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So, to swim? Or not to swim? Blue-Green Algae Contamination

The recent reports of dogs dying after swimming in local lakes and reservoirs has left many dog-owners understandably concerned. During these hot summer days, a swim in a lake or pond can be a huge relief from the heat. But what are the risks associated with swimming in local waters? And what can dog-owners do to protect their treasured pet?

Two potential causes of infectious disease from water exposure are blue-green algae and leptospirosis. One is visible, and one is not.

Blue-green algae is also known as cyanobacteria. It is extremely toxic and can cause clinical signs, such as lethargy, vomiting, diarrhea, seizures, or paralysis within a few hours. The algae typically appears as floating mats or blooms on the surface of the water. It is usually bluish-green, but can also be rust-colored or red. However, unless a microscope is handy, there is no way to determine if pond scum is blue-green algae or something benign. It is important to check the banks of the water for any signs that may be posted warning of blue-green algae. More importantly, check the water, including areas along the banks where wind may have blown the blooms. If any scum is noted, regardless of color or amount, the safest option is to avoid the water completely.

Unlike blue-green algae, leptospirosis is an infectious disease risk that is not detectable. It is a bacterial infection that is most commonly transmitted through indirect contact with the urine of wildlife. Many people associate it with rat urine, as up to 50% of rats are carriers. However, other hosts include deer, opossum, raccoons, skunks, as well as other wildlife. The most common source of infection is stagnant or slow-moving warm water, or contaminated soil. This includes lakes, ponds, and creeks. There is an increased incidence of infection following heavy rain or flooding, and during summer through late fall.
Leptospirosis can lead to serious illness and affect multiple body systems, including the kidneys, liver, lungs, eyes, and muscles. It is also a zoonotic disease, meaning that it is transmissible to humans.

Leptospirosis is becoming an increasing threat across the United States. A significant reason for the rising incidence is urban growth leading to increased exposure to wildlife. It is something to take seriously. However, there is a leptospirosis vaccine that has proven extremely effective in decreasing the prevalence and severity of infection. As a veterinarian practicing in an urban area of Philadelphia, I highly recommend annual vaccination against leptospirosis to all of my dog-owners, whether they live in the city, suburbs, or rural areas.

So, to swim? Or not to swim? My recommendation is to understand the risks and take necessary precautions, which include vaccination and avoiding water if any type of algae or growth is detected. As a veterinarian and dog-owner with a rambunctious, naughty, lovable dog who loves the water….I’m going to keep her up-to-date on her vaccinations, inspect the water thoroughly, and then I’m going to let her run through the Wissahickon.

Author: Dr. Alison Whiter

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