Leishmaniasis

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Leishmaniasis

 

The signs of Leishmaniasis reflect the distribution of the parasite. They commonly include skin problems (especially around the head and pressure points), enlarged lymph nodes and spleen, eye problems, weight loss, lethargy, reduced appetite, nose bleeds, and vomiting and diarrhea.

 

Cats – often localize in skin.

Dogs – invariably develop the visceral disease; renal failure is the most common cause of death.

Incubation period—1 month to several years.

 

SIGNALMENT

Dogs – virtually all develop visceral (systemic), disease; 90% also have cutaneous involvement; no sex or breed predilection.

Cats – cutaneous disease (rare); no sex or breed predilection.

 

SIGNS

Visceral

Exercise intolerance; weight loss, anorexia, diarrhea, vomiting, epistaxis, and melena; lymphadenopathy and cutaneous lesions (90% of cases); emaciation; signs of renal failure (polyuria, polydipsia, vomiting) possible; neuralgia, polyarthritis, polymyositis, osteolytic lesions, and proliferative periostitis rare; fever and splenomegaly (30%); death is usually due to chronic proteinuric nephritis progressing to end-stage kidney disease, nephrotic syndrome, and/or systemic hypertension.

 

Cutaneous

Dogs-  hyperkeratosis is the most prominent finding; excessive epidermal scale with thickening, depigmentation, and chapping of the muzzle and footpads; hair coat dry, brittle, hair loss, intradermal nodules, and ulcers; abnormally long or brittle nails in some patients.

Cats – cutaneous nodules (especially on the ears) usually develop.

 

CAUSES & RISK FACTORS

Travel to endemic travel, where dogs are exposed to infected sandflies.

Transmission by blood transfusion, in utero, and direct contact can occur.

 

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

  • Visceral—blastomycosis; histoplasmosis; systemic lupus erythematosus; metastatic neoplasia; distemper; vasculitis.
  • Cutaneous—other causes of hyperkeratosis.
  • Skin biopsy—hyperkeratotic and nodular lesions; the existence of organisms confirms the diagnosis.
  • Hyperglobulinemia—differentiate from chronic ehrlichiosis and multiple myeloma.

 

CBC/BIOCHEMISTRY/URINALYSIS

  • Hyperproteinemia with hyperglobulinemia—nearly 100% of cases.
  • Hypoalbuminemia—95% of cases.
  • Proteinuria—85% of cases.
  • High liver enzyme activity—55% of cases.
  • Thrombocytopenia—50% of cases.
  • Azotemia—up to 45% of cases.
  • Leukopenia with lymphopenia—20% of cases.

 

OTHER LABORATORY TESTS

  • Serologic diagnosis by IFA or ELISA available—most tests give cross-reaction to Trypanosoma cruzi; differentiate based on clinical signs, history, and the likelihood of exposure. Rapid in-house immunochromatographic tests are also available.
  • PCR—particularly sensitive on bone marrow, lymph nodes, spleen, and skin, but also used to assess blood, bodily fluids, conjunctival scrapings, and histopathologic specimens.

 

DIAGNOSTIC PROCEDURES

  • Cultures—skin, spleen, bone marrow, or lymph node biopsies or aspirates; by the Centers for Disease Control and Prevention.
  • Cytology and histopathology with immunohistopathology—identify intracellular organisms in biopsies or aspirate specimens (listed above).

 

PATHOLOGIC FINDINGS

  • Cell infiltration (mainly histiocytes and macrophages) and characteristic intracellular amastigote form especially in the skin, lymph nodes, liver, spleen, and kidney.
  • Mucosal ulcerations—stomach, intestine, and colon occasionally found.

 

TREATMENT

Outpatient.

  • Emaciated, chronically infected animals—consider euthanasia; prognosis very poor.
  • Diet—high-quality protein; special for renal insufficiency if necessary.
  • Cats—single dermal nodule lesions are best surgically removed.
  • Advise client of potential zoonotic transmission of organisms in lesions to humans.
  • Inform the client that organisms will never be eliminated, and relapse, requiring treatment, is inevitable.

 

CONTRAINDICATIONS/POSSIBLE INTERACTIONS

  • Seriously ill dogs—start antimonial drugs at lower doses.
  • Renal insufficiency—treat before giving antimonial drugs; prognosis depends on renal function at the onset of treatment.
  • Amphotericin B—nephrotoxicity can occur.

 

FOLLOW-UP

  • Treatment efficacy—monitor by clinical improvement and identification of organisms in repeat biopsies.
  • Relapses—a few months to a year after therapy; recheck at least every 2 months after completion of treatment; identified by detecting a rise in blood globulin levels or reappearance of clinical signs.
  • The prognosis for a cure—guarded.

 

MISCELLANEOUS

ZOONOTIC POTENTIAL

  • Leishmaniasis is a notifiable disease reportable to the CDC.
  • Advise owner of zoonotic potential.

 

ABBREVIATIONS

ELISA = enzyme-linked immunosorbent assay

IFA = immunofluorescent antibody test

PCR = polymerase chain reaction

 

Visit your veterinarian as early recognition, diagnosis, and treatment are essential.

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