Sensitivity of diagnostic methods for Mansonella ozzardi microfilariae detection in the Brazilian Amazon Region

Abstract

BACKGROUNDThe human filarial worm Mansonella ozzardi is highly endemic in the large tributaries of the Amazon River. This infection is still highly neglected and can be falsely negative when microfilariae levels are low.OBJECTIVESThis study investigated the frequency of individuals with M. ozzardi in riverine communities in Coari municipality, Brazilian Amazon.METHODSDifferent diagnostic methods including polymerase chain reaction (PCR), blood polycarbonate membrane filtration (PCMF), Knott's method (Knott), digital thick blood smears (DTBS) and venous thick blood smears (VTBS) were used to compare sensitivity and specificity among the methods. Data were analysed using PCMF and Bayesian latent class models (BLCM) as the gold standard. We used BLCM to calculate the prevalence of mansonelliasis based on the results of five diagnostic methods.FINDINGSThe prevalence of mansonelliasis was 35.4% by PCMF and 30.1% by BLCM. PCR and Knott methods both possessed high sensitivity. Sensitivity relative to PCMF was 98.5% [95% confidence interval (CI): 92.0 - 99.7] for PCR and 83.5% (95% CI: 72.9 - 90.5) for Knott. Sensitivity derived by BLCM was 100% (95% CI 93.7 - 100) for PCMF, 100% (95% CI: 93.7 - 100) for PCR and 98.3% (95% CI: 90.6 - 99.9) for Knott. The odds ratio of being diagnosed as microfilaremic increased with age but did not differ between genders. Microfilariae loads were higher in subjects aged 30 - 45 and 45 - 60 years.MAIN CONCLUSIONSPCMF and PCR were the best methods to assess the prevalence of mansonelliasis in our samples. As such, using these methods could lead to higher prevalence of mansonelliasis in this region than the most commonly used method (i.e., thick blood smears).

Filariasis and transfusion‐associated risk: a literature review

“…microscopy) may occasionally lead to misclassification of these two species [32]. Infection rates of Mansonella species in human populations may vary widely both within a particular geographic region and in a particular area over time [13, 33–35]. The natural environment (e.g.…”

In Silico Identification of Novel Biomarkers and Development of New Rapid Diagnostic Tests for the Filarial Parasites Mansonella perstans and Mansonella ozzardi

“…streptocerca , M. rodhaini , Mansonella vanhoofi , Mansonella leopoldi and Mansonella lopeenis 7,24,65 . For such closely related species, nested-PCR can be problematic 32–34,38,40 as a slight change in amplification conditions can result in an assay becoming non species-specific 10,57 . Therefore sequencing of the amplification product is required to discriminate between closely related species 30 .…”

“…In general, these molecular assays are more sensitive than the standard parasitological techniques for the identification of Mansonella spp . 1,10,31–34,38–40 . Nevertheless, their dependence on trained personnel and relatively expensive equipment restricts their widespread adoption 41,42 .…”

Detection of Mansonella ozzardi among blood donors from highly endemic interior cities of Amazonas state, northern Brazil

“…Recently the sensitivity and specificity of different diagnostic methods for M. ozzardi was evaluated in the Brazilian Amazon showing that blood filtration and PCR were the best methods to assess prevalence. 42 We acknowledge that the use of a quantitative realtime PCR for M. ozzardi would be more applicable and useful than the qualitative PCR employed.…”