Does Your Remedy Still Work? FAMACHA and the FECRT

#A reduction of minus 143 per cent

In the King Sabata Dalindyebo study, faecal egg count reductions across the tested drug groups ranged from 85% down to minus 143% (Mavundela, Dzemo & Thekisoe, 2025).

A negative reduction means the animals were carrying more worm eggs after the treatment than before it. The product did nothing at all, the challenge kept building, and the farmer walked away believing his flock was drenched.

That is the situation this lesson exists to prevent. A farmer who has never tested his drenches does not own a worm programme. He owns a cupboard of bottles with unknown contents, and he finds out which ones are empty when a lamb dies.

There are two separate questions, and they need two separate tools. Which animal needs treating? is answered on the ramp, animal by animal. Does the product I am about to use still work? is answered in a laboratory. Confusing them is why so many South African flocks are drenched regularly and dying anyway.

#What FAMACHA is, and where it stops

FAMACHA is a South African invention — developed by Faffa Malan, Gareth Bath and Jan van Wyk and published as a system for managing haemonchosis in sheep and goats by clinically identifying individual animals for treatment (Van Wyk & Bath, Veterinary Research, 2002). It scores the colour of the lower-eyelid conjunctiva against a laminated card, from red through to white. Only the anaemic animals are drenched.

The card is deliberately controlled: "Producers must receive training in order to receive a card" (wormx.info). That is not gatekeeping. Eyelid colour is easy to misjudge in bad light, against a wet card, or by someone who has never been calibrated against a trainer's eye.

Be careful about the exact treatment cut-off. Sources genuinely disagree — some hold that only the poorer categories are routinely treated, others that the best two are never treated, the worst two always, and the middle category is conditional on other risk indicators such as late pregnancy, early lactation, lamb age or poor condition. The research behind this course could not settle which rule is operative. Get it from accredited FAMACHA training and your veterinarian, not from a book.

Now the boundary that gets flocks into trouble.

FAMACHA detects anaemia. That makes it valid for blood-sucking parasites — principally Haemonchus contortus, and to a degree liver fluke. It is not valid for Trichostrongylus, Teladorsagia, Nematodirus or tapeworm, which cause scouring and ill-thrift without making the animal pale. A flock with a scour problem and every eyelid scoring bright red still has a worm problem, and a farmer running FAMACHA alone will not see it.

The reverse trap is just as real: anaemia has causes that are not worms. A pale animal in a wireworm-free winter may be anaemic from coccidiosis, from tick blood loss, or from a mineral deficiency. The card cannot tell you which. It tells you the animal is pale.

#How bad the South African resistance position actually is

Not "a risk". A measured position, and it is worse than most farmers assume.

Van Wyk, Stenson, Van der Merwe, Vorster and Viljoen found anthelmintic resistance in Haemonchus on all 52 sheep farms surveyed in Mpumalanga and KwaZulu-Natal. Four groups were tested. 16% of strains were less than 60% susceptible to three of the four, and 8% were less than 40% susceptible to all four. The authors described small-ruminant production as entering a crisis situation, called the resistance levels "possibly the highest that has so far been recorded in the world", and warned of strains that may soon not be controllable with any existing anthelmintic (OJVR, 1999).
In Limpopo, across five districts — Capricorn, Sekhukhune, Waterberg, Mopani and Vhembe — egg-hatch-test resistance to thiabendazole was found in all five. The authors attributed it to under-dosing caused by a lack of weighing equipment, and to high treatment frequency driven by poor training in anthelmintic use (Mphahlele et al., 2021).
At King Sabata Dalindyebo, 8 of 8 farms carried resistance and every one of the eight was multi-class. Implicated practices: not weighing animals, dosing with syringes instead of calibrated drench guns, and use without veterinary supervision (Mavundela et al., 2025).

The practical conclusion is blunt. On many South African small-stock farms one or more drench groups no longer works, and the farmer does not know which one. Assume nothing in your store works until you have proved it does — but prove it properly, because the proving is where the second expensive mistake happens.

#The FECRT, in three bands and not two

A faecal egg count reduction test is straightforward in principle. Count worm eggs in the dung before treatment, treat, count again after an interval set by the drug class, and calculate the percentage reduction.

The interpretation is where farmers and a lot of farming-press advice go wrong, because the common shorthand — "below 95% means resistance" — is wrong. There are three bands, not two (classification as used by Mavundela et al., 2025):

Faecal egg count reduction	Classification	What you do
95% or above, with the lower 90% confidence limit at 90% or above	Susceptible — the drench works	Keep it. Use it sparingly.
90 to 95%, or confidence limits straddling the cut-offs	Grey zone — reduced efficacy, resistance suspected	Do not retire it, and do not trust it. Repeat the test; check dosing and gun calibration first.
Below 90%, with the lower 90% confidence limit at or below 90%	Resistant	Stop relying on it for that class.

The confidence limit is not decoration. It is why a single number cannot classify a drench on its own, and why the laboratory report matters more than the percentage you work out on the back of an envelope.

One caution the research behind this course flagged and could not resolve: whether the current international guideline thresholds match exactly the bands used in that South African study. Confirm the protocol and the cut-offs with the laboratory doing your counts before you act on a borderline result.

#Work one through

Your veterinarian arranges a FECRT across three drench groups on a mob of lambs. Pre-treatment mean egg count in every group: 1,200 eggs per gram — the order of magnitude South African surveys report for a wet-season flock.

Post-treatment means come back as:

Group A: 240 epg. Reduction = (1,200 − 240) ÷ 1,200 = 80%.
Group B: 72 epg. Reduction = (1,200 − 72) ÷ 1,200 = 94%.
Group C: 24 epg. Reduction = (1,200 − 24) ÷ 1,200 = 98%.

Now classify them.

Group A at 80% is resistant, assuming the confidence limits agree. Stop relying on it. That is not a judgement call.

Group C at 98% is susceptible, provided the lower confidence limit sits at 90% or above. Keep it, and use it as little as you can get away with — it may be the last group you have.

Group B at 94% is the one that matters. It is not resistant. It sits in the grey zone. The farmer who has been told "below 95% is resistance" throws this product away, and he may have just retired a perfectly good drench because he did not weigh the biggest lambs, or because his drench gun under-delivers. Both of those were named as resistance drivers in the Limpopo work. The correct answer for Group B is: repeat the test, and check your dosing and your gun calibration before you check anything else.

That single distinction — grey zone rather than resistant — can be worth an entire drench group to a farm that has only two left.

Do this on the farm

Who does what in a FECRT.

You collect the dung, or an animal health technician does. Fresh samples, from identified individual animals, kept cool, delivered fast. Sample collection and submission to a laboratory sits squarely in the Animal Health Technician's scope of practice (SAVC Day 1 Skills).
A laboratory does the counts. Egg counting is a technique with its own error, and a count done badly makes the whole exercise worthless.
Your veterinarian sets the post-treatment sampling interval, because it differs by drug class. It is not in this course and it should not be guessed.
Your veterinarian or AHT interprets the result against the three bands and the confidence limits.
The dose comes off the label. Every anthelmintic is registered as a stock remedy under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947, or as a veterinary medicine under the Medicines and Related Substances Act 101 of 1965 where it is scheduled (SAVA). The label is the legal instruction, including the withdrawal period. No course gives you that number.
Retest each group you rely on every two to three years, and immediately if treated animals stop responding.

Contested — here is both sides

Is a single FECRT enough to condemn a drench?

For acting on one test: South Africa's resistance position is severe enough that waiting for confirmation costs animals. If a group comes back below 90%, treating it as failed and moving on is the safer error.

For repeating first: the same study that produced the three-band rule reported reductions from minus 143% to 85% across a range of farms where under-dosing, uncalibrated drench guns and unweighed animals were documented. A poor result frequently measures the operator rather than the worm. Retiring a group you cannot replace, on one test, on a farm that already has resistance to two others, is a serious loss.

The reconciliation is the bands themselves. Below 90% with the confidence limits agreeing, act. In the 90 to 95% grey zone, fix your dosing and repeat before you condemn anything. The bands exist precisely because the evidence does not support a single cut-off.

#What to do with this on Monday

Open your medicine store and write down every drench group you own — not brands, groups. Next to each one, write the date of the last time you proved it worked. If the column is empty, you have a diagnostic job, not a treatment plan, and it starts with a phone call to your vet about arranging a FECRT.

And when the results come back, read the middle band before you read the number. A drench at 94% is a drench you probably still own.

#Check yourself

4 questions — answers explained as you go

1A flock is scoured, thin and losing condition, but every animal scores in the healthiest FAMACHA categories. What is the correct reading?
Why: FAMACHA scores conjunctival colour, which makes it a tool for blood-sucking parasites — principally Haemonchus, and to a degree liver fluke. Scouring worms, tapeworm and nasal bot cause ill-thrift without anaemia and will not show on the card at all. Ill-thrift with good scores is a signal to go to the laboratory, not to drench harder.
2A FECRT returns 94% reduction for one drench group. What should the farmer do?
Why: The three-band rule puts susceptible at 95% or above with the lower confidence limit at 90% or above, resistant below 90% with the limit agreeing, and 90 to 95% in a grey zone. Under-dosing and uncalibrated guns were documented resistance drivers in South African surveys, and both produce a borderline result from a working product. Retiring a drench on a single 94% may throw away a group you cannot replace.
3Why does the King Sabata Dalindyebo finding of an FECR of minus 143% matter to a farmer elsewhere?
Why: A negative reduction means the product achieved nothing while the challenge kept building. The farmer sees animals that were drenched and assumes they are protected. That gap between treatment and effect is exactly what the FECRT exists to close, and it is why the eight farms in that study — every one of them carrying multi-class resistance — are a warning rather than a local curiosity.
4Who sets the interval between the pre-treatment and post-treatment samples in a FECRT?
Why: The sampling interval is a technical decision tied to the drug class, and getting it wrong invalidates the result. Sample collection and submission sit within an animal health technician's scope; the interpretation and the interval belong with the vet or the laboratory. The label carries the dose and the withdrawal period, not the test protocol.