(New link)The soil your dog tracks game along may contain a deadly fungus

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Blastomycosis — there's a fungus among us

The soil your dog tracks game along may contain a deadly fungus

By Joe Bartges

DVM

University of Tennessee

Microscopic view of fungal organisms identified in urine from an

adult male Labrador-cross dog with systemic Blastomycosis.

When you take your hunting dog into the field this autumn, you may be

unknowingly exposing it to a deadly fungus that resides in the very

ground your pooch is sniffing in order to trail game.

Blastomycosis is a fungal disease that can affect many organ systems

in your dog. The disease is caused by the fungus, Blastomyces

dermatitidis, which lives in the soil. Dogs most commonly become

infected by inhaling the organism. This means that dogs that spend a

lot of time sniffing the ground in an area where the organism lives

are at risk for infection.

Geographically, areas with moist soil and standing waters, such as

the Mississippi, Missouri, and Ohio River valleys, the Mid-Atlantic

States, and the Canadian provinces of Quebec, Manitoba, and Ontario,

have a high incidence of Blastomycosis. This includes areas along the

Mississippi and Ohio Rivers and the Southeast.

Although Blastomycosis can affect any dog of any age, breed, and

gender, male dogs are more frequently infected than female dogs, and

a greater percentage of female dogs survive treatment.

And, obviously, because hunting dogs spend more time sniffing

potentially infected ground than other dogs, they are at a greater

risk for contacting Blastomycosis.

Symptoms

Close up of an adult male Doberman with Blastomycosis in the eyes.

The lungs are usually the first organ system to become infected, and

the organism spreads to other organ systems including the skin, eyes,

bones, lymph nodes, subcutaneous tissues, nose, brain, and testes.

Clinical signs are vague, but usually include a fever. A cough, often

dry to begin with, is present, and may have been present for months.

The organism can spread to the skin where it causes draining tracts

or to the eyes where it can cause inflammation and blindness.

Usually, the lymph nodes are enlarged, and affected dogs often

experience weight loss to the point of emaciation. As mentioned, many

other organ systems can be involved.

Diagnosis

Diagnosis of Blastomycosis is done best by finding the organism in

aspirates of lymph nodes, in fluid from draining tracts, or in fluid

collected from the lungs.

Chest x-rays often show a " fluffy snowstorm " appearance to the lungs,

which are the fungal organisms and associated inflammation. Although

blood tests are available, they are not as good or as accurate as

finding the organism. In fact, many dogs with full-blown infection

have negative blood tests.

Because the disease is caused by a fungus, the fever and clinical

signs do not clear with antibiotic treatment. This may result in an

infected dog being given steroids to decrease the fever, which, in

turn, causes wider spread of the organism throughout the body.

Treatment

About Joe Bartges

Joe Bartges is a professor of internal medicine and nutrition and The

Acree Chair of Small Animal Research at The University of Tennessee.

He is a Diplomate of the American College of Veterinary Internal

Medicine and the American College of Veterinary Nutrition.

Treatment of Blastomycosis involves using drugs that kill the fungal

organism. Several drugs are available, but the safest and easiest

treatment is to use an antifungal drug called itraconazole. This is a

newer drug that has fewer side effects than older treatments such as

ketoconazole or amphotericin-B.

It is given by mouth one to two times a day for a few months. The

most common adverse effect of itraconazole treatment is anorexia

associated with liver toxicity.

Although the chance of curing a dog is good, some dogs die despite

aggressive treatment and supportive care. Dogs with brain involvement

usually die, but occasionally such a dog can be successfully treated.

The severity of lung disease may worsen in the first 2 to 3 days of

treatment, and is due to an inflammatory response to killing of the

organisms in the lungs. Death usually results from respiratory

failure and occurs in about one-half of the dogs with severe lung

disease during the first week of treatment.

Currently, there is no specific prevention for Blastomycosis except

awareness of the disease in your area and prompt medical attention if

clinical signs develop. You should remember that the organism lives

in the soil and that your dog picked up the infection from the soil;

therefore, your dog may be exposed again.