A golden retriever named Trout was found thin, malnourished and unwell along the Trout River in Jacksonville's Northside last December, weighing just 49 pounds. Months later, after surgery, blood transfusions and weeks of hospitalization, the 95-pound dog is alive — and his case is drawing attention to a rare, hard-to-treat disease lurking in Florida's warm, stagnant waters.
Shayna Rogers rescued Trout along the riverbank in Jacksonville in December 2025, according to News4JAX. Trout was later diagnosed with pythiosis, a rare disorder that News4JAX describes as fungal in nature and that can attack the gastrointestinal tract or cause skin lesions in dogs. He underwent exploratory stomach surgery, and getting the blood needed for his transfusions required significant effort, the outlet reports.
Trout was placed on an aggressive treatment plan under the care of Dr. Walker, a specialist based in Nassau County, per the same report. He received multiple medications along with immunotherapy, and his pythiosis numbers eventually came back lower than five — a result indicating he had turned negative. Trout will be monitored closely for the rest of his life, the station notes.
A Pathogen That Isn't Actually a Fungus
Despite being commonly called a fungal disease, Pythium insidiosum is technically a fungus-like water mold known as an oomycete. According to research documented on Wikipedia, the organism lacks ergosterol in its cell membrane — the very target that traditional antifungal drugs are designed to attack — which helps explain why standard medications so often fail against it. Because the pathogen belongs to the kingdom Stramenopila rather than true Fungi, treatment typically requires surgical or immunotherapeutic intervention rather than a simple prescription.
The threat is far from rare in Florida's freshwater systems. A University of Florida study found Pythium insidiosum in 11 of 19 tested lakes and ponds in North Florida, and in every single one of 25 sampled lakes in Central Florida, according to UF/IFAS. Standing freshwater containing aquatic vegetation poses especially high exposure risk during Florida's warm months, and ponds, swamps and wetlands are considered prime areas for exposure, per News4JAX's report.
Why the Disease Is So Often Caught Too Late
Part of what makes pythiosis so dangerous is how easily it hides from standard veterinary testing. Routine bloodwork and standard fungal cultures frequently fail to detect Pythium insidiosum, and diagnosing it definitively usually requires specialized serology antibody tests or PCR assays, according to Wag!. Because the organism isn't a fungus or bacterium, standard lab panels often misidentify the condition as gastrointestinal cancer or a simple foreign-body obstruction — delays that can prove fatal.
The gastrointestinal form of the disease carries a particularly steep mortality rate. Untreated or non-resectable intestinal cases have historically shown a median survival time of just 26.5 days, as rapid digestive tract thickening leads to tissue blockages, per research published on PubMed Central. Aggressive surgical resection with clean margins offers the best chance at remission, but only when the disease is caught early — something routine testing often fails to allow.
Trout's recovery leaned heavily on immunotherapy alongside surgery. Therapeutic vaccines developed by specialized facilities such as Pan American Veterinary Laboratories use Pythium insidiosum antigens to shift a dog's immune response from a Th2 to a Th1 pattern, improving survival odds when paired with surgery or anti-inflammatory drugs, according to the Whole Dog Journal. That approach works by retraining how the host's immune system recognizes the water mold rather than preventing exposure in the first place.
A Nationwide Blood Shortage Complicates Emergency Care
Trout's transfusions didn't come easily, and that struggle points to a broader systemic issue. Emergency veterinary hospitals across the country face a chronic shortage of canine blood products, prompting major centers like the University of Florida Small Animal Hospital to run dedicated donor programs to supply emergency transfusions, per the AKC Canine Health Foundation. A single dog blood donation can save up to three canine emergency patients, the foundation notes.
While Florida and other Gulf Coast states have long been the epicenter of pythiosis cases, the disease's reach is expanding. Cases have been documented moving northward into more temperate states including Wisconsin, New Jersey, California and Washington State, according to research cited on PubMed. Warmer seasonal temperatures and climate factors are believed to be contributing to the organism's expanding range.
Who's Most at Risk, and How Pets Get Infected
Large-breed dogs under six years old — especially retrieving and hunting breeds — are statistically diagnosed with pythiosis most frequently, largely because of their tendency toward outdoor activity in wet or swampy terrain, according to VCA Animal Hospitals. Active outdoor dogs are simply more likely to drink from or swim in standing water containing the organism's motile zoospores.
Notably, dogs don't have to go swimming to get infected. UF/IFAS research indicates dogs can contract pythiosis by eating damp grass near stagnant water or drinking from small puddles, since microscopic zoospores can cling to wet vegetation and soil in humid environments. Dogs can contract the disease through drinking or swimming in contaminated water alike, per News4JAX's reporting.
Rogers, reflecting on Trout's ordeal, advised that pet owners take dogs with vomiting, overnight diarrhea, poor appetite or a refusal of hard foods to a veterinarian without delay. She also recommended checking dogs' paws and skin for cuts, irritation or injuries after wet or muddy walks, keeping any cuts and scrapes clean and protected, and avoiding letting dogs swim in or drink from stagnant or questionable water.
Adding to the challenge, pythiosis is not a reportable animal disease in the United States, meaning local, state and federal health authorities don't systematically track infection rates or case counts, according to the Mid-South Horse Review. That means tracking relies entirely on voluntary diagnostic lab data and individual veterinary reporting — leaving the true scope of the disease, in Florida and beyond, largely uncounted.
