Hookworm-like eggs in children's faecal samples from a rural area of Rwanda

Abstract

Background: Hookworm eggs identification and quantification is usually carried out by Kato-Katz method. However various structures present in the smear may be confused with eggs of such parasites.

Objective: To document the presence of structures in Kato-Katz slides that could initially be misinterpreted as hookworm eggs.

Method: 497 faecal samples were analysed by Kato-Katz technique, diphasic concentration technique, agar-plate coprocultive and larvae obtained were analysed by PCR and characterized by sequencing.

Result: Hookworm-like eggs were found in 159 (32%) of the samples by Kato-Katz, finally identified as Caenorhabditis elegans by PCR technique.

Conclusion: The diagnosis of human hookworm eggs, only by the use of Kato-Katz technique can lead to false positives because of similarities with eggs of other free-living worms, from wet soils like those of Rwanda that could contaminate stool samples.

Keywords: Hookworm eggs; Kato-Katz method; Rwanda; misclassification.

Figure 1

Hookworm egg in Kato-Katz technique (x400) (A); Hookworm-like egg in Kato-Katz slide (x400) (B), Hookworm-like eggs in Kato-Katz slide (x100) (C).

Figure 2

Hookworm egg (Diphasic concentration technique × 400) (A); Hookworm-like egg (Diphasic concentration technique × 400) (B).

Figure 3

Adult worms of C. elegans (Diphasic concentration technique × 100)

Figure 4

Larvae of C. elegans in water drop from the coprocultive (vision through electronic loupe).