Correction: Serodiagnosis of Tuberculosis in Asian Elephants (Elephas maximus) in Southern India: A Latent Class Analysis.

[This corrects the article DOI: 10.1371/journal.pone.0049548.]

Serodiagnosis of Tuberculosis in Asian Elephants (Elephas maximus) in Southern India: A Latent Class Analysis

Background: Mycobacterium tuberculosis, a causative agent of chronic tuberculosis disease, is widespread among some animal species too. There is paucity of information on the distribution, prevalence and true disease status of tuberculosis in Asian elephants (Elephas maximus). The aim of this study was to estimate the sensitivity and specificity of serological tests to diagnose M. tuberculosis infection in captive elephants in southern India while simultaneously estimating sero-prevalence. Methodology/Principal Findings: Health assessment of 600 elephants was carried out and their sera screened with a commercially available rapid serum test. Trunk wash culture of select rapid serum test positive animals yielded no animal positive for M. tuberculosis isolation. Under Indian field conditions where the true disease status is unknown, we used a latent class model to estimate the diagnostic characteristics of an existing (rapid serum test) and new (four in-house ELISA) tests. One hundred and seventy nine sera were randomly selected for screening in the five tests. Diagnostic sensitivities of the four ELISAs were 91.3-97.6% (95% Credible Interval (CI): 74.8-99.9) and diagnostic specificity were 89.6-98.5% (95% CI: 79.4-99.9) based on the model we assumed. We estimate that 53.6% (95% CI: 44.6-62.8) of the samples tested were free from infection with M. tuberculosis and 15.9% (97.5% CI: 9.8 - to 24.0) tested positive on all five tests. Conclusions/Significance: Our results provide evidence for high prevalence of asymptomatic M. tuberculosis infection in Asian elephants in a captive Indian setting. Further validation of these tests would be important in formulating area-specific effective surveillance and control measures

Quantitative data underlying results in Fig 1A, 1D and 1J.

Quantitative data underlying results in Fig 1A, 1D and 1J.</p

Sensitivity (DSe) and specificity (DSp) of the five serological tests used in the study.

<p>The LCA model was used to calculate the DSe and DSp of each test w.r.t. the antibody it is designed to detect as also presence of at least one antibody. *The Median estimate refers to the 50% quantile while the 2.5% and 97.5% quantiles define a 95% credible interval (CI). ** With respect to.</p

Number of elephants (observed and predicted according to the latent class model) with each test result.

<p>Evaluating the fit of the model by comparing the observed and expected number of elephants with different combinations of tests to see if the assumptions of the substantive model in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049548#pone-0049548-g002" target="_blank">Figure 2</a> were satisfied. 50% refers to the median estimate while the 2.5% and 97.5% quantiles define a 95% credible interval (CI).</p

Original uncropped Western blot and ponceau staining images underlying replicate data in the updated Fig 1.

Original uncropped Western blot and ponceau staining images underlying replicate data in the updated Fig 1.</p

Schematic for the multiple latent variable model used in this study.

<p>The parameters to be estimated are depicted in oval shapes and the observed diagnostic test results are represented in rectangular shapes. While RT contains both the ESAT-6 and CFP10 antigens, the ELISAs are specific for one antigen each.</p

Differential humoral reactivity of four mycobacterial antigens with Asian elephant sera.

<p>For ELISA, elephant sera (1∶200) was allowed to react with ESAT-6 (1 µg/ml) (A), CFP10 (0.5 µg/ml) (D), PE_PGRS11 (0.25 µg/ml) (G) and PE_PGRS17 (0.25 µg/ml) (J). Scatter plots show the total number of animals testing seronegative and seropositive for each antigen. For immunoblotting, 10 µg of each transferred protein ESAT-6 (C), CFP10 (F), PE_PGRS11 (I) and PE_PGRS17 (L) was first stained with Ponceau to check for loading control. Next, individual lanes were cut out of the blot and probed with sera from reference negative and positive animals. B, E, H, K represent immunoblots for one representative negative and positive animal each. The westerns were not quantitative in nature.</p