06: Eq Herd Management

Primary goal of equine parasite management for mature horses

Control of parasite shedding, minimize risk of clinical disease, maintain drug efficacy

Goal of decreasing pasture contamination

Kill adults before patency and to decrease the number of eggs in the environment

Weather patterns that kill eggs/larvae on pasture

Hot and arid or multiple freeze-thaw cycles

Principles to help maintain efficacy of drugs

• Deworm everyone 1-2x/year

• Test and treat high shedders more aggressively

• Maintain refugia

• Don’t treat all the animals with the same thing at the same time

Refugia

Population of parasites that are in refuge from the drug either due to location, life stage, or species

Caveat of “broad spectrum” drugs

Treats lots of parasites, but it’s a lot more limited due to resistance

Cyathostome/small strongyle resistance to the big three drug classes

• Benzimidazoles: widespread

• Pyrimidines: common

• MCL: early indications

Large strongyle resistance to the big three drug classes

• Benzimidazoles: none

• Pyrimidines: none

• MCL: none

Parascaris resistance to the big three drug classes

• Benzimidazoles: early indications

• Pyrimidines: early indications

• MCL: widespread

Parasiticide of choice for Anaplocephala and resistance profile

• Praziquantel; still very effective

• Pyrantel: early indications

Treatment recommendations for the low shedding horse

MCL 1-2x/year and praziquantel if on pasture

Do parasites persist better in cold or heat

Cold

Where do drugs break the parasitic life cycle

Kills adults, maybe kills larvae

Where does pasture management break the parasitic life cycle

Kills the egg, can kill the developing larvae, and can kill infectious L3

In what season do we not usually need to deworm horses in Oklahoma

Summer: eggs and L1 dies on pasture

How do you find the high shedding 20% of the population

Do FECs 2-3 months after deworming, test at least 10% of the herd

What qualifies as a high shedding horse

>500 EPG

What qualifies as an effective dewormer

Decreases egg count by 90%

How to treat appropriately

• Choose the right drug

• Get the right amount of the drug inside the horse

• FECRT

Ideally how often would you retreat high shedding horses

Based on FEC and egg reappearance period

Problem associated with treating based on egg reappearance period

Suppresses contamination, but minimizes refugia

Realistically how often do you treat high shedding horses

As little as possible while keeping the animals clinically healthy

Treatment recommendations for moderate shedders

Treat like low shedders, maybe add a supplemental treatment during transmission season (nicer weather, grazing season)

Foal parasite treatment guidelines

• 2-3 mos: benzimidazoles for ascarids

• 4-6 mos: run a fecal to determine strongyle v ascarid population

• 9 mos: MCL and praziquantel for strongyles and tapeworms

• 12+ mos: MCL for strongyles, treat like a high shedder until 2-4 years old