Algae poses threat to humans as well as animals

Health departments have been trying to inform swimmers and pet owners that they should avoid water with visible algae, since ingesting it can cause severe and sudden illness including convulsions or even death. In our state, three dogs died last year after swimming at a reservoir. One died before his owner could even get him to the car, another died on the way to the vet.

Now, a recent report in the ProMED health tracking network calls our attention to human risks that don’t involved either entering or drinking the algae-contaminated water.

One man, whose dog died after a swim in the lake, was hospitalized last week [week of 19 Jul 2010] after he gave the dog a bath. Within days, the 43-year-old man began having trouble walking and lost
feeling in his arms and feet.

“We weren’t swimming in the lake because it’s disgusting,” said the
victim’s wife, whose husband, is still having trouble with memory loss and fatigue. “Our dog was just covered in that sludge, and my husband washed him.” Washington Examiner, July 30, 2010.

According to one doctor treating the Ohio man, his neurological problems may be permanent. But he’s better off than his dog, who died despite having the algae washed off.

The algae are in the “blue-green algae” family, and are actually not algae but photosynthesizing bacteria, called cyanobacteria. Blooms, or overgrowths, in bodies of water (fresh or saltwater) are encouraged by temperature change and increases in nutrients, often from agricultural runoff into the water. The cyanobacteria, like some algae, make toxins harmful to fish and mammals. Humans have been aware of this mostly through being poisoned by eating shellfish, which concentrate the toxins. The familiar warnings about “red tides” and issuance of “shellfish advisories” result from these conditions.

While it has been known that skin contact with toxic algae could produce illness in humans, the severe results from relatively small exposure—simply washing an algae-slimed dog—seem to be worse than expected.

The lake in Ohio is Grand Lake St. Marys; it’s the largest inland lake in the state by area, but is extremely shallow, with an average depth of only 5 to 7 feet. This shallow lake warms up more, and doesn’t dilute the runoff of agricultural fertilizer and livestock waste as much as if it held more water. Recent algae blooms have killed so many catfish that crews were shovelling up the dead fish. With the lake surrounded by warning signs, the area’s $160 million tourism industry has declined, and a boat race that draws about 30,000 people in late August each year has been cancelled.

Some algae are harmless, but there are many different algae or bacteria that can produce dangerous levels of toxins when they bloom. Some are more harmful than others but it’s foolish to take chances: keep yourself, and children and pets, well away from any water that has a visible algae presence. This can be greenish, reddish, or other colors. Or it can appear as just cloudiness or discoloration in the water, as foam or scum floating on top, as mats on the bottom, or actual filaments or pellets. And don’t let kids or pets wander to areas of a river, stream, or lake that you have not closely checked.

Algae by rocks.jpg


An Ohio factsheet sums up the methods of exposure, and known symptoms:

Skin contact: Contact with the skin may cause rashes, hives, or skin blisters (especially on the lips and under swimsuits).

Breathing of water droplets: Breathing aerosolizing (suspended water droplets-mist) from the lake water-related recreational activities and/or lawn irrigation can cause runny eyes and noses, a sore throat, asthma-like symptoms, or allergic reactions.

Swallowing water: Swallowing HAB-contaminated water can cause:
◦ Acute (immediate), severe diarrhea and vomiting
◦ Liver toxicity (abnormal liver function, abdominal pain, diarrhea and vomiting)
◦ Kidney toxicity
◦ Neurotoxicity (weakness, salivation, tingly fingers, numbness, dizziness, difficulties breathing, death)   Source.

Splashing of water in eyes, or inhaling droplets of contaminated water, can get the toxin into your system. One of the toxins from cyanobacteria, Saxitoxin is “reportedly one of the most toxic, non-protein substances known. It is known that the LD50 (median lethal dose) in mice is 8 micrograms/kilogram. Based on
a human weighing approx. 70 kg (154 lb), a lethal dose would be a
single dose of 0.2 mg.” [Source, ProMED report.]

How much is two-tenths of a milligram? There are a thousand milligrams in a gram, and a dime or a paper clip each weigh about 1 gram. So an amount of toxin weighing the same as two ten-thousandths of a paper clip may be lethal.

Algae,feet in water.jpg


These “Harmful Algal Blooms” can occur in large or small bodies of water; often, but not always, they are in areas where the waterflow is slow (near shore) or nonexistent (stagnant). Small pools or puddles separate from the main body of water can contain algal growth. Even in tiny amounts the toxins can have devastating and sudden effects of humans or animals.

Eating fish or shellfish from contaminated waters is dangerous too. Cooking does NOT render toxins safe.

Algal blooms can be very transient, appearing and disappearing in a matter of days to weeks. If you spot a possible instance and there are no warning signs, it may not have been found yet. Stay away from the water and call your local or state health department so they can track outbreaks, and put up signs.

For the state of Oregon, current advisories can be found online here. The HAB team can be reached by email at, by phone: 971-673-0440; Toll Free: 877-290-6767; or by fax: 971-673-0457. Other states should have similar programs; your city or county health department ought to be able to tell you more.

Why are these toxic algae blooms becoming more common?

The short answer is, better growing conditions for algae. They thrive in warm water, and temperatures are going up. Nutrients (nitrogen and phosphorus) from human activities pour into streams, lakes, rivers, and the ocean, and act like Miracle-Gro for the algae. Sources include runoff from fields treated with fertilizer or manure, spraying partially treated sewage sludge, sewage overflows, and runoff from pastures.

What can be done?

Rising temperatures, that’s a big one. Let’s just look at eutrophication or over-nutrification of water, since that’s something where local efforts can have relatively immediate local effects. Obviously, better treatment of sewage (including livestock waste) and reduced use of fertilizers (in agriculture, on golf courses, in parks, and in our own personal yards) are important steps to work on. On July 1st, 16 states will begin enforcing laws that require dishwasher detergents to be almost phosphate-free. That’s a small but significant improvement; the legislator who introduced the bill into the Pennsylvania legislature estimated that 7% to 12% of the phosphorus entering sewage plants came from automatic dishwashing detergents. New guidelines from the federal Clean Water Act to reduce nitrogen and phosphorus have provided more impetus to these particular efforts.

Not so obvious steps:

At least one study found that use of organic fertilizers led to less nitrogen runoff than use of chemical fertilizers.

Remediation of areas where nitrogen is stored in soil, from decades of deposition by one means or another, is possible but expensive and slow.

And years of research is showing us, surprise surprise, that intact aquatic communities slow the trickle-down of nutrient pollution (from, say, creeks to streams to rivers to a lake) and seem to enable a body of water to better resist eutrophication. Dr. David Schindler (Professor of Biological Sciences, University of Alberta) has studied the problem for decades including 37 years of work on Lake 227, a small pristine lake in the Experimental Lakes region of northern Ontario. He says, for example, that overexploitation of piscivorous (fish-eating) fish seems to increase the effects of eutrophication. (His earlier work energized the campaign to reduce phosphorus pollution.)

A study along the Georgia coast suggests that tidal marsh soils protect aquatic ecosystems from eutrophication, caused by the accumulation of nutrients. And they sequester large amounts of carbon, helping us slow down climate change. I would expect similar results with regard to freshwater wetlands and marshes. When I was a zookeeper I worked with mechanical incubators for bird eggs, none of which was as reliable as one of those “bird-brained” hens of whatever species. We are told that the appropriate native herbivores—bison, wildebeest, and so on—produce more meat per acre and do less damage than introduced species like cattle. And now we’re coming around to seeing that oldmothernature is better at water purification than we are, if we leave existing systems intact (but we never do).

Salt Marsh.jpg

Salt Marsh near Dartmouth, Nova Scotia; more good photos of this marsh here.

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