Geographic distribution and epidemiology of Oesophagostomum bifurcum and hookworm infections in humans in Togo.

In contrast to the rest of the world, infections with Oesophagostomum bifurcum are commonly found in humans in northern Togo and Ghana. In addition, infections with hookworm are endemic in this region. In the present study, a detailed map of the geographic distribution of O. bifurcum and hookworm infections in northern Togo was made. There were a number of foci with high prevalence of infection with O. bifurcum. All the villages examined were infected with hookworm, and the distribution was quite patchy. Women were infected with O. bifurcum more often than men, while infections with hookworm were more prevalent in men than in women. The prevalence and intensity of infection with both parasites were clearly age-dependent. We estimate that more than a 100,000 people in Togo are infected with O. bifurcum and more than 230,000 are infected with hookworm.

Diagnosis of Oesophagostomum bifurcum and hookworm infection in humans: day-to-day and within-specimen variation of larval counts.

Oesophagostomum bifurcum, as well as hookworm infections are hyperendemic among humans in northern Togo and Ghana. For parasite-specific diagnosis a coproculture is obligatory, because only the infective larvae, and not the eggs, can be distinguished morphologically. The sensitivity of duplicate coprocultures from a single stool sample was found to be above 90% in comparison to a gold standard of 10 coprocultures made from a single stool specimen. Prevalence of infection with O. bifurcum and hookworm further increased with the number of coprocultures made from each individual stool. Notwithstanding the high sensitivity, intensity of infection per individual varied considerably from day-to-day and the number of larvae found in different samples out of 1 stool also varied highly, both showing a heterogeneous distribution. Surprisingly, daily fluctuation and within-specimen variation could not be differentiated from each other, probably because of the variation created by the coproculture technique. To estimate the intensity of infection, it is sufficient to make repeated coprocultures from only 1 individual stool sample. Laborious collection of stool samples on subsequent days does not give better estimates of the individual infection status.

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 regarded 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 eggs of O. bifurcum are morphologically identical to those of the hookworm Necator americanus. Stools have to be cultured for 7 days to allow eggs to hatch to the characteristic third-stage (L3) larvae. We evaluated the applicability of specific polymerase chain reactions (PCRs) to amplify DNA from faecal samples as an alternative method for the differential diagnosis of the two infections. Oesophagostomum bifurcum-PCR was positive in 57 of 61 faecal 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 which no N. americanus larvae were found in coproculture. No O. bifurcum DNA was detected in 91 stool samples from individuals from two non-endemic villages. These results prove the usefulness of specific PCR assays as epidemiological tools to estimate the prevalence of O. bifurcum and N. americanus infections in human populations.