Small Animal Dermatology, 3rd edition

462 DISEASES/DISORDERS

 Interferon-gamma production via ELISA from whole blood.

 Quantitative PCR: highly sensitive test; proves infection but not necessarily that infec-

tion has caused clinical symptoms; use in conjunction with other diagnostics.

 Serologic diagnosis: IFAT titer of 1:64 – recombinant antigen immunoassay (where

available); false negatives estimated at 10%; false positives due to cross-reactivity to

Trypanosoma cruzi; ELISA testing – positive in cases with active disease; used to mon-

itor response to therapy.

 Cytology: identification of organism from aspirates of skin, spleen, bone marrow,

lymph node, while diagnostic, can be difficult; aspirates from nodular lesions (espe-

cially skin) are most rewarding (Figure 30.5).

 Histopathology from mucosal ulcerations (endoscopy/surgical biopsy of stomach,

intestine, and colon): histiocytic infiltrate with intracellular amastigotes.

 Renal histopathology: glomerulonephritis and tubulointerstitial nephritis.

 Dermatohistopathology from biopsy:
Macrophage infiltrate with intracellular amastigote forms in tissues from skin,

lymph nodes, liver, spleen, and kidney (Figure 30.6)

Orthokeratosis, hyperkeratosis, and follicular keratosis

Dermal granulomatous or pyogranulomatous nodular inflammation

Sebaceous adenitis

Ulceration with epidermal hyperplasia and neutrophil exocytosis; histiocytic,

lymphocytic, neutrophilic dermatitis

Predominance of macrophages and multinucleated giant cells containing organ-

isms in nodular dermatitis

Subcorneal neutrophilic pustules with or without acantholytic keratinocytes

Nodular to diffuse pyogranulomatous dermatitis without multinucleated giant

cells

Histopathologic changes may occur in “normal-looking” skin of infected dogs

demonstrating systemic disease

Amastigote load tends to be highest in preferential feeding areas of the vector.

THERAPEUTICS

 Treatment aimed at reducing parasite load and resolving secondary clinical disease;

inform client that organisms will never be eliminated; relapse is inevitable.

 Treatment controversial due to potential zoonotic transmission of organism to human

beings from persistently infected dogs; documented cases reportable to the CDC.

 Prognosis very poor in emaciated, chronically infected animals.

 Pentavalent antimonial therapy provides increased quality of life but rarely cures.

 Cats: surgical excision of individual dermal nodules.

 Begin pentavalent antimonial drugs at lower doses in seriously ill patients.

 Prognosis depends on degree of renal insufficiency at the onset of treatment.

 Monitor therapy with frequent CBC, serum albumin, globulin, and creatinine, and

urine protein:creatinine.