Diagnosis of a malayan filariasis case using a shotgun diagnostic metagenomics assay

BACKGROUND: Malayan filariasis is a lymphatic filariasis caused by Brugia malayi. It is easily misdiagnosed in non-endemic areas for atypical symptoms and rare diagnostic experience. A 34-year-old Chinese woman in New York presented with diffuse erythema on her body, swelling of her body, and watery, itchy, red, sore, swollen and stinging of the eyes, and severe night-time itching. No hospital that the patient visited could make a definite diagnosis by conventional diagnostic methods. It is therefore necessary to explore a new effective method to detect the pathogen that infected the patient. FINDINGS: An unbiased metagenomic approach was used in this study. After DNA was extracted from the patient’s eye discharge sample and subcutaneous tissue sample, extended parallel sequencing was performed. The obtained raw reads were aligned to human genome to filter out the reads of the host, and the remaining reads were aligned to a candidate pathogenic protein database and four filarial genomes. The result showed that the reads of B. malayi accounted for an overwhelming ratio in the two samples, which indicated that the patient suffered from malayan filariasis. The subsequent therapeutic efficacy of anti-filariasis treatment validated the result of metagenomics assay. CONCLUSIONS: The present study proved that metagenomic assay can be an effective approach in the diagnosis of parasitic infection. We report a rare case of malayan filariasis from the United States. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1363-2) contains supplementary material, which is available to authorized users.