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parasitic disease Dog Transmissible to humans

Giardiasis of dogs

Giardiasis is caused by a microscopic parasite, Giardia, which attaches to the wall of the small intestine and interferes with the absorption of food. It is one of the most common causes of chronic diarrhea in puppies and young dogs, partic...

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Zoonosis Prognosis FAQ Sources Affected species

What is it?

Giardiasis is caused by a microscopic parasite, Giardia, which attaches to the wall of the small intestine and interferes with the absorption of food.

It is one of the most common causes of chronic diarrhea in puppies and young dogs, particularly in breeders, shelters and multi-dog homes.

Many adult dogs harbor the parasite without becoming ill: they then eliminate it in their stools and contaminate their environment.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Diarrhea Weight loss Dull coat Bloating Vomiting Stunted growth Dehydration Loss of appetite Soft stools Gas and flatulence

Diarrhea that lingers or comes back in waves, often pasty, bulky, greasy and smelly.

Stools may contain mucus, but rarely blood.

Weight loss or stagnation despite a normal appetite.

Swollen belly and dull coat in the puppy, with slowed growth.

Occasional vomiting.

Fatigue and dehydration in prolonged forms.

Many carrier dogs show no signs.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

A single-celled parasite, Giardia duodenalis, which multiplies in the small intestine.

It appears in a mobile form in the intestine and as resistant cysts in the stool.

These cysts are immediately contaminating, which distinguishes Giardia from worms whose eggs must first mature in the external environment.

Puppies and young dogs whose immune systems are still immature.

Community life: breeders, shelters, pensions, exhibitions.

Uncontrolled drinking water, puddles, streams, collective bowls.

Insufficient hygiene of floors and bedding, humid environments.

Dogs already weakened, otherwise parasitized or under treatment reducing defenses.

Recent change in environment, stress from transportation or adoption.

Transmission

Orally, by swallowing cysts present in stools, on the ground, in a bowl, on the coat or in water.

Puddles, stagnant water and shared water sources are typical sources.

The dog is easily reinfested by licking itself, with the cysts sticking to the hair around the anus and on the paws.

The cysts survive for a long time in a humid and cool environment; they do not tolerate drought and heat well.

In a group of dogs, the circulation of the parasite is rapid.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Diagnosis is made on stools: detection of antigens by rapid test, microscopic examination after concentration, or both.

Since the removal of cysts is intermittent, the veterinarian often requests a sample over several consecutive days.

Finding Giardia does not always mean that it explains everything: in a dog with diarrhea, the veterinarian also rules out worms, a dietary error, an infectious disease or an intolerance.

A post-treatment check-up is frequently offered, especially in the community.

Treatment

A specific antiparasitic treatment prescribed by the veterinarian, over a defined period: the usual wormers against roundworms do not act on this parasite.

A single treatment is not enough if the environment remains contaminated: cleaning is an integral part of the treatment.

Bathing or at least washing the dog's hindquarters at the beginning and end of treatment removes cysts stuck to the hair and limits reinfestation.

A digestible diet, sometimes enriched with fiber, helps the intestine recover.

Rehydration necessary in puppies with prolonged diarrhea.

In a group, all animals are treated at the same time, including those without symptoms.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Pick up stools immediately and clean the floors: cysts are mainly destroyed by complete drying, steam and sunlight.

Wash beds, bowls and toys at high temperature, let dry completely.

Give clean, fresh water, prevent the dog from drinking from puddles and stagnant water.

Avoid overcrowding and permanent humidity in kennels.

Screen new arrivals in a breeding or shelter before mixing them with the group.

Wash your hands after picking up stools or handling an affected dog.

Possible complications

Growth retardation and weight loss in puppies.

Dehydration during prolonged diarrhea.

Poor absorption of nutrients, with poor coat quality and long-lasting fatigue.

Maintenance of chronic diarrhea when other parasites or digestive disease coexist.

Frequent relapses as long as the environment is not cleaned up.

When to see a veterinarian

Your dog's diarrhea lasts more than two to three days or returns regularly.

Your puppy is not gaining weight despite a good appetite.

The stools are greasy, pale, very bulky and smelly.

Your dog is down, dehydrated or refuses to drink.

Several dogs from the same household or breeder have diarrhea at the same time.

The diarrhea persists despite classic deworming.

Transmission to humans

Giardia exists in humans, but not all strains are transmitted from one species to another: most of those found in dogs are specific to them, and the risk of human contamination from a dog is considered low.

In humans, giardiasis most often comes from contaminated water or food, and not from the dog in the house.

The precautionary principle remains simple: wash your hands after picking up the stool, prevent the dog from licking the face during the episode, and increase hygiene with young children and vulnerable people.

In the event of prolonged diarrhea in a person in the household, a doctor should be consulted.

Prognosis

Good: Most dogs recover with appropriate treatment and environmental rehabilitation.

Failures almost always come from reinfestation from soil, bedding or coat that is still contaminated, and more rarely from resistance to treatment.

In fragile puppies or immunocompromised dogs, relapses are more frequent and monitoring must be closer.

Frequently asked questions

My dog has Giardia but no symptoms: should it be treated?

Not systematically. In a healthy adult, the veterinarian may decide not to treat. Treatment is more necessary if there are puppies, other animals or fragile people in the home.

Why does diarrhea come back after treatment?

Most often because the dog reinfests itself: the cysts remain on its coat, in its bed or on the ground. Cleaning and washing the hindquarters is as important as the medication.

Can a commercial dewormer treat Giardia?

No. Giardia is not a worm but a microscopic parasite; it requires a specific molecule prescribed by the veterinarian.

Can I get Giardia from my dog?

The risk is considered low, as most canine strains do not infect humans. The usual rules of hygiene are sufficient, and persistent diarrhea in a person in the household requires medical advice.