History
A 5-year-old 31-kg (68.2-lb) neutered male Belgian Malinois (a retired military working dog) was evaluated because of a 1-month history of ulceration and crusting at mucocutaneous junctions, nasal planum, and ear margins and hyperkeratosis of the foot pads. Clinical signs also included hyporexia, weight loss (approx 1.8 kg [4 lb]), polyuria and polydipsia, peripheral lymphadenopathy, and splenomegaly. The dog had been deployed to Afghanistan 3 times in the past 3 years and had been retired 11 months prior to the evaluation because of repeated episodes of exertional hyperthermia.
Clinical and Clinicopathologic Findings
On physical examination, mild, superficial, cutaneous crusting was found on the tips of the pinnae (Figure 1), nasal planum and footpad margins, and mild splenomegaly was noted during abdominal palpation. Rectal temperature, pulse rate, and respiratory rate were within reference intervals. A CBC, serum biochemical panel (including concentrations of total protein, albumin, BUN, creatinine, calcium, phosphorus, sodium, potassium, total bilirubin, and glucose and activities of alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and amylase), and urinalysis were performed (Table 1). Azotemia, low urine specific gravity, and proteinuria suggested that the dog had renal disease; hyperglobulinemia and hypoalbuminemia were attributed to both inflammation and a protein-losing nephropathy. Results of a point-of-care testing kita indicated that the dog was negative for Dirofilaria immitis antigen and antibodies against Borrelia burgdorferi, Anaplasma phagocytophilum, Anaplasma plays, Ehrlichia canis, and Ehrlichia ewingii. Abdominal ultrasonography revealed mild splenic enlargement with normal architecture. Fine-needle aspirates of the spleen were obtained while the dog was sedated (with dexmedetomidine and butorphanol) and submitted for cytologic evaluation.
Photograph of a Belgian Malinois (a retired military working dog) that was evaluated because of ulceration and crusting at the mucocutaneous junctions, nasal planum, and ear margins and hyperkeratosis of the foot pads of 1 month's duration. Notice the crusted ear tips, the only lesions present when the photograph was taken after treatment had been initiated.
Citation: Journal of the American Veterinary Medical Association 251, 12; 10.2460/javma.251.12.1391
Selected serum biochemical and urinalysis data for a Belgian Malinois (a retired military working dog) that was evaluated because of ulceration and crusting at the mucocutaneous junctions, nasal planum, and ear margins and hyperkeratosis of the foot pads of 1 month's duration.
| Variable | Result | Reference interval |
|---|---|---|
| Total protein (g/dL) | 8.5 | 5.4–7.6 |
| Globulin (g/dL) | 5.7 | 1.3–3.2 |
| Albumin (g/dL) | 2.8 | 3.4–4.2 |
| SUN (mg/dL) | 137 | 9–33 |
| Creatinine (mg/dL) | 2.8 | 0.5–1.5 |
| Phosphorus (mg/dL) | 7.3 | 2.4–6.4 |
| Calcium (mg/dL) | 10.4 | 9.7–12.1 |
| Urine specific gravity | 1.017 | — |
| Urine protein-to-creatinine concentration ratio | 13.3 | < 0.5 |
Serum concentrations of sodium, potassium, total bilirubin, and glucose and activities of alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and amylase were within reference intervals.
— = Value is variable and influenced by many factors, including patient hydration status.
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→
Cytologic and PCR Assay Findings
The fine-needle aspirate specimens obtained from the dog's spleen were examined microscopically. Splenic macrophages very rarely contained a few 1- to 3-μm × 2- to 4-μm, ovoid, protozoal amastigotes with an eccentric, purple round nucleus, pale blue cytoplasm, and a distinct, thin, black, bar-shaped kinetoplast occasionally oriented perpendicular to the nucleus (Figure 2).
Photomicrograph of a fine-needle aspirate specimen obtained from the spleen of the dog in Figure 1. Splenic macrophages rarely contain a few protozoal amastigotes. Notice the eccentric nucleus (arrow) and bar-shaped kinetoplast (arrowhead). Modified Wright stain; bar = 5 μm.
Citation: Journal of the American Veterinary Medical Association 251, 12; 10.2460/javma.251.12.1391
A sample of whole blood was collected for PCR assay.b The result indicated that the dog was positive for Leishmania infantum.
Interpretation and Case Summary
Interpretation: L infantum infection in a dog with biochemical evidence of secondary renal disease.
Case summary: leishmaniasis in a retired military working dog.
Comments
Leishmaniasis (or leishmaniosis) is a zoonotic protozoal disease caused by organisms of the genus Leishmania. Humans and several other animal species are susceptible to infection, with clinical signs that vary from cutaneous lesions to more generalized, visceral disease.1–3 Infections develop in many regions of the world, including the Middle East.2 Given the travel history of the working dog of the present report, it seemed most probable that it became infected during one of its deployments to Afghanistan. Autochthonous infection cannot be completely excluded because seropositivity for antibodies against Leishmania spp is present in certain dog populations in the United States. Rare cases of leishmaniasis in dogs that have no travel history outside the United States have also been reported.4
The natural history of Leishmania spp involves a vertebrate host and a sandfly vector.5 The sandfly deposits promastigotes into the host, which then become amastigotes within phagolysosomes of host macrophages. This affinity for macrophages tends to be reflected in the organs most likely to be parasitized in systemic infections, including bone marrow, spleen, and lymph nodes. Cutaneous and mucocutaneous lesions may also develop, with less frequent development of ocular, skeletal muscular, and neurologic lesions.2
Leishmaniasis, caused by infection with L infantum, in dogs is of ten a systemic disease although subclinical infections are common.2 Clinical signs are related to the type of immune response against the organism that the affected dog is able to mount. A strong cell-mediated (T-helper cell 1) response typically favors resistance to disease, whereas an immune response predominated by humoral (or T-helper cell 2) immunity typically results in clinical signs.6 A pronounced humoral response contributes to the pathogenesis of leishmaniasis via a type III hypersensitivity reaction. Immune complex deposition can result in glomerulonephritis and polyarthritis.7 Genetic susceptibility and immune status of the host as well as parasite virulence also likely have roles in disease development.6 In humans infected with certain subgenera of Leishmania, increased parasite virulence appears to associated with increasing load of a Leishmania RNA virus.3 The presence of the viral genetic material appears to elicit a more pronounced inflammatory response by activating additional pattern recognition receptors, compared with the response induced by the Leishmania organisms alone.3 The extent to which such viral genetic material may play a role in canine L infantum infections, if any, is unknown.5
Diagnosis of leishmaniasis is possible on the basis of cytologic findings. Common sites from which fine-needle aspirate specimens are obtained for examination include skin lesions, bone marrow, enlarged lymph nodes, and spleen. Amastigotes are found within macrophages and may also be detected extracellularly. Other diagnostic testing includes serologic assessment, PCR assay, and histologic examination of affected tissue specimens.8 Results of cytologic examination of splenic aspirate specimens and PCR assay of a whole blood sample were used to finalize the diagnosis in the case described in the present report.
The retired working dog of the present report had many signs associated with systemic leishmaniasis including cutaneous and mucocutaneous lesions, lymphadenomegaly, and splenomegaly; laboratory data for the dog supported a diagnosis of kidney disease. Additionally, the serum protein abnormalities in the patient (hyperproteinemia characterized by hyperglobulinemia and hypoalbuminemia) are common in infected dogs, of which up to 72% are hyperproteinemic.9 The dog's history of exertional hyperthermia was not considered to be associated with leishmaniasis and was thought to be an unrelated medical problem.
Leishmaniasis is a known risk for military working dogs deployed to Afghanistan. Because of this risk, dog handlers in Afghanistan are provided with a topical parasiticide that contains imidacloprid, permethrin, and pyriproxfen for application on their dogs as well as a deltamethrin-impregnated collar for each dog to help repel and kill sandflies.10 Following suspected or definitive diagnosis of leishmaniasis in a dog, diagnosticians should consider a discussion with the owners regarding the zoonotic potential of this parasite, particularly the risk for any household members who may be immunosuppressed. For the dog of the present report, medical management of proteinuria was elected along with administration of an antiprotozoal agent (allopurinol). The cutaneous and mucocutaneous lesions and splenomegaly have resolved since treatment initiation.
Acknowledgments
Presented in abstract form at the C.L Davis Northeastern Veterinary Pathology Conference and Slide Seminar, Gaithersburg, Md, May 2015.
The authors thank Drs. Kari J.S. Childs and Justin C. DeVanna for assistance with the management of this case.
Footnotes
SNAP 4DX Plus testing kit, IDEXX Laboratories, Westbrook, Me.
Performed by the Vector Borne Disease Diagnostic Laboratory, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607.
References
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3. Ives A, Ronet C, Prevel F, et al. Leishmania RNA virus controls the severity of mucocutaneous leishmaniasis. Science 2011;331:775–778.
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8. Paltrinieri S, Solano-Gallego L, Fondati A, et al. Guidelines for diagnosis and clinical classification of leishmaniasis in dogs. J Am Vet Med Assoc 2010;236:1184–1191.
9. Koutinas AF, Polizopulou ZS, Saridomichelakis MN, et al. Clinical considerations on canine visceral leishmaniasis in Greece: a retrospective study of 158 cases (1989–1996). J Am Anim Hosp Assoc 1999;35:376–383.
10. Ectoparasite and heartworm control for Military Working Dogs (MWDs). Veterinary Service Activity policy memorandum. Washington, DC: US Department of Defense, 2012.
