A polymerase chain reaction assay for the detection of Wuchereria bancrofti in blood samples from French Polynesia

A polymerase chain reaction (PCR) assay based on a highly repeated deoxyribonucleic acid (DNA) sequence found in Wuchereria bancrofti (the SspI repeat) has been developed to address the shortcomings of traditional diagnostic methods. In this field study in a W. bancrofti endemic region of French Polynesia, 373 human blood samples were collected and 100 mu L of blood were screened by the SspI PCR assay and 1 mu L by membrane filtration. The SspI PCR assay detected 99 of 113 blood samples in which microfilariae had been detected by filtration (sensitivity of 88%) with a specificity of 100%. All the samples missed by the SspI PCR assay had less than 8 microfilariae per mt of blood. To evaluate the efficacy of screening larger blood samples by PCR, both 100 mu L and 500 mu L samples from 50 patients with very low-level microfilaraemia were screened by the SspI PCR assay; the sensitivity increased from 60% to 84% when using the larger volume of blood. Finally, an enzyme-linked immunosorbent assay-based version of the SspI PCR assay was used to screen blood from 12 patients following treatment with diethylcarbamazine, ivermectin, or both. These results showed that the PCR assay closely paralleled the presence or absence of microfilariae in the blood and that no increase in the DNA level was seen immediately following drug treatment.