Risk factors for seroconversion by Leishmania infantum in a cohort of dogs from an endemic area of Brazil

PLoS One. 2013 Aug 22;8(8):e71833. doi: 10.1371/journal.pone.0071833. eCollection 2013.

Abstract

Visceral leishmaniasis (VL) has recently emerged in various urban and peri-urban areas of Brazil and other countries. Understanding the urbanization of VL requires identification of risk factors associated with human and canine infection. To determine the predictors of risk for canine VL, a survey was conducted of 1,443 dogs, from which a cohort was selected (n = 455) and evaluated for approximately 26 months. Serology was conducted with two enzyme-linked immunosorbent assays (ELISA): one conducted in the Laboratory of Zoonosis of the Belo Horizonte Health Department (LZOON) and the other in the Laboratory of Immunopathology of the Federal University of Ouro Preto (LIMP). A molecular diagnostic method (PCR-restriction fragment length polymorphism) and a structured questionnaire were also used. To identify the factors associated with seroconversion, two time-dependent Cox regression models were performed with different sensitivities (model 1, seroconversion by ELISA/LZOON; model 2, seroconversion by ELISA/LIMP). The overall incidences of seroconversion were 6.5/1000 dogs-months and 11.2/1000 dogs-months for ELISA/LZOON and ELISA/LIMP, respectively. Increased risk of seroconversion was associated with short fur (model 1: hazard ratio [HR] 1.9), the presence of dry leaves (model 1: HR 2.8) or manure (model 1: HR 3.5) in the backyard, dogs sleeping predominantly in the backyard (model 2: HR 2.1), the presence of symptoms (model 2: HR 2.0), and positive molecular results during follow-up (model 2: HR 1.5). Decreased risk was associated with insecticide spraying in the house (model 2: HR 0.5). These results indicate that more-vulnerable domiciles, certain dog behaviors, lack of vector control measures, and positive molecular results were associated with the occurrence of canine VL. Furthermore, it is important to emphasize that PCR-positive dogs should be monitored, owing to the possibility of seroconversion. Identifying risk factors for seroconversion in dogs is crucial for developing adequate strategies for VL prevention and control.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Antibodies, Protozoan / blood
  • Antibodies, Protozoan / immunology
  • Brazil / epidemiology
  • DNA, Protozoan / genetics
  • Dog Diseases / blood
  • Dog Diseases / epidemiology*
  • Dog Diseases / parasitology
  • Dogs
  • Endemic Diseases / statistics & numerical data
  • Endemic Diseases / veterinary*
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Incidence
  • Leishmania infantum / genetics
  • Leishmania infantum / immunology*
  • Leishmania infantum / physiology
  • Leishmaniasis, Visceral / blood
  • Leishmaniasis, Visceral / parasitology
  • Leishmaniasis, Visceral / veterinary*
  • Male
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Prevalence
  • Proportional Hazards Models
  • Risk Factors
  • Zoonoses / epidemiology
  • Zoonoses / parasitology

Substances

  • Antibodies, Protozoan
  • DNA, Protozoan

Grant support

This study was supported by the CAPES/PNPD grant 23038.007183/2011–23, DECIT/MS/CNPq/BR/grant 576062/2008-1, FAPEMIG/BR/grant CBB - APQ-3073-4.01/07, CNPq/BR/grant 472554/2007-7 and PPSUS/MS/CNPq/FAPEMIG/SES-MG/grant CBB-APQ-00356-10. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ABR and MC are grateful by the CNPq fellowships and WCV by CNPq and CAPES/PNPD fellowships.