The hidden perils of swimming in open Canadian waters

Taking a long leap off a short pier into cool water is no problem for many Canadians when the lazy, hazy days of summer hit.

Fortunately, most of those refreshing dips are in some of the cleanest waters on the planet.

“By and large swimming in fresh water, swimming in the oceans in Canada is extremely safe. We are very lucky to have very clean water supplies,” says Dr. Isaac Bogoch, an infectious diseases consultant at University Health Network in Toronto.

Still, swimmers should remember that they share lakes, rivers, ponds and oceans with lots of different organisms, big and so small they can’t be seen, some of which can put a damper on that summer fun by sending the swimmer sprinting for the bathroom or dealing with a nasty rash. Most cause only mild symptoms but there are those rare times when tragedy strikes. An Oklahoma swimmer died Aug. 12 after picking up a brain-attacking amoeba while swimming in a lake the week before. Called Naegleria fowleri, the freshwater amoeba is worldwide but on this continent typically only found in the southern U.S. and further south. It gets to the brain via the swimmer’s nose and is almost always fatal.

We don’t have to worry about brain-eating amoebae in Canada, but awareness of what else might be floating about with you in the water is the first step in knowing how to protect your health when enjoying one of the season’s great pleasures. Here are some potential hazards to avoid.

E. coli

This is one of the most common nasties Canadian freshwater swimmers are likely to encounter. It is frequently used as an indicator of overall water safety for monitoring and advisory purposes. E. coli is a bacteria that comes from human and animal waste – poop, basically -- so the closer you are to people and animals, the higher your risk of high amounts of E. coli. Not all E. coli is harmful but some strains are. Swimmers get exposed to it by accidentally getting a mouthful of water, so pay attention to what your mom said and try to keep it closed in water you’re unsure about. The good thing is that E. coli levels can rise and fall relatively quickly and there are acceptable levels. A beach with high E. coli readings one day can come under acceptable limits the next because of changing wind conditions, currents, etc. Exposure to high levels of E. coli can bring on upset stomachs, diarrhea, ear, nose and throat infections as well as rashes, which may prompt a trip to the doctor.

Beaver Fever

It sounds Canadian but its cause – giardia, a microscopic parasite – is worldwide. This is contracted the same way as E. coli, by swallowing contaminated freshwater that contains cysts spread through animal and human feces. It can cause diarrhea, stomach cramps, bloating, vomiting, chills, headache and fever but it is possible to have no symptoms. Treatment may include an anti-parasitic medication prescribed by a doctor.

Swimmer’s Itch

Doctors know this better as schistosomiasis. It is caused by a worm-like parasite found in lakes and ponds as well as coastal waters where there are lots of snails which act as hosts for the parasite’s larvae. In our part of the world, the parasite doesn’t penetrate the human skin barrier but it can latch onto the skin, causing a mild to severe rash. British Columbia’s HealthLinkBC website warns that young children are at highest risk of the parasite because it can be pushed up against the shoreline by wind. Applying sunscreen before swimming can help reduce exposure as well as rinsing off with freshwater immediately after.

Blue-green algae blooms

There are different kinds of algae but blue-green algae, also called cyanobacteria, can be particularly dangerous because of the toxins it produces, called microcystins. Some beaches in Ontario’s Windsor-Essex area were closed this summer because of blue-green algae blooms on Lake Erie.  The blooms happen when there is so much of the algae that it turns into thick, pea soup-like masses, creating a stinky scum. The symptoms they cause in swimmers are typically mild: irritated skin, eyes and ears. If swallowed, they may bring on headaches, diarrhea, nausea or even muscle tremors, in large amounts. Blooms are common when water heats up, is shallow or slow-moving and is hit with an overabundance of nutrients, such as from fertilizer run-off.  Pets can be affected too, so be careful about letting Fido wade off-leash. “Our advice is, ‘Don’t go swimming in algae-contaminated waters,” says Dr. Ray Copes, Public Health Ontario’s chief of environmental and occupational health.

Seabathers’ eruption

Tropical vacationers may have encountered this but there have also been cases off of the U.S. Eastern seaboard. Ocean bathers can end up with itchy rashes and stings from Thimble jellyfish and sea anemone larvae. They typically get caught underneath the swimmer’s bathing suit, which is why it’s important to remove the suit as soon as possible

Cutting yourself

Do not underestimate the risks of infection when you cut yourself in the water. This can happen when you step onto a shell, broken glass left by previous beachgoers or a particularly sharp stone. Your greatest threat at that point is yourself; the germs that are already on your own skin. But there are other waterborne bacteria lurking around that may take the opportunity to invade too, with such fancy names as Aeromonas, Erysipelothrix, Edwardsiella, and Mycobacterium marinum.  “Nothing is common, but if you are going to get an infection, it can come from these organisms,” says Dr. Bogoch. Most symptoms are mild but if you pick up a bacteria called Vibrio vulnificus, found in warmer sea waters, symptoms can be more severe, such as skin ulcers.

Leptospirosis

The disease caused by the bacteria leptospires has been less recognized but is gaining more notoriety thanks to adventure racers who have picked up it up while paddling, rafting and swimming in extreme wilderness locations. It is more common in tropical climates, but can also be found in temperate locations where water may be contaminated from the urine of infected animals. It too can be contracted through a cut or via a mucous membrane, causing flu-like symptoms. In extreme cases it can lead to kidney or liver failure.

Critters

It can seem like a small miracle to encounter one of the many larger creatures that call our waterways home. But they don’t know what you’re all about, so keep your distance. A B.C. woman reported being attacked by a river otter earlier this month while swimming in a lake in the province’s South Cariboo region. She was bitten nine times by the animal, which she first spotted swimming towards her before it disappeared underwater about 10 feet away. “Then it bites me and I scream,” she told a CBC news crew. She was eventually rescued by family members who kayaked out to her.

So what’s a swimmer to do?

The first thing is to keep swimming; you’ve already got a lot of protection thanks to Canada’s extensive water monitoring and safety systems. “Don’t panic, enjoy the summer,” advises Dr. Bogoch.

Waterkeeper, an organization that promotes safe clean water for drinking and recreation, maintains an online “Swim Guide,” and smartphone app that points people to beaches that are safe to swim at in Canada, the U.S., Mexico’s Baja peninsula and New Zealand. All the information is taken from local daily water quality updates.

In addition, “use common sense,” says Krystyn Tully, vice-president of Lake Ontario Waterkeeper. “If the water looks contaminated or has a funny smell or doesn’t seem to be moving, then stay away.”

Here a few other tips:

-          Avoid swimming in urban waterways for 48 hours after heavy rains

-          Avoid flat, stagnant water that is not moving, especially if it is warm

-          Follow local swim advisories. Toronto and Halifax use the international “Blue Flag” program, as do several other Canadian beach locations. If a blue flag is flying that means the beach is generally safe for swimming. In Toronto, lifeguards will also post signs indicating whether the water tested safe the previous day.

-          If you already have a cut, apply an antibiotic ointment and/or bandage to protect it from contact with waterborne organisms

“You definitely should go to the beach at least once a year,” advises Tully. “It’s something that people shouldn’t be afraid of.”