The taxonomy and nomenclature of the genera Toxocara and Neoascaris are examined and the member species redescribed. No generic differentiation can be found and consequently Neoascaris is subjugated within Toxocara. The genus Toxocara is redefined and eleven valid species are listed including one species considered to be that previously described as Ascaris suricattae. Three species previously classified in Toxocara are listed as species inquirendae of this genus.
Comparative studies are made of thebbiology of T. canis, T. vitulorum and T.mackerrasae. T. canis exhibited the most rapid free-living development and T. mackerrasae the slowest. In mice T. canis most readily establishes infection, undergoes the most extensive migration, survives the longest and undergoes the least development whereas T. mackerrasae is the most difficult to establish, undergoes the least extensive migration, exhibits the least ability to survive, but develops to the adult stage.
Development of T. canis in prenatally infected dogs is described. Pregnancy in mice infected with T. canis was found to have little or no significant effect on the larvae. Oxytocin, oestrogen, pregnant mares serum gonadotrophin, hydrocortisone and testosterone exerted significant effects upon the distribution and survival of T. canis larvae in experimentally infected mice.
The development of T. canis in adult dogs fed infected mouse tissues is described in detail.
Intrauterine infection by T. vitulorum in cattle is confirmed, but could not be established in sheep or goats and no mature infection could be established in ruminants, either by direct feeding of embryonated eggs or larvae recovered from mice.
The development of T. mackerrasae to the adult stage is described in mice and rats. An analysis of natural infections of T. mackerrasae in Rattus fuscipes trapped in rain forest in south,eastern Queensland is given. Hydromys chrysogaster is listed as a new host for Toxocara mackerrasae.