Giardia

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RickyEarl

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Feb 23, 2012
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Dallas, Texas
Last week we got a dog from a rescue shelter - cute little puppy. The rescue vet gave her a clean bill of health. Just to be sure we scheduled a visit to our regular vet, which took place Tuesday. Today our vet tols us her stool sample tested positive for giardia.

She is not sypmtomatic, but the vet put her on antibiotics. Since she's been in our pool I want to do the same with it. Ph is about 7.2, which is supposed to help. But the CDC says to basically shock the pool. So, do I take the pool up to regular or mustard algae shock level? How long should I maintain shock levels? Anything else I should do? We're bleaching and/or throwing away the kids' pool toys, which I hope is overkill, but I don't want to do this again.

Thanks
 
Copying chemgeek's post from Fecal Accident.

chem geek said:
Realistically, the only issue with fecal matter is whether it contains protozoan oocysts, specifically Giardia or Cryptosporidium. Without these, any bacteria or viruses will be killed fairly quickly, especially if you've removed physical matter and the rest is dispersed and exposed to chlorine. Unfortunately, the protozoan oocysts are very resistant to chlorine. The official CDC Fecal Incident Response Recommendations for Pool Staff has Giardia with a CT value of 45 and Crypto with a CT value of 15,300. In an SWG pool with an FC that is about 5% of the CYA level, the effective FC level with no CYA is 0.05 ppm. So that means the germ inactivation time to kill 99.9% of Giardia is 900 minutes or 15 hours. For Crypto, it's over 7 months so essentially not killed. This assumes no germicidal effect from the chlorinated cyanurates and that's a reasonable conservative assumption given the CDC data.

In your current pool with an FC of 6.2 ppm and a CYA of 45 ppm, this is roughly equivalent to an FC with no CYA of 0.1 ppm so a 99.9% kill time for Giardia of around 8 hours (if the water temp were 77F -- yours is colder so kill time would be longer).

Odds are that unless your pet had diarrhea then it is less likely that it has a protozoan parasite in its fecal matter in large numbers. Also, you'll note that the guidelines assume that formed stools are much less likely to have Crypto. The CDC Annex for Module 6.5 of the Model Aquatic Health Code (MAHC) shown here describes how 300 samples of formed stool fecal incidents in public pools were analyzed and none had Crypto but 4.4% had Giardia.

If you were to use chlorinating liquid or bleach to raise the FC to the normal shock level of around 40% of the CYA level, then this is equivalent to an FC with no CYA of around 0.6 ppm, assuming you lower the pH before adding the chlorine to prevent the pH from rising too much. That would then kill 99.9% of Giardia in around 75 minutes. Given that this fecal matter was from a dog and not a human and given that it was not diarrhea, you could probably not shock and just wait one day, stay out of the pool, and keep the pump running for 24 hours and then be fine.

Richard
Click to expand...

I would use normal shock level and maintain it for 24 hours. You can use PoolMath to determine your shock level.
 
Why can't you throw the kids' toys in the pool and SLAM them too? You could spray the rafts and floaties with a bleach solution. I wouldn't throw the stuff away.
 
It is often good to throw away pool noodles, as they tend to have many nooks an crannies that are good places for bacteria to hide from chlorine. Anything with a smooth surface is easy to clean, so is often worth keeping.
 
I could see pitching those cheap noodles. I was thinking not so much for diving rings, sticks, goggles and stuff like that. Noodles start to deteriorate after a season or 2 anyway.
 
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