Giardia Facts and Your dog!

No, there is no proof that giardia transferes from dogs to humans!

Giardia is very common in dogs and puppies,giardia infects most dogs and it is considered rather normal for a puppy or dog to have cysts present in stools -it very seldom causes diesease except in very young pups and very old or dibilated dogs, There has never been any proof that giardia passes from dogs to humans, in fact any studies done that test humans, have proven otherwise. The type humans get are totally differnt strains. And I suspect if it did pass .Us breeders would be the first to get it and yet,not I nor, has any breeder I have known ever had giardia? You would think if it were at all transferable we would have it all the time... You still hear vets say it can pass so they can be sure you treat it with there medicines as it does not affect the health of the dog, but all the medicines do is harm the dog? It is as common in dogs as any other organizm and seldom causes disease and the treatment to get rid of it does not work, and only causes harm..

One of the latest studies:// given at the national vet conference - So your vet know's! if they treat your healthy dog for this It is simply a money makeing ventor for them..nothing more and remember the treatment HARMS!

New research provides more information on the debate about testing and treating of healthy dogs for Giardia. Two abstracts on the subject by researchers at Colorado State University were presented at the recent American College of Veterinary Internal Medicine conference.

In the first study (Clark et al), fecal samples were collected from 220 healthy dogs. Giardia was detected in 11.4% of samples, but no dogs carried assemblages (types) known to cause disease in people.

In the second study (Lappin et al), they evaluated whether treatment of healthy dogs that were shedding Giardia would eliminated the parasite. Sixteen infected dogs were treated with either fenbendazole or nitazoxanide. Eight (50%) of the dogs had to be removed from the study because of adverse effects from treatment! Of the dogs that completed the study, Giardia was still detected in 63% of dogs 34 days after treatment, indicating that the infection wasn't eliminated or that dogs were quickly re-infected.

These studies provide more support of the notion that there is no indication to test or treat healthy dogs for Giardia. Testing makes no sense when the parasite is so common but most infected dogs are healthy, and when strains carried by infected dogs are usually of no consequence to people. Giardia is essentially a normal part of the intestinal microflora in many healthy dogs. Treatment of healthy carriers isn't indicated because it can make dogs sick and because it doesn't work very well. Remember: above all do no harm.

The bottom line is don't bother testing healthy dogs for Giardia or treating healthy dogs in normal households.


some general info below: Fort dodge has alot of stuff out there about giardia effecting humans they do not mention it is a different kind- Fort Dodge sells a Giardia vaccine- so they have a vested interest in scaring people

It has been estimated that nearly 36 to 50 percent of puppies, 10 percent of well-treated adult dogs, and up to 100 percent of dogs in breeding kennels are infected with Giardia.1 In a recent unprecedented field study sponsored by Fort Dodge Animal Health involving more than 7,500 pets, it is estimated that as many as one out of eight pets seen by a veterinarian may be infected with Giardia.

Giardia is a one-celled, microscopic parasite that lives in many different and often unexpected water sources, including ponds, lakes, streams, backyard swimming pools and even tap water. Giardia has even been found on contaminated animal haircoats. When ingested, it infects the intestinal tract of pets and humans, causing fever, vomiting and diarrhea, as well as other potentially serious and painful gastrointestinal problems.

Although any pet can contract the disease, dogs most at risk of becoming infected with Giardia include puppies, outdoor dogs, hunting dogs, farm dogs, city dogs, adopted strays, dogs that live in kennels and dogs in multi-pet households. Many researchers believe there is even the possibility of transfer of Giardia infection between pets and people.


Giardia is a single-celled parasite that lives in your dog’s intestine. It infects older dogs but more frequently infects puppies. Dogs become infected when they swallow Giardia that may be present in water or other substances that have been soiled with feces.

How will Giardia affect my dog?
Many dogs infected with Giardia do not get any disease. Giardiasis, the disease caused by Giardia infection, usually results in diarrhea. Having giardiasis a long time can cause weight loss; generally poor condition; and even death, when the disease is serious.

How do I prevent my dog from getting Giardia?
The best way to prevent Giardia infection is to make sure that your dog has safe, clean drinking water. It is important not to allow dogs to drink water from areas where other animals have left their feces.

Your veterinarian can perform a test on your dog’s feces to see if it has giardiasis. If your dog is infected with Giardia, your veterinarian can prescribe safe, effective treatment.

To prevent spreading Giardia (and other parasites), pick up the feces left by your dog immediately and place it in the trash. Be sure to avoid contact with the feces by using gloves, a bag over your hand, or a scooping device.

Can humans be harmed by Giardia?
Giardia is a common cause of diarrhea in people, but dog Giardia is not generally considered to spread from animals to humans. While human Giardia may infect dogs and then be passed on to humans, the majority of human cases are of human origin.



Metronidazole, a `classic` drug in canine medicine, is currently very popular to treat a variety of diseases: giardiasis, various inflammatory processes in the gastrointestinal tract, hepatic encephalopathy etc. The potential myelosuppressive side effects of this drug are well known, but neurological problems seem to be more common and less known, as the excellent summary of the ACVIM shows...


Metronidazole is a synthetic nitroimidazole compound used with increasing frequency in small animal practice. It is commonly prescribed in the treatment of inflammatory bowel disease, gastritis associated with helicobacter, giardiasis and empirical treatment of diarhea.

Metronidazole has also been used successfully to alter intestinal flora in dogs with hepatic encephalopathy and exocrine pancreatic insufficiency. Use of this antibacterial has been advocated in the treatment of osteomyelitis and periodontal diseases. The mechanism of action for these effects are a matter of controversy. It is believed that the drug disrupts DNA and nucleic acid synthesis in bacteria. Its antiprotozoal activity is not adequately explained.

Evans et al in the J Vet Intern Med [17:304-310] recently described its uses, toxicities and treatment of neurologic signs that may occur as an untoward side effect.

Metronidazole has excellent bioavailability with peak serum levels in the canine one hour after oral intake. This rather lipophilic antibiotic is distributed to most body tissues and fluids, including bone, abscesses, the central nervous system (CNS) and seminal fluid.
There is extensive metabolism in the liver before renal and fecal excretion. The elimination half-life in the dog varies from three to 13 hours.

Adverse effects in dogs and cats include neurologic disorders, lethargy, weakness, neutropenia, hepatotoxicity, hematuria, anorexia, nausea, vomiting and diarrhea.

Neurotoxic effects include encephalopathy, cerebellovestibular signs and periopheral neuropathy.

Neurotoxicity following prolonged therapy is most often related to cumulative dose and duration of treatment.

Most canines who develop neurologic signs secondary to metronidazole administration have received weeks to months of therapy, but toxicity after short-term therapy at relatively low dosages (<60 mg/kg/day) has been reported.

In general, higher dosages may produce signs in a shorter time period than moderate to low dosages.

Reversible CNS dysfunction may produce signs including ataxia, recumbency, opisthotonus, positional ystagmus, muscle spasms and occassionally seizures. Cerebrospinal fluid analysis may reveal mildly elevated protein levels.
In humans, a predominantly sensory polyneuropathy may follow large, cumulative doses. Nerve conduction studies suggest sensory axonal degeneration with low-amplitude or absent sensory potentials and minimal, if any, involvement of motor fibers. Sural nerve biopsies of human patients with sensory polyneuropathy, including teased fiber studies and electron microscopy, demonstrated primary axonal pathology with degeneration of both myelinated and unmyelinated fibers. Ahmeda et al in the journal, Neurology (45, 588) reported that magnetic resonance imaging in a single human case with encephalopathy and ataxia showed reversible T2-weighted hyperintensities in the cerebellum, supatentorial white matter and corpus collosum.

The exact mechanism of metronidazole neurotoxicity is unknown.


Source: Pierre Bichsel, Ronald Lyman (2004): Metronidazole: Uses, toxicity and management of neurologic sequllae. In: DVM Newsmagazine Aug 1, 2004;