Nematodes: Roundworms

Large Roundworms of Dogs

Toxocara canis

What does a roundworm (T. canis) ova look like?

Round, thick outer membrane, large dark nucleus

When do roundworm (T. canis) ova become infective?

2 - 4 weeks

How many eggs do female Roundworms (T. canis) produce a day?

75,000 - 85,000 eggs

What parasite are most puppies born with?

Toxocara canis

4 Methods of Transmission of Toxocara canis (roundworm)

1. Direct Transmission

2. Transplacental

3. Transmammary

4. Predation of Paratenic Host

Types of Direct Transmission

Tracheal Migration

Somatic Migration

Tracheal Migration in

Steps

Eggs swallowed → hatch in stomach, larva penetrate intestinal mucosa → migrate to liver then lungs → coughed up

Takes ~ 1 month

Tracheal Migration

Eggs in soil infective in 4 weeks

Migrate & mature in the SI

mostly in young pups

Somatic Migration

Steps

eggs swallowed → hatch in stomach, larva migrate to tissue → development arrested (encysts) in tissue

mostly in adult dogs

Larva encysted in tissue

Hypobiotic larva

Transplacental Transmission

Hybiotic larva reactive during pregnancy → enter puppies in utero

happens in 3rd trimester (day 42)

Transmammary Transmission

Larva shed in mothers milk → swallowed by puppies → tracheal route

pups will develop adults in 3 - 4 weeks

Predation of Paratenic Hosts

Least common route for dogs

Clinical Signs of Roundworm (T. canis)

- Lack of growth

- Potbelly

- Straddled leg appearance

- Vomiting worms

- Cough

- Diarrhea

mostly noted in puppies

Dx of T. canis (roundworm)

- Microscopic exam of feces

- Gross exam of feces and vomit

How common are Roundworms?

1 out of 10 fecal exams contain roundworm eggs

What does Roundworm cause when infecting humans?

Visceral Larva Migrans (VLM)

Roundworm travel in humans

ingest → hatch in SI → bloodstream → tissue

Where can Roundworms migrate to, besides the SI?

Eyes, Ocular Larva Migrans (OLM)

Large Roundworm of Cats

Toxocara cati

What does a T.cati (roundworm) ova look like?

Round, thick outer membrane, large dark nucleus

(bit smaller than T.canis)

When does T. cati (roundworm) become infective?

2 - 4 weeks

Are kittens born with roundworms?

No

Can T. cati (roundworm) be passed tramsmammary?

No

Methods of Transmission of Toxocara cati

Direct, Transmammary, Predation of Paratenic Host

How long does Direct Transmission take for Toxocara cati?

2 months

How long does Transmammary take in Toxocara cati?

2 months

How long does Predation of Paratenic Host take in Toxocara cati?

2 months

Roundworm of both Dogs and Cats

Toxoscaris leonina

What do Toxoscaris leonina ova look like?

Round/oval, thinner outer membrane, large round nucleus

When does Toxoscaris leonina become infective?

1 week

Can T. leonina be transmitted transplacentally or transmamary?

No

Direct Transmission of T. leonina

ingested → develop in SI

Takes 2 - 2 1/2 months

Predation of Paratenic Host of T. leonina

Takes 2 months

Methods of Transmission of Toxoscaris leonina

Direct Transmission

Predation of Paratenic Host

Is Toxoscaris leonina considered Zoonotic?

No