The house we’re renting in California comes equipped with a pool. It’s been too cold to swim in it so far, but it has still been a source of lots of excitement. Mr. and Mrs. Mallard have regular date mornings in it.

Mr. and Mrs. Mallard taking their morning constitutional in the backyard pool. Forgive the graininess. I had to take the photo from a distance through the pool fence so as not to disturb them.
(Photo: Shala Howell)

This morning when I came downstairs for the necessary cup of coffee, I spied a bedraggled brown lump floating on the surface of the pool. I’ll spare you the picture of that, and simply say that on closer inspection, it proved to be a dead mouse.

Bummer. (Also, eww…)

Which brings us to today’s question: “There’s a dead mouse in the pool. Is it time to freak out?”

The 30-second response (“tl;dr” )

Apparently the answer is no. I do not need to swear off swimming forever.

According to the CDC, most dead animals found in pools do not pose a health risk to humans. The germs those animals carry mostly affect their own species. And most of the germs that can affect humans are killed off within a few minutes’ exposure to chlorine. (The important exception to this rule are raccoons, dead calves, and lambs, which I’ll discuss briefly at the end of this post.)

Still, the fact that the CDC maintains a page on how to disinfect your pool after finding a dead animal in it tells me two things:

1. It’s fairly common for wild animals like skunks, birds, mice, gophers, rats, snakes, frogs, and bats to drown in pools.
2. It’s pretty important to clean your pool properly after.

In the 3-minute answer, I’ll tell you how to do that.

The 3-minute answer (or, How to disinfect your pool after a small animal dies in it)

According to the CDC, here’s what you’ll need to do if you find a dead animal in your pool.

Supplies: 

• Disposable gloves
• Net or bucket
• Two plastic garbage bags
• Pool chemicals, including chlorine

Procedure: 

1. Close the pool to swimmers.
2. Put on the disposable gloves.
3. Remove the dead animal from the pool using the net or bucket.
4. Double-bag the animal in plastic garbage bags.
5. Clean off any debris or dirt from the item used to remove the dead animal, and dispose of it in the plastic garbage bags.
6. Remove your gloves and place them in the garbage bags.
7. Close the garbage bags and place them in a sealed trash can to keep wild animals away from the dead animal.
8. Wash your hands thoroughly with soap and water immediately.
9. Disinfect the pool by:
   • Raising or maintaining the free chlorine concentration at 2 parts per million (ppm) for at least 30 minutes
   • Maintaining a pH level of 7.5 or less for at least 30 minutes
   • Raising or maintaining the pool temperature at 77°F (25°C) or higher
10. Confirm that the pool’s filtration system is working properly during this time.
11. Disinfect the item used to remove the dead animal by immersing it in the pool during the 30-minute disinfection time.

The very important exception to this rule: Dead calves, lambs, and raccoons

If you find a dead calf, lamb, or raccoon in your pool, it is perfectly reasonable to freak out. You will need help dealing with the aftermath of this incident, because the germs and worms those guys carry cannot be dealt with by simply increasing the chlorine levels in the pool.

Calves and lambs

Pre-weaned calves and lambs are often infected with Cryptosporidium, a chlorine-tolerant parasite that can infect humans, resulting in a nasty bout of diarrhea that can last anywhere from 1 – 4 weeks in humans with healthy immune systems. You do not want this.

Unfortunately, since the parasite is protecting by an outer shell, it is remarkably resistant to chlorine. So if you find a dead calf or lamb in your pool, you will need to call your local health department for advice. Disinfecting a pool after a calf or lamb dies in it requires a hyperchlorination protocol that most residential pool owners can’t do on their own.

Raccoons

Raccoons can be infected with a worm called Baylisascaris procyonis. Typically spread through the raccoon feces, the worm itself is quite chlorine-resistant, and can infect humans, especially children, causing severe neurologic illness. You don’t want this either.

So, if you find a dead raccoon or raccoon feces around your pool, you will need to have Animal Control or your local health department test the feces or raccoon for the worm. If the test comes back positive, then you will need to either filter your pool for 24 hours or drain the pool, clean it, and then refill it.  The CDC website provides instructions for testing the raccoon remnants and cleaning the pool after.

Related Links: 

• Finding a dead animal in your pool (CDC)
• Raccoons & pools (CDC)
• Directory of Local Health Departments (NACCHO)