By Dr Clive Dalton & Dr Marjorie Orr
Note
This is not a veterinary text book and the listed diseases are very selective. They are in the order which you’ll be most likely to meet them (if they occur) on most farms. This information will help you have a meaningful discussion with your veterinarian who must be called if you have any doubts about the health and welfare of any animals.
Feet problems (lameness)
Cause
- Footrot is the main problem and is caused by a bacterium. It’s more often seen in older sheep.
- Foot scald (interdigital dermatitis) is also caused by bacteria and can affect ewes and even young lambs.
- Foot abscesses are also bacterial infections and are often seen in rams.
- All these bacteria live in the soil and infect the sheep when their skin or hooves are soft after prolonged wet periods or on lush pasture.
- Sheep have varying degrees of lameness from a slight limp to grazing on their knees. Bad cases are very reluctant to move and are clearly in pain.
- In foot scald the area between the toes is red or blanched and looks sore.
- In footrot the horn separates from the foot wall, which is spongy and smells very sour and rotten.
- For scald, moving sheep to drier pastures often cures them.
- Putting them through a footbath of 10% zinc sulphate or 5% formalin usually works well.
- For footrot, more drastic action is often needed, first to trim the overgrown hoof and expose the area to the air and then footbathing.
- A footbath in the form of a pen that they can be held in is better than a race, as some sheep learn to run through holding up sore feet or running along the nib wall on the side.
- Over zealous foot paring that leads to bleeding should be avoided.
- Treating sheep and then turning them out on to the muddy paddock they came from won’t do much good. After treatment, try to let them stand on a clean hard area for some time.
- Abscesses need veterinary treatment and antibiotics, and may be slow to recover.
- Cull persistent sufferers of all foot problems as there is strong farmer evidence that foot problems are inherited and can be eliminated by selection.
Internal parasites
Cause
- These are generally understood to be roundworms found in the fore stomachs of the sheep and also in the small and large intestine.
- The most important roundworms in sheep are Haemonchus, Ostertagia, Trichostrongylus and Nematodirus.
- There are also lungworms (Dictocaulis), liver flukes (Fasciola) and tape worms (Monezia).
- General unthrift and lethargic.
- Loss of appetite and massive weight loss.
- Diarrhoea (scouring).
- Mucus in the faeces.
- Anaemia.
- White sections of tape worms in the faeces.
- Bottle jaw (fluke)
- Because of the increasing risk of worms becoming resistant to the chemicals in drenches, consult your veterinarian to ensure the problem really is worms and that you have a farm plan to deal with them to avoid or delay drench resistance.
- Read the details in Dalton (2006) – see references.
External parasites
Cause
- As the name suggests, external parasites or “ectoparasites” live on the outside skin of animals.
- The main ones are body lice but there are also foot lice and face sucking lice as well as keds, itch mites and ticks.
- Body lice are the main issues and tend to remain in preferred body sites feeding on surface debris. They don’t suck blood like ticks.
- They move up and down the wool staples and this is how they get from sheep to sheep.
- In ideal conditions they complete a life cycle in about 34 days.
- Lice also cause a defect in sheep pelts called “cockle”.
- Sheep rub themselves on any convenient objects like fences leaving wool behind.
- They may bite themselves where the parasites are active.
- The sheep’s fleece looks rough with some fibres pulled out.
- Lice and keds are very host-specific and spend virtually all their life on the animal.
- Keds are not very important but can cause problems in fine-woolled sheep where their faeces stain the wool.
- Heavy lice infestations occur mainly in winter in young and/or in unthrifty sheep that are poorly fed.
- To look for lice, turn the sheep towards the sun and part the wool to expose about 10cm of skin. The lice will move away from the light. Do this two or three times on the sheep as lice live in colonies.
- Up to the 1980s it was compulsory to dip sheep once a year to control lice. This law now does not apply.
- “Dipping” is still the main prevention method and it includes plunge dipping, spray dipping and using pourons.
- Check with your veterinarian for the correct treatment for all external parasites as they too are now building up resistance to the chemicals in treatments.
- The most convenient form of treatment for small flocks and even for some large flocks is now pouron product.
- Injectable formulations are very effective against itch mites.
- Sheep that are kept in good condition generally don’t suffer major problems from external parasites.
- Treat sheep soon after shearing when the wool is short.
- Do not treat sheep with any approved product for at least 6 weeks before shearing unless the directions differ.
Flystrike Cause
- Flystrike is where blowflies lay their eggs on sheep and the resultant maggots eat the sheep’s skin and flesh, often leading to a very painful death.
- There are three species in New Zealand.
- Dirty damp woolly areas on the sheep attract the flies and warm humid conditions favour the eggs to hatch. This takes about 12 hours.
- The Australian green blowfly will strike clean areas of the sheep and is active over a longer period.
- Affected sheep are distressed and will stop and bite the area where the maggots are active. They may run around or stamp their feet.
- The struck areas on the sheep may look dark and wet.
- Struck sheep will hide away in scrub searching for relief as struck areas will attract more flies, both blowflies and others.
- Suffering sheep must be caught and the affected area treated to kill the live maggots. Methylated spirit is a good product for this.
- Shear the woolly area if the wool is long to expose the skin to the air. Maggots don’t like fresh air.
- Put some insecticide on the affected area to prevent further strikes. Many shepherds carry a bottle of dip with them for this job.
- Crutch and dag dirty sheep and if many are getting struck, it may pay to shear and dip them all.
- Good worm control will prevent scouring and hence attracting flies.
- Watch all lambs after docking to make sure none of them have their tail wounds attacked by blowflies. Also watch any sheep with shearing cuts.
- Don’t leave anything dead around the farm to attract blowflies – or use this fact in fly traps baited with rotten meat.
- Pouron or spray-on treatments are available. Consult your veterinarian for advice on which products to use and the time it remains effective. Pay special attention to meat withholding times for the products.
- Remember not to dip for at least 6 weeks before shearing.
Pregnancy (metabolic) diseases
Here the concern is over what are called “metabolic diseases” as they are caused by a ewe’s metabolism going wrong close to birth and soon afterwards. The three main metabolic diseases are shown in the Table below:
Names of metabolic diseases in sheep
Grass staggers
Note this is different to Ryegrass staggers (see later)
Cause
- Low magnesium in the bloodstream which has to be built up for storage in the liver.
- It can occur both before and after lambing.
- Rapid changes in the diet from hay to lush pasture can cause it.
- Ewes are simply found dead. Perhaps there will be scruff marks where she has been staggering and froth on the mouth.
- Very early signs can be subtle and not noticed in a big mob.
- This may progress to increased nervousness and slight shaking when disturbed.
- These can lead to quite dramatic signs like walking with stiff legs, staggering and falling over when mustered.
- When the sheep goes down she will paddle with her legs and hold her head back.
- Treat any ewe showing early signs with magnesium. Check with your vet for the correct product and the way to give it.
- Check with your vet whether to give a calcium injection at the same time as milk fever could be involved.
- Dust paddocks with calcined magnesite before grazing if you expect major problems. Wear a mask when applying the dust.
- Check the soil tests to see if potassium levels are excessively high as this can be a predisposing factor.
Milk fever Cause
- An imbalance of calcium.
- It occurs mainly in older ewes which produce a lot of milk.
- It can happen both before and after lambing.
- Often happens within 24 hours of a sudden stress, e.g. yarding, transport, mustering, bad weather or feed shortage.
- Affected ewes may just be found dead with no obvious signs.
- Restlessness, trembling, staggering, depression and lying down.
- Ewes go down on their chests (rather than on their sides) with their hind legs extended behind them, and head down and extended forwards or turned into their flank.
- May be a discharge from the nose, bloated, and they usually abort dead lambs.
- At the first sign of problems give the sheep a calcium injection. Check with your vet for the correct product and the way to give it.
- It may be wise to give her a magnesium injection too as the two conditions are often seen together.
Sleepy sickness, pregnancy toxaemia
Cause
- This is the most common metabolic disease in sheep and occurs in the six weeks before lambing, especially with ewes carrying multiple lambs (hence the name of twin-lamb disease).
- It is regularly triggered by underfeeding which can happen in snow storms, especially after a period of good feeding. Cold weather and lack of shelter add to the problem.
- Any condition that increases the stress on ewes, e.g. footrot, foot abscess and internal parasites may trigger it.
- Lack of exercise such as when ewes are yarded or held under cover, may also cause it.
- Slow onset of the disease as opposed to the other two metabolic diseases.
- You will notice slowness to move, lethargy, not eating, staggering or aimless wandering, twitching of the face and ears, blindness causing the sheep to lie down usually with her head up.
- Coma and death can occur from 2-7 days.
- 50% of people should be able to smell the ketones (nail varnish smell) in the sheep’s breath. Blood tests will confirm this.
- Dead ewes will have a fatty liver.
- As soon as you suspect the disease, treat the sheep with energy supplements – (some with electrolytes) given by mouth. Check with your vet for the correct products and the way to give it.
- Good feeding is the key to prevention and avoiding variation in the feeding level in the last weeks of pregnancy. Feed high energy concentrates as the sheep’s appetite for bulky feeds will be reduced.
- Make sure ewes have gentle exercise before lambing.
- For valuable ewes, performing a caesarian section will save her life and her lambs.
Bearings (vaginal prolapse)
Bearings can be a frightening sight and the ewe risks infections if she lies on muddy ground.
Cause
- Bearings can be caused by high pressure in the abdomen from a womb full of lambs, a rumen full of frothy herbage, a lot of fat in the abdomen and a full bladder. It’s possible to have a combination of these factors.
- Bearing problems vary greatly between farms and between seasons.
- A mass of pink flesh hanging from the vulva of usually a heavily-pregnant ewe.
- Dry ewes can also have bearings.
- The “bearing” may be the inverted (inside out) vagina.
- If it’s big it may contain the bladder, the cervix and the uterus (womb).
- If it is a massive bearing, call the vet urgently and leave the sheep undisturbed.
- If the bearing has been out a long time and is dry, then the chances of success are poor and euthanasia may be the best option. Saving the lambs by caesarian may be possible immediately after the ewe is dead.
- If the bearing is recent and small, i.e. only a prolapsed vagina, then gently clean and disinfect the prolapse and push it back in. It’s important to empty the bladder before doing this. It helps to point the ewe down hill or get someone to hold her up by the back legs during the task.
- The bearing will then have to be retained to prevent it coming out again. Veterinary treatment involves placing sutures around the vagina and vulva.
- The best farm treatment is to use a commercial plastic retainer held in the vagina by tapes to the sheep’s wool.
- Old methods using safety pins, clips, wool or twine tied across the vagina have variable results and should be used only in the last resort. For any problems seek veterinary help.
- Make sure all these devices are removed before the ewe lambs and before shearing.
- Keep at risk ewes off hilly pasture as lambing approaches and make them take gentle exercise.
- Keep a steady feed supply, avoiding putting ewes into long lush pasture.
- Mark all bearing ewes for culling at the first opportunity.
- Note: There is also “rectal prolapse” which is where the rectum is pushed out and can happen in male sheep too. Often these go back in again on their own, but it’s best to cull the sheep to avoid future problems.
Mastitis Cause
- This is an infection of the udder caused by various bacteria.
- It usually happens in the first weeks of lactation and at weaning.
- There are two main types – simple mastitis and gangrenous mastitis.
- Cold stress and lambing on bare muddy paddocks are often part of the cause.
- With simple mastitis there is little obvious sickness.
- The udder is hot, swollen and painful, usually just on one side.
- The milk is watery, clotted and discoloured.
- The ewe may look lame due to the extra pain in her udder when she walks.
- She will not let the lamb suck so the teat and udder are very extended.
- After a few days the affected side shrinks and becomes hard.
- This is often rapidly fatal.
- Affected ewes are very dull and show little interest in their lambs or eating.
- In the early stages the udder is hot, swollen and painful but soon becomes cold and turns blue-black in colour.
- Only blood-stained watery fluid can be expressed from the teats.
- If the ewe survives, the damaged tissue may slough off leaving an unsightly cavity which heals over leaving a large scar.
- Treatment often fails as the sheep is seen too late.
- For simple mastitis, treatment with antibiotics over three days will work if the ewe is seen early. (Check with vet for correct antibiotic treatment into the udder and into the muscle).
- Empty the udder before putting antibiotic into the teat.
- For gangrenous mastitis, amputation of the teat by a veterinarian allowd the tissue to drain and may save the ewe’s life.
- In both cases of mastitis, udder function will be severely affected for next lactation and the ewe should be culled.
- Little is known about prevention other than lambing on clean paddocks and culling all ewes that have been affected.
- Put ewes that have just weaned lambs on to short feed to reduce milk supply but do not restrict water.
Clostridial diseases Cause
- These are caused by a range of bacteria that are widespread in animals and their environment. Being anaerobic they reproduce in the absence of oxygen in the tissue and produce powerful toxins.
- When oxygen is present they form spores that can live in the soil for many years.
- These are mainly diseases of lambs as older sheep have developed an immunity to them, assisted by yearly vaccinations.
- They include pulpy kidney, tetanus and the gangrene diseases (malignant oedema, blackleg and black disease) which are almost always fatal.
- These vary with the disease but generally death is very rapid.
- Pulpy kidney is a good example where often the biggest lambs in the flock are found dead with little signs of a struggle. They may scour and show convulsions and die within 4-5 hours of the onset.
- With blackleg and malignant oedema (blood poisoning) they are found with blood-stained froth at the nose. They may be sick for 12 hours to a couple of days.
- Often the dead animal may blow up quickly and the skin goes blue/black very quickly.
- With tetanus (lockjaw), lambs gradually become stiff and may show muscular spasms. It is common in lambs within three weeks of docking but it can occur in older animals too.
- Treatment of these conditions is not effective.
- A vaccination programme with a 5-in-1 or a 10-in-1 vaccine is the best prevention as ewes pass immunity on to their lambs. The programme is to vaccinate hoggets twice then do ewes about a month before lambing.
- If lambs need further protection (check with your vet) then they are done at 2-3 months of age when their maternal immunity has passed.
- If ewes are not vaccinated, then lambs should be done at docking (4-6 weeks old).
- Or lambs can be vaccinated from 10-12 weeks old with a sensitising dose followed by a booster 6 weeks later.
Trace element & mineral deficiencies Cause
- These diseases are caused by lack of a range of minerals or trace elements which are deficient in some New Zealand soils and can be induced by fertilisers and feeding.
- Some are called “trace elements” as they are needed in very small amounts (traces).
- The main ones for sheep are cobalt, selenium, copper, magnesium and iodine.
- Ill thrift in lambs with loss of appetite, poor growth, wasting away, watery eyes, scabby ears and death.
- Deficiency is also associated with brain and liver diseases in older sheep.
- A third of New Zealand soils are deficient in selenium.
- Ill thrift in young lambs leading to white muscle disease.
- Infertility in ewes.
- Not common and seen on peat soils and leached sandy loams.
- Weak hind legs, fragile bones, poor growth, infertility, low fleece weight and wool loss.
- Seen on pastures where high nitrogen and potassium fertilisers have been used over time, especially after spring applications.
- Pregnancy and lactation increase the demand for magnesium.
- Ewes show agitation before convulsions and death, especially after the disturbance of yarding or in bad weather like snow storms.
- Some alluvial soils are deficient in iodine, and deficiencies can be induced by feeding brassicas and clovers which contain chemicals (goitrogens) that reduce thryroid hormones.
- Goitre is the main sign of the disease seen in swollen thryroid glands in the neck.
- Poor survival in newborn lambs, and reduced wool production in ewes.
- Both treatment and prevention depend on supplementing animals with the required trace elements well before they need them so body reserves (except for Iodine and magnesium) can be built up.
- Review your fertiliser programme to see what trace elements can be added in the mix.
- Body reserves can be checked by blood tests and liver biopsies through your veterinarian.
- Don’t overdose. Don’t dose with selenium if it has been applied in the fertiliser.
- Also called orf, contagious pustular dermatitis, and is a virus disease seen in lambs.
- The scratches caused by eating thistles and gorse seem to predispose lambs to the infection.
- It is classed as a zoonoses as it can be picked up by humans, especially meat workers handling affected lambs.
- Crusty sores mainly around the lips of lambs up to 6 months old.
- Scabs can also form on the muzzle, ears, lower legs and around the teats of ewes caused by lambs sucking.
- Ewes not letting their lambs suck and lambs not thriving because they are not eating.
- Treatment is not worthwhile. Sores generally heal naturally.
- Antiseptic creams can help secondary infections for small numbers of sheep.
- If the disease occurs regularly on farms, a vaccination programme should be used every year.
- Lambs are vaccinated by scratching the bare skin in the loin area soon after birth or at docking.
- Always wash your hands after handling lambs, especially at docking time.
Johnes disease Cause
- This disease (pronounced as Yoh-neez) is caused by a bacterium that lives in the soil and can persist for years. It’s of growing concern in New Zealand.
- Affected stock pass out the bacteria in faeces to infect other sheep.
- It’s a wasting disease that develops slowly and is seen most often in sheep from 2-4 years of age.
- Many affected animals don’t show signs, especially in younger age groups.
- In the early stages sudden loss of condition in older sheep.
- Severe scouring.
- Lab tests are needed to confirm the disease.
- There is no treatment for affected stock.
- All infected stock should be destroyed to prevent spread of the disease.
- Avoid introducing it to the farm with purchased stock.
- Don’t have any suspect animals on the farm over lambing.
- A live vaccination is available – check with your vet for details.
Facial eczema (FE) Cause
- FE is caused by a toxin produced by the rapidly growing spores of a fungus in the dead litter of pastures, especially when conditions are warm and moist in autumn.
- It is most common in the North Island of New Zealand.
- The toxin damages the liver and bile ducts so it cannot rid the body of wastes and a breakdown product of chlorophyll builds up in the body causing sensitivity to sunlight (photosensitisation), especially on non-pigmented areas.
Stressed sheep showing swollen closed eye, bleeding from rubbing to stop the itch. Should not be out in the sun and should not have been at the saleyard!
- Reddening and swelling of the skin around the eyes, ears, lips, nose and vulva exposed to the sun.
- Sheep rub these itchy areas and make them bleed.
- Affected stock are restless and continually seek shade.
- The skin reddens, swells and then sloughs off leaving raw skin that can become infected.
- Severely affected sheep will be jaundiced seen in a yellowish tinge in the whites of their eyes.
- Provide some shade for affected stock. If there is no natural shade, allow them access to a barn and provide feed or let them graze at night.
- Remove them from the “hot” pasture to allow the skin and liver to recover.
- Provide good high-energy feed – not high protein pasture which puts strain on their damaged livers.
- Give affected stock an oral dose of zinc oxide. Check with your vet as too much can be toxic.
- Jaundiced stock should be offered a diet of hay and water for a few days before gradually introducing high-quality nutritious feed to help the liver recover.
- Apply opaque protective cream to damaged skin to hasten healing and screen the skin from sunlight.
- A veterinarian may give antibiotic injections if severe skin infections occur, and also vitamin B12 injections to boost appetite.
- Jaundiced sheep will not be accepted by meat companies or if slaughtered their carcasses will be condemned.
- Check the area spore counts regularly through your vet clinic, local newspapers or websites.
- Pastures can be toxic once spore counts reach over 40,000 but damage can occur with low spore intake over a long period.
- Obtain the equipment (microscope and slide) to monitor spores on the pasture in your own paddocks or join with neighbours to share the information. Note there is great variation between paddocks, and areas within paddocks, so take plenty of samples.
- You can use the same equipment to measure spores in faeces which is easier to do and more meaningful as you know the animal has ingested these spores.
- By the time 5% of a flock have obvious clinical signs; up to 50% or more of the group will be liver-damaged.
- Regular drenching with zinc oxide or putting zinc sulphate in the water supply is effective if started well before spore counts rise. Never drench with zinc sulphate as it will damage the rumen. (Check with your vet clinic for dose rates).
- Sheep can be given a slow-release zinc bolus that stays in the rumen but it must be the correct size for the weight of the animal to avoid toxicity. (Check with your vet clinic).
- Zinc can be toxic so make sure you do not overdose and that only licensed products are used.
- Pastures can be sprayed with fungicides to make “safe areas” on the farm safe for periods of high spore counts. (Check with your vet clinic).
- Any animals that have been badly affected should be culled after they have recovered. If there is no chance of recovery then they should be euthanased.
- Make sure you boost copper levels in all stock that have been on long-term zinc treatment as zinc strips copper reserves from the animal’s system.
Ryegrass staggers (RGS) Cause
- This is a brain disease caused by a toxin from a fungus that grows in perennial ryegrass.
- It’s not common in the southern half of the South Island of New Zealand.
- The fungus is an “endophyte” i.e. it grows inside the plant where the highest concentrations are in the leaf sheath at the base of the pasture and in the seed heads.
- The toxin damages parts of the brain that coordinate movement.
- When disturbed, affected sheep appear nervous and in mild cases they show slight trembling of the head and of the skin on the neck, shoulder and flank.
- More severe cases show head nodding and jerky movements, swaying while standing and staggering when walking.
- In the worst cases sheep have a stiff-legged gait, take short prancing steps and may collapse with rigid spasms that last for several minutes.
- The disease is not fatal but sheep often die as a result of accidents – falling into holes, drains and creeks. They may not be able to drink.
- There is no cure for severely affected stock.
- Remove affected animals from the hazardous pasture if you have other pasture available.
- If not then hold them in yards and feed supplements (hay/silage/meal) with plenty of water.
- Try to avoid stressing them through excess handling.
- The best long-term solution is to replace ryegrass pastures with endophyte-free cultivars or safe endophytes.
Poisons Cause
- These include poisonous plants, fungal toxins in pasture, algae and chemicals.
- Many cases of poisoning are accidental.
- One or more of the plants can cause diarrhoea, regurgitating rumen contents, unusual excitement, dullness, body tremors, pain (teeth grinding, reluctance to move, arched back) and convulsions.
- If poisoning is suspected, a veterinarian should be consulted without delay.
- Garden prunings should not be thrown into the paddock. Many plants are poisonous to sheep and are often more palatable when wilted.
- Rubbish dumps should be fenced off and native scrub checked for poisonous plants before allowing sheep access to it.
- Blue lupin (a fungal toxin in lupins can cause lupinosis)
- Bracken (Pteridium esculentum)
- Devilwood (Ageratina adenophora & A. riparia)
- Foxglove (Digitalis purpurea)
- Goat’s rue (Galega officinalis)
- Hemlock (Conium maculatum)
- Jerusalem cherry (Solanum diflorum & S. pseudocapsicum)
- Laburnum
- Macrocarpa (Cupressus macrocarpa)
- Ngaio (myoporium laetum)
- Oak (acorns) (Quercus sp.)
- Oleander
- Orange cestrum (Cestrum aurantiacum)
- Ragwort (Senecio jacobaea)
- Rhododendron
- Rhubarb
- St John’s wort (Hypericum perforatum)
- Tutu (Coriaria arborea)
- Yew (Taxus baccata)
- Sheep can be overdosed with zinc, copper or selenium.
- Fertilisers should be allowed to wash in before grazed by stock.
- 1080 poisoning can occur when poisoned bait is accidentally dropped on to pasture or when stock gain access to land used for a poison drop.
- Overdosing with organophosphate insecticides or anthelmintics can cause toxicity.
This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.
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kimera
What causes a 7 month old male to keep picking up his leg then lay down
ReplyDeleteMost likely it is footrot which needs treating by paring off excessive long hoof and applying some treatment recommended by a veterinarian as a spray. The sheep needs to kept out of mud.
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