Embryonic stages of toxocara canis in eggs

ABSTRACT

Observation of Toxocara canis fertile eggs removed from the vagina uterina of female worms showed that they are ovoid to spheroid and have a shell formed of four layers, the outermost is pitted. Infertile eggs were less uniform in shape and did not have well developed shell layers. To study the developmental stages and in trying to determine the infective stage, cultivation of eggs in 1% formalin was done. It was found that the first stage larva appeared at the eighth day of cultivation, and the first moult on the twelfth day followed by the second moult over days 14-16 as proved by finding of transient loose double-layered sheath over the definitive cuticle. This proved that the infective stage is the third stage larva inside the egg. Infectivity to mice appeared on day 18, reached the maximum at 32 days and gradually declined thereafter. The infective larva did not develop or form a sheath during in vitro culture