A PCR-based assay have been previously described to detect Wuchereria bancrofti in mosquitoes and in human blood samples. However, the efficiency of PCR amplification may vary between samples depending on the presence of PCR inhibitors, leading sometimes to false negative results. To overcome this drawback, an internal standard plasmid (pWB11) was constructed. It can be added to each PCR reaction for coamplification along with the target W. bancrofti DNA (Sspl DNA repeat) using the same pair of primers. PCR products from W. bancrofti DNA or from pWB11 are 34 bp different in size and can be visualized either on agarose gel or by DNA ELISA using two different oligonucleotides probes.