At first, Omar Mall thought the small red bumps on his hands were mosquito bites. The next day, however, Mr. Mall, who had been visiting his uncle's cottage in Muskoka, developed an itchy rash that spread across his chest and legs. He had been attacked by small worm-like parasites called schistosomes that live on or near the water's surface and thrive during hot weather.
"I wasn't even swimming at the time," Mr. Mall, 21, of Toronto, said. "It came from the shower, which uses untreated lake water."
The waterborne worm is having a blockbuster year because of this summer's endless heat wave. It can make summer holidays so miserable that authorities are out issuing warnings to swimmers in cottage country. Campers arriving at Bon Echo Provincial Park north of Kingston are greeted by park staff whose first words are, "Do you know about swimmer's itch?"
"It has been a hot summer and that's when we see these cases appear," park superintendent Bruce Bateman said. While the park doesn't monitor water temperature, Mr. Bateman said the shallow beach waters need to be around 22 C for the parasite to thrive. The first reported case at the park came over the August long weekend.
At the Bracebridge Medical Centre, Dr. Faizal Bawa has treated around 20 cases this summer and he blames the hot, dry weather. "Anything growing in the water grows faster when the water heats up."
Swimmer's itch is common in lakes, ponds and rivers across Canada. The parasites hatch in water snails, then float on the surface until they find aquatic mammals, ducks and other waterfowl they can latch on to. This exchange typically happens near the shoreline where the microscopic larvae thrive in warm, shallow water -- the same conditions that attract bathers in the heat of summer.
When swimmers come into contact with the parasite, the larvae begin to burrow into the skin, which can trigger an allergic reaction that brings on redness, swelling and, at times, severe itching.
Humans are not suitable hosts for this unwanted guest and the parasite dies within 24 hours. But the effects can last for weeks.
"We've had quite a number of calls reported from Muskoka," said Fran Gelder with the Simcoe Muskoka District Health Unit in Barrie. "We know it's in our beaches and we'd like people to be aware of it."
Repeated exposure tends to increase the severity of the reaction, Ms. Gelder said. "If you get it, chances are you'll get it again."
Tracking the exact incidence of swimmer's itch is next to impossible, said Rob Bartlett, a public health officer with Ontario Parks, because it's not monitored by the Ministry of Health. "It's not communicable so there's really nothing we can do about it except warn people of its presence and how to minimize the risk of coming in contact with the parasite."
For an irritation that is as common and widespread as our countless lakes and waterways, the defence is refreshingly simple: a vigorous rub down with a coarse towel before your skin dries.
"Don't let Mother Nature dry you because that's when the larvae begin to burrow," said Delia Brereton, a pharmacist in Parry Sound who has seen her share of unsuspecting vacationers in search of relief. She said the larvae can even penetrate bathing suits if they are left on to dry, adding that children and their caregivers are generally more vulnerable because they often spend long periods of time in shallow waters. She recommended sufferers take an antihistamine and stay out of the water for a few days until the itching and redness subside.
For Mr. Mall, who loves swimming in lakes and rivers, there's less fun in taking the plunge. But that's not about to stop him. "Now if I know there's a beach party, I'll take a Benadryl beforehand and that usually works."