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Toxocara canisVeterinary and
zoonotic importance,diagnosis and control
Professor Dennis Jacobs
The Royal Veterinary College (University of London)
www.rvc.ac.uk
Toxocara canisToxocara canisveterinary importanceveterinary importance
Very common in puppies
Heavy infections:
suboptimal growth-rates or weight-losspot-belly (swollen abdomen)
diarrhoea/ vomiting
worms passed
Smaller worm burdens in adult dogs
Toxocara canisToxocara canis life-cyclelife-cycle
T. canis:T. canis: infection of infection of puppiespuppies
L2
Spontaneous expulsion occurs from 6 weeks old
T. canis:T. canis: infection of infection of the bitchthe bitch
Somatic larvaeSomatic larvae waiting for:
pregnancy
T. canis:T. canis: infection of infection of non-canine (paratenic) hostsnon-canine (paratenic) hosts
Somatic larvaeSomatic larvae Waiting for:
their host to be eaten by another animal
Basic epidemiological cycle
Prenatal and transmammary
transmission
Egg in environment
Remember!
Egg excretion in pups starts between
2 and 3 weeks of age
Patent infections in adult dogs
especially nursing bitches
Paratenic hosts
Significant for fox, wolf, dingo etc
Also a paratenic host!
Human infection
Toxocara canisToxocara canis public health importancepublic health importance
Visceral larva migrans (VLM)
Ocular larva migrans (OLM)
Occult toxocariasis2.5% seropositive in
United Kingdom
The key to the epidemiology of T.canis is ..
.. the egg in environment
Control of Control of ToxocaraToxocara in dogs in dogsTreatment objectivesTreatment objectives
Short term:welfare of pups
Short term:welfare of pupsLonger term:stop eggs getting
into environmentX
Control of Control of ToxocaraToxocara in dogs in dogsTreatment objectivesTreatment objectives
X
X
X
XX
Reduces accumulation of somatic larvae in bitch
Reduces risk of human infection
Chemotherapeutic targets in puppiesChemotherapeutic targets in puppiesWhat worms are we trying to kill?
New adults appear soon
after treatment if larvae
not killed!
Migrating larvae
Adult worms
Control of T.canis:PiperazinePiperazine
Widely used
Cheap, available from supermarkets etc.
Efficacy v adults: ~85%
Efficacy v larvae:Efficacy v larvae: NONENONE
Therefore, frequent doses needed
Treat at 2, 4, 6, 8 and 12 weeks of age
Control of T.canis
Compounds that do not kill migrating larvae
do not eliminate egg-output(as new adults quickly appear)
Therefore, they
perpetuate the hazardperpetuate the hazard
for puppies and humansfor puppies and humans
Control of T.canis: FenbendazoleFenbendazole
In pups:
3 x 50 mg/kg
Efficacy v adults: ~100%
Efficacy v larvae:Efficacy v larvae: ~ 95%~ 95%
Treat at 3 and 6 weeks of age
Somatic larvaeSomatic larvae
Another chemotherapeutic target in Another chemotherapeutic target in the bitchthe bitch
X
killing these will
protect pups
and reduce the future output of eggs in the environment
X
Prevention of prenatal and Prevention of prenatal and transmammary transmissiontransmammary transmission
Only licensed treatment in UK is:
FENBENDAZOLE
25 mg/kg/day
daily from Day 40 of pregnancy
to 2 days post-partum
Don’t forget!Don’t forget!
Treat nursing bitches for adult worms
Hygiene important!Note: eggs resistant to
disinfectants
Treat adult dogs at least 2x per year
Another ascarid worm in dogs -
Toxascaris leonina
Toxascaris leoninaToxascaris leoninais like T.canis except:
Infects: dogs and cats also bears etc
Most important routes of transmission:embryonated eggs
eating ‘paratenic’ hosts (mice etc)
NO prenatal infection
NO transmission via milk
NO body migration
Zoonotic importance: probably little or none
Ascarid worms in cats:
Toxocara cati
Toxascaris leonina
Toxocara catiToxocara catiis like T.canis except:
NO prenatal infection
Most important routes of transmission:via milk
by eating paratenic hosts (mice etc)
Infects: cats and other felidae
Zoonotic importance: uncertain
DiagnosisDiagnosis
ToxocaraToxocara
Toxascaris
Nematode eggs in dog faecesNematode eggs in dog faeces
WhipwormWhipworm
HookwormHookworm
ToxocaraToxocara
ToxascarisToxascaris
Identifying ascarids Identifying ascarids
T.canis T.catiT.leonina
Dog Cat
The end
Any questions?
www.rvc.ac.uk