A two-year-old female mongrel dog was referred to the Zoonosis Control Center in Fortaleza, Brazil for clinical and corporal evaluation. This animal presented with weight loss, skin lesions, onychogryphosis, and splenomegaly. Blood samples were collected for hematological and biochemical evaluation, revealing anemia, lymphocytosis, and hyperproteinemia.
After seroreactivity to Leishmania infantum was confirmed by Dual Path Platform (DPP) and Enzyme Linked Immunosorbent Assay (ELISA), the animal was euthanized according to animal welfare recommendations as a disease control measure determined by the Ministry of Health of Brazil. Macroscopic analysis of organs revealed no changes except for splenomegaly and several nodular formations in the spleen (Figure 1).
FIGURE 1 Splenomegaly and several nodular formations in naturally infected dog by Leishmania infantum.
Fragments of these nodules were collected and subjected to histological processing (H&E) for structural and functional evaluation. Capsular thickening and inflammatory infiltrate, including lymphocytes, neutrophils, megakaryocytes, and amyloid deposition, were observed. Amyloidosis was confirmed in a Congo red-stained sample by optical and polarized light microscopy (Figure 2). L.infantum amastigotes were detected inside the nodules by immunohistochemical analysis (Figure 3).
FIGURE 2 Spleen amyloidosis (Congo red and polarized light microscopy) in naturally infected dog by Leishmania infantum(400x).
FIGURE 3 Leishmania infantum amastigotes detected inside the nodules by immunohistochemical analysis in spleen of naturally infected dog (400x).
Nodular hyperplasia is a common splenic condition that corresponds to a lesion formed by hyperplasic lymphoid cells or large concentrations of amyloid proteins, erythrocytes, myeloid cells, and megakaryocytic cells1. These nodules may be associated with chronic and inflammatory processes2, such as canine visceral leishmaniasis3, and are more common in older dogs. Nodular hyperplasia can cause hematomas and consequently hemoperitoneum1.
Thus, we conclude that splenic nodular hyperplasia and amyloidosis are alterations related to the presence of L infantum in the spleen. These observations characterized the chronic inflammatory process observed in this case.
