Day 3: Ascarid Flashcards
What is the morphology and generalized life cycle of ascarids
Big worms in all animal species
Direct lifecycle with no intermediate host
Which ascarid is found in dogs
Toxocara canis
Toxascaris leonina
Which ascarid is found in cats
Toxascaris leonina
Toxocara cati
What is the morphology of Toxocara canis
Very large stout-bodied worms (6-10 inches long)
What is the lifecycle of Toxocara canis
Dogs infected when they ingest an egg containing L2 larva or migrating larva across the placenta
L2 hatches out of the egg and penetrates the intestinal wall
L2 larvae carried to the liver and migrate
L2 larva carried to lungs via circulation and molt to L3
L3 larva coughed up and swallowed
L3 larva molt to L4 and adults live in small intestines
How long is the prepatent period for Toxocara canis
4 weeks unless acquired in utero then it is 3 weeks
When does Toxocara canis perform tracheal migration
Occurs in puppies <3 months of age or in older dogs
When does toxocara canis perform somatic migration
Dogs >3 months
Larvae are carried to the lungs by circulation then to the muscles, liver and kidney where they arrest
Male dogs are a dead end source
Female dogs, larvae are mobilized during second month of pregnancy into the vasculature and cross the placenta and infect pups in utero
Pups pass eggs in feces shortly after birth (by 3 weeks) due to transplacental transmission
Parenteral larval stores in bitches will infect litters for at least 2 gestations
What are the routes of infection for Toxocara canis
Transplacental (most common)
Transmammary
Ingestion of embryonated egg from ground or in feces when bitch licks pups
Ingestion of paratenic host that has eggs within it (mouse)
What are the clinical signs of toxocara canis in young puppies with heavy infections acquired in-utero
Pneumonia
Inflammation of the stomach and intestines
Marked distension of the abdomen
Severe diarrhea
Vomiting
Dehydration
Death can occur in 12-72 hours
What do clinical signs depend on for Toxocara canis
Age of dog
Number of worms
Location of worms
Stage of worms
What are the clinical signs of toxocara canis in puppies that are 6 weeks to 6 months after early infection
Pot bellied appearance
Thin even when eating
Intermittent diarrhea
Occasionally anemic
Worms may be found in vomitus
What happens to older dogs and cats that become infected with toxocara canis
Thin with a poor haircoat due to resistance
What is the morphology of toxascaris leonina
Smaller than toxocara canis
Found in the dog and cat
What is the lifecycle of toxascaris leonina
Prepatent period is 6 weeks
Simple lifecycle
All development occurs in GI tract
What are the routes of infection of toxascaris leonina in dogs
Ingestion of egg with infection larvae
What are the routes of infection of toxascaris leonina in cats
ingestion of paratenic hosts (mouse) that ingested an egg
What are the clinical signs of Toxascaris leonina
Not serious unless many worms
Diarrhea
Poor body condition
Dehydration
What is the morphology of toxocara cati
Smaller than toxocara canis
Found in cat
Rare in dogs
What the route of infection of toxocara cati
ingestion of paratenic host
Transmammary transmission (Rare)
migration outside of GI tract (Rare)
What are the clinical signs of toxocara cati
Usually mild
Thin
Often vomit immature or adult worms
What is the morphology of Parascaris equorum
Horse roundworm
Very large stout adult worms (6-8 inches long)
What are the clinical signs of Parascaris equorum
Affects foals <6 months of age
Migrating larvae can cause “summer colds” with coughing
Fever
Anorexia
Diarrhea
Respiratory signs
Nasal discharge
Congestion
What is the clinical pathology of parascaris equorum
Masses of these large worms can cause bile duct and intestinal obstruction or perforation
Intussusceptions can occur
Blockage can lead to debilitation
Poor growth
Death
