Parasitology ascarids Flashcards
The most important pathogenic mechanism in canine hookworm is?
severe anemia caused by blood feeding worms
T/F? In order to differentiate small vs large strongyles we measure the amount in the feces?
False
Order ascaridida
roundworms
large, stout bodies
bigger than other nematodes
very successful in all vertebrates
direct life cycle
live in lumen of small intestine, feed on lumen contents
do not attach
ascarid life cycle
- Eggs passed in fresh feces
- Development to infective stage (egg with L3): 2-4 weeks
- Infective stage is L3 embryonated egg (larva inside)
- The infective larva does not hatch until the egg is swallowed by a host
- Some species go straight to the intestine after ingestion by host and develop to adults (Ascaridia galli in chickens)
Some, including important mammalian species, have larval migratory phase in definitive host (Parascaris spp. in horses
Toxocara spp. in dogs and cats)
ascarid eggs
- Unembryonated, thick shell
- Highly resistant to environmental conditions
- Disinfectants largely ineffective, may survive years
Patent infections
infection with adults that are reproducing
equine ascarids
parascaris
Adults in small intestine
1. Eggs passed in manure
2. Larvae hatch in intestine, penetrate wall
3. Hepatotracheal migration
-Carried to liver in blood
-Enter hepatic portal system
-Reach lungs about 1 week PI
-Coughed up and swallowed
-Return to small intestine
4. PPP about 3 months
parascarids clinical importants
equine ascarids
Common in young horses
Low worm burdens may be subclinical
Adults in small intestine
Competition with host for nutrients
* Poor condition, rough hair coat, pot belly
* Very heavy infection can lead to perforation or impaction
Larvae in lungs (heavy infection)
* Mechanical and inflammatory damage
* Nasal discharge
Patent infections occur in foals and young horses (<2-3 years)
Immunity develops, adults rarely have patent infections
Adults don’t play a role in parasite transmission
Different from strongylid nematodes, where even adults animals have some worms in GI tract
toxocara
order ascarids (roundworm)
in small animals
Dogs and other canids: T. canis
Cats and other felids: T. cati
toxacara canis life cycle
Similar to Parascaris in the environmental portion
* Eggs passed in feces of infected animals
* Take at least 3-4 weeks in environment to become infective
* Can survive long periods if protected from desiccation
In host:
1. dog ingests eggs
2. if puppy: hepatotracheal migration (ppp 3 weeks, takes 3 weeks after birth to see in feces)
3. if adult: somatic migration (infective larvae arrested in tissues of bitch, ppp 4-5 weeks)
-larvae in lungs of pups (infect in uterus), shed in milk
4. paratenic host: somatic migration, then eaten by dog
dogs can have somatic/heptatotracheal, horses only have hepatotracheal
hepatotracheal migration
- Carried to liver in blood
- Enter hepatic portal system
- Reach lungs about 1 week PI
- Coughed up and swallowed
- Return to small intestine
toxacara canis routes of transmission
Ingestion of infective eggs
Transplacental
Transmammary infection
Paratenic hosts
What route of transmission occurs in ascarids but not hookworms?
transplacental
what route of transmission occurs in hookworms but not ascarids
skin penetration
toxocara canis clinical signs
Most clinical signs seen in puppies
Low burdens: no or few signs
Moderate to heavy burdens
* Diarrhea/constipation
* Colic and pot belly
* Vomiting (worms can be seen)
* Poor hair coat
* Intestinal obstruction
* Pneumonia
toxocara cati life cycle differences from canis
Somatic reservoir appears to be less important
Some transmammary transmission occurs, transplacental does NOT
Longer PPP
