Toxocara canis (1)

Question 1

What is the common name?

Answer 1

Roundworm

Question 2

What is the final host?

Answer 2

Dogs

Question 3

What are the paratenic hosts?

Answer 3

Rodents or birds

Question 4

Describe an adult

Answer 4

10-15 cm

Small finger like process on the tail of male

In small intestine - stretched out straight

Question 5

Describe egg

Answer 5

Thick shell

Dark brown

Round

85x75 micro m

Pitted

Question 6

What are the modes of infection?

Answer 6

Per os - longest route of infection

Transplacental or prenatal

 - Common
 - Less migration

Transmammary

 - Common
 - Less Migration

Paratenic Host - longest route of infection

Question 7

Describe the life cycle

Answer 7

Egg -> egg with L2: 2-4 weeks

Most puppies are born with Toxocara

PPP: 3-8 weeks

Question 8

What is important about life cycle?

Answer 8

Takes time for larvae to show up in egg

Transplacental/Transmammary

 - Transplacental - 1 time infection
 - Transmammary - continuous infection

Question 9

What is the site of infection?

Answer 9

Small intestine

Question 10

Describe the Pathogenesis

Answer 10

Puppies born infected or become infected shortly after birth

Acquires immunity - can alter the intestinal lining: L3 less able to
penetrate to begin
hepatic-tracheal
migration

Pregnant bitch - change in immunity enables arrested larvae to resume
development

PH route of infection in adult dogs

Entire nematodes pass with feces and vomitus

Heavy infections in puppies

Clinical signs before eggs

Visceral larval migrans and ocular larval migrans in humans
- L3 excreted in feces and dies

L3 that do not penetrate intestinal wall, migrate to distribute via circulatory system to tissue
- Development arrested

Few might continue to small intestine to develop into adult worms

Question 11

Describe what happens in pregnant bitches

Answer 11

Look for eggs in feces because indication that mother has larvae that have developed into adults and larvae in Transplacental/Transmammary

3 routes - usually harbors sufficient somatic L3 to infect several litters
- L3 -> placenta at 6 weeks gestation -> Fetal liver (via blood)
- Transplacental - pups most common
- L3 migrate to mammary glands -> milk, first 3 weeks of lactation
(Transmammary)
- L3 -> small intestine in bitch
- Per os - most common in young dogs

Question 12

Describe heavy infections in puppies

Answer 12

Prenatal or Transmammary infections can die from pneumonia

 - Result in tracheal migration
 - No egg in feces because it is a larval migration

Vomit after each meal

Question 13

Describe the clinical signs

Answer 13

Depend on:

 - Age of dog
 - Number of T. canis

Moderate infections: Few issues

Heavy infections

 - Severe abdominal discomfort 
 - Death
        - Rupture/obstruction of intestines
 - Migratory phase: Pneumonia 
 - Pot Belly appearance 
 - Vomitting
 - Diarrhea
 - Unthrifty pup
 - Feces range from normal to unformed and mucoid

Question 14

How do you diagnose?

Answer 14

Egg in fecal flotation - Adults at necropsy, or in feces/vomitus

Vet has responsibility to diagnose and inform the public

Question 15

How do you treat?

Answer 15

Anthelmintics used to L4, immature adult, and adult

Treatment of pregnant bitch decrease transmission

Adult nematodes easily removed

Adult dogs

 - Treat monthly
 - Treat every 3-6 months

Question 16

How to prevent?

Answer 16

Dispose of fresh feces

Control should be in puppies

 - Prevent transfer to somatic stages
 - Treat pregnant bitch 
 - Frequent treatment of puppies
        - Treat at 2, 4-5 and 8 weeks of age
        - Treat at 3, 6, and 10-12 weeks of age
 - Treat to kill L4 and immature adults pre-egg shedding

Question 17

What is important about Toxocara canis?

Answer 17

It is ZOONOTIC - causes Visceral Larval Migrans (VLMs)