Toxocara small animals Flashcards
Morphology of ascarirds
10-40cm long
3 lips, no bursa, wings
> Wings are large in toxocara catii
What is the most common route of transmission of toxocara canis
Transplacentally
Structure of a toxocara canis egg
Dark orange/yellow
Beehive strucutre outer shell
Life cycle of toxocara canis
Larvae develop to L3 stage WITHIN EGG in environment; then eaten and hatches out in intestine –> migrates to liver via CdVC to heart to lungs –> coughed up and swallowed; THEN reaches intestine to become an adult
What happens when human ingest toxocara canis eggs
Larvae can’t do the somatic migration properly
–> Get erratic migration to tissues including eye and brain
What happens when puppies ingest infective L3s of toxocara
Normal life cycle; migration via liver, heart, lungs, intestine; become adults in intestine
–> Get pot0belly
What happens with adult dogs (>6mo) ingest toxocara infective L3s
Immune response mounted which stops somatic migration
–> Get sequestration of larvae in tissues by immune system
–> Remain alive for rest of dogs life and can REACTIVE in PREGNANCY to give TRANS-PLACENTAL transmission
Why do toxocara larvae reactivate during pregnancy
Due to immunosuppressive effects of progesterone
Normal PP of full toxocara canis life cycle
4-5 weeks
What is the PP of toxocara canis in puppies infected transplacentally
2-3 weeks; because half of migration has already happened while in utero
How does toxocara canis lifecycle work when puppies infected in utero
Re-activation of larvae 3 weeks before parturition; migrate to fetus and moult just before birth –> go to lungs and stop here
THEN: at birth, complete migration up trachea, down pharynx and to intestine
When should we treat dogs for toxocara canis
At 2-3 weeks after birth; to protect against transplacental infection
Then at 4-5 weeks after birth; to protect against eggs acquired since birth
Then every month until 6 months; because PPP normally = 4-5 weeks
From 6 months: should be immune; only treat if immunsuppressed
How would we treat toxocara canis bitch to prevent transmission to offspring
Would have to treat daily with fenbendazole from 3 weeks pre-parturition (around the time the larvae reactivate)
Development of toxocara canis larvae in pups when acquired from milk (first 3 weeks after birth)
No migration; just develop in the intestine to adults
What happens in dogs/foxes ingest hypobiotic L3s from paratenic hosts of toxocara canis
NO MIGRATION; just continue development in the intestine
