Safe Swimming: Guard against Giardia

July 24, 11:13 AMHealth Care ExaminerDoctor Lissa

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Swimming and summer. In the last post we talked about one of the scourges of summer fun, Crytosporidium.   This time, let's consider another pest we can do without.  I know what you're thinking, but I really am not trying to keep you out of the pool.  I just want you and your family to be safe and have fun at the same time.  It is possible.  Really.  But first you need to know what you're up against.

So, with that said, let's consider  Giardia;  the easiest to eradicate but still easily spread.  It is the most commonly diagnosed waterborne (drinking and recreational) intestinal protozoan parasite in the U.S., with an estimated 2.5 million cases annually.  

Most cases involve children under the age of 5, especially children in daycare centers, where Giardia cyst passage can be as high as 35%-50%. 

Water is the main source of infection with the parasite found in 80% of untreated water supplies such as lakes, streams, and ponds.  15% of municipal water supplies have it too. 

Here are some known facts about Giardia:

• Method of transmission is fecal to oral
• Injesting as few as 10 cysts can cause infection (an infected person can shed up to 1 trillion cysts with each bowel movement)
• It takes 30-60 minutes to be killed by chlorine in a swimming pool
• Cysts can survive for weeks or months in cold surface water
• The incubation period is 7-14 days after ingestion of cysts
• Symptoms last 7-10 days in most people
• Among those who swallow the cysts: 5-15% pass cysts without developing symptoms, 30-70% have no evidence of infection, and 25-50% develop acute diarrhea.  (This also means that those who have no symptoms can still infect other people)
• Symptoms include diarrhea, malaise, abdominal cramps, nausea, anorexia, weight loss, flatulence, greasy stools, malabsorption of vitamin B-12, Vitamin A, protein and D-sylose.
• Weight loss (10-20% of body weight) is usual in symptomatic cases.  50% lose at least 10 pounds.
• Some people develop chronic diarrhea (more than 14 days) and have profound malaise and abdominal pain
• Periods of diarrhea can alternate with periods of constipation or normal bowel habits for months.

Well, I know this is gross and not the sort of thing you want to dwell on, but wait, there is help available!

• First, call your doctor right away if you believe you may be symptomatic.  It won't go away by itself!
• Finding the parasite is hard, so you may need to be tested at least 3 times nonconsecutively before it is found
• A number of drugs can be used to treat the disease,  with Flagyl as the drug of choice. 
• Remember, even if you can smell chlorine, that doesn't mean the water is safe from Cryptosporidium or Giardia.

The best defense is to keep the pathogens, both Cryptosporidium and Giardia, from getting in the water.  That means if you own a pool, be vigilant about the cleanliness of the swimmers you have in the pool.  If you are in a public facility, again, notice how many swimmers are in the water, the relative ages( number of small children in diapers), and keep the pool water out of your mouth. 

If you have a bird bath or standing water in your back yard, be careful the water is as clean as possible.  There have been outbreaks of Giardia in dogs who drank water in bird baths or other standing water that was not clean.  Also keep your yard clean of animal feces and keep your pets away from other animal waste.  It is not known if dogs and cats can transmit Giardia to humans but the best advice is to assume they can unless it is disproven.

The same CDC guidelines for Cryptosporidium apply to Giardia, so you may want to revisit the previous post for those recommendations again. 

Again, have a great time swimming and enjoying your time outside.  Just consider the environment, don't swallow the water and seek help if you think you may have been exposed.