7 Scary Diseases Your Dog Can Get from Water

The temperature’s rising, and as summer enters full swing there’s nothing more refreshing than a dip in the water. While the vast majority of pets get through their water experience with nothing more than a wet coat, there are some organisms in common recreational water sources than can pose a health risk for your dog. We spoke to veterinarians across the U.S. and came up with a list of the seven most commonly diagnosed waterborne diseases in dogs


Leptospirosis is a common waterborne disease caused by the bacteria Leptospira. Many strains of Leptospira are found worldwide, but it is most usually found in warm areas with high rainfall. The bacteria can infect both humans and dogs, though is more common in dogs. Dogs at highest risk are those who routinely swim in stagnant bodies of water, rivers, lakes, and streams. Infection usually occurs when a mucous membrane or cut comes into contact with


With a nickname like “swamp cancer,” you know it’s nothing good. Pythiosis is a rare but severe waterborne disease caused by a fungal-like organism called Pythium insidiosum. While more commonly known as a disease of plants, pythiosis can also infect animals—with terrible results.

Found in warmer climates with plenty of standing water, pythiosis is most commonly seen in the Gulf

Blue/Green Algae

Freshwater lakes and ponds are highly inviting to a water-loving dog, but beware of bodies of water with a dense buildup of blue-green algae. Under specific environmental conditions, most often during the summer months, photosynthetic bacteria can build up—a condition known as a blue-green algae harmful algal bloom (HAB). These algae can produce toxins with severe effects on pets and people.


One of several microscopic parasites known to cause diarrhea in both dogs and humans, Giardia lamblia is an organism many dog owners are familiar with. Infected animals shed oocysts in their stool, which are hardy and can persist a long time in cool, moist environments, where they can then pass into water sources and back into a host.

Long known to be a cause of traveler’s diarrhea in humans, Giardia also causes a sudden onset of diarrhea in dogs. While both humans and dogs can be infected, it is not considered a major zoonotic disease as most human cases are caused by other humans, and is not normally passed from dogs to people.

Although some dogs may experience severe dehydration and weight loss if infected for long periods, most cases of Giardia are mild and self-limiting. Symptomatic treatment and medications can hasten recovery in affected pets.




One of the nastier waterborne diseases, cryptosporidiosis is caused by the parasiteCryptosporidium. Both the parasite and the disease are often referred to as “crypto” by those unfortunate enough to have encountered it.

Multiple species of Cryptosporidium exist in different animal species and some can cross-infect humans. The parasite is protected in the environment by a thick outer shell, which makes it able to survive the environment for a long time and even resist chlorine disinfectants. It is one of the most common waterborne diseases linked to recreational water. Dogs are infected by ingesting the infective oocysts in contaminated food or water.

Crypto causes watery diarrhea, which can lead to severe dehydration. Fortunately for dogs, most cases are mild or subclinical and are rarely life-threatening. Symptoms usually resolve within two weeks, with appropriate treatment.




Dog owners in Texas and Louisiana have an additional organism to look out for in their water loving dogs: Heterobilharzia Americana, a flatworm that is the causative agent of canine schistosomiasis. The organism penetrates the skin of the dog while swimming or wading in contaminated freshwater, then migrates through the lungs into the liver. The adults produce eggs that penetrate the GI tract, which are shed in the feces and infect the intermediate host, freshwater snails.

The clinical signs are associated with the inflammation caused by the eggs, and usually manifests as vomiting, diarrhea, weight loss, and lethargy. The eggs can be found in the feces, though treatment can be challenging due to the chronic nature of the inflammatory lesions.
While this organism does not live in humans, the parasites can burrow into the skin and cause a rash known as “swimmer’s itch.”


Owners whose dogs are prone to ear infections can usually see it coming: the shaking head, the scratching at the ear canals, the stinky head. It is one of the most common reasons dogs are brought to the veterinary clinic. While otitis externa is a disease with multiple causes, such as bacteria, yeast, and underlying allergies, one of those causative agents can be found in the water


Know the Water Before You Take the Dive

Know where your pup is putting his or her paws wet; if you wouldn’t swim in it, they probably shouldn’t either.

It’s important to keep in mind that serious illness resulting from swimming is very rare in dogs, and the most important health risk to pups in the pool or pond is still drowning. Nonetheless, if your pet shows signs of illness after a swim, don’t forget to mention recent water exposure when you take him or her in to be looked at. Keep safe and keep cool!

Image: jfmichurski / via Thinkstok http://www.petmd.com/dog/slideshows/parasites/

1 Comment

  1. momo

    As a nurse I know that not only can these organisms can infect your dogs, they can also infect you.
    With this very hot weather upon us we are all looking for ways to cool off. Please be careful. Don’t swim where these organisms thrive! You or your dog!


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