FUNGAL INFECTION:
NEW DNA TESTS FOR BLASTOMYCOSIS AND ASPERGILOSIS
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 :
test code - D409; samples - whole blood (EDTA tube) and
a swab sample from an affected area in a sterile container.
