Florida issues ‘Swamp cancer’ warning for dog owners after pet nearly dies

A Florida woman and a veterinarian are warning dog owners to keep their pets away from warm, stagnant water after an Australian Shepherd mix spent nearly a year fighting a rare and potentially deadly disease commonly known as “swamp cancer.”

FOX 13 Tampa Bay reporter Ariel Plasencia shared the story of Summer, an active young dog from Bartow who developed severe vomiting and bloody diarrhea after drinking from a neighborhood lake in July 2025.

Months of testing, a hospital stay, an ultrasound, and a biopsy eventually led veterinarians to diagnose Summer with pythiosis, an illness caused by a fungus-like organism found in swampy water and wet soil.

Summer survived, but her owner, Katelynn Wedeman, said the disease came dangerously close to killing her.

“I just don’t want another pet owner to ever hear the word ‘pythiosis’ before it’s too late,” Wedeman told Plasencia. “Because it was really almost too late for her.”

Summer Became Seriously Ill After Drinking Lake Water

Summer normally spends her time chasing the children in her family, practicing agility exercises, and taking part in dock diving.

That energetic life changed after she drank from a lake near the family’s Bartow home.

Wedeman said the dog soon began vomiting, passing bloody diarrhea, and struggling to keep water down. Her condition grew serious enough that the family knew they were dealing with more than a routine stomach problem.

“I was crying,” Wedeman recalled. “I was like, ‘Something’s wrong. Something’s wrong.’”

Summer was taken through months of medical appointments and tests as veterinarians tried to identify the source of her symptoms.

The final diagnosis was a condition Wedeman had never heard of.

“That was the first time I ever heard that word,” she said of pythiosis.

The unfamiliar name is part of what makes the disease so frightening. Many owners know to watch for toxic algae, parasites, or bacteria in outdoor water, but pythiosis may not come to mind until a dog is already severely ill.

What Is ‘Swamp Cancer’?

Pythiosis is caused by a fungus-like organism that thrives in warm, wet environments, particularly stagnant ponds, swamps, retention areas, and muddy shallow water.

Dogs may become infected by swallowing contaminated water or by swimming with cuts or open wounds that allow the organism to enter the body.

Plasencia reported that gastrointestinal pythiosis can produce large masses inside a dog’s intestinal tract, creating symptoms that may resemble cancer or another major digestive illness.

That appearance is why the disease is sometimes called swamp cancer, although the organism is not a true cancer.

Dr. Bob Encinosa, owner of Boyette Animal Hospital in Riverview, said the masses can look like enormous tumors.

“What you see often looks like a massive tumor,” Encinosa told FOX 13.

Without tissue testing and biopsies, he said some cases may be mistaken for growths that cannot be removed.

“And unless the owners are willing to pursue histopathology and take biopsies and so forth, it often, I think, goes undiagnosed as just an unresectable mass,” he explained.

That possibility makes an early and accurate diagnosis especially important. A dog may appear to have an ordinary digestive illness at first, while the disease continues causing damage inside the body.

Disease Is Extremely Difficult to Treat

Encinosa described pythiosis as “ridiculously difficult to treat.”

Unlike many fungal infections, it does not respond well to most common antifungal medications.

“Surgical excision is the method of choice,” he said, although surgery may still need to be followed by immunotherapy or chemotherapy in an attempt to destroy the remaining organism.

Boyette Animal Hospital had already treated one fatal case during 2026, according to Plasencia. That dog had reportedly become infected after swimming in a retention pond.

The disease’s resistance to medication leaves owners and veterinarians with fewer options, particularly if a mass has spread or cannot be removed completely.

This is one reason the early symptoms should not be dismissed when they become severe or persistent. Vomiting and diarrhea are common in dogs, but bloody stool, an inability to hold down water, rapid decline, or symptoms that do not improve deserve urgent attention.

Summer’s survival appears to have depended on her family continuing to search for an explanation rather than accepting that she simply had an upset stomach.

Warm, Muddy Water Carries the Greatest Risk

Encinosa advised owners to avoid letting dogs enter warm, shallow, muddy water, especially during Florida’s hottest months.

“If you can touch the bottom, don’t put your head under the water,” he said.

The veterinarian explained that many of the dangerous organisms live in the mud at the bottom. When dogs, swimmers, or changing water conditions stir up that mud, the organisms may move into the surrounding water.

“A lot of these organisms are residing in the mud at the bottom,” Encinosa said. “And when things get stirred up, that’s when they become dangerous.”

Neighborhood lakes and retention ponds may look inviting to an overheated dog, particularly when temperatures rise. Yet those small, slow-moving bodies of water can provide ideal conditions for organisms that would be less concentrated in cleaner, colder, or faster-moving water.

Owners should also remember that drinking is not the only possible route of infection. A dog with a cut on its paw, leg, or body may face risk simply by wading or swimming in contaminated water.

Preventing access is far easier than treating the disease once it takes hold.

A Year of Medication and Recovery

Summer’s treatment continued for almost a full year.

Plasencia reported that the dog required a large number of medications before finally reaching the end of her intensive treatment plan.

Even with that progress, Summer’s care is not completely finished. She is expected to remain on immunotherapy for the rest of her life.

Her family also plans to keep her far away from stagnant water going forward.

Summer has been able to return to many of the activities that once defined her life, including agility work, playing with the children, and dock diving in controlled conditions.

Her recovery is encouraging, but it also shows how much effort, time, and medical care may be required after exposure from something as ordinary as a drink from a neighborhood lake.

One moment near the water led to a year of fear and treatment.

Owner Hopes Other Families Learn From Summer

Wedeman chose to share Summer’s story because she did not want other pet owners to learn about pythiosis only after their dogs became critically ill.

Her warning is simple: stagnant water should not be treated as harmless just because it looks calm or familiar.

A pond located near a home may feel safer than an unknown wilderness area, but dangerous organisms do not depend on how ordinary the setting appears.

Plasencia’s FOX 13 report also offers a useful reminder that outdoor water hazards change with the season. Hot weather can warm shallow ponds, lower water levels, and create conditions in which harmful organisms become more concentrated.

Dog owners should carry clean drinking water during walks, stop pets from drinking from ponds or puddles, and inspect them for wounds before allowing any swimming.

They should also contact a veterinarian quickly if serious digestive symptoms begin after exposure to lakes, retention ponds, swamps, or muddy water.

Summer’s case had a much better ending than it might have. She survived, returned to an active life, and is completing the most demanding part of her treatment.

Her family now hopes that the story of how close they came to losing her will persuade other owners to pause before letting a dog jump into warm, stagnant Florida water.