Giardiasis in Dogs

Giardia sp. are intestinal parasitic protozoa that can affect a dog's gastrointestinal tract. The clinical picture they cause is called giardiasis. It's very prevalent, since regular deworming doesn't work against protists. It's especially common in puppies.

Most often, the dog catches it by eating feces or water contaminated with these protozoa. Intermittent diarrhea that resists conventional treatment can make us suspect this parasitic infection. Let's look at all its symptoms so we know how to identify it.

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What Is Giardia sp.?

Giardia are protozoa belonging to the genus Giardia. The term "sp." refers to any species within this genus, with Giardia duodenalis being the most common in dogs. Hosts can be dogs and cats, though it can affect all species.

It's a flagellated protozoan, meaning it has several flagella, whip-like appendages that help it move. In addition, it has a sucker disc on its ventral side, which it uses to attach to intestinal microvilli.

How Does My Dog Get Infected With Giardia sp.?

Transmission is direct via the fecal-oral route, and sources of infection are the feces of any contaminated animal, water (streams, ponds, brooks, wells), or a contaminated environment. So, dogs will become infected if they ingest any of the substances described above contaminated with Giardia cysts.

The cysts can survive for months in the environment, especially in cold water, and resist the products commonly used to treat water.

Symptoms of Giardiasis in Dogs

Very often, Giardia sp. presents subclinically, meaning we won't notice any or almost any symptom. This is more common in adult dogs, since they have a more developed immune system. In these cases, discovering it, if at all, will be accidental.

On the other hand, in younger dogs, puppies, or immunocompromised dogs in worse hygienic conditions, it's common for a clinical picture to appear, with symptoms resulting from the damage this parasite causes by attaching to the intestine and absorbing nutrients. These can occur separately or several at once. They will be:

1. Diarrhea and constipation. There can be a period of diarrhea followed by constipation. In cases of diarrhea, it's not uncommon to see steatorrhea (fatty diarrhea).
2. Abdominal pain and/or intestinal noises.
3. Flatulence.
4. Weight loss.
5. Dehydration.

How Is the Presence of Giardia sp. Diagnosed?

If our dog is young and has diarrhea consistent with what we've described, the vet can confirm or rule out the diagnosis through an examination of a stool sample.

For this exam, a sample can be taken from the anus if it's had a recent bowel movement, or the owner can bring one, collected and transported in a container. From this sample, a "snap" test is run, which every clinic has nowadays. The sample is mixed with a specific conjugated liquid to show the presence of giardia.

Within 15 minutes, we'll have a fairly specific result. The vet will then start treatment, which we'll describe next.

Treatment for Giardia sp.

Treatment is based on two drugs. One is fenbendazole, and the other is metronidazole. The environment also needs to be disinfected. This may seem like intense treatment at first glance, but the truth is these are very resistant parasites, and chronic relapses can occur if we don't correctly follow these guidelines.

That said, each vet, based on their own knowledge, may apply modifications to treatment days or drugs, but the one described is an effective treatment based on my clinical veterinary experience. Every dog, with or without symptoms, in whom Giardia sp. is detected, should be treated to prevent environmental contamination.

The test should be repeated a month after diagnosis and the start of treatment, to make sure it's no longer positive for this parasite.

Can It Be Prevented?

To prevent our dog from catching Giardia sp., besides keeping it from drinking in potentially contaminated places, we need to prevent it from eating other animals' feces or being kept crowded in some space, since breeding facilities are often places where this type of parasite develops. So it doesn't hurt, if you get a dog from a breeder or store, to have it checked at a vet clinic.

Since regularly used internal anti-parasite products don't usually eliminate Giardia sp., a dog can have it even if we treat it periodically. That's why the vet needs to be the one who takes a stool sample to detect it, or works from a sample brought in.

Since it can be hard for symptoms to show up, any diarrhea is reason to see the clinic, especially if the dog is a puppy. On our part, we need to implement routine hygiene measures (to prevent this and other conditions).

These measures include: washing our hands after handling feces and always before preparing food. In addition, fruits and vegetables need to be thoroughly washed with drinking water. Cooking eliminates Giardia sp.

So, it won't be a serious condition or disease in itself, but strong treatment needs to be applied to eliminate it from our animal, as well as from the environment. With basic hygiene measures, we'll prevent the contamination from spreading.