Equis ISSN 2398-2977

Histoplasmosis

Synonym(s): Pseudofarcy Pseudoglanders Epizootic Lymphangitis

Contributor(s): Graham Munroe

Introduction

  • Cause: rare, contagious disease of equidae caused by a saprophytic soil fungusHistoplasma farciminosum.
  • Following skin trauma, insect bites or inhalation, the organism establishes chronic infections in a variety of systems.
  • Mainly seen in endemic areas especially Africa, particularly in overcrowded circumstances.
  • Signs: can lead to chronic ulcerative dermatitis, conjunctival infections and respiratory tract disease.
  • Diagnosis: laboratory confirmation by direct visualization of the organism or culture.
  • Treatment: usually euthanasia as part of slaughter/reporting control policy.

Pathogenesis

Etiology

  • Histoplasma farciminosum  Histoplasma spp  :
  • Dimorphic fungal soil saprophyte.
  • In soil: mainly mycelial form.
  • In lesions: yeast form.

Predisposing factors

General
  • Contaminated soil.
  • Traumatized skin.
  • Overcrowding:
  • Cavalry.
  • Transportation.
  • Contaminated equipment.

Specific

  • Biting flies:
  • May serve as vectors.
  • MuscaandStomoxysspecies.
  • Inhalation of organism.

Pathophysiology

  • Rare contagious disease of equidae caused by dimorphic fungusHistoplasma farciminosum  Histoplasma spp  , a saprophyte in the soil.
  • Trauma and insect bites are the major routes of infection.
  • Transmission via direct contact, contaminated equipment and biting flies.
  • Rapid spread.
  • Several forms of the disease.
  • Soil saprophyte.
  • Disease is transmitted in several ways:
  • Direct contact with organism in soil or discharges.
  • Contaminated equipment and other fomites.
  • Biting flies.
  • Route of entry determines form of the disease.
  • Dermal form occurs subsequent to contaminated soil contacting traumatized skin.
  • Biting flies feeding on ocular discharges and secretions   →   conjunctival infections.
  • Inhalation of the organism   →   the pneumonic form.
  • Rapid spread once in a group.

Timecourse

  • Incubation period ranges from several weeks to 6 months.
  • The organism is thought to persist in the environment for up to 3-4 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.
  • al-Ani F K (1999) Epizootic lymphangitis in horses - a review of the literature. Rev Sci Tech 18 (3), 691-699 PubMed.
  • Johnston P F, Reams R et al (1995) Disseminated histoplasmosis in a horse. Can Vet J 36 (11), 707-709 PubMed.
  • Rezabek G B, Donahue J M et al (1993) Histoplasmosis in horses. J Comp Pathol 109 (1), 47-55 PubMed.
  • Connole M D (1990) Review of animal mycoses in Australia. Mycopathologia 111 (3), 133-164 PubMed.
  • Cornick J L (1990) Diagnosis and treatment of pulmonary histoplasmosis in a horse. Cornell Vet 80 (1), 97-103 PubMed.
  • Gabal M A & Mohammed K A (1985) Use of enzyme-linked immunosorbent assay for the diagnosis of equine Histoplasmosis farciminosi (epizootic lymphangitis). 91 (1), 35-37 PubMed.
  • Selim S A, Soliman R, Osman K, Padhye A A & Ajello L (1985) Studies of histoplasmosis farciminosi (epizootic lymphangitis) in Egypt - Isolation of Histoplasma farciminosum from cases of histoplasmosis farciminosi in horses and its morphological characteristics. Eur J Epidemiol (2), 84-89 PubMed.
  • Soliman R, Saad M A & Refai M (1985) Studies of histoplasmosis farciminosii (epizootic lymphangitis) in Egypt - Application of a skin test ('Histofarcin') in the diagnosis of epizootic lymphangitis in horses. Mykosen 28 (9), 457-461 PubMed.
  • Goetz T E & Coffman J R (1984) Ulcerative colitis and protein losing enteropathy associated with intestinal salmonellosis and histoplasmosis in a horse. Equine Vet J 16 (5), 439-441 PubMed.
  • Blackford J (1984) Superficial and deep mycoses in horses. Vet Clin North Am Small Anim Pract (1), 47-58 PubMed.
  • Saunders J R, Matthieses R J & Kaplan W (1983) Abortion due to histoplasmosis in a mare. JAVMA 183 (10), 1097-1099 PubMed.
  • Hall A D (1979) An equine abortion due to histoplasmosis. Vet Med Small Anim Clin 72 (2), 200-201 PubMed.
  • Dade A W, Lickfeldt W E & McAllister H A (1973) Granulomatous colitis in a horse with histoplasmosis. Vet Med Small Anim Clin 68 (3), 279-281 PubMed.
  • Panciera R J (1969) Histoplasmic (Histoplasma capsulatum) infection in a horse. Cornell Vet 59 (2), 306-312 PubMed.


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