Modern Equine Parasite control Flashcards
What parasites to condier in ADULT horse?
- Cyathostomins (small strongyles/small redworms)
- Tapeworms
- Oxyuris equi (equine pinworm)
- Strongylus spp. (large strongyles)
- Gasterophilus spp. (‘bot’)
- Dictycaulus arnfieldi (lungworm)
What additional species in foals and yearlings ?
- Parascaris spp. (ascarids)
- Strongyloides westeri (thredworm)
Describe how cyathostomins come about?
- Encysted larvae in the mucosa (submucosa) of the caecum and colon
- Over winter as the temperature decreases, they undergo hypobiosis
(arrested development)
What potentially severe clinical dx can happen from cyathostomins?
when large numbers of L4 larvae
emerge at once from the intestinal mucosa
* Late winter / early spring
* Acute Larval Cyathosominosis
* Colic
* Diarrhoea
* Hypoalbuminemia
* Weight-loss
Who is more at risk of Cyahostomins?
Young horses (1-5yrs) and possibly geriatric horses, and horses with PPID
(pituitary pars-intermedia dysfunction or ‘Cushing’s disease’) more at risk
of disease
In terms of detection? Cyahostomins
- Up to 95% of burden encysted over winter therefore not
laying eggs - FWEC (Faecal Worm Egg Count) unhelpful when encysted
- Serum ELIZA test available
How to interpret ELISA?
- Interpret with caution
- A positive test does not mean there is clinically relevant
mucosal cyathostomin burden - Can be useful to ‘rule-out’ cyathostomin infection
- Care in severe disease (will be affected by low globulin
concentration)
How to treat cyathostomins?
Hard to treat – only 2 wormers with efficacy against the
encysted stage
* Fenbendazole - 5 day course (++resistance)
* Moxidectin
Describe tapeworm in horse
- Anoplocephala perfoliata is the most common equine tapeworm
- Infection occurs when horses ingest infected oribatid mites whilst grazing
Pathophy of tapeworms?
Tapeworms erode the intestinal mucosa at the site of attachment
* Can result in:
* disturbances of motility ‘Spasmodic’ colic
* Intussusception (commonly ileal, ileo-caecal or caeco-caecal)
* Impactions (commonly ileal)
Is FWEC sensitive for tapeworms?
No as eggs not evenly distributed in faeces -> shed within gravid proglottids released from adult tapeworms
Tapeworm ELISA ?
Yes useful
* Antibodies persist for 3-6months
* Tests validated to show that high levels of antibodies correlate to higher numbers
of tapeworms
* Serum
* Saliva
tx for tapeworm?
- Resistance emerging
- Praziquantel
- High dose Pyrantel
Which strongylus species in our large strongyles?
- Strongylus vulgaris
- Strongylus endentatus
- Strongylus equinus
Prevalence of strongylus spp ?
- Very rare in well managed equine populations
- Low prevalence in the UK – currently
- In countries like Denmark and Sweden where strict prescription-only legislation has
reduced anthelmintic use, it has re-emerged
What do storngylus spp cause?
Larval stages migrate through the crainial mesenteric arteries that supply
blood to the intestines
➢ Non-strangulating intestinal infarction
* Colic
* Peritonitis
What is the most important paraésite in foals?
Parascaris equorum (ASCARIDS)
Why are younger foals more predispoed?
After the first 6-7months of age, ascarids are naturally eliminated and cyathostomin and tapeworm burdens
start to increase
What can ascarid infection cause?
- Poor condition
- Respiratory disease
- Intestinal impaction
T/F Ascarids produce a lot of eggs?
TRUE -> eggs also very resilient in environment -> can overwinter and affect next year’s foals
When are foals at highest risk fo dx with ascarids?
Times of stress -> Weaning; yearling prep/sales
How can we test for ascarids?
Testing via FWEC from 3-4months
* Not recommended before this due to long prepatent period (10 weeks or over)
TX for ascarids?
LICENSED:
* Benzimidazoles (Fenbendazole) *Resistance reported
* Tetrahydropyrimidines (Pyrantel) *Resistance reported
* Macrocytic lactones (Moxidectin and Ivermectin) *Resistance common
What to be careful with when tx foals ascarids?
foals with high burdens as some anthelmintics causes paralysis of the parasites and can cause acute intestinal impaction
* Macrocytic Lactones
* Pyrantel salts
What is the name for pinworms?
Oxyuris equi
Describe Pinworms
- Not fatal! (No significant damage to GI tract)
- Can cause significant perianal irritation
- Eggs deposited by adult females on the perianal region
= Pruritus
How do horses get infected with pinworms?
- Infection from ingestion of eggs in the environment
- Paddock, stable, fencing, equipment etc (where the horse rubs!)
Best diagnostic for pinworms?
TAPE
Licensed tx for pinworm?
- Fenbendazole**
- Pyrantel**
- Ivermectin and moxidectin (resistance reported)
(Re infection common)
What to do on top of systemic tx?
thorough cleaning of contaminated surfaces and daily washing of perianal region
What is the name for equine lungworm?
D I C T Y O C A U L U S A R N F I E L D I
When do we see equine lungworm?
- Donkeys are the usual reservoir but don’t tend to get clinical disease
- Rare in horses
- Infection rarely patent
- Larvae are susceptible to desiccation on pasture
- Infected when sharing pastures with donkeys
Pathophys of lungworm ?
- Adult lungworms live in bronchioles
➢ Mucopurulent bronchitis
➢ Cough and nasal discharge
Diagnosis of Lungworm?
tracheal aspirate samples
describe Liver fluke (Fasciola hepatica)
- Rare but recognised (co-grazing with cattle and sheep – wet marshy conditions)
- Intermediate host snail - Galba (Lymnaea) truncatula
- Hepatopathy
- Antemortem diagnosis challenging
- Treatment – off licence
- Triclabendazole (resistance common)
- Closantel
Describe Gasterophilus spp (‘bot’)
- Commonly found in the stomach of equids
- Eggs are laid by adult flies on the equid’s hair coat
- Ingested by grooming
- Not considered pathogenic
Describe threadworm (Strongyloides westeri) ?
- In foals
- Lactogenic transmission from mare
- Occasionally associated with diarrhoea - rare
Describe resistance with anthelmintics?
- Resistance reported for ALL anthelmintics in the UK
- No new classes of anthelmintics being developed for horses
- Growing evidence of negative consequences of certain anthelmintics
(ivermectins and other parasiticides) on the environment (insects and
aquatic life) - Interval deworming no longer acceptable for mature horses
T/F anthelmintics in UK are POM-VPS?
TRUE
Can be prescribed by any Registered Qualified Person (RQP – vet, pharmacist,
or SQP (suitably qualified person))
* Education is the key as vets cannot control the distribution
Goals of targeted worming programs?
- Reduce clinical dx risk
- Reduce burden on pasture
- NOT to eradicate all worms in all horses
Describe the BEVA Protect me too acronym ?
- Practice policy
- Risk asses
- Other methods of control
- Target treatment to high sheders
- Environmental sustainability
- Check for drug efficacy
- Test for tapeworms
- Monitor the herd
- Educate
- Too – protect anthelmintics as well as antibiotics
What does other methods of control involve?
Describe targeting tx to high shedders
- 20% of horses carry 80% of burden
- Reduce anthelmintic use
- Maintain refugia (a population of anthelmintic susceptible worms)
How can we check for drug efficacy?
Faecal Egg Count Reduction Tests (FECRTs)
* FECRTs should be performed annually where there are horses that require treatment.
* FECRT can be used to assess the efficacy of anthelmintics in individual animals, but groups of horses (at least
6 where possible) are better for detecting resistance.
Method for FECRTs?
- Perform FEC on a group of >5-10 horses on a farm
- Deworm all horses with one anthelmintic
- Repeat FEC 14 days after treatment (use same FEC technique)
- Calculate FECR of individual horse based on formula;
- Calculate average FECR for treated group
How do we check for drug efficacy?
Egg Reappearance Period (ERP)
* How long it takes from the date of administering the anthelmintic for the parasite eggs to reappear in the faeces again
* Most relevant for macrocytic lactones (moxidectin/ivermectin)
Method for ERP?
repeat FEC 6 weeks from date of admin
How to test for tapeworms?
Tapeworm ELISA
Larval cyasthostomins ?
– to treat in the autumn?
* Encysted larvae so FWEC will not detect
* Disease rare from 5-20yrs old
* In young or old horses with unknow history who are at higher risk consider testing serum ELIZA and if exposure may
warrant treatment with moxidectin
Anthelmintic choice?
Authorisation ages for foals?
TESTING FOR FOALS AND WEANLINGS <12 MONTHS?
How to deal with donkeys and hybrids?
- Targeted worming as for horses
- FEC and FECRT as for horses
- Sedimentation test for lungworm L1 larvae
- NOT tapeworm ELIZA (unvalidated)
- NOT cyathostomin ELIZA (unvalidated)
- Consider lungworm in donkeys or horses grazing with donkeys
BEWARE LICENSING - > NOT praziquantel or moxidectin
