title: Low parasite load estimated by qPCR in a cohort of children living in urban area endemic for visceral leishmaniasis in Brazil.
abstract: BACKGROUND
  An important issue associated with the control of visceral leishmaniasis is the need to identify and understand the relevance of asymptomatic infection caused by Leishmania infantum. The aim of this study was to follow the course of asymptomatic L. infantum infection in children in an area of Brazil where it is endemic. The children were assessed twice during a 12-month period.
  
  
  METHODS
  In this population study, 1875 children, ranging from 6 months to 7 years of age, were assessed. Blood samples were collected on filter papers via finger prick and tested by ELISA (L. infantum soluble antigen and rk39). Seropositives samples (n = 317) and a number of seronegatives samples (n = 242) were subjected to qPCR. After 12 months, blood samples were collected from a subgroup of 199 children and tested for Leishmania spp. to follow the course of infection.
  
  
  RESULTS
  At baseline qPCR testing identified 82 positive samples. The prevalence rate, as estimated for 1875 children based on the qPCR results, was 13.9%. The qPCR testing of whole blood samples collected from a cohort of children after 12 months (n = 199) yielded the following results: of the 44 (22.1%) children with positive qPCR results at baseline, only 10 (5.0%) remained positive, and 34 (17.1%) became negative; and of the 155 (77.9%) children with negative qPCR results, 131 (65.8%) remained negative, and 24 (12.1%) became positive at the follow-up measurement. The samples with positive findings at baseline (n = 82) had a mean of 56.5 parasites/mL of blood; and at follow-up the mean positive result was 7.8 parasites/mL.
  
  
  CONCLUSIONS
  The peripheral blood of asymptomatic children had a low and fluctuating quantity of Leishmania DNA and a significant decrease in parasitemia at 1-year follow-up. Quantitative PCR enables adequate monitoring of Leishmania infection.
authors.affiliation: Laboratório de Epidemiologia de Doenças Infecciosas e Parasitárias, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Letícia Helena
authors.initials: LH
authors.lastname: dos Santos Marques
authors.forename: Luciana Inácia
authors.initials: LI
authors.lastname: Gomes
authors.forename: Iara Caixeta Marques
authors.initials: IC
authors.lastname: da Rocha
authors.forename: Thaís Almeida Marques
authors.initials: TA
authors.lastname: da Silva
authors.forename: Edward
authors.initials: E
authors.lastname: Oliveira
authors.forename: Maria Helena Franco
authors.initials: MH
authors.lastname: Morais
authors.forename: Ana
authors.initials: A
authors.lastname: Rabello
authors.forename: Mariângela
authors.initials: M
authors.lastname: Carneiro
mesh_terms: D000953:Antigens, Protozoan / Q000097:blood; D058070:Asymptomatic Diseases / Q000453:epidemiology; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007223:Infant; D018314:Leishmania infantum / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D007898:Leishmaniasis, Visceral / Q000453:epidemiology*; D008297:Male; D059208:Parasite Load; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D000953:Antigens, Protozoan