Dog’s Worst Friend

US dogs face a deadly threat from algae-spawned toxins lurking in lakes, but there may be an antidote.

By | May 1, 2014

FRESHWATER?: Sampling at Pinto Lake, California, during a toxic algal bloomRAPHAEL KUDELA

Annabelle’s family didn’t know it, but she was dying. Two hours earlier, she had ridden along in a canoe drifting through Middle Foy Lake near their Montana home. As the canoe neared the shore on this autumn day in 2010, Annabelle leapt from the vessel, as an excited Australian Shepherd is prone to do, and swam the rest of the way to the bank. Once ashore, she licked her wet fur—a casual reflex that almost spelled her undoing.

The lake water and her coat were tainted with microcystin, a liver toxin produced by some species of blue-green algae—or cyanobacteria—thriving in the water. Quick thinking, a Google search, and an experimental therapy would ultimately save Annabelle’s life, but her case spotlights a hidden danger that abounds in freshwater bodies throughout the country. One out of three US lakes harbors hazardous levels of toxin-releasing cyanobacteria, according to the Environmental Protection Agency (EPA).

The blooms are sparked by a deluge of organic nutrients, such as those found in fertilizers, pouring into aquatic habitats. Recreational waterscapes near farms and residential lawns typically harbor such compounds, and climate change may be further driving cyanobacterial growth. And the problem is escalating. “There is widespread agreement within the scientific community that the incidence of cyanobacterial harmful algal blooms (HABs) is increasing both in the U.S. and worldwide,” says an EPA spokesperson in an e-mail.

Dogs often fall prey to such bacterial outbreaks, according to a recent study led by the Centers for Disease Control and Prevention (CDC). Their penchant for drinking stagnant water or diving headlong into contaminated ponds makes them susceptible to accidental poisoning. Nearly 100 dogs were killed by cyanobacterial toxins between 2002 and 2012, according to the CDC’s survey of veterinary hospital records, news reports, and state-agency archives dating back to the 1920s. “It’s really important that the CDC is showing an interest,” says toxicology expert Val Beasley, a professor emeritus of comparative biosciences at the University of Illinois at Urbana-Champaign. Yet the CDC study offers a mere glimpse into this burgeoning dilemma.

“A comprehensive review [of HABs] is impossible in this era because there isn’t mandated reporting,” says Beasley. For instance, the Harmful Algal Bloom–Related Illness Surveillance System (HABISS), a CDC database of reports on algal toxicity cases that served as another source of information for the CDC survey, was limited to just 13 states.

We are increasingly aware that many dogs and other pets are exposed to these toxins every year, and that the blooms are likely increasing.—­Raphael Kudela, University of California, Santa Cruz

Beasley argues that mandatory reporting and a centralized database are vital to management efforts, which can include interventions such as planting vegetation between water bodies and farms to sop up excess nutrient pollution.

“The cyanobacterial blooms are an alarm that is going off and will continue to go off until we start to manage the world more wisely,” says Beasley.

The algal toxin can affect humans as well. “Microcystin scares me a ton, especially because of the potential human health issues that are being missed,” says Melissa Miller, a veterinarian and wildlife pathologist with the California Department of Fish and Wildlife who coauthored the CDC report.

Kelly Rankin, Annabelle’s veterinarian, desperately needed a network like HABISS after the sick pooch was admitted to her clinic a couple of days after her exposure. “I couldn’t find any information beyond just routine supportive care for liver failure—I was scouring my veterinary literature and the Internet when I happened upon the San Francisco Chronicle article,” recounts Rankin. That newspaper story reported on a 2010 paper Miller published about microcystin poisoning in 21 California sea otters. This was the first report linking the death of a marine mammal to the freshwater toxin. Scientists had previously assumed that microcystin quickly broke down in saltwater.

As Annabelle lay dying, Rankin called Miller to ask if a treatment existed. Miller suggested cholestyramine, a drug that had allayed microcystin poisoning in rat studies, but had never been tested in canines. Cholestyramine was once a mainstay for the human treatment of elevated cholesterol, before the discovery of statins. It works in two ways. First, the drug enters the intestine and sequesters bile salts attached to microcystin. By binding the salts, cholestyramine ensures their excretion instead of their recirculation to the liver, where the toxin causes organ failure. Cholestyramine has also been shown to strongly bind microcystin, both in vitro and in the living rat intestine, which may protect the liver, kidneys, and colon from harmful inflammation and disease.

“I started [the drug] that day and literally by the next, the dog was on the mend,” Rankin says. The collaboration also helped establish Annabelle’s microcystin exposure, which was 4,000 times greater than the dose designated as “safe” by the World Health Organization. Together, Rankin, Miller, and other scientists published the details of Annabelle’s recovery with cholestyramine, so that veterinarians and the general public would be aware of this emerging toxin and its antidote (Toxins, 5, 1051-63, 2013).

“[Annabelle] ingested 1,000 micrograms of toxin. If [she] ate or drank the pond scum, that would be akin to the volume of a soda can,” says Raphael Kudela, a coauthor of Annabelle’s case study and phytoplankton ecologist at the University of California, Santa Cruz, who screened Annabelle’s fecal samples.

A fast, accurate test for cyanotoxins doesn’t exist, but one is desperately needed for comprehensive surveillance of contaminated lakes or for patients who visit veterinary and human emergency rooms, where cases may go overlooked. CDC budget cuts ended the HABISS program in 2012, so a national hub for case reports, which could aid prevention and treatment, is still lacking.

“We are increasingly aware that many dogs and other pets are exposed to these toxins every year, and that the blooms are likely increasing,” says Kudela. And new findings on the chronic impacts of cyanotoxin poisoning have him worried. “We know that even low-level exposure results in decreased reproduction in fish, and probably promotes cancer in mammals, such as dogs and humans.”

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Avatar of: Doug Easton

Doug Easton

Posts: 13

May 14, 2014

Thank you. I have a black Lab that swims wherever there is water and goes to a small lake every weekend. I will send the link to our Vet's office. This is not only practical but interesting science.

Avatar of: Dr Edo

Dr Edo

Posts: 30

May 14, 2014

One wonders if the land application of sewage sludge (biosolids) within these drainages is involved. Sewage sludge is applied to forests and derives from the removed solids of wastewater treatment (sewer) plants. Certainly, with the slipshod way that the US-EPA promotes and regulates this material, called a hazardous waste, it should be a primary suspect. By definition, sewage sludge is a hazardous waste because of the infectious characteristics. See for example: "Increased frequency of drug-resistant bacteria and fecal coliforms in an Indiana Creek adjacent to farmland amended with treated sludge", Can J Microbiol. 2004 Aug;50(8):653-6,

Dr Edo McGowan, Medical Geo-hydrology

Avatar of: mightythor


Posts: 83

May 14, 2014

Are there any reports of acute microcystin toxicity in humans? Inquiring minds want to know, especially those belonging to lake swimmers. The article is vague on this point. Does the reference to "potential human health issues that are being missed" imply that there are no documented human health issues?

A related question: if "low level exposure ... probably promotes cancer in mammals such as dogs and human," should lake swimmers consider cholestyramine prophylaxis?

Avatar of: algaelady


Posts: 4

May 16, 2014

There are many records of blue green algae in freshwater (aka: cyanobacteria) and freshwater dinoflagellate algae (aka: red tide) making people sick enough to go to the emergency room.  The irony of this article is that this congressman leads a fight that has blocked and tabled the US Harmeful algae act that funds monitoring and assessment of harmful freshwater and marine algae species and even funds the training of doctors and veterinarians to recognize, treat and document cases of algal toxin symptoms in humans and animals. That medical training used to be optional for states decide whether to use or not.  Texas was the only coastal state to choose not to have that medical training.  Then when the US harmful algae task force advised for that to become mandatory, congress suspended the act and has not funded it for several years now since 2008. Even if it is re-funded it now stands to have its funding cut in half and completely ignore freshwater dinoflagellates which other countries all over the world know need assessment for toxins whenever they occur in bloom numbers  and fund such monitoring ......but in US Harmful Algae act, Freshwater dinoflagellate algae are considered harmless and not included inspite of science journal articles to the contrary.  The US is way behind but some states like Florida offer doctors and the public lots of education and resources and knowledge of outbreaks so that people won't be afraid of the water and know when it is safe.



Avatar of: algaelady


Posts: 4

May 16, 2014

Center for Disease Control website advise for when to avoid human contact with bodies of water under its section about harmful ameoba's applies to avoiding harmful algae too. It says to avoid contact with bodies of water if either or any of these conditions exist: low dissolved oxygen, high water temperatures or retaining storm water inputs.  These conditions also shift algal communities species composition from beneficial species that provide many environmental services for free to species that can cause alot of problems and extra expenses for both water quality maintenance and for treatment of algal toxicity in people and animals. In Central Texas SPringfed streams and lakes none of these conditions have existed historically until recently since over pumping of our aquifers especially during critically low aquifer levels has left our springfed habitats with all three of these conditions due to low or ceasing springflows.

Avatar of: algaelady


Posts: 4

May 16, 2014

This is another extra expense for taxpayers and for individuals dealing with health problems that could be avoided by not allowing groundwater marketers to make decisions about how to manage our aquifer levels and springflows and allowing them to mismanage the research about impacts on our economies and human and wildlife health.

Avatar of: algaelady


Posts: 4

May 16, 2014

more stormwater inputs are retained when it storms after a long dry spell while springflows are too low to flush the inputs out. After such storm events after a long dry spell while springflows are low: please avoid jumping into the waters and avoid allowing your pets to do so.


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