1. Veterinary and zoonotic importance,
Toxocara canis
Veterinary and zoonotic importance,
diagnosis and control
Professor Dennis Jacobs
The Royal Veterinary College (University of London)

2. Toxocara canis veterinary importance
Very common in puppies
Heavy infections:
suboptimal growth-rates or weight-loss
pot-belly (swollen abdomen)
diarrhoea/ vomiting
worms passed
Smaller worm burdens in adult dogs

3. Toxocara canis life-cycle

4. T. canis: infection of puppiesL2
Spontaneous expulsion occurs from 6 weeks old

5. T. canis: infection of the bitch
Somatic larvae
waiting for:
pregnancy

6. T. canis: infection of non-canine (paratenic) hosts
Somatic larvae
Waiting for:
their host to be eaten by another animal

7. Basic epidemiological cycle Prenatal and transmammary transmission
Remember!
Egg excretion in pups starts between
2 and 3 weeks of age
Egg in environment

8. Patent infections in adult dogs especially nursing bitches

9. Significant for fox, wolf, dingo etc
Paratenic hosts
Significant for fox, wolf, dingo etc

10. Human infection
Also a paratenic host!

11. Toxocara canis public health importance
Visceral larva migrans (VLM)
Ocular larva migrans (OLM)
Occult toxocariasis
2.5% seropositive in United Kingdom

12. The key to the epidemiology of T.canis is ..
.. the egg in environment

13. Control of Toxocara in dogs Treatment objectives
Short term:
welfare of pups

14. Control of Toxocara in dogs Treatment objectives
Short term:
welfare of pups
Longer term:
stop eggs getting into environment X X X X X X
Reduces accumulation of somatic larvae in bitch
Reduces risk of human infection

15. Chemotherapeutic targets in puppies What worms are we trying to kill?
Migrating larvae
New adults appear soon after treatment if larvae not killed!
Adult worms

16. Control of T.canis: Piperazine
Widely used
Cheap, available from supermarkets etc.
Efficacy v adults: ~85%
Efficacy v larvae: NONE
Therefore, frequent doses needed
Treat at 2, 4, 6, 8 and 12 weeks of age

17. Control of T.canis perpetuate the hazard for puppies and humans
Compounds that do not kill migrating larvae
do not eliminate egg-output
(as new adults quickly appear)
Therefore, they
perpetuate the hazard
for puppies and humans

18. Control of T.canis: Fenbendazole
In pups:
3 x 50 mg/kg
Efficacy v adults: ~100%
Efficacy v larvae: ~ 95%
Treat at 3 and 6 weeks of age

19. Another chemotherapeutic target in the bitch
Somatic larvae X
killing these will
protect pups
and reduce the future output of eggs in the environment X

20. Prevention of prenatal and transmammary transmission
Only licensed treatment in UK is:
FENBENDAZOLE
25 mg/kg/day
daily from Day 40 of pregnancy
to 2 days post-partum

21. Don’t forget! Hygiene important! Treat nursing bitches for adult worms
Note: eggs resistant to disinfectants
Treat adult dogs at least 2x per year

22. Another ascarid worm in dogs -
Toxascaris leonina

23. Toxascaris leonina is like T.canis except:
Infects: dogs and cats also bears etc
NO prenatal infection
NO transmission via milk
NO body migration
Most important routes of transmission:
embryonated eggs
eating ‘paratenic’ hosts (mice etc)
Zoonotic importance: probably little or none

24. Ascarid worms in cats:
Toxocara cati
Toxascaris leonina

25. Toxocara cati is like T.canis except:
Infects: cats and other felidae
NO prenatal infection
Most important routes of transmission:
via milk
by eating paratenic hosts (mice etc)
Zoonotic importance: uncertain

26. Diagnosis
Toxascaris
Toxocara
Toxocara

27. Nematode eggs in dog faeces
Whipworm
Hookworm
Toxocara
Toxascaris

28. Identifying ascarids
Cat
Dog
T.canis
T.leonina
T.cati

29.
The end
Any questions?