JPC SYSTEMIC PATHOLOGY
Signalment (JPC Accession # 1752289): Mixed breed dog
HISTORY: Tissue from a mixed breed dog with a two-year history of chronic dermatitis with pruritus. Before death the animal had periodic epistaxis.
HISTOPATHOLOGIC DESCRIPTION: (U-P03a) Kidney: Multifocally expanding the renal interstitium, separating and surrounding cortical tubules and glomeruli, and expanding the pelvic subepithelial connective tissue, are numerous plasma cells, macrophages, fewer lymphocytes and neutrophils, and occasional homogenous eosinophilic material (proteinaceous fluid). Macrophages are often expanded by numerous intracytoplasmic 3-4 um round to oval protozoa, which contain 1-2 um diameter, basophilic nuclei with adjacent perpendicular basophilic kinetoplasts (amastigotes). Multifocally glomeruli have one or more of the following changes: increased numbers of mesangial cells and glomerular capillary loops thickened by eosinophilic, homogenous material (membranoproliferative glomerulonephritis); amastigotes within mesangial cells or macrophages; glomerular tufts adhered to the parietal epithelium (synechia); cuboidal parietal epithelium lining Bowman’s capsule (hypertrophy); surrounded by marked amounts of fibrous connective tissue (periglomerular fibrosis); and uriniferous space expanded by variable amounts of eosinophilic homogenous material (proteinosis). Multifocally, proximal tubules and collecting ducts have one or more of the following changes: lined by attenuated epithelium; mildly ectatic and contain moderate amounts of proteinaceous material (tubular proteinosis); rarely contain a basophilic, granular material (mineralization). Multifocally, the subepithelial pelvic connective tissue is expanded by the previously described inflammatory cells including infected macrophages and the overlying epithelium is mildly hyperplastic with occasional transmigration by neutrophils.
U-P03b: Kidney (Giemsa): There is multifocal positive purple staining of amastigote nuclei and adjacent kinetoplasts.
MORPHOLOGIC DIAGNOSIS: Kidney: Nephritis, interstitial, lymphoplasmacytic and histiocytic, multifocal, moderate, with membranoproliferative glomerulonephritis, and myriad intrahistiocytic amastigotes, etiology consistent with Leishmania sp., mixed breed, canine.
ETIOLOGIC DIAGNOSIS: Renal leishmaniasis
CAUSE: Leishmania sp.
CONDITION: Visceral leishmaniasis
SYNONYMNS: Kala-azar, Dum dum fever
- Chronic disease caused by obligate intrahistiocytic, diphasic (promastigotes, amastigotes) protozoan parasite
- Affects lymph nodes, skin, spleen, kidney, liver, bone marrow, gastrointestinal tract, and lungs
- Transmission by:
- Bite of female sandfly
- Rhipicephalus sanguineus tick has been experimentally infected, but this has not been found to occur naturally
- Reports of transmission by blood transfusions and vertical transmission
- There are three forms of the disease:
- Cutaneous leishmaniasis
- infantum, L. tropica, L. mexicana, L. braziliensis
- Sandfly bites around muzzle, ears, eyes
- Long standing lesions have “typical” granulomas
- Mucocutaneous leishmaniasis
- Central America
- Animals not frequently infected in nature
- Nodular mucosal leishmaniasis affecting the oral cavity, tongue, nose and penis have been reported in the dog
- Visceral leishmaniasis
- infantum (L. chagasi), L. donovani
- Wide geographic distribution
- Mimics histoplasmosis
- Canine leishmaniasis used to be a sporadic disease in U.S.; it is now considered endemic because, since 1999, there have been outbreaks of infantum (chagasi) primarily in foxhounds in U.S. and Canada
- German shepherd dogs, boxers, Dobermans and long-coated cocker spaniels may be predisposed; collie breeds and Ibizian hounds may be resistant
- Skin lesions occur in >80% of dogs with visceral involvement
- Zoonotic potential - Dogs are the primary reservoir for human infection
- Virulence factors:
- Activates complement, leads to C3b deposition on parasite’s surface
- Prevents membrane attack complex from inserting into the parasitic membrane
- Once inside macrophage, it protects the parasite within the phagolysosome by scavenging oxygen free radicals and inhibiting lysosomal enzymes
- Cleaves complement and lysosomal enzymes
- Proton-transporting ATPase
- Maintains parasite pH at 6.5 even while in phagolysosome with pH of 4.5
- Severity of disease is determined by the host immune response
- Th-1 response > elimination of Leishmania by activated macrophages (TNF-a, IL-2 and IFN-y mediate protective response)
- Th-2 response > prevents effective killing of Leishmania organisms; +/- antigen/antibody complexes
- Progression of disease is characterized by the down regulation of Th-1-related cytokines (IFN-y, TNF-a) and genes encoding IL-17A, iNOS and IL-10 in the spleen and liver
- Infected macrophages are also lysed by CD8+ cytotoxic T cells in a histocompatibility complex-restricted process that can be suppressed in symptomatic dogs with a high parasitic load; Chronic disease can lead to T-lymphocyte depletion, with proliferation of B cells
- Autoantibodies > immune-mediated thrombocytopenia and anemia
- Circulating immune complexes (CIC) > vasculitis, polyarthritis, uveitis, glomerulonephritis
- Chronic proteinuric nephritis due to CIC deposition in kidneys is the leading cause of death in dogs with leishmaniasis
- Sandfly takes a blood meal from infected host > ingests mononuclear cells containing amastigotes (Leishman‑Donovan bodies) > amastigotes multiply by binary fission in the mid-gut > transform into flagellated promastigotes > sandfly feeds and injects many promastigotes into host (transmission) > phagocytized by macrophages > revert to non-flagellated amastigotes (leishmanial form) > begin multiplying by binary fission locally (cutaneous/ mucocutaneous forms) or throughout reticuloendothelial system (visceral form) > rupture out of macrophage > infect new cells
- Transmission may also occur vertically or via blood transfusion
- Prolonged incubation period of 3 months – 7 years after sandfly bite
TYPICAL CLINICAL FINDINGS:
- Asymptomatic proteinuria, which often is the only indication of renal involvement, may predispose to arterial thromboembolism, muscle wasting and cachexia
- Nonspecific: fever, lethargy, cachexia, poor body condition, rough haircoat
- Nonpruritic, exfoliative generalized dermatitis, most severe in facial, aural, and periocular regions, and onychogryphosis
- Secondary infections are common (demodicosis, pyoderma, pneumonia)
- Coagulopathy – epistaxis due to secondary immune-mediated thrombocytopenia
- Systemic hypertension
- Proteinuria, azotemia, elevated creatinine
- Anemia—hemolytic, regenerative, with increased serum iron and spherocytes
- Elevated total protein, hypergammaglobulinemia (IgG, polycolonal or monoclonal), hypoalbuminemia
- Nephrotic syndrome (proteinuria, hypoalbuminemia, hyperlipidosis, peripheral edema)
TYPICAL GROSS FINDINGS:
- Alopecia, exfoliative, nodular, or papular dermatitis, onychogryphosis, ulcers around muzzle, ears, eyes
- Splenomegaly, dark brown to black on capsular surface
- Hepatomegaly, dark brown, possibly with numerous granulomas
- Kidneys darker than normal
- Gastrointestinal ulceration; enteritis / colitis
- Soft red bone marrow
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Kidney: Glomerulonephritis from immune complex deposition in vessel walls
- Glomerulosclerosis (without IC deposition), mesangioproliferative glomerulonephritis, membranoproliferative glomerulonephritis
- +/- nonsuppurative interstitial nephritis, amyloidosis, and intrahistiocytic amastigotes
- Liver: numerous granulomas
- Splenic follicles are hyperplastic (early) or atrophied (advanced)
- Widespread plasmacytic, lymphocytic, or histiocytic inflammation, most severe in spleen, liver, lymph nodes, bone marrow
- Atrophic myositis of masticatory muscles
- A recent study found that cardiac lesions, such as lymphoplasmacytic or granulomatous myocarditis (especially in the right atrium), myocardial necrosis and increased interstitial collagen, are prevalent in dogs with leishmaniasis (even if there are no clinical signs of cardiac disease)
- Intrahistiocytic amastigotes
- Ovoid to round, 2.5 – 5 um long, 1.5 to 2.0 um wide
- Kinetoplasts (giant mitochondria) perpendicular to nucleus (red to purple on Giemsa)
- Can occasionally be seen in other leukocytes, endothelial cells or fibroblasts
- Skin: Granulomatous perifolliculitis and perivascular dermatitis
- Exfoliative dermatitis- orthokeratotic hyperkeratosis
- Papular dermatitis- nodular to diffuse pyogranulomatous dermatitis
- Onychogryphosis- lichenoid mononuclear dermatitis
- Often within parasitophorous vacuole, ovoid amastigote with a double membrane-bound nucleus
- Kinetoplast is perpendicular to nucleus
- Flagellum in a flagellar pocket near nucleus
ADDITIONAL DIAGNOSTIC TESTS:
- Cytology or histology to demonstrate amastigotes
- Serology - Seropositive animals may not show clinical signs of illness but may still act as a reservoir for human infection; there is controversy over the relevance of a positive titer
Organisms that may appear similar microscopically:
- Trypanosoma cruzi (amastigote form) – intracellular, within pseudocysts primarily in muscle, especially heart muscle; multiply by binary fission; round to oval, 1.5-4um, contain a nucleus, and a rod-like kinetoplast parallel to nucleus, no free flagellum or undulating membrane
- Histoplasma capsulatum – intracellular; up to 10 cytoplasmic 2 X 3 um in diameter yeast characterized by a clear, 1 um wide halo surrounding a 1 um basophilic center; replication is by narrow-based budding
- Histoplasma capsulatum var. farciminosun – see above
- Toxoplasma gondii – intracellular; numerous 2-4 μm, round, basophilic, surrounded by a thin clear ring (tachyzoites within a pseudocyst)
- Neospora caninum – intracellular; 2 x 5 um lunate zoites arranged in small clusters (tachyzoites) and within cysts (bradyzoites); cysts are up to 40 um and have a thick eosinophilic hyalinized wall
- Neorickettsia helminthoeca – intracellular; gram negative; organisms are 0.3-2.0 um, pleomorphic cocci or rods
- Wild rodents are a reservoir host for cutaneous and mucocutaneous forms in humans
- Wild and domestic dogs are main reservoirs for the visceral form in humans
- Cats, horses, and other mammals are susceptible but are considered secondary or accidental hosts
- Dogs: Leishmania amastigotes have been found in the cytoplasm of neoplastic cells (fibrosarcoma, T-cell lymphoma, adrenocortical adenoma)
- Aresu L, Benali S, Ferro S, et al. Light and electron microscopic analysis of consecutive renal biopsy specimens from Leishmania-seropositive dogs. Vet Pathol. 2013;50(5):753-60.
- Baneth G, Solano-Gallego L, Mendez S. Leishmaniases. In: Greene CE, ed. Infectious Diseases of the Dog & Cat. 4th ed. St. Louis, MI: Elsevier Saunders. 2012;734-749.
- Brachelente C, Muller N, Doherr MG, et al. Cutaneous leishmaniasis in naturally infected dogs is associated with a T helper-2-biased immune response. Vet Pathol. 2005;42(2):166-75.
- Costa FAL, Goto H, Saldanha LCB, Silva SMMS, Sinhorini IL, et al. Histopathologic patterns of nephropathy in naturally acquired canine visceral l Vet Pathol. 2003;40(6):677-84.
- Ferri F, Zini E, Auriemma E, et al. Splenitis in 33 dogs. Vet Pathol. 2017 Jan;54(1):147-154.
- Ferro S, Palmieri C, Cavicchioli L, et al. Leishmania amastigotes in neoplastic cells of 3 nonhistiocytic canine tumors. Vet Pathol. 2013;50(5):749-752.
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- Rosa FA, Leite HAC, Braga ET, et al. Cardiac lesions in 30 dogs naturally infected with Leishmania infantum chagasi Vet Pathol. 2014;51(3):603-6.
- Saridomichelakis MN, Koutinas AF. Cutaneous involvement in canine leishmaniosis due to Leishmania infantum (syn. chagasi). Vet Dermatol. 2014; 25(2):61-71.
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