Dogs with divergent serology for visceral leishmaniasis as sources of Leishmania infection for Lutzomyia longipalpis phlebotomine sand flies - an observational study in an endemic area in Brazil

PLoS Negl Trop Dis. 2020 Feb 20;14(2):e0008079. doi: 10.1371/journal.pntd.0008079. eCollection 2020 Feb.

Abstract

Visceral leishmaniasis (VL) is a neglected tropical disease, caused by Leishmania (Kinetoplastida, Trypanosomatidae) species. In Brazil, the transmission of this parasite essentially occurs through the bite of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) previously infected with Leishmania infantum. Aiming at preventing VL expansion over the country, integrated control actions have been implemented through a Visceral Leishmaniasis Surveillance and Control Program (VLSCP). Among the actions currently adopted by the program, the screening-culling of seropositive dogs for canine VL (CVL) is particularly polemic. Dogs with negative or divergent serology for CVL remain in their owner's domicile and are monitored by public health agents. In the present study, we determined the prevalence of CVL and analyzed the implementation of the VLSCP screening-culling action, in an area in Brazil where there has been a recent expansion of VL. Canine census surveys were conducted semiannually for two years (Aug/2015 to Feb/2017). Serological diagnosis of CVL was performed in accordance with current VLSCP protocol: immunochromatography (TR-DPP) followed by enzyme-linked immunosorbent assay (ELISA EIE). 6,667 dogs were serologically screened for CVL, of which 567 (8.5%) were positive in both tests and 641 (9.6%) had divergent results. A variable percentage (6.3% to 65.4%) of the dogs in the latter group became positive within nine months from the first result. Xenodiagnosis was conducted in canine samples belonging to any of the three possible serological statuses for CVL-positive, divergent or negative. Leishmania spp. DNA was detected in Lu. longipalpis that fed on 50.0% (5/10) of dogs with positive serology and on 29.4% (5/17) of dogs with divergent serological status for CVL. Therefore, dogs with divergent serology for CVL may be as Leishmania-infective to Lu. longipalpis as seropositive ones. Even with the adoption of euthanasia for seropositive dogs, part of the canine population will continue to serve as a source of Leishmania infection for phlebotomine sand flies.

Publication types

  • Observational Study, Veterinary
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brazil / epidemiology
  • Disease Reservoirs / veterinary
  • Dog Diseases / epidemiology
  • Dog Diseases / parasitology*
  • Dogs
  • Feeding Behavior
  • Female
  • Leishmaniasis, Visceral / epidemiology
  • Leishmaniasis, Visceral / parasitology
  • Leishmaniasis, Visceral / veterinary*
  • Psychodidae / parasitology*
  • Serologic Tests

Grants and funding

ESD received a grant (APQ-03490-13) from the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG). CLFD is a productivity fellow of FAPEMIG (BIP- 00182-18). ESD is a research fellow of Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We are grateful for support from the Coordination for the Improvement of Higher Education Personnel (CAPES) through the Print/Fiocruz/CAPES Program.