What is a fecal egg count (FEC)?

A FEC measures the number of parasite eggs per gram (EPG) of manure using a McMaster or Mini-FLOTAC technique. It estimates the worm burden and helps classify horses as low, moderate, or high shedders for targeted deworming.

How often should I run a fecal egg count?

Every 6 months is the standard recommendation. The two best times are spring (March–April) and fall (September–October), when parasite transmission peaks. Additional testing after treatment (FECRT) helps detect resistance.

Why rotate deworming drugs?

Using the same drug class repeatedly selects for resistant parasites. Rotating among different classes (macrocyclic lactones, benzimidazoles, tetrahydropyrimidines) slows resistance development. Each drug targets parasites through a different mechanism.

Can I skip deworming if my horse tests as a low shedder?

Low shedders still need 1–2 treatments per year (typically spring and fall) to control small strongyles and bots. Zero treatment is not recommended — the goal is to treat less, not never.

ToolsConductScience tool

FEC-BasedFree in-browser calculator

Parasite Control Planner.

Generate a targeted deworming schedule from fecal egg count data. Drug rotation, FEC rechecks, and ICS calendar export.

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Validated2026-04-08

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Parasite Control Parameters

Plan start date

Last FEC (EPG)

Number of horses

Override interval (months)

12-Month Parasite Control Plan

Enter a start date to generate the parasite control plan.

Based on AAEP Internal Parasite Control Guidelines (2019). Targeted deworming based on FEC data is the current standard of care. Always consult your veterinarian for horse-specific parasite management.

How It Works

Enter your horse’s most recent fecal egg count (EPG) and a start date. The planner classifies shedder status (Low under 200 EPG, Moderate 200–499, High 500+), sets treatment frequency (2–4 times per year based on shedder status), rotates drugs through 5 anthelmintic classes to prevent resistance, schedules FEC testing every 6 months to reassess shedder status, and schedules an annual FECRT to measure treatment efficacy (under 90% reduction indicates a resistance concern). Drug rotation groups: Group A includes Ivermectin (large/small strongyles, bots, ascarids) and Moxidectin (encysted small strongyles, bots). Group B is Fenbendazole (small strongyles larvicidal, ascarids). Group C is Pyrantel pamoate (small strongyles, ascarids, pinworms). Group D is Praziquantel combo (tapeworms).

Targeted Deworming

Calendar-based rotational deworming (treating every 8 weeks regardless of egg count) is outdated and drives anthelmintic resistance, the number one threat to equine parasite control. The modern approach recognizes that only 20–30% of horses in a herd are high shedders responsible for 80% of pasture contamination. Low shedders may only need 1–2 treatments per year. FEC testing identifies which horses need treatment and how often. To collect a sample, gather 2–3 fresh fecal balls (under 4 hours old) in a zip-lock bag, label with horse name and date, refrigerate, and deliver to your vet within 24 hours at a typical cost of $15–35 per sample. FECRT protocol: run FEC before treatment, then 10–14 days after treatment with the same technique; egg count reduction under 90% suggests drug resistance.

Method

Shedder classification: Low (< 200 EPG, 2 treatments/year), Moderate (200–499 EPG, 3/year), High ( $\geq$ 500 EPG, 4/year). FEC tests scheduled every 6 months. FECRT annually. Drug rotation cycles through 5 anthelmintic classes (Ivermectin, Moxidectin, Fenbendazole, Pyrantel, Praziquantel combo). Based on AAEP Internal Parasite Control Guidelines (2019). All computation runs locally in your browser — no data is uploaded.

Validated

Last validated 2026-04-08. Calculations are designed for planning and documentation support; verify procurement decisions against manufacturer specifications or institutional SOPs.

How to cite

How to Cite

ConductScience Team (2026). Parasite Control Planner [Web application]. ConductScience. https://conductscience.com/tools/parasite-control-planner

Equine Parasitology

The primary internal parasites of horses are small strongyles (cyathostomins), large strongyles (S. vulgaris), ascarids (P. equorum), tapeworms (A. perfoliata), and bots (Gasterophilus). Small strongyles are the most significant — they encyst in the intestinal wall and can cause eosinophilic enteritis or larval cyathostominosis upon mass emergence. Anthelmintic resistance is now widespread in small strongyles, particularly to benzimidazoles (fenbendazole) and pyrantel. Ivermectin and moxidectin remain effective against most populations but resistance is emerging. This is why targeted deworming guided by FEC data is essential for long-term parasite control.

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