Determining the prevalence of Oesophagostomum bifurcum and Necator americanus infections using specific PCR amplification of DNA from faecal samples

Until recently infection of humans with Oesophagostomum bifurcum was regard ed as a rare zoonosis. But in northern Togo and Ghana its prevalence is 50% or more in certain villages. Diagnosis is hampered by the fact that the eg gs of O. bifurcum are morphologically identical to those of the hookworm Ne cator americanus. Stools have to be cultured for 7 days to allow eggs to ha tch to the characteristic third-stage (L3) larvae. We evaluated the applica bility of specific polymerase chain reactions (PCRs) to amplify DNA from fa ecal samples as an alternative method for the differential diagnosis of the two infections. Oesophagostomum bifurcum-PCR was positive in 57 of 61 faec al samples known to contain O. bifurcum L3 larvae in coproculture. Necator americanus PCR was positive in 137 of 146 faecal samples known to contain N . americanus L3 larvae in coproculture. PCR also detected 26 additional O. bifurcum cases in 72 samples from O. bifurcum endemic villages in which no O. bifurcum larvae were found and 45 N. americanus cases in 78 samples in w hich no N. americanus larvae were found in coproculture. No O. bifurcum DNA was detected in 91 stool samples from individuals from two non-endemic vil lages. These results prove the usefulness of specific PCR assays as epidemi ological tools to estimate the prevalence of O. bifurcum and N. americanus infections in human populations.