Histopathological and parasitological study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum

Abstract

BackgroundThe aim of this study was to provide a systematic pathological and parasitological overview of the gastrointestinal tract (GIT), including the stomach, duodenum, jejunum, ileum, caecum and colon, of dogs naturally infected with Leishmania.MethodsTwenty mongrel dogs naturally infected with Leishmania (Leishmania) infantum and obtained from the Control Zoonosis Center of the Municipality of Ribeirão das Neves, Belo Horizonte Metropolitan area, Minas Gerais (MG) state, Brazil, were analyzed. The dogs were divided into two groups: Group 1 comprised nine clinically normal dogs and group 2 comprised 11 clinically affected dogs. After necropsy, one sample was collected from each GIT segment, namely the stomach, duodenum, jejunum, ileum, caecum and colon. Furthermore, paraffin-embedded samples were used for histological and parasitological (immunohistochemistry) evaluation and a morphometrical study were carried out to determine the parasite load (immunolabeled amastigote forms of Leishmania). The Friedman and the Mann Whitney tests were used for statistical analysis. The Friedman test was used to analyze each segment of the GIT within each group of dogs and the Mann Whitney test was used to compare the GIT segments between clinically unaffected and affected dogs.ResultsThe infected dogs had an increased number of macrophages, plasma cells and lymphocytes, but lesions were generally mild. Parasite distribution in the GIT was evident in all intestinal segments and layers of the intestinal wall (mucosal, muscular and submucosal) irrespective of the clinical status of the dogs. However, the parasite load was statistically higher in the caecum and colon than in other segments of the GIT.ConclusionThe high parasite burden evident throughout the GIT mucosa with only mild pathological alterations led us to consider whether Leishmania gains an advantage from the intestinal immunoregulatory response (immunological tolerance).

Expression of Regulatory T Cells in Jejunum, Colon, and Cervical and Mesenteric Lymph Nodes of Dogs Naturally Infected with Leishmania infantum

“…We observed parasites associated with the inflammatory response throughout the mucosa, but without inducing severe pathologies, such as ulcers or necrosis. The immunohistochemical morphometric analysis revealed higher parasite loads in the colon than in the jejunum, as previ-ously reported by our group (25) and in accordance with other reports (31)(32)(33)(34)(35)(36).…”

“…Six dogs of unknown age, obtained from the Control Zoonosis Center of the Municipality of Carandaí, Minas Gerais State, Brazil, and negative for Leishmania infection by all tests, were used as controls. Dogs were confirmed to be Leishmania-free by immunohistochemistry (21)(22)(23)(24)(25). This protocol received the approval of the CETEA-UFMG (protocol 139/2012).…”

“…For the semiquantitative analysis, the inflammatory mononuclear cells in the organ samples were evaluated using the following scores: slight, 1 to 9 cells per field over 20 fields; moderate, 10 to 30 cells per field over 20 fields; and intense, Ͼ30 cells per field over 20 fields. For quantitative analysis, the images were analyzed with Zeiss KS300 software, viewed on video, and downloaded to a computer-assisted image analysis system (Kontron Elektronik/Carl Zeiss, Germany) (25).…”

Pathologic Mechanisms Underlying the Clinical Findings in Canine Leishmaniosis due to Leishmaniainfantum/chagasi

“…46 Finally, in a recent study where the whole gastrointestinal tract of asymptomatic and symptomatic leishmanial dogs was examined histologically, the typical, though mild, lesions of the disease were demonstrated all over its length, along with a high parasitic load, which was more intense in the colon, regardless of clinical status. 114 The relationship between cardiopulmonary disease and L. infantum is rather unclear with its pathological conditions-notably, nonsuppurative myocarditis, fibrinous pericarditis, and pneumonia-being a rare occurrence. 53,135,145 The underlying pathology of CanL-associated meningoencephalomyelitis, which would explain the various neurologic signs observed (eg, seizures, painful and rigid neck, paraplegia), is consistent with a granulomatous and/or neutrophilic meningitis, central nervous system granulomas, spinal hemorrhages, vasculitis, or brain infarcts.…”

Alterações eletromiográficas e histopatológicas da musculatura de cães naturalmente infectados por Leishmania infantum

“…Estudos histopatológicos têm sido realizados na musculatura lisa e esquelética de cães com LV, incluindo músculos mastigatórios 8 , apendiculares 8,11 , intra, peri e extraoculares 12 , cardí-acos 13,14,15 , bronco-pulmonares 13 e intestinais 16 . Tais avaliações revelaram a presença de infiltrado inflamatório composto por macrófagos, linfócitos e neutrófilos, áreas de degeneração, atrofia e necrose de miofibras, vasculite neutrofílica, proliferação de tecido conectivo fibroso e, em alguns casos, presença de formas amastigotas de Leishmania sp.…”