Fungi are a large family that includes mushrooms. They live in soil and
organic material. Many types of fungi spread via airborne spores. Fungus
spores, which resist heat and can live for long periods without water, gain
entrance to the body through the respiratory tract or a break in the skin.
Fungal diseases can
be divided into two categories. There are fungi that affect only the skin or
mucous membranes, such as ringworm and thrush. In the
other category, the fungus is widespread and involves the liver, lungs, brain,
and other organs, in which case the disease is systemic.
Submissive urination is normal canine communication. Dogs do
it to show social appeasement. When a dog submissively urinates, he’s trying to
convey that he’s not a threat. Not all dogs submissively urinate. However, some
will urinate when they’re exceptionally excited or feeling submissive or
intimidated. Dogs who submissively urinate usually do so when greeting people
or animals (especially unfamiliar ones), during exciting events, while playing,
during physical contact, such as petting,...
Good hygiene is important when handling and caring for a dog with any fungal
infection. The risk to humans is low, but these are difficult diseases to
This disease is found in the central United States near the Great Lakes, the
Appalachian Mountains, Texas, and the valleys of the Mississippi, Ohio, and
Missouri rivers. These areas have nitrogen-rich soil that facilitates growth of
the causative fungus (Histoplasma capsulatum). Spores are found in soil
contaminated by the dung of bats, and chickens and other birds. Spores are
breathed in by dogs, people, or other animals.
In most cases, histoplasmosis is subclinical or inapparent, occasionally
producing a mild respiratory infection. There is an acute intestinal form,
however, that attacks the small bowel and colon. The principal signs are weight
loss and intractable diarrhea. A systemic form is characterized by fever,
weight loss, vomiting,
muscle wasting, coughing,
enlargement of the tonsils and other lymph nodes, as well as involvement of the
liver, spleen, bone marrow, eyes, skin, and, rarely, the brain.
The diagnosis is made by chest X-ray, blood studies, and identification of
the histoplasma organism in cytology, biopsy, or culture specimens.
Treatment: Oral anti-fungal drugs of the imidazole group, including
ketoconazole, itraconazole, and fluconazole, are particularly effective in
treating histoplasmosis that is not life-threatening. In dogs with severe
infections, amphotericin B is often combined with one of the imidazoles.
Amphotericin B is potentially damaging to the kidneys.
Coccidioidomycosis (Valley Fever)
This is the most severe and life-threatening of the systemic fungal
diseases. Coccidioidomycosis is found in dry, dusty parts of the southwestern
United States, and in California and neighboring Mexico. (Note that
coccidioidomycosis is not the same disease as coccidiosis, a disease caused by
Infection occurs by inhaling spores. Most cases are subclinical or
inapparent. A severe form affects the lungs and produces acute pneumonia. If the disease becomes systemic, it may
involve the long bones (most common), liver, spleen, lymph nodes, brain, and
skin. Affected dogs will often have a chronic
cough, weight loss, lameness, and fever.
The diagnosis is made by identifying the organism (Coccidioides immitis)in
cytology, biopsy, or culture specimens.
Treatment: Coccidioidomycosis can be treated effectively using one of the
imidazole group of antifungal agents (as described for Histoplasmosis).
Prolonged treatment for up to a year is required to try to prevent recurrence.
However, relapses are common.