Sporotrichosis

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Sporotrichosis
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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.

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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.

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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.

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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.

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Clinical signs

• The disease has low morbidity, mortality and long
  course.
• Sporotrichosis may be grouped into 3
  formslymphocutaneous, 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.

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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.

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Postmortem Lesion

• There are no obvious lesions except cutaneous
  one.

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Diagnosis

• Field diagnosis
• It depends on history, epidemiology and clinical
  signs of the disease.

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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.

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Differential diagnosis

• This disease may be misdiagnosed clinically with
  glanders, epizootic lymphangitis and ulcerative
  lymphangitis.

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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 toxicityanorexia, 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.

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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.