Giardia is a threat to dogs and humans

BY JULIE IRWIN, VMD, SEATTLE VETERINARY ASSOCIATES

Giardia is a protozoan parasite that is infectious to both humans and pets all over the world. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide. Nearly 33% of people in developing countries have had giardiasis. According to the CDC, Giardia infection is the most common intestinal parasitic disease affecting people in the United States.

We are certainly seeing a rise in the numbers of our veterinary patients being diagnosed with Giardiasis. However, it is unclear whether the rise in the number of cases is due to a true increase inthe incidence of the disease or whether it is due to better methods of detection.

Method of transmission 
Giardia cysts are shed in the feces from infected people or animals and can persist in the environment for extended periods of time. When animals or humans ingest these cysts, the parasite attaches to the lining of the intestine in the new host. 

An infected person might shed 1-10 billion cysts daily in their feces and this might last for several months. However, swallowing as few as 10 cysts might cause someone to become ill. Giardia may be passed from person-to-person and from animal-to-animal. There is also some concern that certain subspecies can be passed from animal-to-person. 

Contaminated water is the classical source of a Giardia infection. This is one of the reasons that backpackers and campers are advised to boil or treat water obtained from fresh rivers or lakes prior to drinking. 

Symptoms 
Infection with Giardia causes problems with normal intestinal absorption of vitamins and other nutrients. This leads to a profuse, watery foul-smelling diarrhea. Animals and humans can also be carriers of the organism without showing any symptoms. 

Diagnosis
In the past, diagnosis in our veterinary patients was difficult. The stool sample being examined needed to be fresh, plus Giardia rarely show up on the usual fecal flotation testing methods used to detect other parasites. Additionally, Giardia cysts can be shed intermittently, so infections can be missed on a single fecal float. 

Recently a commercial ELISA test has become available, which tests for the presence of Giardia proteins in the feces. This method has dramatically improved the ability to detect Giardiainfections and the test can be completed in the office. 

Treatment 
A broad spectrum dewormer called fenbendazole (Panacur®) seems to be the most reliable treatment at this time. Metronidazole (Flagyl®) in relatively high doses has been a classical treatment for Giardia but studies show that it is not always effective as a sole agent. In some cases, the medications are used together. 

Environmental Decontamination
Treatment with medication should also be combined with environmental decontamination.Because infected pets may have been shedding cysts into the environment for some period of time before detection, it is important to thoroughly clean the environment to prevent re-infection. Guidelines from the CDC for cleaning of the environmental are listed below. In addition, because cysts can stick to the fur of the infected patient and be a source for re-infection, the positive animal should be bathed at least once in the course of treatment. 

Carpets: Steam clean the area at 158° F for 5 minutes or 212 F for 1 minute. Read the product labels for specifications, and follow all instructions.

Other items: Dishwasher-safe toys and water and food bowls can be disinfected in a dishwasher that has a dry cycle or a final rinse that exceeds one of the following: 113° F for 20 minutes, 122° Ffor 5 minutes or 162° F for 1 minute. If a dishwasher is not available, submerge dishwasher-safe items in boiling water for at least 1 minute. Toys and bedding can be washed in the washing machine and then heat-dried on the highest heat setting for 30 minutes. If a clothes dryer is not available, allow items to thoroughly air dry under direct sunlight. 

The Yard: 

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  Wear gloves when handling feces.


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  Remove feces promptly and put it in a plastic bag.


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  Limit access to common outdoor spaces, where possible, if pets have diarrhea or are being treated for Giardia. It has been demonstrated that dogs that play at dog parks are at greater risk for infection.
  


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  Eliminate any source of standing water.


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  Do not allow any new animals, especially young ones, to enter the yard or other outdoor spaces until the patient has been shown to be free of Giardia.

Giardia is hard to completely eliminate from the environment, but there are things you can do to help decrease the risk of pet reinfection and of human infection. Please remember that despite your best efforts to clean the environment, Giardia can persist in outdoor spaces and pet reinfection is possible. 

Follow up
In most cases, we do recommend follow up after treatment for Giardia to ensure that the organism has been completely cleared. In general, a fecal flotation is checked two weeks post-treatment to ensure that the animal is no longer shedding cysts. The ELISA test can be repeated 6-8 weeks post-treatment to ensure that the organism is no longer present. 

Julie Irwin, VMD

Julie Irwin, VMD was born and raised in Cleveland, Ohio. She attended Cornell University, where she received her Bachelor of Arts degree with a dual major in Mathematics and Biology. She then attended the University of Pennsylvania School of Veterinary Medicine, graduating in 1998. Julie and Steve met in veterinary school and were married shortly after graduation. Julie’s other interests include rowing, cross-country skiing and hiking. She and Steve, along with their three children, have recently relocated to Seattle and are enjoying exploring the Pacific Northwest.

Source: http://www.seattledogspot.com/blog/dog-blog/post/giardia-is-a-threat-to-dogs-and-humans