written by: Dr. Muhammad Usman
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Dogs love to play in the dirt whether it’s catching a ball, leaping for a Frisbee or burying a bone. Unfortunately, contaminated soil can carry harmful organisms including Blastomyces dermatitidis (fungi) that causes blasto in dogs.
Blastomycosis is a systemic fungal infection that affects animals and humans. The fungal spores are accidentally inhaled into the lungs where they settle in the small airways. At that point, the spores reproduce and spread throughout the body.
Thankfully, blastomycosis is not contagious and dogs who do become ill have a good chance of a full recovery with medical treatment.
Is My Dog At Risk of Developing Blasto?
According to the Centre for Disease Control, these fungi thrive in moist soil. The spores are found in organic matter or plant debris. You can’t see or taste this type of fungi, but it’s out there just waiting for a dog’s (or human’s) unsuspecting sniff.
The fungal spores that cause blastomycosis is considered endemic within North America. Your dog is more likely to encounter it if you live anywhere within the midwestern, south-central, or southeastern states of the United States. Places like the Mississippi River Valleys, Ohio River Valley, and Northern Wisconsin are considered endemic geographic areas.
In Canada, this fungi can be found in wooded and damp areas throughout the eastern provinces from Ontario to Nova Scotia.
Diagnosis of Blastomycosis in Dogs
If you notice signs of blastomycosis in your dog, bring him/her to the veterinarian for a clinical examination as soon as possible. The veterinarian will check your dog for a variety of conditions and may consider blastomycosis if you live in endemic regions of the Atlantic states or Canada.
Veterinarians can perform blood work to determine whether your dog has been exposed to the organism and whether he/she has developed any antibodies to it. Unfortunately, the tests are not 100% accurate and could produce a false negative in the early stages of the disease.
If your dog is experiencing oozing from the skin, pus, or skin lesions, the veterinarian may take a biopsy for a conclusive diagnosis.
Test to Diagnose Blasto in Dogs
Blastomyces Antigen Test
In addition to the standard method of identifying Blastomyces yeasts through traditional blood work, veterinarians can also run a specific antigen test known as MiraVista Diagnostics’ Blastomyces Antigen Test.
This test is considered highly sensitive, cost effect, and rapid.
Chest radiographs (x-rays) are performed to detect abnormalities in the lung that could signify the presence of Bastomyces.
A small urine sample is taken and examined for signs of bacteria.
Enzyme Immunoassay (EIA)
An Enzyme Immunoassay is another type of antigen test whereby veterinarians look for characteristics of the blood serum that could indicate disease.
Normally, the first thing a veterinarian will do is a complete physical examination. He/she will likely listen to the lungs, examine the eyes, and look at the skin for signs of lesions.
The veterinarian may ask several questions to identify the risk of blastomycosis. These questions could include the symptom timeline, whether the dog has been in wooded areas, etc.
Treatment of Blastomycosis in Dogs
Affected animals need antifungal medications (oral or injection) that must continue for several months to fully eradicate the organism.
This particular antibiotic attachs to the cells of the infectious organism. Veterinarians will want to assess renal function throughout treatment.
During the initial care of dogs with severe or increasingly progressive blastomycosis, amphotericin B can be offered to increase the recovery rate. Combined treatment of Amphotericin B along with an antifungal medication may reduce side-effects of Amphotericin B.
Itraconazole is the most widely recommended drug to treat blastomycosis. This medication can be administered orally and has fewer side-effects than other treatment options.
Fluconazole is a medication used to treat the kinds of fungal infections that can invade the mouth, throat, esophagus, lungs, bladder, genital area, and blood.
Voriconazole has a broader range of action, enhancing its effectiveness against blastomycosis. It is used to treat more severe disease caused by yeast or other types of fungus.
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Can Humans Get Blastomycosis?
Blastomycosis is not contagious and people cannot contract the illness from their pets or from other people. It is possible, however, for humans to inhale the spores and succumb to the same signs of blastomycosis (see below).
Can Blastomycosis Be Prevented?
Unfortunately, there is no vaccination to prevent blastomycosis in dogs. Your best defense is knowledge and an understanding of the signs and symptoms. Puppies or dogs with compromised immune systems may be at higher risk.
The risk of blastomycosis can be minimized by avoiding exposure to places where the organism exists, but this may be not easy, particularly for dogs that live near these areas.
Hunting dogs are particularly vulnerable to the disease, especially if they live in an endemic region.
What Happens After a Dog Inhales the Spores?
Once a dog inhales the spores into the lungs, the fungi can take on different properies that enable it to move through the bloodstream to other organs.
· Mycelial form. This form is present and is infectious in the environment.
· Yeast. This type is present mostly in tissues that are not contagious.
These dogs may become severely sick, and clinical symptoms may differ according to the organ that is impaired.
5 Signs & Symptoms Not to Ignore
When a dog inhales the blastomycosis-causing fungal spores, they settle into the lungs and continue to multiply, exposing your dog to even more health complications.
Signs of illness include:
A temperature of more than 103F is considered a fever in a dog.
Coughing in a dog can signify anything from kennel cough to blastomycosis. Other conditions that can cause a dog to cough include heart disease, heartworms, collapsed trachea, pneumonia, or canine influenza.
In 65% – 85% of blastomycosis cases, severe lung involvement exists, sometimes resulting in:
- exercise intolerance
- shortness of breath
- cyanosis (lack of oxygen causing blueness of the skin)
- respiratory distress.
Lung lesions can often be clinically silent, but in any dogs suspected of developing blastomycosis, a thoracic radiographic test is recommended.
3. Inflamed Lymph Nodes
Lymph node inflammation occurs In 30% to 50% of infected dogs.
Lymph nodes are small masses of tissue located throughout the body. In the presence of an infectious agent, these tissues become enlarged and drain into the regional lymph nodes. This process, known as hyperplasia, occurs when white blood cells and plasma cells multiply due to a triggering substance.
In some cases, dogs with allergies will develop chronically swollen lymph nodes.
The easiest place to detect swollen lymph nodes are along the jaw or shoulder of the dog.
4. Eye Conditions
In 20% to 50% of cases, eye disease will result, with the most frequent abnormality being endophthalmitis (infection of tissue or fluid in the eye).
Early detection and care is necessary to maintain vision. Other problems arising from blastomycosis can include:
- Uveitis (eye inflammation)
- Glaucoma secondary to obstruction of the iridocorneal angle
- Corneal edema
- Optic Neuritis
- Retinal detachment
5. Skin Infections – Dermatologic Symptoms
Infected dogs will also have legions that might be oozing and wet in appearance across the nose. The infection can migrate to other parts of your dog’s body if left unchecked, causing site-specific problems. The fungal disease may migrate to one or many locations.
In 30% to 50% of affected dogs, dermatologic symptoms occur. Ulcerated skin lesions that drain pus are the most common.
Other Signs of Blasto in Dogs
In addition to the top 5 signs of Blasto in dogs noted above, there are a few other things to watch for including:
- Lack of Appetite
- Signs of pain
- Pus-filled sores on the skin
- Lameness due to bone infection.
Although less frequent, the following sites can be affected by blastomycosis:
- nasal passages
In just 3% to 6% of cases, dogs may have central nervous system disorders including depression, lethargy, neck pain, circling, cranial nerve deficits, head pressing, epilepsy, and ataxia.
Large breed hunting dogs and dogs frequently engaged in outdoor activities are at greater risk of contracting blastomycosis due the nature of their environment. However, any dog can become sick through the inhalation of spores, however.
Blastomycosis therapy is effective but may take several weeks before signs of improvement occur. The best way to help your dog is to adhere to the veterinarian’s instructions. Continue to provide any prescribed medication until the veterinarian has determined the infection has healed.
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