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

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

Toxocara canis life-cycle

T. canis: infection of puppies L2 Spontaneous expulsion occurs from 6 weeks old

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

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

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

Patent infections in adult dogs especially nursing bitches

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

Human infection Also a paratenic host!

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

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

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

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

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

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

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

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

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

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

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

Another ascarid worm in dogs - Toxascaris leonina

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

Ascarid worms in cats: Toxocara cati Toxascaris leonina

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

Diagnosis Toxascaris Toxocara Toxocara

Nematode eggs in dog faeces Whipworm Hookworm Toxocara Toxascaris

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

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