Lecture 17 Large and small strongyles of horses Flashcards
what is the usual site for superfamily Strongyloidea
large intestine
3 features of strongyloidea
- bursa in male
- large buccal capsule
- leaf crown
what are the hosts of strongyloidea
horses
pigs
ruminants
birds
what is the lifecycle of strongyloidea
L1-(L3) -- in faeces (L3) on -- herbage L3 migrates -- into int. gland L4 emerges -- to lumen final moult in lumen
can strongyloidea do extra migration and how would this effect the PPP
yes, makes PPP longer
what subfamily is known as large strongyles that infect horses
strongylinae
what characterizes large strongyles of horses
large, globular buccal capsule
what are the two most important genera of large stongyles in horses
strongylus
tridontophorus
What species of Strongylus are there including the one that is not in Australia
what is this generas common name
S. vulgaris S. edentatus S. equinus S. asini (donkey, zebra- not in aus) - common name- red worms or blood worms
Where are large strongyles of horses located?
cecum and colon
what is the life cycle of the large strongyle in horses
Eggs passed out in feces
- eggs in feces develop into L1, L2, L3 stage larvae
- L3 move to the grass
- L3 ingested
- L3 penetrates intestinal wall->abdomen at L4->back into intestine
- L4->adult and lays eggs
What problems can L4 of large strongyles in horses cause when they are migrating in the abdomen
can cause colic
What is an identifying factor of Strongylus vulgaris and is it a large or small strongyle
two dorsal lobed or ear shaped teeth
large strongyle
What is the life cycle of Strongylus vulgaris? direct or indirect?
• L1 and L2 develop in faeces, feed on bacteria
• development to L3 stops below 8oC
• L3 exsheaths (L2 sheath) in small/large intestine
• migrates into intestinal wall
• migrates in wall of arteries and ascends
to root of cranial mesenteric arteries
• remains for several weeks
• returns to gut in blood stream
• enters lumen
what is the PPP for strongylus vulgaris
6 months
what do adult strongylus vulgaris feed on
mucosa of gut and blood
1 female can ingest 10ml of blood an hour
What are 3 effects that strongylus vulgaris have on the horse host?
- Migration within arteries damages intima-> thrombi.
- Inflammation in walls of vessels-> deposition of fibrous tissue, thickening of
vessel walls and narrowing of lumen. - verminous arteritis
- Thrombi may occlude vessels, cause intermittent colic or severe ischaemia leading
to infarction and gangrene. - Adults can cause anaemia, elevated white cell count, eosinophilia.
3 points of epidemiology of strongylus vulgaris of the horse
- prevalence in Victoria has been reduced (85->25%)
- Larvae most abundant in spring killed in summer, winter stops development
- peak egg laying 10 mo after infection
- foals develop immunity
What are 3 features of Strongylus edentatus
- buccal capsule is wider anteriorly than posteriorly
- no teeth in buccal capsule
- very common species
- larger than S. vulgaris (2.3-4.4 cm)
what is the life cycle of strongylus edentatus
- L3 exsheaths in caecum
- burrows into gut wall
- enters portal veins
- migrates to liver
- spends 8 weeks in liver
- migrates to sub-peritoneal tissues
- returns to gut via mesentery
how long is the PPP for strongylus edentatus
10 months
what is the effect on the horse host of strongylus edentatus
- Aberrant larvae found in kidney, lung, testes.
• migrating larvae cause lesions - feed on blood
• adults cause anaemia (normocytic normochromic)
What are 3 features of strongylus equinus and is it a small or large strongyle
• 3 teeth in buccal capsule
• deepest buccal capsule
• tropical species- low prevalence in australia
-large strongyle
what is the life cycle of strongylus equinus
and what is the effect on the horse host?
• L3 exsheaths in caecum • L3 migrates into gut wall, • peritoneal cavity & liver • spends 6-7 weeks in liver • migrates via pancreas to gut - anemia
what is the PPP of strongylus equinus and what do the adults feed on (think of strongylus common name)
8 months
blood- common name is red or blood worms
what is another important genera in the subfamily stongylinae (large strongyles) other than strongylus
what is the main feature of this genera
triodontophorus
3 teeth
also oesophagus and craterostomum
what is the lifecycle of triodontophorus
• L3 exsheaths in caecum • L3 migrates into gland • moults to L4 • L4 emerges into lumen • final moult in lumen NO EXTRA INTESTINAL MIGRATION
Because triodontophorus has no extra intestinal migration what is the PPP
9 weeks
shorter than strongylus that has extra intestinal migration
what is the effect of tridontophorus on the horse host and is it a large or small strongyle
• graze on epithelial lining of gut
• occur in groups
• cause ulceration & blood loss
- large strongyle
what subfamily is considered the small strongyles of horses
cyathostominae
what is characteristic of cyathostominae
all have cylindrical buccal capsule (not globular like large)
occur in large numbers (15000) but won’t show symptoms until 1-200000
what is the lifecycle of the genus cyathostomum
• L3 exsheath in caecum • enters caecal glands • moults to L4 • L4 re-emerges to lumen • final moult in lumen -no extra intestinal migration
what is the PPP of cyathostomum and is hypobiosis important
5 weeks minimum
yes hypobiosis is important- seasonal pattern and if adults are removed emergence may be synchronus
at what stage and where would hypobiosis occur in cyathostomum (small strongyle of horse)
stage L4 in the intestinal mucosa
risk of damage if high number of encysted L4 emerge from hypobiosis at the same time
what is the effect on the host of cyathostomum
- adults feed on gut content
- not pathogenic
- very large numbers (1x106) cause diarrhoea
- normally 115,000 larvae encysted
- visible from external surface
- massive emergence causes severe diarrhoea
how could you diagnose cyathostomum
- find eggs in faeces
- use McMaster chamber
- > 300 epg pathogenic
- larval culture to identify genera
