Exam 3: Managing Parasites in Horses

equine benzimidazoles resistance

• cyathostomins widespread

• pinworms none

• Parascaris early indications

• n/a tapeworms

equine pyrimidines resistance

• cyathostomins widespread

• pinworms none

• Parascaris early indications

• Tapeworms early indications 

Equine macrocyclic lactones resistance 

• cyathostomins early indications

• pinworms widespread

• Parascaris widespread

• tapeworms n/a

praziquantel equine resistance

• tapeworms early indications

what are the goals of an equine parasite control program

• to minimize the risk of parasitic disease

• to reduce infection pressure

• to maintain and prolong the efficacy of existing anthelmintics

step by step anthelmintic efficacy testing 

• find a group of egg count postive horses at least 5 sharing the same pasture 

• count as many parasite eggs as possible pre-treatment 

• administer anthelmintic at labelled dosage 

• collect new fecal samples at 14 days post treatment 

• determine fecal egg counts using the same technique and number of slides 

• calculate the 90% confidence intervals 

evidence of good efficacy

• lower limit is above the lower threshold → the worst possible efficacy is still within the acceptable range

evidence of resistance

the upper limit is below the upper threshold → the best possible efficacy is still less than the expected efficacy for that drug

baseline treatments in adult hrses 

• 1-2 larvicidal treatments (ivermectin or moxidectin) within annual cycle for large strongyles, bots, and spirurid nematodes 

• 1-2 cestodcidal treatments (praziquantel, Anoplocephala perfoliata) 

  • su

suveillance based treatment for adult horses

• supports refugia

• all additional treatments should target high shedders >500epg during transmission season

timeline for treatment of foals

• two treatments for Parascaris spp at 2-3mo, 5 mo, using Benzimidazoles

• perform first FEC at 5-6 months to track decline of ascarid and subsequent dominance in strongyles

• subsequent FEC 6-9 mo

• yearling → follow protocol for high shedders (treatment in spring, middle of transmission season, fall)

treatments for foals 6-9 mo after subsequent FEC 

• macrocyclic lactone for strongyles 

• praziquantel for tapeworms 

• remember praziquantel only in  combinatio with ML 

• benzimidazole if ascarids still present 

treatment for horses 2-4 years

• 3-4 treatments for stongyles within annual cycle- before, mideay, toward end of grazing season

• larvicidal treatment at least once

• cestocidal treatment at least once