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
What is the pathogenesis of Toxocara canis during the intestinal phase:
- light infection
- heavy infection
- very heavy infection
- huge infection
- light infection: few clinical signs
- heavy infection: unthriftiness, stunted growth with dry and dull coat
- very heavy infection: vomiting with worms or worms in feces
- huge infection: cachexia
What is the pathogenesis of Toxocara canis during the migratory phase (4)
- eosinophilic gastroenteritis
- lung issues
- focal lesions from dead larvae
- eosinophilia in dogs and humans (called VLM or OLM in humans)
how should you treat heavy infections of Toxocara canis
Fenbendazole
What is the feline roundworm called
Toxocara cati
What is the canine roundworm called
Toxocara canis
What are the characteristic features of Toxocara cati
cervical alae (cuticular extensions) that give an arrowhead appearance
what do Toxocara cati eggs look like
thick-shelled, pitted, containing a single cell
how do you distinguish Toxocara canis and Toxocara cati eggs
based on history (is this a dog or a cat)
what is the lifecycle of Toxocara cati - what type of life cycle is this
DIRECT life cycle
infective eggs containing L3s are ingested -> L3s undergo tracheal migration in young cats and somatic migration in older cats -> transmammary infection in lactating cats
T/F paratenic hosts are involved in the lifecycle of Toxocara cati
T -> can cause a short-lived infection in older cats that are able to hunt
what is the pathogenesis of Toxocara cati
- vomition with worms
- unthriftiness and diarrhea (uncommon)
What type of roundworm infects both dogs and cats
Toxascaris leonina
how can we tell apart Toxocara cati and Toxascaris leonina
Toxascaris leonina does not have the cervical alae (cuticular extensions)
describe the egg of Toxascaris leonina
smooth outer shell; undulating inner shell; single cell or pair of cell that does not fill the entire egg shell
what is the lifecycle of Toxascaris leonina - what type of life cycle is this
DIRECT life cycle
infective L3 eggs ingested -> eggs release L3 into the intestine -> mucosal migration
what is the PPP of Toxascaris leonina
2 months
what is the pathogenesis of Toxascaris leonina
usually not a heavy burden and not as pathogenic as Toxocara
What roundworm species infects equids
Parascaris equorum
Describe the appearance of Parascaris equorum adults and eggs
heavy-bodied adults, eggs sub-spherical with a thick protein coat
what is the life cycle of Parascaris equorum
direct with tracheal migration through liver and lung
what is the PPP of Parascaris equorum
10-12w
what is the pathogenesis of Parascaris equorum
- unthrifty, loss of appetite, hypoalbuminemia
- colic with heavy burdens
how should you treat Parascaris equorum
fenbendazole
what roundworm affects swine
Ascaris suum
what is the appearance of Ascaris suum
- adults
- eggs
- heavy bodied adults
- eggs sub-spherical with a thick protein coat
what is the life cycle of Ascaris suum
direct with tracheal migration through the liver and lung
what is the pathogenesis of Ascaris suum (3)
- milk spots on the liver
- pulmonary hemmorhage/edema
- enteritis with growth retardation
how can we treat and control Ascaris suum
- all in/all out facilities
- deworming sows prior to farrowing
- in-feed anthelmentics
what is the intestinal roundworm of birds
Ascaridia galli
describe the appearance of Ascaridia galli
- adults
- eggs
adults: heavy bodied
eggs: smooth shell
what is the life cycle of Ascaridia galli
DIRECT
L3 in eggs ingested -> L3 enters mucosa and matures to L4 -> re-enters lumen of intestine -> adult
what is the pathogenesis of Ascaridia galli
- hemmorhage/diarrhea
- reduced production
What is the cecal worm of birds
Heterakis gallinarum
what birds are affected by Heterakis gallinarum
chicken, turkey, other species
Describe Heterakis gallinarum adults and eggs
Adults: slender; in ceca
Eggs: thick, smooth shell
describe the life cycle of Heterakis gallinarum
Direct with mucosal migration in the ceca
what is the significance of Heterakis gallinarum
intermediate host of Histomonas meleagridis
which roundworm is a zoonotic threat to humans? what animals do we get it from
Baylisascaris procyonis -> causes VLM
We get it from accidental ingestion of rabbit feces
