As summer arrives, more pet owners get outdoors with their dogs to hike and explore. Unfortunately, this may result in an uptick of blastomycosis cases, a fungal disease common in the Midwest.
Dr. Jennifer Reinhart, a small animal internal medicine specialist at the University of Illinois Veterinary Teaching Hospital, wants to improve outcomes for patients with blastomycosis. Her new study evaluates the feasibility of high-flow nasal oxygen therapy as a first line of support for these patients.
What Is Blastomycosis?
“Blastomycosis is an infection caused by the fungus Blastomyces dermatitidis,” Dr. Reinhart explains. “It affects lots of different animals, although dogs in particular seem predisposed.
“Clinical manifestations of blastomycosis can affect the lungs, lymph nodes, bone, brain, skin, and all sorts of different organs, or even go systemic.”
Blastomycosis can infect humans, though it typically does so in people who have immunosuppression.
“Immunosuppression increases the risk of infection in dogs and cats as well, but we also see blastomycosis in completely healthy animals,” says Dr. Reinhart. “The major risk factor relates to where you live. The disease primarily occurs in the Midwest: Illinois, Wisconsin, Minnesota, and Michigan.”
Blastomyces dermatitidis can be found in the soil in the environments where it is endemic. It can be contracted by inhaling the fungal spores.
Signs and Treatment of Blastomycosis
While blastomycosis causes a variety of clinical signs, it tends to affect the lungs the most. “Dogs may or may not have symptoms of disease, but when they do, these can include difficult breathing, coughing, exercise intolerance, and lethargy,” Dr. Reinhart states.
“These patients have a massive amount of inflammation in their body, so they can also have severe fevers. Skin lesions, blindness, eye pain, and lameness may also be noticeable symptoms.”
Doctors diagnose blastomycosis by finding the fungus on samples taken from skin lesions, lymph nodes or lungs. These techniques use swabs or needles to take small amounts of tissue for diagnosis. A urine test can be used when minimally invasive procedures are preferred.
Treatment involves antifungal drugs, such as itraconazole or fluconazole. These drugs must be taken for many months in order to clear the infection.
“This treatment works only if the patient has survived the initial acute phase of illness,” Dr. Reinhart states. “Patients are most likely to die during the acute initial phase, when they have respiratory and neurologic signs. Usually, if you can get the pet through the first couple of weeks, they can do really well, but it takes a long time.”
High-Flow Nasal Oxygen Therapy
“The survival rate for dogs with severe respiratory disease due to blastomycosis is only about 50%,” says Dr. Reinhart, “which is unacceptable. We need to figure out what we can do to support them initially, so they can get through the worst of the clinical signs.”
The current standard of care for dogs diagnosed with blastomycosis that are exhibiting difficulty breathing involves oxygen supplementation via an oxygen tank or cage. Neither approach, however, allows for 100% oxygenation of the pet. In more dire situations, dogs are anesthetized and intubated for ventilation. Ventilation allows for 100% oxygenation at a higher flow rate but requires anesthesia for long periods, thus, is more expensive.
In her study, Dr. Reinhart takes the first step in evaluating a different kind of oxygen support, high-flow nasal oxygen therapy (HFNOT). HFNOT uses nasal cannulas. These are similar to what you might see in a hospitalized person, where a clear plastic tube rests under the nose. Two shorter tubes come out of the main tube and enter each nostril.
“The biggest benefit of HFNOT is that it not only provides oxygen but also humidifies the air. This allows us to push a lot higher flow rate than an oxygen cage,” says Dr. Reinhart.
HFNOT also allows air to reach more alveoli, the spaces in the lungs responsible for oxygen transport into the blood. This increases the amount of surface available for gas exchange.
Feasibility Study to Inform Larger Trial
HFNOT is already used for treating dogs with blastomycosis, but only after traditional oxygenation techniques fail.
“My current study tests the feasibility of a standardized protocol for HFNOT,” explains Dr. Reinhart. “This won’t prove definitively that high flow is needed or better for patients. Instead, the data we collect will help us design a larger study to examine whether patients benefit from starting HFNOT right away.”
Eligibility for the trial includes a diagnosis of blastomycosis, the need for hospitalization and oxygen therapy, and referral to the University of Illinois. The study helps subsidize costs associated with treatment and hospitalization.
Every dog enrolled in the study will receive the standard of care for the treatment of blastomycosis. One group will receive traditional oxygen therapy and, if their condition worsens, will be placed on HFNOT. The other group will receive HFNOT right away.
“We are very conscientious that this study does not in any way decrease an animal’s chances of surviving,” Dr. Reinhart assures.
To learn more about the study, read the trial announcement on the Veterinary Teaching Hospital website: https://go.vetmed.illinois.edu/BlastoTrial
By Lauren Bryan
