Can Giardia spread to humans or other pets?

Giardia can be transmitted through contaminated faeces or water, and there is a risk of spread to other pets and potentially to people. Careful faeces disposal and environmental cleaning are important — consult your vet and a healthcare professional if you have concerns.

How does the vet test for Giardia infection?

Common tests include faecal microscopy to look for cysts or trophozoites and PCR pathogen detection. Taking multiple samples can improve detection rates; your vet will decide the appropriate tests and frequency based on your pet's situation.

How long does treatment take before improvement is seen?

Clinically, diarrhea in most animals improves within a few days to one week after starting treatment, but completing the full course and scheduling a recheck are essential to confirm parasite clearance. Follow your vet's recommended schedule for follow-up visits.

How can I prevent reinfection at home?

Remove faeces promptly and clean the environment with hot water or an appropriate disinfectant. Separate affected pets from healthy ones, avoid potentially contaminated water sources, and arrange regular check-ups as advised by your vet.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Giardia in Dogs & Cats: Symptoms, Stool Testing & Treatment Guide [2025]

Giardiasis is a common intestinal parasitic infection that causes chronic diarrhea. It is more prevalent in young pets and in densely housed environments. Treatment with antiparasitic medication is effective and should be combined with thorough environmental cleaning.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap editorial team

Sources: WSAVA, AVMA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek immediate veterinary care (emergency)

•Persistent vomiting with inability to eat or drink, accompanied by weakness
•Stool remains bloody or black, with a large amount present
•Obvious dehydration, such as dry mouth, poor skin elasticity, and severe lethargy

Schedule a veterinary visit as soon as possible (within 24-72 hours)

•Repeated or intermittent diarrhea lasting more than one day
•Loose stool with a greasy, foul odor that continues to occur
•Decreased appetite or noticeable short-term weight loss

01What Symptoms Indicate a Problem?

Giardia infection typically presents with diarrhea, which may be intermittent or recurrent, and can affect appetite and energy levels.

Recurring or intermittent diarrhea, which may persist for days to weeks
Loose or greasy stools, often with an unusual odour
Reduced appetite or noticeable weight loss over a short period
Occasional vomiting or signs of mild dehydration
Decreased energy or lower activity levels than usual

Seek emergency care immediately if you notice the following symptoms:

⚠️ Persistent vomiting preventing eating or drinking, accompanied by weakness
⚠️ Continuous bloody or tarry stools in large amounts
⚠️ Obvious dehydration — dry mouth, loss of skin elasticity, and severe lethargy

02How to Monitor at Home: Observation Checklist and When to Seek Emergency Care

Keeping a home record of bowel movements and energy levels can speed up veterinary assessment and provide useful medical history.

Note when diarrhea started, how often it occurs, and how many days it has lasted
Photograph or video the stools for reference, recording colour and consistency
Weigh your pet daily or track weight changes to assess the rate of loss
Monitor whether appetite and water intake have changed noticeably
Watch for persistent vomiting or blood in the stools
If symptoms continue or worsen, schedule a vet visit as soon as possible

03How Will the Vet Make a Diagnosis? Common Tests and Procedures

Diagnosis is primarily based on stool examination and physical assessment; blood work or advanced testing may be added when needed to evaluate overall health.

Stool testing

microscopy for cysts/trophozoites and PCR pathogen detection

Physical examination to assess degree of dehydration and body condition score

Blood and biochemistry panels to evaluate electrolytes and general health

Imaging or endoscopy if needed to rule out other intestinal diseases

Follow-up stool testing after treatment to confirm parasite clearance

Clinics with PCR testing capability or gastrointestinal expertise are recommended

04How to Treat and Care for Your Pet After Diagnosis? Medication, Diet & Home Care Guide

Treatment focuses on antiparasitic medication, supportive care, and environmental disinfection, followed by recheck testing to confirm clearance.

Complete the full course of medication as directed by your vet and attend all follow-up appointments
Temporarily switch to a bland, easily digestible diet during recovery
Ensure adequate hydration and electrolyte replenishment; monitor urine output and energy levels
Thoroughly clean and disinfect living areas and promptly remove all faeces to reduce the risk of reinfection
Schedule a follow-up stool test or PCR after treatment to confirm parasite clearance
If symptoms recur or do not improve over time, consider a referral for specialist evaluation

05What to Prepare Before Your Vet Visit? Key Information to Help Your Vet Diagnose Quickly

Note when symptoms started, how they developed, and any changes you have observed

List recent diet, outings, and contact history (including other pets)

Bring a current list of all medications and supplements your pet is taking, including doses

Collect a fresh stool sample (keep refrigerated and deliver promptly for testing)

Take a short video of your pet's energy level and bowel movements

Consider calling ahead or finding a clinic with gastrointestinal testing capability

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.

Related Symptoms (You May Also Be Looking For)

Diarrhea

Loose stool