title: Histopathological and parasitological study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Twenty 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The 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).
authors.affiliation: Departamento de Patologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brasil.
authors.forename: Aldair J W
authors.initials: AJ
authors.lastname: Pinto
authors.forename: Maria M
authors.initials: MM
authors.lastname: Figueiredo
authors.forename: Fabiana L
authors.initials: FL
authors.lastname: Silva
authors.forename: Trycia
authors.initials: T
authors.lastname: Martins
authors.forename: Marilene S M
authors.initials: MS
authors.lastname: Michalick
authors.forename: Washington L
authors.initials: WL
authors.lastname: Tafuri
authors.forename: Wagner L
authors.initials: WL
authors.lastname: Tafuri
mesh_terms: D000818:Animals; D001938:Brazil / Q000453:epidemiology; D004283:Dog Diseases / Q000453:epidemiology / Q000276:immunology / Q000469:parasitology* / Q000473:pathology*; D004285:Dogs; D005260:Female; D041981:Gastrointestinal Tract / Q000469:parasitology* / Q000473:pathology*; D007150:Immunohistochemistry / Q000662:veterinary; D018314:Leishmania infantum / Q000502:physiology*; D007898:Leishmaniasis, Visceral / Q000453:epidemiology / Q000469:parasitology / Q000473:pathology / Q000662:veterinary*; D008297:Male; D059208:Parasite Load / Q000662:veterinary