4 – Ascarids Flashcards
Nematodes of dogs and cats
- Family Ascarididae
- Ascarids (roundworms)
- Toxascaris leonia (dogs and cats)
- Toxocara canis (dogs)
- Toxocati (cats)
- Baylisascaria spp. (dogs)
Toxascaris leonia (Northern roundworm)
- Small (couple cm)
- Long narrow alae on head
- 3 lips
- NO caudal projection on mall
- Eggs in females
Toxascaris leonia eggs
- Thick smooth shell
- Single cell
Toxascaris leonia lifecycle: dogs
- Eggs shed in poop of host
- Single shell egg
- L1-L3 inside egg (1-4 weeks)
- Eggs with L3
- Ingested by host (or paratenic host)
- Mucosal migration (through gut lumen and develop on outside)
- Come back into GI tract for nutrients=adults
Toxascaris leonia lifecycle:cats
- Eggs shed in poop of host
- Single shell egg
- L1-L3 inside egg (1-4 weeks)
- Eggs with L3
- Ingested by paratenic host (or definitive host)
- Mucosal migration (through gut lumen and develop on outside)
- Come back into GI tract for nutrients=adults
Toxascaris leonia diagnosis
- Fecal flotation, coproantigen, coproPCR
- Large adult worms in stool or vomit
Toxascaris leonia clinical signs (juveniles)
- Often asymptomatic
- Pot belly
- Poor growth
- Staring coat (‘clumpy’)
- Diarrhea
- Respiratory signs
- Seizures and death (very rare)
Toxascaris leonia: epidemiology and ecology
- Common in dogs in western Canada (not found in cats)
- Global distribution
- Canid and felid definitive hosts (prevalence and intensity highest in young)
- Wide range of vertebrate paratenic hosts
- NOT zoonotic
- Eggs survive months to years in environment (freeze tolerant)
Toxocara canis (canine roundworm): adults
- Long skinny alae
- 3 lips
- Male tail: caudal projection
- Eggs in female worms
Toxocara canis: eggs
- Thick, rough shell
- Larvae
Toxocara canis: life cycle young pups (under 3 months)
- Adults produce eggs and go into environment
- 2-8 weeks in environment (L1-L3, egg with L3)
- Hepatotrachael migration
a. GIT, liver, R heart, lung, coughed up and then swallowed again to GIT
*PPP: 4-5 weeks
Toxocara canis: life cycle (older than 6 months)
- Eggs with L3 go in via somatic migration
- Larvae in tissues: hypobiotic
- ‘reactivate’ in late pregnancy: cross placenta into fetal liver
- AND transmammary infection via larvae in milk (if infected late in pregnancy)
- (after birth: hepato-tracheal migration to develop patent infection, shed eggs 2-3 weeks old)
Age intensity curve
- If young prenatally infected transplacentally=higher load of adult worms
- If ingested eggs when young=higher load in intestine
o Switch to somatic
Toxocara canis: life cycle (dog of any age)
- If through paratenic host=mucosal route
- Inside the mucosal lining to go from L3 to L5
*every time they need to molt they need to feed=happens in lumen
*go inside lining to molt!
Toxocara canis: diagnosis
- Fecal floation, coproantigen, coproPCR
- Large adult worms in vomit or stoll
Toxocara canis: clinical signs (puppies)
- Often asymptomatic
- Pot belly
- Poor growth
- Staring coat
- Diarrhea
- Respiratory signs (more likely than leonia)
- Seizures and death (rare)
Toxocara canis: epidemiology and ecology
- Most common parasites in dogs in Canada
- Global distribution
- Canid definitive hosts (prevalence and intensity HIGHEST in young)
- Wide range of paratenic hosts
- People are accidental paratenic hosts
- Eggs survive months to years in environment
Toxocara cati (feline round worm): adult
- Short, wide alae
Toxocara cati: eggs
- Thick rough shell
- Single cell
- *need to do genetic testing
Toxocara cati: life cycle (young cats, less than 6 months)
- Adults shed eggs w/SINGLE cell
- L1-L3, eggs with L3 ingested (2-4 weeks in environment)
- Hepatotracheal migration
*PPP: 8 weeks
Toxocara cati: life cycle (pregnant cat)
- Eggs with L3 are ingested (late pregnancy or early lactation)
- Somatic migration and then larvae into tissues
- Larvae shed in milk throughout entire lactation
*patent as young as 6 weeks of age
Toxocara cati: life cycle (any age cat)
- Adults shed eggs with single cell
- L1-L3, eggs with L3 (2-4 weeks in environment) into paratenic host
- Once in cat, mucosal migration
*PPP: 6 week
Toxocara cati: diagnosis
- Fecal floatation
- Coproantigen
- CoproPCR
- Large adult worms in vomit or stool
Toxocara cati: clinical signs (kittens)
- Asymptomatic (less severe than T. canis)
- Pot belly, poor growth and coats
- Diarrhea
- Respiratory signs
- Seizures and death (rare)
Toxocara cati: epidemiology/ecology
- Most common parasites in CATS in Canada
- Glob distribution
- Felid definitive hosts (highest in young)
- Wide range of paratenic hosts
- People MAY be accidental paratenic hosts (less likely than w/dogs)
- Eggs survive months to years in environment
Toxocara canis and humans as accidental paratenic hosts
- Visercal, ocular, neural
- Occult: asymptomatic
- Liver, lungs, eyes
- Ex. kids in garden boxes, gardeners
Baylisascaris procyonis (raccoon roundworm)
- Dogs serve as DH, PH and mechanical transport hosts
- Larval migrans in PH (dogs and people)
- Single celled eggs in fresh feces of DH (differentiated by fecal floatation, coproantigen, coproPCR)
Baylisascaris procyonis (direct lifecyle)
- Racoon sheds eggs (or dog)
- 2 weeks in environment
- Eggs with L3 larvae ingested by racoon (or dog)
Baylisascaris procyonis (indirect lifecyle)
- Racoon sheds eggs
- Eggs with L3 larvae in environemtn
o Can be up to 180 paratenic hosts - Ingested by racoon (or dog)
Baylisascaris procyonis: epidemiology and ecology
- Wherever racoons are (NA, Europe, asia)
- Very rare in dogs (0.005% of fecal samples)
- Highly variable infection rate in racoons
Baylisascaris procyonis: paratenic host (dog)
- Very bad
- Dead end host (buried or cremated)
- Dx: clinical signs, histology, serology
- Tx: non specific
Baylisascaris procyonis: definitive host (dog)
- Not bad for this dog
- Source of eggs in environment
- Dx: single celled eggs in fresh feces
- Tx: as for other GIN
Baylisascaris procyonis: mechanical transport host (dog)
- Not bad for this dog
- Spread of eggs in environment
- Dx: larvated eggs in fresh feces
- Tx: none needed
Control of GI nematodes (GIN) in YOUNG dogs and cats
- Administer anthelmintic treatment: 2, 4, 6, 8 weeks of age
o Followed by monthly treatments to the age of 6 months (later for kittens) - Can synchronize with vaccination
- Conduct fecal exams 2-4 times during 1st year of life (1-2/year in adults)
Control of GI nematodes (GIN) in PREGNANT or NURSING dogs and cats
- Treat nursing females at 2 weeks post partum
- Treat pregnant females off label
Control of GI nematodes (GIN) in adult dogs and cats
- Only HIGH risk pets
- Pets in high risk households
- Pets with positive fecal tests
*test twice a year, treat 3-4 times a year
High risk animals
- Young (under 6 months)
- Highly exposed (dog parks, outdoor access, hunters, raw diets)
- Highly susceptible
- Clinically ill animals
- *test at least twice a year
- *treat 3-4 times/year
Animals in high risk households
- YOPI (young, old, pregnant, immunocompromised)
Animal management to prevent parasites
- Regular disposal of feces
- Feed cooked or canned food
- Spay females
Public health measures to prevent parasites
- Hand washing
- Cover sandboxes
- Wash veggies
- Cook meat thoroughly
