As the algae grow, they produce oxygen that gets trapped in the entangled strands of algae. Filamentous algae form on near-shore bottom sediments or submerged objects in ponds and lakes where there is good transparency and where sunlight reaches the bottom of the pond or lake. This is a common and troublesome aquatic plant that forms dense, hair-like mats. (But just in case, you may want to keep some treatments handy.)įor questions about lakes and lake management contact Widseth Smith Nolting’s water quality scientist Lorin Hatch at or 21.It's probably filamentous algae, sometimes called moss or pond scum. With some prevention, you can enjoy your summer itch-free. Our area boasts some of the state’s finest lakes. More snails equal a greater probability for swimmer’s itch. Rip-rap is an excellent surface for snail eggs to attach. Second, avoid placing rip-rap on your shore. A smaller number of birds in an area reduces the chance of the parasite being passed into the aquatic stage. If you don’t towel off, the flukes will stay in the evaporating water on your skin, burrowing into your pores and then dying, causing the itch.īefore anyone enters the water, there are measures you can take to lessen the impact of fluke hosts in your swimming area. They will die quickly on your towel and fall off. If fresh water is not available, then towel off immediately the cercaria cannot penetrate the skin if you rinse or wipe them off first. Rinse off with fresh water right after getting out of the lake. If you’re not sure if there’s been an outbreak, then avoid an area with an onshore wind wind that blows from the water toward the shore can blow in and concentrate a larger population of flukes. How can swimmer’s itch be prevented? First, avoid swimming in areas where it’s a known problem. Some bird hosts include common mergansers, mallards, Canada geese, swans, and red-winged blackbirds. In other words, a certain species of fluke can only carry out its life cycle in one species of snail and one species of bird. It should be noted that there may be over a dozen species of itch-causing flukes in Minnesota, each tending to be species-specific. This is the stage that causes swimmer’s itch. The cercaria must now find a bird host to complete its life cycle, so it tends to reside near the surface of the water. The emergent larva (cercaria), which is 1/80 of an inch long and transparent, exits the snail as another free-swimming, non-feeding form. It then goes through two sporocyst stages that take about a month. The larva enters its second host, a snail. It is free-swimming but non-feeding and survives for about a day. What hatches out of the egg is the aquatic larval stage (miracidium) of the parasite. Eggs are passed into the water via feces, where they can hatch within an hour under favorable conditions. The adult parasite lives in the waterfowl host, then passes along its eggs to the bird’s digestive tract. The two-month life cycle involves two hosts - a bird and a snail. The culprit of swimmer’s itch is the larval stage of a parasitic blood fluke that occurs naturally in most lakes. Cases lasting several days should been seen by a dermatologist. A mild over-the-counter antihistamine or corticosteroid cream can provide relief, or you may want to try soaking in a bath with Epsom salts, baking soda, or oatmeal. Children tend to get more than their fair share of the itch because they usually swim more, may have more sensitive skin than adults, and may have a harder time overcoming the urge to scratch. It’s characterized by red bumps (known as papules) that look like bad mosquito bites. The itch usually occurs within two to seven days after exposure in the water. Known technically as cercarial dermatitis, swimmer’s itch is that annoying skin rash you can get from swimming in some lakes. Understanding how it happens will help you avoid it. Fortunately, we don’t get the truly nasty forms of swimmer’s itch found in tropical areas, but it can get in the way of what should be an enjoyable time at the lake. Nothing can spoil summer in Minnesota quite like a case of swimmer’s itch.
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