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
Differences in transmission of toxocara catii compared to canis
No transplacental transmissin
Transmammary transmission only occurs if there has been ACUTE infection in pregnancy
Tracheal migration route is likely throughout life
What is different about toxocara leonine
(morphologically similar to T canis; BUT doesnt affect dogs/foxes)
NO MIGRATION: just briefly move within intestine wall
What is cutaneous larva migrans caused by
HOOKWORMS: penetration of skin by larvae
What are the three syndromes that toxocara can cause zoonotically; LARVA MIRGANS
Ocular
Encephalic
VIsceral
Finding ascarids on a puppy PM
quite likely; most puppies have them
NB: if you find worms in peritoneum remember this probably happened POST-MORTEM
Drugs used to treat toxocara canis
Piperozine (non perscription) works against intestinal stages only
Fenbendazole, avermectins: good against tissue stages BUT need high dose and frequent dosing to be effective aginst hypobiotic larvae in the tissues
FOr puppies: Nitrosconate
How does fenbendazole work against toxocara canis
Binds tubules; causes slow death
- = a benzimidazole
