Gazette Vet: Is It Safe to Let Your Dog Swim Yet?


If you’ve been following the news over the past month, you may have heard stories of dogs across the country getting sick and even dying from harmful blue-green algae blooms in water. If you’ve followed local news, you may have heard about a dog who died after swimming in the Rivanna river and contracting leptospirosis. What are these diseases, and can my dog go back into the water yet?

I’ve lived in Virginia for most of my life and every year around this time (late July into early September), ponds and lakes get pretty nasty. Weeks of hot and dry weather lead to perfect conditions for our local water supplies to stagnate, shrink up, and grow all sorts of stuff in them.  So, is this algae problem I’ve been hearing about something brand new? Not really, but maybe a little.

Let’s first talk about the algae problem. Red tides, blue-green algae, and cyanobacteria all refer to different types of algae blooms that can be seen in local water sources this time of year. Some are non-toxic, while other algae can produce severe toxins that can create significant health problems if ingested. The best term is “harmful algae blooms.”  

I don’t know about your dogs, but on a hot summer day when my dogs see water, they want to go into it, no matter how nasty. And invariably, they are going to drink some. Or a lot. Mix this “normal” dog behavior with a harmful algae bloom and you have a recipe for a big problem.  

Algae like a few things to grow—sunlight, warm temperatures, and stagnant water. This is pretty much late summer in much of the U.S. and has been forever. Human behavior of course affects this problem with fertilizer runoff and altered natural water supply (i.e. dams, irrigation, changing water tables…).  My neighborhood ponds, which are quite nice in the fall and winter, are downright gross in the late summer. Of course they are. The ponds are there because a relatively low-flow local stream was dammed up long ago, creating the pond in the first place, and then you’ve got 150 homes who occasionally fertilize their lawns and the rain runoff eventually drains into these ponds.  

There isn’t a lot of easy-to-find data on the incidence of these harmful algae blooms in recent years vs. let’s say 20 years ago, when fertilizer, pollution, and development were still plenty present.  Harmful algae blooms have been documented over the past 30 years. Were dogs regularly dying then? This also becomes a reporting and news distribution question. If a dog died 20 years ago of “severe gastrointestinal disease,” would a local veterinarian have even suspected an algae bloom?  With today’s social media storms, all you need is one sensational story on Facebook to spread like wildfire across the nation. The question is, is this a concern for you right now?

The recent leptospirosis case is similar. Leptospirosis is a water-borne bacteria that can cause severe kidney and liver damage. Lepto is nothing new. We learned all about it when I graduated from veterinary school in 2002. There is a vaccine for it, but not all dogs receive it, and vaccines are also not 100%.  This one reported case made the local news headlines, but is that cause for concern for you?

My answer: we have to respect that plants and animals and diseases all have cyclical swings depending on environmental factors.  Some years there may be tons of rabbits in your neighborhood; do we really know why? Perhaps this year was a particularly bad/successful year for harmful blue-green algae? We can also recognize that human activity is contributing these problems, particularly with pollution/fertilizer runoff and our effects on natural water supplies. It mostly comes down to common sense. Don’t let your dogs swim in nasty water. Especially in August when it’s been dry and the water is discolored green/brown/blue/red. 

I have never let our dogs swim in our neighborhood ponds, mostly because I think they’re kind of gross and I don’t want to bathe the dogs afterwards. And also because I’ve always figured they might get some sort of diarrhea from the water. But at Sugar Hollow where the mountain spring water flows cool and fast all summer long? Go for it! The Rivanna river is somewhat in between. It’s a river, so at least its moving. But if you’ve been to the Rivanna during a low water period, it doesn’t smell great and should garner some suspicion. If you wouldn’t swim in it, maybe your dog shouldn’t either.  

Last, regarding leptospirosis, there is a good vaccine for this. Admittedly, the leptospirosis vaccine has a slightly higher risk of side effects versus other vaccines, so we sometimes skip this vaccine in really small dogs or dogs with autoimmune diseases. We try to prevent something (lepto), but also don’t want to cause reactions or have side effects. Overall, significant reactions from leptospirosis vaccines that would require intervention from us are uncommon.  

Fortunately, it’s September and after a few good rains and some cooler temps, we can forget all about this until next summer! 


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