Summertime in this region brings lots of fun on the water, but there are some unpleasant health concerns that may come along with the sun. So far there haven’t been reports of blue-green algae blooms or swimmer’s itch on Pend Oreille or Priest, but it is always good to know what might occur.
Blue-green algae blooms:
You may have noticed a number of health advisories in northern Idaho this summer due to blue-green algae blooms. Fernan, Avondale and Hayden Lakes have all had toxic blooms during this hot, dry summer. No health advisories have been released for Pend Oreille or Priest at this time, but it remains a possibility.
Blue-green algae is another name for cyanobacteria. Cyanobacteria are closely related to other bacteria, but they can photosynthesize like plants. They are a common part of the phytoplankton population in most lakes and ponds. Cyanobacteria can reproduce quickly, creating a “bloom”, in times when temperatures are warm, sunlight is abundant, and nutrients such as phosphorus and nitrogen are plentiful. Some cyanobacteria create toxins that are released when they die. These toxins can pose a health risk to people and animals that drink or inhale the waters during a bloom.
Blue-green algae blooms can cause clear water to become discolored to red, brown, green or blue and a green scum layer may form on the surface of the water. Blue-green algae are difficult to pick up because they are small organisms that break apart. If you can pick up strands or it feels slimy or cottony then this is a harmless regular green algae. A large number of dead fish or other animals in the water or sudden sickness or death of a pet that drank from surface water can be indicative of a toxic cyanobacteria bloom. If you see something suspect please call the Idaho Department of Environmental Quality at 208-769-1422 or the Panhandle Health District at 208-415-5220.
These blooms can last for a long time, but they often disperse with a rain event or cold snap. Although these blooms are natural events, curbing the addition of nutrients to the water may lessen the chances of a bloom. Ways to limit nutrient additions to the water include: minimizing fertilizer application to lawns and gardens; retaining or creating a vegetative buffer on the stream bank; maintaining septic systems; and keeping livestock and pet waste out of the waterway.
Swimmer’s Itch
Swimmer’s Itch, cercarial dermatitis, is a skin rash that forms as an allergic reaction to a parasite that is can be present in in lakes or ponds. These parasites enter human bodies mistakenly when in search of an avian host. Humans are not suitable hosts so the parasite dies immediately, but they cause an allergic reaction in the skin. The rash is typically raised, itchy papules that last under a week. The rash is uncomfortable, but not serious.
For success the swimmer’s itch parasite, schistosomes, must have both an avian host and a snail host during its life cycle. This pairing of hosts is becoming more likely on Pend Oreille due to the invasive plant species, flowering rush. Flowering rush is the perfect host for snails and waterfowl love to eat it. In quiet bays this can make for the optimal environment for swimmer’s itch to take off.
