The Parasite Protocol and Sheep Scab Law

#You may already have no working drench

A South African survey found anthelmintic resistance in Haemonchus on all 52 sheep farms tested in Mpumalanga and KwaZulu-Natal. The authors did not hedge: small-ruminant production was "entering a crisis situation", the resistance levels were "possibly the highest that has so far been recorded in the world", and strains were emerging that "may soon not be controllable by treatment with any of the existing anthelmintics" (Onderstepoort J Vet Res, 1999).

It got worse. In Limpopo in 2021, egg-hatch testing found thiabendazole resistance in all five districts surveyed (Veterinary World 14(2)). In communal sheep in King Sabata Dalindyebo in the Eastern Cape, all eight farms sampled carried resistance to at least two drug classes (Mavundela et al. 2025).

On many South African small-stock farms one or more drench groups no longer works, and the farmer does not know which one. If you have not run a faecal egg count reduction test, you do not know what is in your cupboard — only what it cost.

#The animal that kills your best sheep

Haemonchus contortus — wireworm, barber's pole worm — is a blood-sucking nematode of the abomasum. It does not primarily cause diarrhoea. It causes anaemia, bottle jaw and sudden death, often in the best-conditioned animals, which is exactly why farmers misdiagnose it.

The seasonal shape is measurable. In Limpopo, nematode prevalence ran at 88–100% in the hot wet season at 1 210–1 861 eggs per gram, against 75–80% in the cold dry season at 453–1 202 epg (Veterinary World 14(2)). Warm and wet builds the challenge; in the cold dry months the worms sit inside the animal as arrested larvae.

#FAMACHA, and the courage to walk past a healthy sheep

FAMACHA is a South African invention — developed by Faffa Malan with Gareth Bath and Jan van Wyk — that scores the colour of the lower-eyelid conjunctiva against a five-category laminated card and treats only the anaemic individuals (Van Wyk & Bath 2002). That is targeted selective treatment: drench the animals that need it, leave the rest.

The card is deliberately controlled: producers must receive training in order to receive a card (wormx.info), because a misread eyelid is a dead sheep. Sources differ on the exact treatment cut-off — whether category 3 is routinely treated or only in vulnerable classes — so take the operative rule from accredited training and your vet, not from a course.

Two boundaries matter more than the cut-off. FAMACHA detects anaemia, so it is valid for blood-suckers — principally Haemonchus, and to a degree liver fluke — and not for Trichostrongylus, Teladorsagia, Nematodirus or tapeworm, which cause scouring and ill-thrift without anaemia. A flock with a scour problem and every eye scoring 1 still has a worm problem. And anaemia has non-parasitic causes: coccidiosis, tick blood loss, mineral deficiency.

The reason to do any of this is refugia — the worms not exposed when you treat: larvae out on the pasture, and worms inside the animals you left alone. Resistant survivors must be diluted by susceptible larvae from refugia, or they become the entire next generation.

#Grazing height is the first lever

This is the cleanest place in the course where a regenerative principle and a veterinary one point at the same decision. Infective Haemonchus larvae concentrate in the bottom few centimetres of the sward. Graze the camp to the ground and you feed your sheep the larvae; graze for a high residual and most of the challenge stays below the mouth. Residual is soil armour and a barrier between the flock and the worms in one act.

Recovery period is the second lever, and a parasite tool as much as a plant tool: short returns onto wet, warm Highveld veld recycle larvae straight back into the flock.

The third lever is species mix: where the enterprise allows it, put cattle through the camp as a dead-end host for sheep nematodes before the sheep return. Then say the honest version, not the one you will hear at a farmers' day — no South African field trial testing multi-species or leader-follower grazing against Haemonchus could be found for this course. Stack it on top of residual and recovery; do not substitute it for either.

Never take a dose, a treatment interval or a withdrawal period from a course. Every anthelmintic and dip is a registered stock remedy under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947 — the label is the legal instruction, and it carries the meat withdrawal period.

#Reading a drench test properly

The test is simple: faecal egg counts before and after treatment, for each drench group you use, with the post-treatment sampling interval set by the drug class and by the laboratory counting. Interpreting it is where farmers and much of the farming press go wrong, because there are three bands, not two (Mavundela et al. 2025):

Work an example. A pre-treatment mean of 850 eggs per gram and a post-treatment mean of 120 epg gives (850 − 120) ÷ 850 = 85.9%. Below 90%: that product is resistant in your flock, and "but we've always used it" does not change the answer. Change one number — a post-treatment mean of 68 epg gives 92%, the grey band, where you check your dosing and repeat rather than bin the product. "Below 95% means resistance" is a common shorthand, and it will make you throw away a drench that is merely being under-dosed.

#Sheep scab: the disease you may not diagnose

Everything above is your decision. Sheep scab is not.

Sheep scab (Psoroptes ovis) is a controlled disease under the Animal Diseases Act 35 of 1984, read with the Animal Diseases Regulations, R.2026 of 26 September 1986 (DALRRD). Itching, tangled or pulled wool, bare scabby patches — that is the trigger. You do not confirm it, you do not treat and hope, you do not move the animals.

#The legal point most sources get wrong

Ask ten sheep farmers what the scab rule is for bought-in sheep and most will say "two treatments, seven to ten days apart". Half of that is right.

The Regulations require that sheep moved onto your land be treated twice with an effective remedy before being mixed with your other sheep. But the interval between those two treatments is not stipulated in the Regulations — seven to ten days is recommended practice, not the legal rule. That window is prescribed for infected and contact animals in a declared outbreak, a different situation entirely (AgriOrbit; R.2026 of 1986). The interval, the product and the schedule come from the state veterinarian and the label. Nowhere else.

#The rest of the health load, and the honest gaps

Blowfly strike. Lucilia cuprina is South Africa's principal primary strike fly, and prevention is management-led before it is chemical: crutching — removing wool from the breech and inside the legs — eliminates the moist, soiled sites where eggs are laid (Farmer's Weekly). Organophosphate and benzoylurea resistance in L. cuprina is widespread internationally, so a chemical-only strategy degrades the way a drench does.

Foot rot spreads where sheep stand on wet, muddy, heavily-trafficked ground — water points, gateways, the night kraal, the laneways, not the paddock. The first lever is spatial: move the water, move the kraal, keep off sodden camps. Pasteurellosis follows transport, mixing, weather change and yarding — the events a high-density or feedlot-finishing system generates. Reduce the stressor stack rather than medicating through it.

#Before the next lesson

Book the faecal egg count reduction test for every drench group you own, and book the FAMACHA training before you need the card. Then walk your camps and write down the grazing exit height you will hold for the ewe-and-lamb mob. That number does more for your worm burden than anything you can buy.

Lesson 3 sets the lambing date, and it is the same decision: lambing into the spring flush puts newborn lambs and freshly lambed ewes into the rising wireworm season.