets, signs of infection occur within a few days of exposure, and can include lethargy, abdominal cramping, watery diarrhea, loss of appetite and weight loss.

Symptoms usually resolve without treatment, though occasionally the diarrhea persists, and the animal can become dehydrated. The severity of the disease depends on the immuno-competence of the dog or cat.

Preventing infection. To prevent your pet from contracting crypto, don't allow him to sample animal feces or drink from bodies of water that could be contaminated. Keep sick animals separate from healthy ones, and clean and disinfect areas where animals have been ill or had diarrhea.

Since cryptosporidiosis is primarily a disease of young animals with immature immune systems, as well as immunocompromised pets, the best way to prevent your dog or cat from becoming ill after exposure is to make sure her immune system is healthy.


How infection occurs. Your pet can only be infected by ingesting whipworm eggs from soil or other substrates containing eggs. In the small intestine, larvae hatch from ingested eggs and burrow into the mucosal lining. From two to 10 days later, they move on to the cecum and grow into adult worms.

The eggs are not infectious when passed in feces. They need several weeks in soil to develop into infective larvae inside their shells. A dog or cat eats contaminated soil or objects in the soil and the cycle of infection begins.

Common symptoms. Many pets show no clinical signs of illness with a whipworm infection. Symptoms when they do occur can include bloody diarrhea, dehydration, weight loss, anemia and even death in severe cases.

Preventing infection. Re-infection with whipworm from contaminated environments is a significant concern. The eggs are extremely resilient and resistant to most cleaning methods and even freezing temperatures. They can be dried out with strong agents like agricultural lime, but the preferred method is to replace contaminated soil with new soil or another substrate.

Regularly picking up poop from your yard and other areas your pet frequents will help reduce the risk of further contamination of soil.


How infection occurs. Your dog or cat can acquire a tapeworm infestation by eating part or all of an intermediate host (e.g., birds, fish, reptiles and rats) carrying tapeworm eggs, larvae or cysts. Fleas and lice also harbor tapeworm eggs.

The most common method of transmission is through ingestion of adult fleas, birds, rodents, rabbits or through scavenging. Free-roaming pets with access to freshly killed wild or domestic animals are at increased risk of acquiring tapeworms, as are animals with heavy lice and/or flea infestations.

Common symptoms. Most of the time, pets with tapeworms don’t show signs of discomfort. Because the worms feed slowly and steadily on blood and nutrients over a long period of time, they don’t cause acute or dramatic symptoms.

On the rare occasion when symptoms of a tapeworm infection do occur, they are usually pretty generic and can include itchiness around the anus, licking of the anal and perianal area, butt scooting, weight loss without loss of appetite, increased appetite without weight gain, poor coat or skin condition, distended or painful abdomen, diarrhea, lethargy and irritability.

Once in a great while, a heavy infestation of adult tapeworms causes partial or complete intestinal blockage, which is a true medical emergency. These parasites can be difficult to diagnose, and sometimes the only noticeable symptom is what looks like grains of white rice (tapeworm segments) stuck to or crawling through the fur around a pet’s rear end.

Preventing infection. Eliminate all adult fleas and/or lice in your pet’s environment. You should also keep your pet a safe distance from potentially infected intermediate host animals, most commonly birds, rats, rodents and rabbits, as well as garbage.


How infection occurs. Your pet may eat contaminated feces or dirt, or he might run through contaminated soil, then lick his paws and ingest the hookworm eggs in that manner. Puppies and kittens can acquire hookworm from an infected mother’s milk.

Common symptoms. A puppy or kitten who acquires hookworms can become lethargic, weak, malnourished and anemic. It isn’t uncommon for young pets to die from an infestation. Infected adult dogs and cats may show symptoms of poor appetite and weight loss.

Preventing infection. To prevent a hookworm infestation, it’s important to get rid of any potentially infective feces from wild or stray animals around your property that might tempt your pet. Also, keep your dog or cat away from the poop of other animals while you’re walking or hiking outdoors.

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