What is Giardia?
Giardia is a parasitic infection caused by the Giardia parasite Giardia intestinalis (also known as Giardia duodenalis or Giardia lamblia). This single-celled parasite infects the small intestine of dogs and other mammals.
Giardia is one of the most common intestinal parasites found in dogs. Studies show Giardia infections in dogs range from 3-39% of the general dog population. Puppies and dogs that live in kennels or shelters or drink from contaminated sources are at higher risk of infection.
Giardia parasites attach themselves to the intestinal wall and prevent proper absorption of nutrients. This can lead to gastrointestinal signs like diarrhea, vomiting, gas, and greasy stools.
How do dogs get infected?
Dogs become infected with Giardia when they ingest the parasite’s cysts, usually through contaminated water or food. The Giardia cysts can spread between dogs through contact with infected feces.
Specifically, dogs acquire Giardia infection in the following ways:
- Drinking water that has been contaminated with Giardia cysts from animal feces [1]. Giardia can spread quickly between dogs that drink from streams, ponds, puddles or other surface water sources.
- Eating food or objects contaminated by feces from an infected animal [2]. Giardia cysts can survive for weeks to months in the environment.
- Coming into contact with the feces or contaminated fur of another infected dog or animal [3]. Giardia spreads easily between animals in crowded or unsanitary living conditions.
In summary, dogs get infected with Giardia by ingesting the parasite’s cysts, usually through contaminated water or food sources. The infection can also spread from contact with infected animals.
Signs and symptoms
The most common signs of Giardia infection in dogs include diarrhea, vomiting, weight loss, and fatigue. According to the CDC, diarrhea caused by Giardia can range from soft and mushy to watery with a greenish tint [1]. The stool often has a very foul, sulfurous odor as well. Vomiting may be profuse but intermittent. Dogs with Giardia tend to have decreased appetite and may show evident weight loss. They often seem extremely fatigued.
Other signs may include excess gas, abdominal discomfort, and nausea. Giardia can damage the intestinal villi which impairs nutrient absorption, leading to weight loss. The parasites attach to the intestinal wall, causing inflammation and interfering with digestion. All of these factors contribute to the common symptoms seen in Giardia infection.
In some cases, an infected dog may not show any symptoms at all. However, these dogs can still shed Giardia cysts in their feces and infect other pets and people. So prompt diagnosis and treatment is important even if symptoms are not apparent.
Diagnosis
Giardia is diagnosed through testing of fecal samples from the dog. The most common method is to look for Giardia cysts through microscopic examination of a fecal smear or fecal flotation. However, this method can miss infections as cysts are shed intermittently in feces. More sensitive diagnostic tests look for Giardia antigens in the feces rather than the cysts themselves. These antigen tests can detect the parasite even when only a few cysts are being shed. According to the VCA, antigen testing combined with fecal flotation offers the most accurate diagnosis.
Some tests that may be used include:
- Direct smear
- Fecal flotation
- Immunofluorescence assay
- ELISA antigen testing
Since shedding is intermittent, it is recommended to test symptomatic dogs with a combination of direct smear and antigen testing for the most reliable results. Multiple tests over time may be needed to definitively diagnose giardiasis according to VCA and Today’s Veterinary Practice.
Treatment
The primary medications used to treat giardiasis in dogs are:
Metronidazole – This antibiotic is commonly prescribed to treat giardiasis. It works by stopping the growth of giardia parasites. Metronidazole is given for 5-10 days. Source: https://vcahospitals.com/know-your-pet/giardia-in-dogs
Fenbendazole – Fenbendazole is a deworming medication that is effective against giardia. It is typically given daily for 3-5 days. Fenbendazole works by interfering with the parasites’ ability to absorb nutrients. Source: https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/health-info/giardia-infection-treatment-and-prevention
Quinacrine – Quinacrine is an anti-malarial drug sometimes used to treat giardiasis when other medications have failed. It works by damaging the giardia’s DNA. Quinacrine must be used cautiously due to potential side effects. Source: https://todaysveterinarypractice.com/parasitology/giardiasis-in-dogs/
Can it resolve without treatment?
Giardia is a parasite that can cause a condition called giardiasis in dogs. Mild cases may resolve on their own without treatment in some dogs. This is because the dog’s immune system may be able to fight off the infection over time.
However, most veterinarians recommend treating even mild cases, as Giardia infections can be difficult to eliminate without medication. Allowing the infection to persist increases the risk of the parasite spreading and causing continuing clinical signs.
Moderate or severe cases of giardiasis require treatment with prescription medications like metronidazole or fenbendazole. These antiparasitic drugs are effective at killing off Giardia and reducing the shedding of infectious cysts into the environment. Without treatment, chronic giardiasis can lead to dehydration, weight loss, vitamin deficiencies, and other complications in dogs.
While Giardia may eventually resolve on its own, treatment speeds up recovery and minimizes the spread of infection. After treatment, dogs should be retested to ensure the Giardia is fully cleared from their system. With prompt treatment and proper prevention measures, most dogs make a complete recovery from giardiasis.
Prevention
There are several ways to help prevent giardia infection in dogs:
Provide clean, fresh water daily. Giardia cysts can contaminate water bowls and other water sources. Scrub water bowls with soap and hot water daily to remove any cysts.
Practice good hygiene. Pick up and dispose of dog feces promptly, and disinfect any areas that may be contaminated. Bathe dogs regularly during treatment to reduce spread of cysts. Wash hands after handling infected dogs or cleaning up feces.
Deworm dogs regularly. Giardia infection is associated with some types of intestinal worms. Keeping dogs on a regular deworming schedule can help prevent co-infections.
As giardia spreads through contaminated feces, limiting access to feces from infected dogs is also important. This may include separating dogs, keeping dogs out of standing water sources, and disinfecting shared play areas.
Prognosis
With prompt veterinary treatment, most dogs make a full recovery from Giardia and go on to lead normal, healthy lives. The prognosis is excellent as long as the infection is properly diagnosed and treated.
As noted by Cornell University’s College of Veterinary Medicine, “With proper treatment, most dogs fully recover from giardiasis” (Source). Treatment may involve prescription medications like fenbendazole and metronidazole to kill off the Giardia parasites.
However, Giardia can be fatal if left untreated. Debilitated or geriatric dogs and those with weakened immune systems are at highest risk for complications and poor outcomes. According to VCA Hospitals, “Debilitated or geriatric animals and those with incompetent immune systems are at increased risk for complications” (Source). Therefore, prompt diagnosis and appropriate treatment are crucial.
With the proper medical care, most dogs fully recover within 1-2 weeks. However, reinfection is possible if the dog ingests cysts again in the future. Ongoing prevention measures like environmental disinfection may be recommended.
Recurring infections
It’s common for dogs to experience recurring Giardia infections. Even after treatment, dogs may continue to have Giardia cysts in their intestine that can lead to reinfection. According to one study, the rate of recurrence after initial treatment was around 22-52% [1].
There are a few reasons dogs may experience repeat infections:
- Incomplete elimination of cysts from the intestines after treatment
- Re-exposure to infected feces or contaminated environments
- A weakened immune system that struggles to control the infection
To reduce recurrences, it’s important to strengthen the dog’s immune system and follow prevention tips to avoid reinfection. A wholesome diet, probiotics, and supplements may help boost immunity. Thoroughly cleaning the home and yard, picking up all feces promptly, and preventing access to contaminated sources like standing water can also protect against repeat infections.
If infections keep recurring, the vet may recommend longer or more aggressive treatment. But a strong immune system gives dogs the best chance of clearing Giardia infections and keeping them at bay.
When to see a vet
It’s important to seek veterinary care if your dog has diarrhea for over 24 hours, is vomiting, losing weight, or lethargic when infected with giardia.
Diarrhea lasting more than a day can lead to dehydration and electrolyte imbalances, which can be dangerous if left untreated. Persistent vomiting makes it difficult for your dog to keep food and water down. Weight loss and lethargy are also concerning signs that point to an infection that is more severe.
According to the Cornell University College of Veterinary Medicine (source), you should take your dog to the vet if diarrhea persists more than 1-2 days during or after treatment. They recommend bringing a fresh fecal sample to help diagnose the issue.
Your veterinarian can provide IV fluids if your dog is dehydrated and prescribe medications to stop vomiting and diarrhea. Getting prompt treatment can help your dog recover quicker and prevent complications.