Abstract
Ascarididae nematodes of genera Toxocara and Toxascaris are of significant epizootic relevance among predatory mammals from families Canidae and Felidae. Localization of these nematodes in the definitive hosts, their morphology, as well as the measurements of eggs and adult worms are similar. Recently, molecular techniques have provided alternative approaches for the identification of ascarid species. A common feature of the life cycles of these generally monoxenous nematodes is the significant participation of small rodents. In case of Toxocara spp., the rodent plays the role of paratenic host but optional intermediate host for T. leonina. Several studies indicate co-occurence of both T. canis and T. leonina in domestic and wild canids as well as T. cati and T. leonina in felids. Although the infections of humans with T. canis and T. cati are common worldwide, larvae of T. leonina has the potential to cause human disease as emerging zoonosis.