|
Most agents of parasitic fungi exist as an organism in soil, decaying vegetation and feces, and on decaying animal
matter and tissues. The soil is the primary source of most infections, which can be acquired by ingestion, inhalation,
or even through the skin. Those fungi capable of producing infection in animals, such as blastomycosis, histoplasmosis
and coccidioidomycosis are regarded as primary systemic mycoses. Opportunistic fungi, such as aspergillosis, and
cryptococcosis, usually require a host that is debilitated, or immune-suppressed, to establish infection. PCR assays
for the detection of fungal nucleic acids may be the optimal diagnostic approach because they are more sensitive and
rapid than culture-based methods.
Blastomycosis is a fungal disease caused by Blastomyces dermatitidis and occurs primarily in
humans and dogs, but has also been described in horses, cats and even sea lions. B. dermatitidis infects
primarily young dogs that have access to the outdoors. A dog infected with blastomycosis can show many signs such as
fever, weight loss, and loss of appetite. Respiratory signs are most common, including coughing and respiratory
distress. After B. dermatitidis becomes established in the lungs, it disseminates throughout the body. The
preferred sites in the dog are skin, eyes, bones, lymph nodes, subcutaneous tissues, brain and testes. Less commonly
affected sites are mouth, nasal passages, prostate, liver, vulva and heart. Dogs with blastomycosis usually have
clinical signs that include anorexia, weight loss, cough, ocular disease or skin lesions. HealthGene Laboratory
recently began offering a DNA (PCR) test for B. dermatitidis: test code - D407; samples - whole blood
(EDTA tube), lung aspirates and a swab sample from an affected area (from eye, skin or genitals) in a sterile container.
Also, urine samples should be submitted for dogs with urinary tract or prostatic blastomycosis.
Aspergillosis is a fungal disease caused by Aspergillus species. Aspergillus is saprophytic
fungus, ubiquitous in the environment, that generally causes either nasal or pulmonary and disseminated infections in
dogs and cats. The fungus affects the nasal chambers but lesions can occur in several organs, including the eye. Of
unknown origin, infection could come from injury or surgery to the face and nose, or suppression of the immune system.
It first begins in the posterior region of the nasal cavity with a nasal discharge that may last for months before
becoming purulent and bloody. Nasal pain, sneezing and lethargy accompany these symptoms, and as the disease progresses
the fungus may destroy and replace the spongy nasal passages with masses of fungi growth. If not diagnosed and treated,
the fungi continue to grow into the cranium and the soft tissue around the eye. Diagnosis in the early stages of
invasive pulmonary aspergillosis is very difficult, as clinical and radiological signs are nonspecific and sensitivity
of fungal culture is low, even when combined with direct microscopic examination. The diagnosis of invasive aspergillosis
by molecular methods such as nested PCR has been performed successfully with blood samples from infected animals.
HealthGene’s DNA (PCR) test for Aspergillus species: test code - D409; samples - whole blood (EDTA tube) and a
swab sample from an affected area in a sterile container.
|
