Protozoal Parasites

Protozoal parasites are single celled organisms that, once ingested, live in the lining cells of the intestines and cause damage to those cells. The two most often encountered in veterinary medicine are Coccidia and Giardia. Many healthy dogs and cats will become infected with protozoal parasites but never develop symptoms. Young puppies and kittens and debilitated pets are more at risk for developing disease. Diarrhea is often the first sign of infection. In severe cases, watery foul smelling diarrhea may be accompanied by loss of appetite, vomiting, lethargy and dehydration. Left untreated, severe cases of protozoal parasitism may lead to death.

While living in the intestines, protozoa reproduce as cysts or oocysts that are passed in the stool. These cysts are hardy and persist in the environment for months. Giardia cysts are infective as soon as they are passed in the stool. Coccidia oocysts become infectious if the environmental conditions are right, sometimes hours after being passed but more often 8-10 days later. Our pets ingest them when contacting infected stool or soil. This can be direct contact or indirect, such as sniffing an infected dog's anus and then licking their nose. Pets can also ingest cysts from contaminated water found in natural waterways, like streams, ponds, lakes and rivers or man-made reservoirs like swimming pools. Foods can become contaminated if washed in unsafe water. Pets who hunt can be exposed by eating an infected rodent.

You may be thinking "That's all very interesting but what I really want to know is how to get rid of these pests!"

Unlike infections caused by bacteria or viruses, our pets do not develop immunity to protozoa. Because the cysts can be difficult to eradicate, pets often get re-infected so treating the environment is essential to controlling these parasites.

As I mentioned before, Giardia cysts and Coccidia oocysts are hardy. Coccidia can remain infective in the environment for several months. Giardia survives for several months in cold water and soil. The species of Coccidia and Giardia that typically infect our dogs and cats tend to be specific to their chosen hosts and so do not usually pose a risk for humans. However, there are other strains that infect animals and humans so practicing good hygiene is the best approach.

Good hygiene starts with wearing gloves to clean up and dispose of stools as soon as possible in covered waste containers. Cat litter pans should be changed and disinfected daily. Wash hands for at least 20 seconds after cleaning any contaminated areas.

Now let's talk about disinfectants. Three of the articles I read suggested bleach as the disinfectant of choice. First developed and marketed in the 1920s, bleach has a broad spectrum germicidal activity but doesn't clean and poses health hazards for humans. Bleach is caustic and irritates skin and eyes. Breathing in bleach fumes can cause persistent inflammation of the lungs and increase the risk for cancer. However, it is still commonly used in many households. Non-porous surfaces in the home and kennel areas must be cleaned with soap and water before disinfecting with diluted bleach solution. For coccidia, the recommendation is 250mls (8 ounces or 1 cup) of bleach in one gallon of water. For giardia, dilute 1-2 cups of bleach in one gallon of water. Test surfaces first to see if they will tolerate the bleach. Wipe surfaces and allow them to air dry.

Lysol is another household disinfectant that has been shown to be effective at killing the cysts and can be used instead of bleach. Be sure to follow label directions.

Steam cleaning is an effective way of destroying oocysts and cysts on soft surfaces in the home like carpet and furniture.

Since the 1970s, many of the disinfectants used in veterinary medicine employ quaternary ammonium compounds for the active ingredient. These have been modified over the years to improve efficacy against a wider range of organisms. While safer to use than bleach, they can still cause irritation to skin and mucous membranes, especially in the eyes and lungs. The most popular product sold today is called KennelSol and can be acquired from Amazon. Read the label carefully before using.

In the early2000s, accelerated hydrogen peroxide (AHP) was introduced as a safer and more effective disinfectant. AHP carries the lowest toxicity rating given by the US Environmental Protection Agency. Accelerated means AHP products kill pathogens more quickly and clean much better than regular peroxide. Marketed as Rescue Disinfectant, the efficacy of AHP is supported by over 30 studies. In one study, AHP s were the only disinfectant that prevented the transfer of bacteria to other surfaces. Available on Amazon, read label directions carefully before using the concentrate.

Giardia cysts are susceptible to drying out so allowing the environment to dry thoroughly after cleaning is helpful. Exposure to sunlight is the only way to eliminate the cysts in outdoor areas like lawns and gardens. Gardeners should wear gloves when digging in contaminated soil and wash their hands afterwards.

Once your dog completes its course of medication, all dogs in the home should be bathed with pet shampoo to remove any contaminated stool residue. All bedding and other pet laundry can be disinfected after washing by drying at the highest heat setting of your dryer for at least 30 minutes. Dishwasher safe toys and bowls can be disinfected in a dishwasher that has a dry cycle or a final rinse cycle. If you don't have a dishwasher, submerge these items in boiling water for a couple minutes. It's important to clean and disinfect pet items regularly during treatment and for a few days afterwards.

Protozoal parasites can be persistent and thorough cleaning and disinfecting of the environment will help prevent re-infection. Try to avoid possible sources of contamination such as infected waterways. Also, keep in mind, healthy pets are less likely to develop symptoms.