What Can Dogs Drink? Learn The Dangers Of Drinking Lake Water

It’s warm outside, maybe even hot where you live. Everyone’s enjoying outdoor summer activities, including your dog! Everyone gets to go to the park, camping, hiking, to the lake, to the beach … but with all of this outside activity, it is important to think about the water your dog drinks.

When you are out hiking and come across a puddle, stream, or river, or are at the lake house down by the water your dog will naturally want to drink that water. But, did you know that drinking from those types of water sources can be very bad for your dog! There are dangers lurking in outdoor water sources that can make your dog (and maybe even you) very sick!

What’s the Problem?

Dogs will pretty much eat and drink just about anything and everything but that doesn’t mean it’s good for them. Outdoor sources of water can have organisms like parasites, bacteria, toxic algae, or even chemical runoff that can be very detrimental (even deadly) to your dog.

Once a dog is infected with parasites some of them can even be transferred to humans.  That means once your dog is infected, you could become infected too.

Microscopic Protozoan Parasites

A protozoan is a microscopic single-celled organism such as a sporozoan, ciliate, flagellate, or amoeba. There are different kinds of protozoa and they can be found in just about every possible habitat. These little creatures are way too small for us to see with the human eye.

Giardia and Cryptosporidium are protozoans commonly ingested by drinking from outdoor sources of water such as rivers and lakes. These little buggers get into the gastrointestinal system and can cause:

  • stomach upset
  • weakness/exhaustion
  • severe diarrhea and vomiting
  • intestinal bleeding
  • weight loss
  • lethargy

Healthy dogs can often have these parasites with no symptoms but if a pet is ill, has an underlying medical condition, or is older these protozoans can be pretty dangerous.

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Blue-Green Algae

Blooms of blue-green algae in lakes and ponds is a definite red flag! This algae is toxic to dogs and can be deadly! Blue-green algae is a microscopic bacteria often found in freshwater streams, ponds, and lakes. These bacteria can produce toxins that can affect mammals that drink the water (that means humans, dogs, livestock, etc.).

When blue-green algae is in bloom the water kind of looks blue-green in color or like pea soup. It can also look like there is green or blue paint on the surface of the water. Wind often blows these floating algae towards shore making it easily accessible to dogs and people.

The Pet Poison Helpline indicates concentrations of the blue-green algae vary throughout the year but it is most abundant during hot weather times mid to late summer and in nutrient-rich water.

Not all blue-green algae are toxic but it is impossible to tell without laboratory testing. For this reason, it is best to consider all blue-green algae as potentially toxic and to stay away!

For some animals, a very small exposure such as just a few multiples of blue-green algae contaminated water could result in fatal poisoning!

Symptoms of blue-green algae poisoning are:

  • Vomiting
  • Diarrhea
  • Black, tarry, lady stool
  • Pale mucous membranes, jaundice
  • Seizures
  • Disorientation
  • Coma
  • Shock
  • Neurological issues
  • Difficulty breathing
  • Excessive secretions (salivating, lactating, etc.)
  • Blue discoloration of mucous membranes and skin
  • Death


Various types of bacteria can be lurking in outdoor water sources contaminated with feces. These strains of bacteria include Salmonella, E. coli, Leptospira, and Campylobacter.

Mild cases of infection some of these bacteria can result in diarrhea but others could be more severe.

Leptospirosis, caused by Leptospira bacteria lurks in muddy, stagnant and/or slow-moving waters. Animals such as raccoons, opossums, skunks, rats, and mice are common carriers of this bacteria. The organism is shed in the urine of these animals and contaminates the water and soil near these water sources.

The organism is transmitted when other animals (or humans) come in contact with the contaminated soil or water. If a dog becomes infected it will then bring this bacteria home, shedding the bacteria in its urine – potentially leading to infection of members of your family.

If the infection is not caught soon enough, it can cause kidney and/or liver damage and death.

There is a leptospirosis vaccine for dogs. If you live in an environment where your dog is at higher risk or live a lifestyle where there is a higher likelihood of your dog becoming acted talk to your veterinarian about this vaccination.

E. coli can also be transmitted from pet/animal to human and vice versa.


The hot Southern states have the Heterobilharzia americana flatworm to watch out for – mainly in muddy or swampy areas and bayous.

When a dog is in contaminated freshwater this flatworm can penetrate the dog’s skin and will then migrate through the lungs (possibly causing hemorrhage) and then to the liver. After maturing into the adult form in the liver, the parasite migrates to the rectum, bladder, liver, intestines, and/or veins that carry blood from the intestines to the spleen, lungs, and liver.

Symptoms of infection are often hard to distinguish from other diseases but include:

  • Diarrhea, abdominal pain
  • Vomiting
  • Weight loss
  • Lethargy
  • Enlarged liver
  • Enlarged spleen
  • Enlarged lymph nodes
  • Anemia

The organism cannot live in humans but can cause a skin rash commonly known as swimmers itch.

Hazardous Chemicals

We, humans, are using chemicals on everything. It’s inevitable that these chemicals runoff into puddles, lakes, rivers, etc. Some of these chemicals such as pesticides can be incredibly dangerous as they build up in a body over it.

Bring Fresh Water

Summer is a time of fun and outdoor activities but it is important to be aware of the water your dog drinks. With the microscopic monsters potentially lurking in outdoor water sources, the best idea is to just bring some fresh water for your dog to drink. You can grab one of your traveling coffee cups, a bottle of water from the fridge or any sort of covered container to put water in. This way you don’t need to worry if your dog will have fresh water to drink.

There are also many drinking canisters and vessels made especially for dogs.

Here’s to safe water fun!

Has your dog ever gotten sick from drinking contaminated water?

Share your experience in the comments below.

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