nematodes 4 Flashcards
order ascaridida-ascarids
roundworms
large, stout-bodies
bigger than most other nematodes
highly successful parasites in all vertebrate classes
direct life cycle
live in lumen of small intestine
feed on lumen content, host fluids
does not attach
females are very prolific
ascaridida- ascarids eggs
eggs passed in fresh feces-unembryonated, thick shell
highly resistant to environmental conditions (last up to 10 years)
development to infective stage (egg with L3) 2-4 weeks
egg is not infective until it is fully embryonated
infective larva does not hatch until the egg is swallowed by a host
patent infections not usually hard to detect
life cycle-ascaridida-ascarids
some go straight to the intestine after ingestion by host and develop to adults
some, including important mammalian species have larval migratory phase in definitive host
equine ascarids life cycle
adults in small intestine
females bigger up to 50 cm
eggs passed in manure
larvae hatch in intestine and penetrate the wall
then hepatotracheal migration
carried to liver in blood, and enter hepatic portal system
reach lungs about 1 week PI
coughed up and swallowed
return to small intestine
PPP about 3 months
parascaris-clinical importance
common in young horses
low worm burden may be subclinical
adults in small intestine
competition with host for nutrients
poor conditions, rough hair coat, pot belly
very heavy infection can lead to perforation or impaction
larvae in lings (heavy infection)
mechanical and inflammatory damage
nasal discharge
parascaris equorum
patent infection occurs in foals and young horses
immunity develops adults rarely have patent infections
adults dont play a role in parasite transmission
different from strongylid nematodes, where even adults animals have some worms in GI tract
ascarids in small animals
dogs and other canids-Toxocara canis
cats and other felids- Toxocara cati
toxascaris leonia-small animals (Dogs and cats)
toxocara canis life cycle-environment
eggs passed in feces of infected animals
takes 3-4 weeks in environment to become infective
can survive long periods if protected from desiccation
complex life cycle
toxocara canis life cycle
adults T canis in small intestines-eggs containing one cell in feces-eggs containing infective larvae in soil
either egg ingested by paratenic host OR ingested by dog
if ingested by dog-either somatic migration, then infective larvae arrested in tissue of the bitch-then either larvae in lungs then back to small intestine or straight to small intestine
if ingested by dog-hepatotracheal migration-then back to small intestine
if ingested by paratenic host- somatic migration-infective larvae arrested in tissue of paratenic host-then eaten by dog then small intestine
if ingested by paratenic host-
hepatotracheal migration
greater proportion in dogs < 3 months of age
occurs in adult but a lower proportion
somatic migration
more likely in older > 3 months of age more immune animals
toxocara canis- route of transmission
ingestion of infective egg
transplacental-most common-not in hookworms
transmammary-most common in hookworms
paratenic host-transport
toxpcara canis-clinical signs
most clinical signs in puppies
low burden-few or no signs
moderate to heavy burden-diarrhea/constipation
colic and pot belly
vomiting (Worms can be seen)
poor hair coat
intestinal obstruction
pneumonia
toxocara canis-diganosis
patent infection
fecal exam
somatic reservoir
3 most common canine nematodes
hookworms
roundworms
whipworms
