toxocara canis veterinary and zoonotic importance, diagnosis and control professor dennis jacobs the...

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