Toxocara Canis

Question 1

Toxocara canis

Answer 1

Most common ascarid or roundworm of canids

Question 2

Morphology

Answer 2

Long, white, straight
Prominent cervical alae – lancelet shaped
Males up to 10 cm; females up to 20 cm long

Question 3

Egg

Answer 3

Thick, pitted shell (mamillated)
Deep brown color
Survive several years in soil
Ideal conditions, 2 weeks to become infective (L2)

Question 4

Life Cycle (Direct Transmission)

Answer 4

Ingestion of infective embryonated eggs (L2), release of larvae in GI tract, migrate to liver, to lungs, up trachea, swallowed, go to small intestine where molt to L5, produce eggs in about 1 month (prepatent period)

Called hepatotracheal migration

In older dogs, larvae migrate via circulation to various tissues and organs and encyst there. Therefore, few adult worms are found in the gut.

Question 5

Life Cycle (Transplacental transmission)

Answer 5

Primary route of infection for puppies
Encysted larvae in bitch’s tissues become activated at day 42 of gestation and migrate to the fetal liver. Eggs may appear in fecal exams by three weeks of age.

Question 6

Life Cycle(Transmammary transmission)

Answer 6

Encysted larvae pass in the bitch’s milk to nursing puppies. No migration occurs.
Relatively unimportant route in puppies, and may not occur.

Question 7

Life Cycle (Ingestion of paratenic hosts)

Answer 7

Many animals serve as paratenic hosts

More important method in wild canids.

Question 8

Clinical Signs

Answer 8

Vary from none to death
Unthriftiness
Pot-belly
Dull hair coat
Diarrhea or constipation
Rarely, intestinal obstruction, possibly followed by intestinal rupture
Verminous pneumonia

Question 9

Diagnosis

Answer 9

Adult worms in feces or vomitus

Ova (eggs) on fecal flotation

Question 10

Control:

Answer 10

Most canine dewormers are effective – Pyrantel pamoate in Nemex, Strongid, Drontal Plus most often used
Deworm at 2-3 weeks of age; repeat every 2 weeks, depending on situation until on heartworm prevention
Common heartworm preventatives also prevent/treat roundworm infections

Question 11

Public Health Significance

Answer 11

Ingestion of L2 eggs by humans may cause Visceral or Ocular Larval Migrans (VLM/OLM)
Much more common in children
Larvae migrate through the body, usually to the liver or lungs, but occasionally to the CNS or eyes. Blindness may result if the larvae invade the retina. Up to 600 cases per year reported in the U.S.
EDUCATE the public.

Question 12

Baylisascaris Procyonis

Answer 12

Roundworms of raccoons, may cause OLM/VLM and might sometimes infect dogs.