Control Of Equine Alimentary Parasites Flashcards
(39 cards)
- What are helminths?
- What are Cestodes?
- What are nematodes?
- What are cyathostomes?
- What are Strongyles?
- Worms.
- Tapeworms.
- Roundworms.
- Roundworms - small redworms.
- Roundworms - large redworms.
- What are strongyloides?
- What are ascarids.
- What are dictyocailus?
- What are oxyuris?
- Roundworms - threadworm.
- Roundworms - roundworm.
- Roundworms - lungworm.
- Roundworm - pinworm.
Cyathostomes.
Small redworm.
CAN ENCYST IN LARGE INTESTINAL MUCOSA FOR 2-3 YEARS!
- CAN MASS EMERGE AS HYPOBIOSED LARVAE (early spring), CAUSING A MASSIVE INFLAMMATORY REACTION AND SEVERE DIARRHOEA.
OFTEN FATAL.
Strongylus vulgaris.
Cause problems during migration of larvae (direct migratory path).
- causes verminous arteritis.
- travel from GIT to cranial mesenteric artery and back again.
- can cause ischaemic areas of LI
— fatal.
Adults live in LI.
Relatively rare nowadays since use of avermectins.
Strongyloides westeri.
Clinically affects foals.
Infects foal through dam milk or via skin penetration.
- Induces diarrhoea ~6m later.
Ascarids - Parascaris equorum.
Gain reasonable immunity.
At greatest risk 6 months old, up to 2 years old.
Can cause SI obstruction.
- surgical colic.
— removal of worms.
Greatest risk after using an effective anthelmintic when there is a high burden.
Dictyocaulus arnfieldi.
Lungworm cycle NOT completed in horse.
Adult worms do not attain sexual maturity here.
Donkey is the usual host.
Oxyuris equi.
Pinworm.
Adults in the colon.
Female worm migrated down GIT
- deposits eggs around anus, cemented to the skin with a sticky substance.
— horse develops severe anal pruritus.
Anoplcephala.
Tapeworm.
Incidence of spasmodic colic increases with burden.
Can cause intussusception (ileo-caecal, caeco-caecal).
Thickened SI wall at ileo-caecal junction leads to food (ileal) impaction, leading to a surgical colic.
Gasterophilus.
Botflies.
Not proven to cause any problems.
Seen more with advent gastroscopy.
Can remove (some) eggs from hair with a bit knife.
- What was the main focus of the old worming recommendations.
- Why can the old worming recommendations not be used anymore.
- Strongyles.
- Resistance.
Tapeworm and encysted cyathostome, which are important causes of disease, may be neglected.
- Impact of resistance?
- Do we need to worry about parasite burdens in horses?
- Fewer drugs are effective with no new drugs in the horizon.
Resistance increases the complexity of parasite management programmes. - Most horses tolerate even large worm burdens without any effect on health.
Clinical disease is rare.
But disease does occur.
Define resistance.
The genetically transmitted loss of sensitivity in parasite populations previously sensitive to the same drug.
Due to artificial selection by horse wormers, sensitive worms are killed, leaving only resistant ones to multiply and create new generations of resistant worms.
What are refugia?
Parasites in the horse’s environment that are not exposed to an anthelmintic at each dose.
These will include:
- pasture stages — eggs, L1, L2, L3.
- parasites in untreated horses.
- some larval stages in the horse? E.g. encysted.
Increasing refugia is likely to slow down resistance.
Measuring resistance.
FECRT = faecal egg count reduction test.
No anthelmintic treatment for at least 8 weeks prior (12 weeks if moxidectin used as longer egg reappearance period).
FEC before treatment.
Administer anthelmintic.
Repeat FEC 2 weeks after treatment.
This testing does not work for tapeworms.
Principles parasite control now.
Resistance problems have occurred from blanket / inappropriate anthelmintic usage.
We want a reservoir population of parasites to help reduce resistance.
- do not aim for wipe-out of all parasites.
Now over 50% horse owners use a targeted parasite control programme (though some may be a random).
Needs a co-ordinated vet-led approach.
Parasite control principles 2.
Targeted worming - worm those that need it.
Poo pick fields ~weekly.
No overgrazing.
Consider needs of adults, foals and pregnant mares.
Different things at different times of year.
What to do when a new horse arrives at the premises.
Challenges of parasite control nowadays.
Owners generally want to give anthelmintics as low effort, cheaper, don’t want horse to have worms, have always given wormers.
Anthelmintics don’t have to be prescribed by a vet.
Worming plans available from drug companies may not be reliable as may be centred around sale of their product.
Owners generally have no clue what drug they are using or what that will treat.
Considerations when forming a parasite control plan.
What parasites are you aiming to treat?
- based on horse’s age, time of year, worming history.
Adult or larval stages.
Is the treatment justified?
- likely challenges.
- resistance vs clinical disease.
Which active ingredient has expected efficacy?
- consider original spectrum and known resistance.
Any contraindications.
CANTER risk assessment.
Anthelmintics - main groups.
Avermectins - Ivermectin, moxidectin.
Benzimidazole - fenbendazole.
Praziquantel.
Pyrantel.
Moxidectin/Ivermectjn available in combo with praziquantel too.
Anthelmintics to treat cyathostomes,
Ivermectin will kill adults but need moxidectin to kill encysted ones.
Could use 5-day course of fenbenbazole but lots of resistance.
If cyathostomiasis, treat with moxidectin and corticosteroids concurrently.
Use once or twice per year during winter (guidance changes!)
Anthelmintics to treat Strongyles.
Ivermectin (try to use).
Moxidectin (save for a resistance problem and encysted cyathostome).
Pyrantel - not as effective — resistance.
Fenbendazole - not as effective — resistance.
- What is classed as a low level of Strongyles?
- How frequently do you need to do a faecal egg count?
- 200 eggs/gram of faeces on FEC.
- varies between spp. - After egg reappearance period of the anthelmintic that is being used.
Much more understandable from the client’s perspective to carry out ~every 12 weeks.
Anthelmintics to treat ascarids.
Often affecting horses <2yo.
Most sensitive to Pyrantel.
Then avermectins.
