Low Parasite Load Estimated by qPCR in a Cohort of Children Living in Urban Area Endemic for Visceral Leishmaniasis in Brazil

<div><h3>Background</h3><p>An important issue associated with the control of visceral leishmaniasis is the need to identify and understand the relevance of asymptomatic infection caused by <em>Leishmania infantum</em>. The aim of this study was to follow the course of asymptomatic <em>L. infantum</em> infection in children in an area of Brazil where it is endemic. The children were assessed twice during a 12-month period.</p> <h3>Methodology</h3><p>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 (<em>L. infantum</em> 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 <em>Leishmania</em> spp. to follow the course of infection.</p> <h3>Principal Findings</h3><p>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.</p> <h3>Conclusions</h3><p>The peripheral blood of asymptomatic children had a low and fluctuating quantity of <em>Leishmania</em> DNA and a significant decrease in parasitemia at 1-year follow-up. Quantitative PCR enables adequate monitoring of <em>Leishmania</em> infection.</p> </div

Agreement between serological and qPCR results for <i>L. infantum</i> infection in children (n = 559) living in the northwestern region of Belo Horizonte in 2010.

<p>Kappa<0.1.</p><p>Abbreviation: qPCR, quantitative polymerase chain reaction.</p

Parasite load of children remained positive tested by qPCR results at baseline and follow-up.

<p>The samples that tested positive at baseline had a mean concentration of 56.5±33.4 parasites/mL of blood. At follow-up, the mean parasitemia of children who remained positive was 7.8±7.0 parasites/mL (baseline, dark; follow-up, clear).</p

Diagnosis of asymptomatic infection in 199 subjects by qPCR at baseline and 12-month follow-up in Belo Horizonte, Minas Gerais (2009–2010).

<p>Abbreviations: follow-up; qPCR, quantitative polymerase chain reaction.</p

Estimate by qPCR of the prevalence of <i>L. infantum</i> infection in children living in the northwestern region of Belo Horizonte (n = 1875).

<p>Abbreviations: CI, confidence interval; qPCR, quantitative polymerase chain reaction.</p