Sporotrichosis
Definition
• It is a non contagious chronic infectious
disease of equine, humans and other
domestic animals, caused by Sporothrix
shenki, characterized by cutaneous
nodules and ulcers on the limb with or
without lymphangitis and lymphadenitis.
Etiology
• Sporotrichosis is caused by Sporothrix
schenckii, a dimorphic fungus, which form
single walled, spherical, oval or cigar
shape spores. It grow on sabouraud
dextrose agar.
• Predisposing factors:
▫ Cutaneous wounds and presence of the
animals in muddy unhygienic stables.
Epidemiology
• Distribution: S. schenckii can be found worldwide and present in
Egypt.
• Animal susceptibility: Sporotrichosis occurs most often in
horses. Cases have also been seen in cats, dogs, rodents, cattle,
goats, swine, mules, camels, non-human primates, birds, and
various wild animals including foxes.
• Seasonal incidence: The disease increase during winter seasons.
• Mode of transmission:
• The pus discharged from the lesions of the infected animals is the
main source of contamination of beddings, grooming, utensils and
other fomites.
• Infection occurs through cutaneous wounds or abrasions either by
direct contact or indirect contact with contaminated surroundings
and fomites.
Pathogenesis
• The organism gain access through wounds and
abrasions in the skin, invades the subcutaneous
tissue causing nodular ulcerating lesions, and then
spreads through lymphatics.
• Finally, the nodules ulcerate and discharge pus.
• Inflammation of the lymph vessels and lymph nodes
may be observed.
• Involvement of bones and visceral organs with fetal
termination is rare, but has been reported in dogs
and horses.
Clinical signs
• The disease has low morbidity, mortality and long
course.
• Sporotrichosis may be grouped into 3 forms—
lymphocutaneous, cutaneous, and disseminated.
• The lymphocutaneous form is the most common.
▫ Small, firm dermal to subcutaneous nodules, 1-3 cm in
diameter, develop at the site of inoculation (usually
about fetlock).
▫ As infection ascends along the lymphatic vessels,
cording and new nodules develop.
▫ Lesions ulcerate and discharge a serohemorrhagic
exudate.
▫ Although systemic illness is not seen initially, chronic
illness may result in fever, listlessness, and
depression.
Clinical signs
• The cutaneous form remains localized to the site
of inoculation, although lesions may be
multicentric.
• Disseminated sporotrichosis is rare but
potentially fatal and may develop with neglect of
cutaneous and lymphocutaneous forms.
Infection develops via hematogenous or tissue
spread from the initial site of inoculation to the
bone, lungs, liver, spleen, testes, GI tract, or
CNS.
Postmortem Lesion
• There are no obvious lesions except cutaneous
one.
Diagnosis
• Field diagnosis:
▫ It depends on history, epidemiology and clinical
signs of the disease.
Diagnosis
• Laboratory diagnosis:
•
• Samples: Pus, blood and serum sample.
• Laboratory examinations:
• Direct microscopic examination of stained pus smear to detect cigar
shape spores.
• Isolation of the organism on sabaurods dextrose agar and identification
of the organism from colony morphology and biochemical reactions.
• FAT, it gives positive result with samples of infected animal.
• Animal inoculation, inoculation of mice I/P with pus material of
infected animal, local lesion (granuloma) can be observe after 3 w of
inoculation and peritoneal exudate contain cigar-shape fungi in
peritoneal cavity.
• Serological test as latex agglutination test.
Differential diagnosis
• This disease may be misdiagnosed clinically with
glanders, epizootic lymphangitis and ulcerative
lymphangitis.
Treatment
• Systemic treatment with iodides such as potassium
iodide orally (0.5-1 mg/kg, bw) as 1-2 dose daily for
7 days or sodium iodide I/V (40 mg/kg, bw) as 2-5
doses then one dose daily till cure.
• During treatment, the animal should be monitored
for signs of iodide toxicity—anorexia, vomiting,
depression, muscle twitching, hypothermia,
cardiomyopathy, cardiovascular collapse, and death.
The dose of iodides may be stopped or reduced if
signs of iodism appear.
• Local application of iodides daily to ulcers after
evacuation of contents.
Control
• Early diagnosis, isolation and treatment of
infected animals,
• Prophylactic treatment of all cutaneous wound
and abrasions and
• Adequate hygiene to prevent spread of infection.