18: SA Roundworm

Best way to prevent infection with intestinal helminths

Pick up after your cat and dog

Life cycle of ascarids

Direct

SA roundworm species of importance

• Toxocara canis

• Toxocara cati

• Toxascaris leonina

• Baylisascaris procyonis

Roundworms that infect dogs

T. canis, T. leonina, and B. procyonis

Roundworms that infect cats

T. cati and T. leonina

Additional host in roundworm life cycles

Paratenic host

Where do SA roundworms set up shop

• Small intestine

• Heptatotracheal migration

• Mammary tissue

• Somatic sequestering

When and in who does T. canis arrest and sequester in tissues

Before it gets to the small intestines in older dogs

T/F: T. canis is zoonotic

Yes :(

Morphologic features of T. canis eggs

LARGE egg with golf ball type pitting of wall

Morphologic features of T. canis adults

One of the largest SA intestinal parasites; big round white worm with narrow cervical alae and 3 lips

T. canis infectious stage

Larvated egg

Routes of T. canis infection in order of likelihood

• Transplacental

• Ingestion of eggs

• Ingestion of PH

• Transmammary

PPP of T. canis

2-4 weeks, closer to 2 weeks if transplacental

Demographic most likely to be diagnosed with T. canis

Puppies

In which patients is somatic sequestration of T. canis a dead end for the worm

Males and spayed females

CS associated with T. canis

• Poor doing puppy

• GIT signs ± obstruction

• Blocked bile ducts

• Resp signs! Migration!

Primary diagnostic for T. canis

Really any fecal testing

Most sensitive diagnostic for T. canis

Fecal Ag test

Key differences between T. cati and T. canis transmission

• No age cut off for shedding vs somatic sequestration - even adult cats shed eggs!

• No transplacental transmission

Morphologic features of T. cati egg

Similar to T. canis, just smaller

Morphologic features of T. cati adults

Larger feline nematode with broad cervical alae and 3 lips

Infectious stage of T. cati

Larvated egg

Routes of T. cati transmission in order of likelihood

• Ingestion of PH

• Ingestion of larvated egg

• Transmammary

PPP of T. cati

8 weeks

CS associated with T. cati

• Pot bellied

• Vomiting and diarrhea

• Respiratory signs → migration!

Primary diagnostic for T. cati

Like T. canis basically any fecal test works

Other SA parasites that can cause respiratory disease

Lungworms and hookworms!

Regional/situation distribution of T. leonina

More northern distribution and more in captive animal situations (zoos and catteries)

How is the life cycle of T. leonina different than that of T. canis/cati

No hepatotracheal migration, so it stays entirely in the GIT

Morphologic features of T. leonina eggs

Smooth outer shell with ruffled inner membrane

Routes of T. leonina infection

Ingestion of eggs or PH

CS associated with T. leonina

Not often pathogenic

Diagnostics used for T. leonina

Basically any fecal test

Go-to treatment for SA roundworms

Pyrantel

Other parasiticides for SA roundworms and associated uses

• Fenbendazole: pregnant animals

• MCL (+ pyrantel): prevention

Management principles for SA roundworms

• Clean up poop

• Limit wildlife

• Prevent predation

• Routine deworming → especially for pregnant mamas

Primary host of B. procyonis

Racoons

How do dogs fit into the life cycle of B. procyonis

Dogs can act as a DH, PH, or transport host

When is it really bad if a dog is infected with B. procyonis

If it is the PH

Routes of B. procyonis infection

Ingestion of eggs or PH

What does B. procyonis do in the dog as a DH

Dog is has intestinal infection, and it actively sheds eggs

What does B. procyonis do in the dog as a transport host

The dog ate non-infectious eggs that pass through before they become infectious and get deposited somewhere else

What does B. procyonis do in the dog as a PH

Larva migrans → systemic disease

CS associated with B. procyonis in the dog

Generally none, occasionally neurologic signs due to aberrant migration

Morphologic features of B. procyonis eggs

Small, dark egg with a thick proteinaceous coating

Morphologic features of B. procyonis adults

Similar to other roundworms but with no obvious cervical alae

Diagnostics for B. procyonis

Fecal float, Ag, or PCR

Treatment for B. procyonis

Anything with RW efficacy

SA RW most commonly transmitted to humans

T. canis

SA RW that causes the most severe disease in humans

B. procyonis → visceral, ocular, and neural larval migrans