Experimental Infection of Dogs with Leishmania and Saliva as a Model to Study Canine Visceral Leishmaniasis

Dirceu Joaquim Costa,Maiana Pitombo,Melissa Abbehusen,Clarissa Teixeira,Joelma Trigo,Manoel Barral-Netto,Cláudia Brodskyn,José Carlos Miranda,Rayssa M De Araujo Carvalho,Lucilene Amorim,Flávia Nascimento,Maria Do Socorro Pires Cruz,Aldina Barral,Kyoshi Fukutani,Camila I De Oliveira,Ana Lucia Abreu-Silva

doi:10.1371/journal.pone.0060535

Abstract

BackgroundCanine Visceral Leishmaniasis (CVL) is a zoonotic disease caused by Leishmania infantum, transmitted by the bite of Lutzomyia longipalpis sand flies. Dogs are the main domestic reservoir of the parasite. The establishment of an experimental model that partially reproduces natural infection in dogs is very important to test vaccine candidates, mainly regarding those that use salivary proteins from the vector and new therapeutical approaches.Methodology/Principal FindingsIn this report, we describe an experimental infection in dogs, using intradermal injection of Leishmania infantum plus salivary gland homogenate (SGH) of Lutzomyia longipalpis. Thirty-five dogs were infected with 1×107 parasites combined with five pairs of Lutzomyia longipalpis salivary glands and followed for 450 days after infection and clinical, immunological and parasitological parameters were evaluated. Two hundred and ten days after infection we observed that 31,4% of dogs did not display detectable levels of anti-Leishmania antibodies but all presented different numbers of parasites in the lymph nodes. Animals with a positive xenodiagnosis had at least 3,35×105 parasites in their lymph nodes. An increase of IFN-γ and IL-10 levels was detected during infection. Twenty two percent of dogs developed symptoms of CVL during infection.ConclusionThe infection model described here shows some degree of similarity when compared with naturally infected dogs opening new perspectives for the study of CVL using an experimental model that employs the combination of parasites and sand fly saliva both present during natural transmission.

Highlights

Canine visceral leishmaniasis (CVL) is caused by an intracellular protozoan parasite Leishmania infantum
Since dogs present many symptoms observed in humans, with a long period of asymptomatic infection followed by wasting, anaemia, enlarged lymph nodes, and fever, the canine model is important to study VL pathogenesis and for development of pre clinical trials related to therapy
An experimental canine model for VL is highly desirable previous attempts to infect dogs have used the inoculation of a high number of parasites intravenously that in some occasions did not result in disease development [5,6,7]

Summary

Introduction

Canine visceral leishmaniasis (CVL) is caused by an intracellular protozoan parasite Leishmania infantum. It is endemic in the Mediterranean Basin, South America and parts of Asia [1]. Domestic dogs are the main reservoirs and different control strategies, such as the use of insecticide impregnated collars or elimination of infected dogs have not been effective to decrease human incidence of VL [2]. Development of a vaccine for CVL has been identified as a research priority by WHO/TDR [3] and mathematical models have highlighted canine vaccination as the potentially most practical and effective means of impacting disease control in humans [4]. Canine Visceral Leishmaniasis (CVL) is a zoonotic disease caused by Leishmania infantum, transmitted by the bite of Lutzomyia longipalpis sand flies. The establishment of an experimental model that partially reproduces natural infection in dogs is very important to test vaccine candidates, mainly regarding those that use salivary proteins from the vector and new therapeutical approaches

Methods

Results

Discussion

Conclusion