Blastomycosis

What is Blastomycosis?

Blastomycosis is a fungal disease caused by the organism Blastomycosis dermatitides. It is primarily seen infecting dogs, humans and rarely, cats.

How does your pet get the infection?

Your pet can become infected by inhaling the organism from the soil. It is not known to be transmitted from individual to individual or from animals to humans. Each individual acquires the infection independently and directly from the environment. It is common to see hunting dogs that root and dig in the ground become infected. New house or cottage building or renovations, or soil excavations, may also expose infected soils from deep below the ground which could increase the chance of your pet getting the infection.

Where is Blastomycosis found?

Blastomycosis can be found in soils extending from the Mississippi-Missouri-Ohio River basin, which reaches up into the Lake of the Woods area. These areas include Sioux Narrow, Dryden, Red Lake, Kenora and surrounding areas. Blastomycosis grows best during warm moist weather and in acidic soils such as occurs in cedar swamps. There is not lab available to test soils for the organism because handling of infected soils can cause human infections.

What are the signs of the disease?

Clinical sings may be multiple. Since the route of the infection is usually by inhalation, the most common signs first seen involve the lungs. These include a chronic, persistent cough, dyspnea (trouble breathing), lack of exercise tolerance, weight loss, persistent or intermittent fever, poor appetite or anorexia (not eating at all) and depression.

If the infection moves to other parts of the body, signs may also include lameness, bone swellings, skin sores, skins swellings, enlarged lymph nodes and blindness.

How is Blastomycosis diagnosed?

The diagnosis is based on the history, the clinical signs, the animals’ habits (i.e. likes to dig, hunts) and where the animal lives or has visited over the past few months. Veterinary tests include chest radiographs (pneumonia), direct smears from the throat or sores, fine needle biopsy of enlarged lymph nodes or swellings, transtracheal washes and serological blood tests.

What treatment is given?

Treatment is most beneficial to animals that are still able to stand and still have an appetite, with a relatively limited degree of debilitation. Three treatments are available which we utilize in various combinations at this time:

1) Amphotericin B is given intravenously three times per week over a period of three weeks until the therapeutic level is reached. The advantage of Amphotericin B is that it is a fungicidal (kills the fungus). The disadvantage in using this drug is that it is very toxic to the kidney and can result in kidney failure and death. It can also cause temporary depression. After Amphotericin B injections are completed, a second drug called Ketoconazole may be given for one to two months to guard against relapse.

2) Ketoconazole is an oral tablet that is fungal static. This means that is prevents the organism from growing but it does not directly kill it. Instead, we rely on the animals’ immune system to kill and clean out the organism while the drug prevents it from multiplying. Ketoconazole is less toxic than Amphotericin B but more side effects are seen. It causes depression and gastric upset, which may be alleviated by giving the medicine with food. Long-term use can occasionally cause permanent cataracts and temporary hair coat changes. The dosage depends on the size of the animal. We usually start at a low dose to minimize side effects and gradually increase the dosage to therapeutic levels. The treatment lasts one month past the cessation of the disease clinical signs and upon obtaining a clear chest radiograph. This can be anywhere from three to six months or up to one year. The cost of the drug is a drawback in that costs can mount as treatment time increases. [80-85% recovery rate]

3) 3) Itraconazole Sporanox is a new fungicidal drug which has been released in the United States and Canada. It has the least amount of side effects on the animal, the shortest treatment time and is, so far, proving to have quite a good cure rate. It can cause appetite suppression and vasculitis. The major disadvantage to using this drug is its extremely high cost. Although there may be a large financial outlay initially, the advantages include shorter treatment time, fewer side effects and a good cure success rate which make it the least costly in the end. [95 % recovery rate]

In any of the treatments chosen the owners must be prepared to dedicate themselves to the palliative care of their animal. This may involve special dishes and hand feeding or even force-feeding their pet if necessary. The owner must understand that this will take a great deal of time and energy on their part.

What is the prognosis?

Prognosis for animals with this disease is guarded. Recovery is dependent upon how advanced the disease is within the animal and how quickly the diagnosis can be made and treatment initiated. The type of treatment chosen may also play a part in the chance for survival. Early diagnoses and early treatment are the main keys to success.

What if treatment is not desired or successful?

If the animal is not responding to treatment or if the owner has opted for no treatment, then euthanasia is advised. The animal cannot be buried because their remains will re-infect the soil and help to spread the disease. It is for this reason that cremation is enforced. The ashes may then be buried by the owners if so desired.