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The final life cycle involves transmission of L3 larvae to pups through the milk. Hypobiotic L3 larvae are reactivated and are either already present in the mammary glands or travel to them and are capable of passing in the milk during the first 3 weeks of lactation. There is no further migration in the pup when the larvae are ingested in this way and the remaining life cycle of the worm is completed in the small intestine of the pup.
The final life cycle involves transmission of L3 larvae to pups through the milk. Hypobiotic L3 larvae are reactivated and are either already present in the mammary glands or travel to them and are capable of passing in the milk during the first 3 weeks of lactation. There is no further migration in the pup when the larvae are ingested in this way and the remaining life cycle of the worm is completed in the small intestine of the pup.
As well as the above life cycles ''T. canis'' can infect paratenic hosts such as mice, rats and some birds. In these animals the L3 larvae migrate to tissues hypobiose until the hosts tissues are consumed by a dog in which the worm can complete its life cycle. The prepatent period of ''T. canis is 4 - 5 weeks.
As well as the above life cycles ''T. canis'' can infect paratenic hosts such as mice, rats and some birds. In these animals the L3 larvae migrate to tissues hypobiose until the hosts tissues are consumed by a dog in which the worm can complete its life cycle. The prepatent period of ''T. canis'' is 4 - 5 weeks.
=Epidemiology=
=Epidemiology=
''T. canis'' is present worldwide with a wide range of prevalances in different areas from 5 - 80%. Adult animals carry the fewest worms since initial infection causes immunity which leads to the shedding of adult worms from the intestines. The largest numbers of worms are found in dogs less than 6 months old who have not yet gained immunity to the worms. The high levels of prevalence of this species worldwide is largely due to the difficulty in controlling its spread. The eggs are extremely resistant in the environment and so can persist for several years. The females lay very large numbers of eggs, up to 700 per gram of faeces, making the removal of such a large number difficult. This final reason for such a large spread is the long lasting reservoir of hypobiotic larvae that can be reactivated in pregnancy in the bitch, these are not susceptible to anthelmintics and so are only eliminated by preventing pregnancy or the death of the host.
=Control=
=Control=