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Giardia in Cats and Dogs

When it comes to Giardia in the kennel or cattery, the concern is less about treatment and more about the long-term plan to manage it. Giardiasis affects cats and dogs of any age and is most commonly transmitted from mom or by drinking contaminated water.


Giardia is a tiny, one-celled parasite that lives in the small intestine of affected animals. It is difficult to diagnose as not all infected animals show clinical signs. Symptoms are more visible in younger and older animals. The first clinical sign of Giardia is usually diarrhea with a strong odor or excessive mucus. Dehydration may also occur due to the diarrhea.


Giardia can be difficult to see under a microscope, and it often takes a trained eye to identify them accurately. Screening tests are also available. In these tests, the feces is mixed with a solution, placed in a well and then "snapped" down to start the test, which checks for a protein from the Giardia organism. Snap tests are useful as a piece of the puzzle; they are not a definitive test. Though negative tests are true negatives, false positives are very common and may be deceiving. If you have a positive snap test and you're not sure if it's correct, send feces to the lab for more accurate diagnosis. Since a snap test can read positive for four weeks after Giardia is removed from the gut, don’t be too quick to call the treatment a failure!


There are many ideas about treating and preventing Giardia. The top four are:
  1. Safeguard® or Panacur® (Fenbendazole) are 96% effective, safe and can be used in dogs or cats. Treatment is done for five days to rid the gut of the organism and often repeated in the house pet one week later to ensure removal.
  2. Metronidazole has traditionally been used to treat Giardia, but there has been resistance. It has been shown to be only 60% to 70% effective in dogs and has a sharp metallic taste which is nearly impossible to get down a cat more than one or two days. Treatment is daily for eight days to clear infection.
  3. Metronidazole and Safeguard® combined. This popular treatment is a third choice for dogs as it combines two approaches to clearing infection. It is 98% effective with Safeguard® having most of the effect in clearing the organism.
  4. Secnidazole given at 30 mg/kg single dose orally has proven to be effective in treating cats. It clears most cats of Giardia with one dose which is helpful since cats do not like to take meds orally. Secnidazole has also been used in dogs successfully. The drawback is it is a limited use drug and must be acquired with prescription from a compounding pharmacy.

Bathing is also important. Giardia oocysts are sticky and will stay on the hair coat, particularly the back legs. The oocysts are directly infective. This means the oocysts passed in the stool can immediately re-infect the animal when grooming themselves. Bathe the dog or cat with Chlor 4 Shampoo on last day of treatment. The chlorhexidine will kill the oocysts and the shampoo will mechanically remove. Concentrate on the back half of the body, as this is where the Giardia usually sticks. If you don’t bathe them, they can re-infect themselves, making your treatment ineffective.

Since Giardia is stubborn, contaminated kennels and catteries should be scrubbed and disinfected. Chlorhexidine disinfectant is effective against the spores at room temperature and quaternary ammonia is effective at both room temperature and colder. Make sure you clean and disinfect litter boxes also and allow to dry thoroughly before allowing cats to use them. Caution: Follow manufacturer's instructions when using quaternary ammonia or bleach solutions. Quaternary ammonium is not safe around nursing babies. (Read Read Fading Puppy and Kitten Syndrome)


Long-term control starts with the mother. When she is heavily pregnant, the stress will decrease her resistance to parasites. Using Fenbendazole three days in a row after day 50 of gestation is helpful in preventing the transfer of parasites, including Giardia to babies. Use Fenbendazole five to six days in a row with problem dog moms or problem queens who have had previous Giardia litter issues!

Bathing the mother before whelping or queening is also helpful when fighting the problem. Alternatively, some breeders will clip the hair on the back legs and belly to remove the oocysts the mom carries on her hair. Either technique is effective. The goal is preventing transfer to babies!

For puppies or kittens, deworm three days in a row with Safeguard® at six and eight weeks of age for prevention. The six week prevention is crucial because this is the age Giardia sets up in the intestine with most Giardia diarrhea starting at 8 to 10 weeks. The goal is to eliminate any Giardia that have found their way into the baby before you have to deal with diarrhea.


The problem with routine Giardia prevention is we kill the susceptible Giardia, leaving any resistant Giardia to reproduce. If dealing with resistance, traditional Giardia treatment has to be altered for a time. The resistant Giardia needs to be eliminated, if possible, to avoid spreading.

If resistant Giardia is an issue, your veterinarian may prescribe Secnidazole – most Giardia issues clear with one dose. Ronidazole has also been shown to be effective against resistant Giardia in dogs. In addition to the drug treatment, bathing the dog with a shampoo containing chlorhexidine (Chlor 4 Shampoo) is important for the efficacy of the treatment.


With all parasites, you want to think long-term control. If you just treat the babies without considering where the parasite is coming from, you'll eventually get resistance that overwhelms your medication. Every year you should have fewer and fewer parasite numbers in your kennel or cattery. Roundworms, hookworms, whipworms, Coccidia and Giardia should all be accounted for in your preventative program. If babies don’t get the parasites from mom, you don’t have to get them back out! If you have any questions about parasite control, feel free to give us a call.

If you need help, call us at 1-800-786-4751.

-Dr. B
Don Bramlage, DVM, Director of Veterinary Services at Revival Animal Health

The materials, information and answers provided through this website are not intended to replace the medical advice or services of your personal veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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