Microscopic parasites Giardia and Coccidia just might be the cause of your puppy’s illness, or your dog’s persistent diarrhea.
Giardiasis is the disease caused by an infection of Giardia parasites. Giardia organisms spread through the dog’s contact with contaminated feces, which may be in water, on grass, on other animals – anywhere in the dog’s environment.
The protozoa are ingested by your dog while in the form of cysts, analogous to fertilized eggs that are waiting for the right conditions to develop. Once inside the dog, the cysts open up and release a flagellate form (trophozoite) of the organism, which use their whip-like appendages to migrate to the small intestine, where they multiply. They continue to move into the colon, where they enter the cyst form, waiting for release in the dog’s feces. Incubation is five to 14 days after ingestion.
Although both the cyst and the trophozoite forms can be released in the dog’s feces, only the cyst can survive out of the host. Humidity and crowding favor their survival, but the hardy Giardia have been noted to survive for months in cold water.
The presence of Giardia in the gut causes the intestinal epithelial barrier to lose proper function, although scientists are still trying to figure out the precise biochemical mechanisms responsible for this. Interestingly, Giardia causes disease without penetrating the intestinal epithelium, invading the surrounding tissues, or entering the bloodstream. Fortunately, the disturbance to the epithelium resolves quickly when the parasite is cleared from the dog with appropriate treatment.
Coccidiosis in Dogs
Coccidiosis is the disease caused by a Coccidia parasite. Coccidia are spore-forming protozoan. They are extremely hardy, withstanding even freezing temperatures, and can exist in the environment for a very long time. Dogs pick up the protozoa through ingesting contaminated feces (either by eating feces, or stepping or laying in it and later licking their feet or fur); ingesting an infected animal, such as a rodent; or eating or drinking from a contaminated source. Birds can pick up infected feces and spread it to far-reaching areas.
The dog ingests the Coccidia as immature oocysts. Once inside, the oocysts release sporozites that invade the cells of the intestinal lining, where they reproduce rapidly and cause destruction of those cells. As the sporozites reproduce, more oocysts are released into the environment to be picked up and spread to another host.
Unlike Giardia, whose method of damaging the intestinal epithelium is still unknown, Coccidia have a clear, physically destructive affect on the lining of the intestine. Infection with this protozoa causes even more dramatic diarrhea – explosive, uncontrollable diarrhea! – than Giardia. Left untreated, coccidiosis is far more dangerous than giardiasis, as it can lead to damaged intestinal lining, severe dehydration, and death.
Diagnosing a Coccidia or Giardia Infection
The most common symptom of an infection of either protozoan parasite is diarrhea. Given that there are so many things that can cause diarrhea in puppies and dogs, veterinarians will often ask whether the suffering canine has shown any other symptoms, including, loose or watery feces, dehydration, nausea, vomiting, gas, weight loss, or apparent abdominal pain.
Some infected dogs, however, will exhibit none of these – just persistent, sometimes intermittent diarrhea. This symptom alone warrants a harder look at that feces! Call your veterinarian’s office and ask if you can bring in a stool sample for testing. Your vet will likely want to see your puppy at the same time you bring in a sample, but if your dog is an adult and has been seen by his vet recently, she may run tests on the stool before asking you to bring him in.
You should bring a fresh feces sample, less than 24 hours old and not dried out. You don’t need to collect the entire stool; a teaspoon to a tablespoon of feces is enough! Ideally, use a small Ziploc bag to collect a small amount of your dog’s stool; a doggy poop bag is fine, but something that seals the odor in the bag is much more considerate. Refrigerate any sample that you plan to take to the vet later that day or the next day (another reason to use a bag that seals tightly!).
The first test that is usually performed is a fecal flotation or centrifugation fecal flotation. In the former, some of the feces is mixed with a solution that helps any parasite eggs or cysts float to the top; after a few minutes, a microscope cover slip is then touched to the top of the solution. Any parasite eggs or Giardia or Coccidia oocysts present will stick to the glass, and will be visible under a microscope. In the latter, the sample is mixed with a solution and then spun in a centrifuge to help the parasite eggs or cysts rise to the top.
When the cysts are present in your dog’s feces, these low-tech tests will find them. But negative results for these tests do not mean your dog is clear of infection. Not all feces that comes out of your dog will contain the cysts, even if he’s infected with one of these protozoan pests; they are shed intermittently, as the organisms reproduce. So, if your vet still suspects giardiasis or coccidiosis, she will likely run another, higher-tech test.
Giardia can be detected with an in-house SNAP ELISA (enzyme-linked immunosorbent assay) test, which is highly effective in detecting Giardia, or a fecal IFA (immunofluorescence assay) test. The latter test is usually done at an outside lab and results may take a couple of days.
For suspected infections of Coccidia that do not show on a flotation test, your veterinarian may request a PCR (Polymerase Chain Reaction) assay, which is a reliable but more expensive procedure.
Or, your veterinarian might just recommend that she treat your dog for a suspected infection; a positive response to treatment confirms the presumptive diagnosis.
Prevent Parasites with Proper Hygiene
Regardless of the medication your veterinarian prescribes, your attention to your dog’s hygiene will be vital to eliminating the parasites once and for all.
“It is critical to bathe your dog on the final day of treatment to remove any cysts that may be on the dog’s hair, especially around the anus,” Dr. Fatcheric says. If you neglect that step, you’re not going to get rid of the parasite. Be especially mindful of the hind-end area and back legs. Discuss the use of a chlorhexidine shampoo with your veterinarian.
Because these organisms are generally hardy and can exist in the environment for long periods, it’s important to disinfect the areas the dog frequents.
The Centers of Disease Control (CDC) recommends you clean all hard surfaces – floors, crates, trash cans – with soap and water, rinsing thoroughly. Steam-clean carpets with the solution recommended for your cleaner.