Felis ISSN 2398-2950

Histoplasmosis

Contributor(s): Susan Dawson, Rhea Morgan

Introduction

  • Cause:systemic fungal infection caused by Histoplasma capsulatum  Histoplasma capsulatum  .
  • Endemic in many temperate and subtropical regions of the world.
  • Organism is soil-borne; microconidia of the mycelial form are infectious
  • Signs:nonspecific debilitation, respiratory signs, ocular signs, cutaneous lesions, lameness, occasional gastrointestinal signs.
  • Diagnosis:cytology, histopathology.
  • Treatment:itraconazole Itraconazole, ketoconazole Ketoconazole, fluconazole   Fluconazole, amphotericin B Amphotericin B.
  • Prognosis:good for localized and poor for generalized infections.

Pathogenesis

Etiology

Predisposing factors

General

  • Many animals may be exposed, develop subclinical infections and spontaneously recover.
  • Overwhelming infection and compromise of the immune system may lead to disseminated infection.

Specific

  • Living in an endemic area.
  • Travel history in endemic area.
  • Most affected cats are not positive for feline leukemia or feline immunodeficiency viruses

Pathophysiology

  • Infection occurs via inhalation of microconidia. Once in the lungs, the organism converts to an intracellular yeast phase and spreads within mononuclear phagocytes to regional lymph nodes and other organs of the body.
  • Most common organs affected are the lungs, lymph nodes, bone marrow, liver, spleen, eyes and bones.
  • Organs affected occasionally are the intestines, mouth, nose, and central nervous system.
  • Organisms are engulfed by phagocytic white blood cells. If host immunity is overwhelmed the organism replicates with the reticuloendothelial system, resulting in widespread disease and death.

Timecourse

  • Incubation = 12 - 16 days.
  • Duration = weeks to months.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Aulakh H K, Aulakh K S & Troy G C (2012) Feline histoplasmosis: a retrospective study of 22 cases (1986-2009). JAAHA 4(3), 182-187 PubMed.
  • Clinkenbeard K D, Wolf A M & Cowell R L et al (1998) Feline disseminated histoplasmosis. Compend Contin Educ Pract Vet 11, 1223-1232.
  • Hodges R D, Legendre A M & Adams L G et al (1994) Itraconazole for the treatment of histoplasmosis in cats. J Vet Intern Med (6), 409-413 PubMed
  • McCalla T, Collier L & Wigton D et al (1992) Ocular histoplasmosis in the cat. Vet Pathol 29, 470.
  • Wolf A M (1988) Successful treatment of disseminated histoplasmosis with osseous involvement in two cats. JAAHA 24 (5), 511-516 VetMedResource.

Other sources of information

  • Wolf A M (1998) Histoplasmosis. In: Greene CE (ed) Infectious diseases of the Dog and Cat.2nd Ed. WB Saunders, Philadelphia, pp. 378-383.
  • Taboada J (2002) Systemic mycoses. In: Morgan RV, Bright RN, Swartout MS (eds) Handbook of Small Animal Practice. 4th Ed. WB Saunders, Philadelphia, pp.1075-1089.


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