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 a mong humans in northern Togo and Ghana. For parasite-specific diagnosis a c oproculture is obligatory, because only the infective larvae, and not the e ggs, can be distinguished morphologically. The sensitivity of duplicate cop rocultures from a single stool sample was found to be above 90 % in compari son to a gold standard of 10 coprocultures made from a single stool specime n. Prevalence of infection with O. bifurcum and hookworm further increased with the number of coprocultures made from each individual stool. Notwithst anding the high sensitivity, intensity of infection per individual varied c onsiderably from day-to-day and the number of larvae found in different sam ples out of 1 stool also varied highly, both showing a heterogeneous distri bution. Surprisingly, daily fluctuation and within-specimen variation could not be differentiated from each other, probably because of the variation c reated by the coproculture technique. To estimate the intensity of infectio n, it is sufficient to make repeated coprocultures from only 1 individual s tool sample. Laborious collection of stool samples on subsequent days does not give better estimates of the individual infection status.