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PAGES: DOI: 10.1590/0074-02760170321 Full paper
Sensitivity of diagnostic methods for Mansonella ozzardi microfilariae detection in the Brazilian Amazon Region

Jansen Fernandes Medeiros1,+, Gilberto Fontes2, Vilma Lopes do Nascimento3, Moreno Rodrigues4, Jacob Cohen5, Edmar Vaz de Andrade6, Felipe Arley Costa Pessoa7, Marilaine Martins3

1Fundação Oswaldo Cruz-Fiocruz, Laboratório de Entomologia, Porto Velho, RO, Brasil
2Universidade Federal de São João Del-Rei, Divinópolis, MG, Brasil
3Fundação de Medicina Tropical Dr Heitor Vieira Dourado, Gerência de Parasitologia, Manaus, AM, Brasil
4Universidade Federal de Rondônia, Laboratório de Bioecologia de Insetos, Porto Velho, RO, Brasil
5Universidade Federal do Amazonas, Departamento de Oftalmologia, Manaus, AM, Brasil
6Universidade Federal do Amazonas, Centro de Apoio Multidisciplinar, Manaus, AM, Brasil
7Fundação Oswaldo Cruz-Fiocruz, Centro de Pesquisa Leônidas e Maria Deane, Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Manaus, AM, Brasil


BACKGROUND The 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.

OBJECTIVES This study investigated the frequency of individuals with M. ozzardi in riverine communities in Coari municipality, Brazilian Amazon.

METHODS Different 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.

FINDINGS The 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 CONCLUSIONS PCMF 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).

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Financial support: FAPEAM
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Received 07 August 2017
Accepted 17 November 2017