6.9 Nematodes - Roundworms Flashcards
What are the general features of nematodes (5)
- elongate, tubular bodies
- thick, resistant cuticle
- muscles under cuticle
- simple alimentary tract
- separate sexes
What is the anatomy of female roundworms
- pair of blind-ended ovaries leading to uterus
- common vagina and vulva
- will store sperm for protracted periods
what is the anatomy of male roundworms
- single convoluted tubule gives rise to testes, vas deferens, and ejaculatory duct
- have a copulatory bursa -> can be pronounced in some groups
what is the life cycle of all nematodes
egg -> L1 -> L2 -> L3 -> L4 -> L5 -> adult
most parasitic nematodes have how many hosts
just one
what are some examples of the routes of infection of nematodes (6)
- infective forms penetrate of the skin
- ingestion of infective forms
- transplacental transmission
- transmammary transmission
- predator-prey transmission with IH or PH
- vector-borne transmission
what are the 3 different types of migrations nematodes can undergo as part of their life cycle? which 2 are associated with one another?
- tracheal migration
- somatic migration
- mucosal migration
Tracheal and somatic are associated
Describe tracheal migration
L3 nematodes journey from GI tract to heart to lungs to alveoli -> rupture of alveoli -> up airways to the trachea -> swallowed -> gut
Describe somatic migration
L3 nematodes stay in the blood to be distributed throughout the body
Describe mucosal migration
L3 nematodes penetrate the gastric pits or mucosa to develop and return to the lumen as an adult
What is the proper name for roundworms
ascarids
what are the general features of the roundworms (ascarids)
- robust and heavy-bodied
- host-specific
- eggs are resistant to environmental stress
- usually infect SI of definitive hosts
- lots involve tracheal migration
roundworms (ascarids) typically have a _______ life cycle
direct
describe the typical life cycle of the roundworms
females incredibly prolific and lay many eggs -> eggs mature to L3 in the environment -> ingestion of L3 eggs -> L3s penetrate the small intestine and undergo (typically tracheal) migration (note: many alternate routes such as hypobiosis, transmammary, transplacental) -> larvae return to the small intestine and mature to adults -> adults lay eggs
T/F paratenic hosts may be involved in roundworm life cycle
T
T/F roundworm eggs are infectious for short periods
F; extended periods
what is the typical pathogenesis of roundworms
- poor growth
- may have a potbelly
- obstructions if massive numbers
- minor lesions from migration
what is the name for the pathogenesis of zoonoses due to roundworms and why does it happen
ocular or visceral larval migrans (OLM or VLM) due to tracheal migration
describe the general features of Toxocara canis:
- adults
- eggs
- large, heavy bodied-adults in the small intestine (up to 18cm)
- thick-shelled, pitted egg containing a single cell
how do most pups acquire Toxocara canis
transplacental migration of larvae from the bitch to the fetus
describe the life cycle of Toxocara canis - what type of life cycle is this
DIRECT (no intermediate host)
larvae develop to infective L3 in the egg -> infective eggs ingested -> migration of larvae depends on age and immunity of host (<3m pup = tracheal; 3-6m pup = increasingly somatic; >6m = somatic only) ->
describe transplacental transmission of Toxocara canis
mom ingests infective eggs -> larvae undergo somatic migration and become hypobiotic -> during pregnancy some arrested larvae become mobilized -> enter lung and liver of fetus and wait for birth -> after birth complete tracheal migration
what is the typical PPP of Toxocara canis and the shortened PPP if there is transmammary/transplacental migration
Typical: 4-5w
Transmammary/transplacental: 3w
how might an adult dog get a Toxocara canis infection WITHOUT migration
by ingesting a paratenic host containing larvae
