Aspectos clínicos e parasitários de cães infectados naturalmente por Leishmania spp. em duas áreas de transmissão intensa com diferentes características ambientais e sociais

Abstract

The canine visceral leshmaniasis is an important public health disease in Brazil and around the word. Dogs are considered important reservoir and source of Leshmania infantum infection to human due to their high prevalences of infection, the presence of amastigote forms in the skin and because they are found in the domestic and peri-domestic environment. The objective of this study was to evaluate the clinic, parasitological and serological aspects of the canine leishmaniasis in dogs naturally infected in two endemic distinct area. Hematological, biochemical and serological assays were performed, as well as the histopatologic exams of the entire ear skin of 41 dogs coming from Conceição de Jacareí/RJ and 42 dogs of the Campo Grande/MS. When histopathology was used as an auxiliary tool for diagnostic of CVL, the efficacy of detection of the infected animal double compared to the serological test only. The main clinical manifestations as skin lesions, generalized lymphadenomegaly and hepatosplenomegaly were found in dogs from the two studied areas. However, the intensity and frequency of the clinical signs varied between the two localities: while in Conceição de Jacareí/RJ the majority of animals were asymptomatic, the clinical profile of dogs from Campo Grande/MS was predominantly polysymptomatic. The inflammatory infiltrate constituted a common histological finding in the skin of infected dogs, always associated to the presence of parasites. Nevertheless, the infiltrate in dogs from Campo Grande/MS was predominantly moderate and intense with mononuclear cells and neutrophils in the majority of the dogs. The severity changes in the dermis connected tissue associated to the lost of normal architecture and consequent substitution of the thick collagen fibers by the thin fibers were frequently found in dogs with intense inflammatory infiltrate, necrosis areas and presence of abundant amastigote forms. The amastigote forms were found independently of the symptoms and the geographic area. In animals with clinical signs that harbor few or none amastigotes, the inflammatory infiltrate was mainly constituted by lymphocytes and macrophages. When many parasites were present, the infiltrate was additionally constituted by polymorphonuclears (neutrophils). The association between the presence of polymorphonuclears in intact dog skin with clinical characteristic of CVL would increase diagnostic efficacy. A significant finding was that 75% of asymptomatic dogs with skin parasites were found in both localities. In this sense, the skin may be considered an important reservoir of amastigote forms in asymptomatic dogs. In endemic areas dogs with clinical symptoms are promptly selected to serological test and consequently discarded. In this manner, dogs with no clinical symptoms (but with skin parasites) constitute an important source of infection to the vectors. The same idea may be correlated to sero-negatives animals, a half of the animals with amastigote forms would act as important reservoir hosts to human.