Root-knot nematodes (Meloidogyne spp.) are among the most economically damaging genera of plant-parasitic nematodes worldwide1. Although they are not pathogenic to humans, their eggs may eventually be found in human stools2 and owing to their similarity with eggs of pathogenic nematodes must be correctly identified to avoid unnecessary treatments. Recently, researchers reported the presence of eggs similar to those of Trichostrongylus spp. (identified as Meloidogyne eggs) in three (0.5%) of 586 stool samples collected from East Kwaio, Solomon Islands2. From 2008 to 2014, 332,132 stool samples, referred to a private laboratory network (Datalab) in Salvador, Brazil, were examined using the Lutz method; 61 (0.02%) were positive for Meloidogyne eggs (Figure 1).
FIGURE 1 A Meloidogyne egg showing a thin, hyaline shell and refractive internal corpuscles located between the shell and the morula, resembling lipid droplets.
Meloidogyne eggs may be identified based on their shape, size, and absence or presence of characteristic internal structures3. Meloidogyne eggs have thin hyaline shells without visible markings, elongate-ovoid with rounded ends. One of the sides can be concave or slightly flattened. They measure 82-120µm in length × 24-43µm in width and can be seen inside a juvenile cell mass in the first division phase or in a fully formed larva. They may present internal refractive corpuscles, located between the shell and the morula, which are important to distinguish them from eggs of Trichostrongylus spp. and hookworms. The presence of corpuscles, resembling air-sacs, on one of the poles, between the morula and the shell is very characteristic, although not always present. However, during its development, the concavity and the air-sacs may disappear, and the egg becomes plano-convex or even biconvex.
