What is Giardia?
Giardia is a microscopic parasite that causes an intestinal infection called giardiasis. The Giardia parasite infects the small intestine, where it attaches to the lining and causes irritation, inflammation, and other gastrointestinal symptoms.
Giardia infection is caused by ingestion of Giardia cysts through contaminated water or food sources. The Giardia parasite is spread through the feces of infected humans or animals. Once ingested, the cysts transform into trophozoites that attach to the intestinal wall and reproduce, shedding more cysts into the feces which can further spread the infection.
Dogs become infected with Giardia by ingesting cysts through contaminated water or by eating infected feces. In dogs, Giardia most often spreads at parks, kennels, shelters, dog daycares or other areas where dog feces may accumulate.
How is Giardia Transmitted?
Giardia is transmitted when dogs ingest the parasite from contaminated sources. The main routes of transmission include:
Ingesting Contaminated Feces or Food/Water
The most common cause of Giardia transmission is when dogs swallow feces or food/water contaminated with Giardia cysts. The cysts can spread between dogs through contact with infected feces in the environment or shared water sources.
From Infected Animals or Humans
Giardia can also spread through contact with infected dogs, cats, wildlife (e.g. beavers) or even humans. The parasite can be passed between species. Close interactions with symptomatic, infected animals or humans can lead to Giardia transmission if cysts are ingested.
Giardia Symptoms in Dogs
Some common symptoms of Giardia infection in dogs include:
Diarrhea – Dogs with Giardia often experience acute, watery diarrhea. Their stool may be abnormal in color and foul-smelling.
Dehydration – The diarrhea and vomiting associated with Giardia can result in dangerous fluid loss and dehydration. Signs of dehydration include lethargy, dry gums, sunken eyes, and loss of skin elasticity.
Weight loss – Giardia prevents dogs from properly absorbing nutrients from food. This leads to weight loss despite a normal appetite.
Fatigue – Dogs with Giardia tend to become lethargic and fatigued due to dehydration and improper nutrient absorption. They have little energy or interest in activity.
Giardia Diagnosis
If you suspect your dog has Giardia, your veterinarian will likely run diagnostic tests to confirm. The two main tests used to diagnose Giardia in dogs are:
Fecal Exam
A fecal exam involves looking at a stool sample under a microscope to check for the presence of Giardia cysts and trophozoites. This is an easy, inexpensive test that can provide quick results. Your vet will likely take multiple stool samples over several days, as shedding of the parasite can be intermittent. A fecal flotation may also be performed, using a solution to separate parasite eggs, cysts and oocysts from stool for better visualization.
ELISA Test
An ELISA (enzyme-linked immunosorbent assay) test can also be used to check for the presence of Giardia antigens in your dog’s stool. This lab test is very accurate and detects antigens that are present whether the parasite is in its cyst or trophozoite form. An ELISA test is often recommended to confirm diagnosis, as it is more reliable than a regular fecal exam.
Giardia Treatment
Treatment for giardia usually involves medications to kill the parasites. The most common medications used are:
Metronidazole – This antibiotic is often the first choice for treating giardia in dogs. It is given orally for 5-10 days. Metronidazole is highly effective against giardia and works by disrupting the parasites’ DNA and protein synthesis, killing them.
Fenbendazole – Fenbendazole is a common deworming medication that also has anti-giardia properties. It is typically given daily for 3-10 days. Fenbendazole works by inhibiting the giardia parasites’ ability to absorb glucose, leading to their death.
Quinacrine – Quinacrine is another medication that can be used to treat giardia. It is given daily for 5 days. Quinacrine accumulates in the parasites, causing damage to their DNA. This prevents the giardia from reproducing and eventually kills them.
In severe cases, a combination of metronidazole and fenbendazole may be used. Dogs generally respond well to treatment within a few days, however a follow up vet visit is recommended to confirm the giardia is fully eliminated.
Is Giardia Contagious to Humans?
Yes, giardia is a zoonotic disease, meaning it can be transmitted between animals and humans. The primary way giardia spreads is through the fecal-oral route. When a dog is infected with giardia, the parasite is shed in the dog’s feces. The giardia cysts can then contaminate food, water, or surfaces if proper hygiene is not maintained. Humans can accidentally ingest the cysts by consuming contaminated food or water or through hand-to-mouth contact after touching contaminated surfaces. Once ingested, the giardia cysts can cause an infection in humans, leading to acute gastrointestinal symptoms like diarrhea, abdominal cramps, bloating, and nausea.
So while giardia poses minimal direct transmission risk from touching an infected dog, the bigger concern is environmental contamination that can inadvertently infect humans. Practicing good hygiene like washing hands and disinfecting areas the infected dog contacts is important to reduce risk of environmental spread. Additionally, promptly picking up and disposing of any dog feces can help remove sources of cysts and minimize contamination.
Giardia Prevention
There are several ways to help prevent the spread of giardia in dogs and to humans:
Proper Hygiene
Washing hands thoroughly with soap and water after handling dog feces or cleaning up accidents is crucial. Avoid direct contact between hands and mouth without proper handwashing. Disinfect any surfaces exposed to feces as well.
Clean Water
Provide dogs with clean, filtered water and avoid allowing them to drink from puddles, lakes, or streams where giardia cysts may be present. Clean water bowls regularly with soap and hot water.
Control Exposure to Feces
Pick up and properly dispose of dog feces quickly to prevent contamination of ground and water sources. Keep dogs away from areas potentially contaminated with feces from infected animals. Clean up accidents inside the home thoroughly. Controlling exposure limits spread of cysts.
Can You Touch a Dog With Giardia?
While Giardia is highly contagious between animals, the risk of transmission to humans from casually petting or touching dogs with Giardia is relatively low. The main route of Giardia transmission is through ingestion of contaminated feces. As such, you are more likely to contract Giardiasis from exposure to the feces of an infected dog rather than from petting or touching the dog’s fur.
However, it is still possible for Giardia cysts to be present on a dog’s coat, so washing your hands after touching dogs suspected of having Giardia is recommended. Use warm water and soap and wash for at least 20 seconds. This will help remove any cysts that may have transferred from petting the dog.
In summary, while petting or touching dogs with Giardia poses a relatively low risk, it’s still a good idea to wash your hands afterwards. The highest risk comes from exposure to the feces of infected animals. But diligent handwashing can help prevent transmission through contact.
Other Precautions
If your dog has been diagnosed with giardia, it is important to take precautions to prevent the parasite from spreading and causing further contamination. Here are some other key precautions to take:
Cleaning Contaminated Areas
Thoroughly clean any areas that may have been contaminated by your dog’s feces or vomit. Giardia cysts can survive for weeks or months in the environment. Use a stronger disinfectant that is labeled to kill parasites. Bleach solutions may also be effective. Focus on cleaning places like your dog’s crate, potty areas, toys, bedding, and any soft surfaces your dog may have accessed.
Bathing Your Dog After an Outbreak
It’s a good idea to give your dog a bath after a giardia outbreak has passed. Use a quality pet shampoo and wash your dog away from bathrooms or kitchens to avoid contamination. Make sure to thoroughly rinse all shampoo residue off. This bathing can help remove any lingering cysts from your dog’s coat. Grooming tools should also be disinfected after use to prevent reinfection.
When a Dog is No Longer Contagious
After treatment for giardia is completed in full and negative fecal test results consistently show, this indicates the infection has likely cleared and the dog is no longer contagious. Typically, the dog will need to complete the full course of prescribed medication, which usually lasts 5-10 days depending on the protocol. Fecal testing is then repeated after treatment to verify the parasite is gone.
Once two consecutive negative fecal tests are obtained after finishing treatment, the dog can be considered non-contagious. Some vets may recommend waiting until 3 negative stool samples show no more cysts before stopping precautions. Monitoring with consistent fecal exams helps ensure the giardia has been fully eliminated before discontinuing any protective measures against spread.
With medication and negative test results, owners can feel reassured the dog’s giardia infection has resolved and the contagious period has ended. Still, re-testing and vigilance is a good idea since re-infection is possible. Once fully recovered and no longer contagious, normal interactions can resume while maintaining reasonable hygiene.