GI - equine parasites Flashcards
What parasite causes massive inflammatory reaction, severe diarrhoea and often death in horses when they all emerge at once?
Cyathostomes
What do cyathostomes look like?
Small redworm
Where do the cyathostomes encyst? For how long?
Encyst in the large intestinal mucosa for 2-3 years
How do you treat cyathostomiasis?
Moxidectin - be careful of inflammation from dead worms causing colitis
Concurrent corticosteroids to reduce inflammation
What do strongyles cause in horses?
Verminous arteritis - block the blood vessels
Where do the strongyles reside/migrate in horses?
Migrate from the GI tract to the cranial mesenteric artery and back
What is used to treat strongyles?
Avermectins - so now rare
What worm parasite affects foals?
Strongyloides westeri
How do foals get infected by strongyloides?
Through dams milk
Skin penetration
What does strongyloides westeri cause in foals?
Induces diarrhoea 6 months later
What is an example of an ascarid in horses?
Parascaris equorum
When are horses at greatest risk of parascaris ascarid?
From 6 months to 2 years - after this they gain immunity
What does parascaris equorum cause in horses?
Small intestinal obstruction - surgical colic
When are horses at greatest risk of parascaris equorum causing surgical colic?
After using an effective anthelmintic when there is a high burden
What are the organs affected by the parascaris lifecycle?
Intestinal wall > Liver > Bronchi in lungs > Small intestines
What is to note about the dictyocaulus arnfieldi life cycle?
Not completed in the horse - the donkey is the usual host
What worms cause anal pruritis? Why?
Oxyuris equi - live in colon, females migrate down and stick eggs to anus
What tapeworm can horses get?
Anoplocephela
What is the intermediate host of anoplocephela tapeworm?
Oribatid mite
What do anoplocephela tapeworms cause in horses?
Spasmodic colic
Intussuseption
Thickened ilio-caecal junction wall - ileal food impaction
What red eggs can be found in the stomach as an incidental finding/dont cause a problem?
Gasterophilus - bot fly
How do bot fly eggs get into the stomach?
Bot fly lays eggs on horses legs
Horse grooms itself and eats them
What horse wormer has the highest resistance?
Fenbendazole
What is resistance?
The genetically transmitted loss of sensitivity in parasite populations previously sensitive to the same drug
What is refugia?
Parasites in the horses environment that are not exposed to an anthelmintic at each dose
Eg. on pasture, untreated horses, some larval stages
How does refugia impact resistance?
Increasing refugia is likely to slow development of resistance
What is a way of measuring resistance?
Faecal egg count reduction test
How do you do a faecal egg count reduction test?
No wormer for 8 weeks prior
FEC before treatment
Give wormer
Repeat FEC 2 weeks later
How many horse owners are using a targeted parasite control now?
50%
What are ways of using parasite control to cause minimal resistance?
Targeted worming
Poo pick fields
Dont overgraze
Different things at different times of year
What are the challenges of using parasite control to cause minimal resistance?
Owners want to give anthelmintics
Cheaper than targeted parasite control
What are the 4 main groups of anthelmintics in horses?
Avermectins
Benzimidazoles
PRaziquantel
Pyrantel
What wormer do you use for cyathostomes? When?
Moxidectin - kills encysted too
Once a year in winter
What wormer do you use for strongyles?
Ivermectin - least resistance
When should you worm for strongyles?
If FEC greater than 200 eggs/gram
Do FEC every 12 weeks
What wormer is most sensitive for parascaris?
Pyrantel
What wormer do you use for strongyloides westeri?
Ivermectin - in foal or de-worm mare 2 weeks before due date
What wormer do you use for tapeworms (anaplocephala)? When?
Praziquantel
Twice a year, after tapeworm ELISA
What wormer do you use to treat dictocaulus, gasterophilus and oxyuris?
Ivermectin
What are the problems of FEC?
Costs same as wormer tube - (£10)
Only counts eggs - misses encysted, non producing adults)
More expensive if find all horses have it
What are the problems with the tapeworm ELISA?
Looks for tapeworm antibodies so can tell if has been exposed but antibodies stay high for 6 months after treatment so cant tell if you have resistance
How can you use pasture management to reduce worms?
Poo pick
Reduce stocking density
Graze with ruminants
How should you worm pregnant mares?
Treat with ivermectin a few weeks before due date
How should you worm a new horse to the yard?
Moxidectin and praziquantel
Keep off pasture for 3 days
What worm eggs does a faecal egg count test?
Strongyles
