Differentiation of Toxocara canis and T-cati eggs by light and scanning electron microscopy

In this study, we investigated the morphological identification of Toxocara canis and T. cati eggs on the basis of light and scanning electron microsc opic (SEM) observations. T. canis and T. carl eggs used in this study were recovered from the uteri of respective gravid female worms. Measurement of egg size was not helpful in the differentiation of these species, because a pproximately 90% of eggs measured were of similar size. Using SEM, we were able to differentiate T. canis eggs from T. cati eggs based on their respec tive characteristic surface structures. Both species have subspherical eggs with markedly pitted surfaces like those of a golf ball, but the surface p itting in T. canis is more coarse than that in T cati, In this study, howev er, these differences were not absolute, as 16% of T. canis and 29% of T. c ati eggs showed surface pitting that was uncharacteristic of their species. Of the 16% of T. canis eggs that could not be differentiated by surface st ructure, 3% had pitting resembling T. cati, and the remaining 13% showed in termediate type surface pitting. Similarly, 5% of T. cati eggs resembled T canis, and 25% of these were of intermediate type. Light microscopic observ ation yielded results similar to those of SEM, indicating that light micros copy is also a useful tool for the identification of Toxocara eggs. (C) 200 0 Elsevier Science B.V. All rights reserved.