Table 1.
Factors associated with the presence of anti-Strongyloides IgG antibodies in the population of five farming settlements in Amazonas State, Brazil (2010-14) in unadjusted (empty model) and adjusted multiple logistic regression analysis.
Fig 1.
Distribution of participants in consecutive surveys carried out in farming settlements in Amazonas State, Brazil, according to anti-Strongyloides IgG antibody status.
Panel A, blood draws approximately 12 months apart (data from 2010 vs. 2011, 2011 vs. 2012, 2012 vs 2013, and 2013 vs. 2014; n = 408 comparisons); Panel B, blood draws approximately 24 months apart (data from 2010 vs. 2012, 2011 vs. 2013, and 2012 vs. 2014; n = 262 comparisons); Panel C, blood draws approximately 36 months apart (data from 2010 vs. 2013 and 2011 vs. 2014; n = 130 comparisons); Panel D, blood draws approximately 48 months apart (2010 vs. 2014; n = 45 comparisons). Anti-Strongyloides IgG responses were stratified as negative (absorbance ≤ 0.286; light gray), low (absorbance between 0.287 and 0.561; light purple) and high (absorbance > 0.561; purple), with the absorbance value of 0.561 corresponding to the median absorbance value among positive samples during the study. Numbers of individuals within each antibody status category are shown. Data from Panel A (see also the italicized numbers in S2 Table) were used to estimate the 12-month seroconversion rate: of 213 initially seronegative participants, 47 (22.1%) had low antibody titers detected 12 months later (nil-to-low conversions) and 6 (2.8%) had high antibody titers detected 12 months later (nil-to-high conversions).
Fig 2.
Individual anti-Strongyloides IgG antibody trajectories among 51 participants who presented one or more seroconversions event during consecutive surveys in farming settlements in Amazonas State, Brazil, 2010-2014.
Data are displayed in four panels from left to right and each row within a panel represents an individual (n = 12 in the leftmost panel and n = 13 in the other panels). Seroconversion events were defined as an IgG-positive test (absorbance > 0.286) preceded by a negative test 12 months earlier. Samples are ordered in relation to the time of seroconversion and empty spaces indicate missing samples at specific time points. Color codes indicate antibody test results: white means negative (absorbance ≤ 0.286) and coral orange tones indicate quartiles of absorbance in positive samples, 0.287 to 0.366 for the first quartile (lightest tone), 0.367 to 0.561 for the second quartile (coral), 0.562 to 1.121 for the third quartile (darker tone), and above 1.121 for the fourth quartile (brown). By definition, all samples collected 12 months before seroconversion (time point “-12”) were negative. Arrows indicate two participants with two seroconversion events each (months 0 and 24).