Figure 1 . Toxocara spp . life cycle [ 4 ] 1 . Eggs are shed in faeces . 2 . Eggs become infective with L3 larvae after 1 – 4 weeks in the environment . 3 . Eggs are ingested . 4 . Eggs hatch in the end host ( EH ) and the larvae penetrate the gut wall . In puppies ( T . canis ) and kittens ( T . cati ), hepatic – tracheal migration occurs and adult worms develop in the small intestine . 5 . In older dogs the larvae usually lie dormant in tissues , but can be activated by hormones in bitches during late gestation and can infect their puppies . 6 . Puppies are infected via the transplacental and transmammary routes . Kittens are infected via the transmammary route . 7 . Eggs can be eaten by a paratenic host and the larvae remain dormant . 8 . The paratenic host is eaten by the EH . 9 . Humans can become accidental hosts by ingesting infective eggs . 10 . Humans can also be infected through eating undercooked meat . 11 . Larvae penetrate the gut wall and travel to the tissues , where they may cause damage leading to clinical toxocariasis .
Figure 2a . Hookworm egg [ 6 ] . Figure 2b . T . canis egg [ 6 ] .
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