Giardiasis in Dogs

This protozoan parasite, having the capacity to infect your dog’s intestinal tract, can be responsible for various gastrointestinal reactions, or they won’t cause any symptoms at all. How do you know if your canine family member has it? Get his feces checked at least twice a year.  This infection is considered zoonotic meaning that it can be passed to humans as well as many other mammals (wild and domesticated) and birds, too. Giardiasis in a puppy, an elderly dog, or a canine with compromised immunity can become a dangerous condition.

Giardiasis in dogs is defined as an intestinal protozoal infection seen in most domestic and wild mammals, many birds and also people; it can become a chronic condition.

This intestinal attacker doesn’t really care whose intestine it occupies, with humans, mammals and many bird species being prime targets for infestation.  Here are some of the intestinal symptoms which can be noted in humans and animals when this attacker is present:

• Vomiting
• Diarrhea - can be acute or intermittent 
• Lethargy
• Weight loss

Potential targets of this attacker may suffer with the above symptoms or they may have none of the symptoms at all. 

Types  

There are two forms of the giardia organism which causes the giardiasis:

• Trophozoite - The fragile feeding form, located in the gut
• Hardy cystic form - Shed in feces  and can survive for several months in various environments, especially in water and damp environments

There are also three major morphologic groups of the organism:

• G muris - Passed from mice
• G agilis - Passed from amphibians

The third group is passed from various warm-blooded animals and within this group are four species:

• G ardeae and G ptissaci  - Passed from birds
• G microti - Passed from muskrats and voles
• G duodenalis (G intestinalis and G lamblia) - Passed from a large mammalian host range which is known to infect both people and domestic animals

Giardia is the organism responsible for giardiasis in dogs.  This one-celled organism is a parasitic species, not a worm, or bacteria or virus.   There are seven identified genotypes, being designated A through G:

• Dogs are commonly affected by genotypes C and D  
• Cats are commonly affected by genotype F
• Humans are commonly affected by genotypes A and B
• Genotypes E and F are seldom reported

This parasitic organism is picked up when a dog (or other host) swallows giardia in the cystic stage of development usually through contact with feces (either via direct contact or indirect contact). Once in the small intestine, it becomes the trophozoite form (the feeding form), the form which enables it to attach itself to the intestinal mucosal lining, absorbing nutrients and multiplying via binary fission.  After the dividing of the cell (binary fission), some of the cells become the cyst form and are eventually passed in the feces where it can live for several months to infect another host.  The organism can be picked up by eating or sniffing the ground or water which has been contaminated.

If you suspect that your canine family member has picked up any organism, a stool specimen should be provided for evaluation by your veterinary professional.  This is a practice which really should be done at least annually, preferably twice a year, for the overall health assessment of your pet, regardless of the age of the animal.  This is especially so since many dogs can be afflicted with giardiasis and not display any of the symptoms noted above.  

Your veterinary professional will always need a complete history from you each time you visit with your pet.  He will do a physical examination and will need the stool specimen from your dog mentioned above to test for a variety of organisms which are common to our canine family members.  He will be looking at stool consistency and color, whether the stool contains blood or mucus and what organisms (and the stages of those organisms) which may be found in the stool.  Once your veterinary professional has collected all of this information, he will be able to develop a treatment plan or plan of action for your pet.

Frequently, if the cysts are found in the feces of an otherwise healthy adult canine, and if there are no symptoms (diarrhea) being displayed, the infection can be considered transient and thus less significant.  But, if the cysts are found in the feces of a puppy or a debilitated adult canine, any vomiting and severe, watery diarrhea could be fatal without appropriate and timely treatment.  

If your veterinary professional arrives at a diagnosis of giardiasis in your dog, and, if he feels that treatment is necessary or recommended, there are two medications which are commonly used for treatment of this infestation. A regimen of either fenbendazole or metronidazole have been used successfully to treat giardiasis in dogs.  The regimen generally is administered for a period of 3 to 10 days and both medications can be used together successfully as needed.  Dietary changes may be recommended to help reduce the looseness of the stools if diarrhea is present, as well as supportive care including fluids if the canine is dehydrated.  Other supportive care may be recommended if the condition of the canine requires it.

While the prognosis for most canines who have been diagnosed with giardiasis is good, it is important to know that, in the case of infestation in debilitated or older canines and even those whose immune systems are compromised, there is an increased risk of serious complications (which include death).  In view of this, it is important, once your dog is diagnosed and treated, to have him retested two to four weeks after the recommended treatment has been completed.  

Also, since the organism is shed in feces and it can live for months outside the body of the host, it is imperative that the environment be cleaned and monitored for fecal material.  Your veterinary professional can give you some guidance on how to clean and maintain the kennels and grounds to keep your canines and human family members healthy and safe.