Sheep Health Issues

Author: Don Moir, Department of Agriculture, Narrogin

A few of the most common conditions affecting sheep used for meat production are considered briefly. For more detailed information, readers should consult their private veterinarian or consultant.

Enterotoxaemia

(Pulpy Kidney)

This is a disease caused by changing diets from low to high quality feeds as occurs with grain feeding, or moving sheep onto crop stubbles or good green feed. It also may be seen in lambs suckling ewes on lush green feed. This disease is most often seen in lambs and weaners but can affect sheep of any age.

Signs

• Sudden death. Sheep are usually found dead without any symptoms having been observed.

• The head may be thrown back, and there can be convulsions.

• There can be frothing at mouth.

Control

• This is by a vaccination given to lambs at marking and weaning, and annually thereafter. Ewes are given an annual booster four weeks before lambing to protect the lamb for the first six weeks of life.

Hock joint swollen with arthritis

Arthritis

This is a common condition in lambs after marking, or less often in the first four weeks of life. It is caused by the entry of bacteria into the body via marking wounds or the umbilical cord in newborn animals. Arthritis is due to a high environmental contamination with specific bacteria (Erysipelas, Streptococcus,Haemophilus) that build up in sheep yards and under conditions of high stocking densities.

Signs

• Hot painful swelling of one or more joints in the legs. Lambs are lame, reluctant to walk, and become ill thrifty. They may die through poor mothering.

Control

• Carry out marking and mulesing in temporary yards in a clean paddock. Ensure the use of hygienic measures with clean instruments. Clean the wounds and change disinfectant solutions often. Wash blood from hands often.

• For persistent problems consider the options of vaccination or prophylactic treatment with your veterinary consultant.

More information about this problem is available in the Farmnote 4/94, Sheep Arthritis.

Internal Parasites

i) Worms of sheep are a major cause of economic loss due to mortalities, ill thrift, reduced wool growth and scouring with subsequent fly control measures (crutching, jetting, strike treatment). Also, they can contribute to other conditions such as nutritional ill thrift of weaners and pregnancy toxaemia. Sub clinical production losses occur without the producer’ s knowledge. The widespread incidence of resistance to drench chemicals has made control programs more complex.

Signs

• These may be sub clinical, that is, no obvious signs.

• There can be various combinations of ill thrift, anaemia, scouring and death.

Control

• Biannual test for drench resistance.

• Use a control program that incorporates paddock and stock management, worm egg count monitoring, chemical rotation and a drenching strategy.

• Prime lambs may need to be drenched on a lower worm egg count than is used for other lambs to maintain maximum growth rates.

ii) Coccidiosis. This is caused by a protozoan parasite of the small intestine that is present in virtually all sheep flocks. It is normally present in sheep in small numbers and causes no harm. However, when seasonal conditions result in poor conditioned ewes with reduced milk production, lambs are forced to graze pasture at an earlier age and to a greater degree than normal and this results in an increased intake of coccidia.

Increased intakes of the parasite in lambs can also occur in hand feeding situations where patches of ground become heavily contaminated. The condition is usually seen in lambs up to eight weeks of age. Most of the lambs will self-cure and then become immune.

Signs

• A dark scour, sometimes containing blood.

• Lambs are unthrifty, anaemic with a low mortality rate, except where poor nutrition continues.

Control

• Supplementary feeding of the ewes.

• Change the trail-feeding site regularly.

• Affected prime lambs can be treated (consult a veterinary practitioner).

Scabby mouth

Scabby Mouth

This disease is also known as contagious ecthyma or Orf. It is caused by a virus that can live for years in the environment. Scabby mouth is important because it is a threat to the viability of the live sheep trade, but it can also cause economic loss of condition in young sheep during outbreaks on farms. The virus gains entry through skin damage to the mouth that can be caused by thistles and stubble or via damage to the feet caused by long, wet grass. The disease can cause skin lesions in humans.

Signs

• Scabs develop around the mouth, above the hoof or less commonly on the udder of ewes and scrotum of rams.

• Animals may have difficulty eating or walking with subsequent loss of condition. Self-cure takes three to four weeks.

Control

• Vaccinate lambs at marking. It is important that all sheep to be exported have been vaccinated.

There is more information about this problem in the Farmnote 19/97, Scabby Mouth.

Acidosis (Grain poisoning)

This is caused when sheep are introduced too quickly to diets high in grain. It also is seen when self-feeders run out of grain for several days and are then refilled with a consequent engorgement by sheep.

Signs

• Scouring, rapid breathing, inappetance, depression.

• Occasionally lameness, bloating.

• Death in severe cases.

Control

• Introduce sheep to grain feeding gradually over a two-week period.

Healthy Sheep

Bloat

This is not a common problem in sheep. However, it may occur on young, rapidly growing legumes such as lucerne or clover. It is caused by froth forming in the rumen, which prevents the animal from belching.

Signs

• Swelling of the left flank.

• Discomfort, rapid breathing

• Sheep get up and lie down frequently. They may collapse and die in severe cases.

Control

• Treat affected animals with a drench of 40 millilitres of paraffin or any vegetable oil for short-term control.

• Restrict grazing time on dangerous pastures.

• Provide access to hay.

• Strip graze.

Lupinosis

This is a disease caused by consumption of the toxic phomopsins that are produced by a fungus that colonises lupin plants. Although the fungus infects the plant while it is growing, it only produces enough of the toxin to produce lupinosis after the plant has died and has subsequently been exposed to rainfall or heavy dews. For this reason lupinosis is usually a disease seen in summer and autumn when sheep are grazed on lupin stubbles.

In the feedlot, lupinosis may also occasionally result from the feeding of crop fines collected when harvesting lupins, or the feeding of lupin seconds containing large proportions of discoloured seeds. The phomopsins primarily damage the liver, so the clinical signs are usually related to liver disease. However, in young growing sheep the liver damage may also cause altered metabolism of selenium and vitamin E, resulting in the development of lupinosis-associated myopathy, a disease similar to white muscle disease or nutritional myopathy.

Signs

• These may vary greatly depending on how much toxin is consumed. Feed intake may be reduced, or there may be a complete loss of appetite.

• Sheep may not put on weight in a situation when they should, or there may be obvious loss of weight and condition.

• As the disease progresses there will be lethargy, wandering and “star gazing”, jaundice, depression and death.

Control

• Plant only Phomopsis-resistant lupin cultivars.

• Observe sheep regularly while grazing lupin stubbles or stands of sandplain lupins during summer and autumn. If they are not growing as well as might be expected, always suspect lupinosis and move the sheep to non-lupin pasture.

• Do not feed lupin seed to sheep suspected of having lupinosis; their livers cannot handle the high protein diet and they develop ammonia toxicity.

• Sheep should be removed from lupin stubbles at least a week before going to the abattoir. Some may have internal jaundice associated with subclinical lupinosis, and their carcases will be rejected. The one-week break from lupins is usually sufficient to allow the jaundice to resolve.

• Ensure that young sheep grazed on lupin stubbles have adequate selenium and vitamin E.

Pregnancy Toxaemia

This is caused by an inadequate intake of energy during late pregnancy and is exacerbated by ewes having multiple foetuses. It may be induced by a sudden cessation of eating caused by adverse weather, or the moving or yarding of flocks. Over-fat ewes are most prone to the problem. It can also result in the birth of dead lambs.

Signs

• A loss of appetite.

• Sheep become separated, depressed and wander aimlessly.

• They appear blind, ignore dogs and people, become recumbent, comatose, and die.

Control

• Monitor the condition of pregnant ewes by weighing and/or condition scoring.

• Be prepared to supplementary feed pregnant ewes.

• Pregnancy-test high multiple birth flocks and feed according to their pregnancy status.

Healthy Ram

Cheesy Gland

Also known as yolk boils, abscess and caseous lymphadenitis (CLA). The bacterium Corynebacterium pseudotuberculosis causes abscesses to form in lymph nodes and lungs of sheep and goats, leading to losses in wool production, carcase condemnation or trimming at abattoirs and some mortalities. Spread is commonly associated with shearing and dipping.

Signs

• Abscess formation under skin or internally.

• Pus is light green to cream colour.

• Occasional death in adults for no obvious reason.

Control

• Vaccinate lambs at marking and weaning. Yearly boosters before shearing are essential to lower flock prevalence.

• Minimise the time sheep are kept in close contact after shearing.

• Avoid dipping sheep if no lice are present.

Pink Eye

A bacterial infection of one or both eyes. It is aggravated by congregation in dusty conditions and irritation by flies. Most sheep recover from pink eye. However,up to four per cent may become permanently affected if left untreated. This problem may be confused with grass seeds in eyes.

Signs

• Inflammation and tears from affected eyes.

• Cornea becomes red then white as condition progresses.

Control

• Avoid yarding during outbreak. If necessary, draft-off affected animals and isolate them.

• Treat with antibiotic eye ointment.

Pneumonia

Caused by a variety of bacteria. Pneumonia is most commonly seen in young sheep on dry, dusty feeds. Irritation from dust allows bacteria to invade and cause inflammation and infection.

Signs

• Nasal discharge, coughing, high temperature and lethargy.

Control

• Avoid finely hammer-milled feeds.

• Dampen feed or add a dust suppressant, for example, tallow.

• Treatment of clinical cases may require antibiotic treatment as advised by a veterinarian, with strict adherence to withholding times.

Healthy Sheep

Salmonellosis

Contamination of feed or water sources with faecal material can lead to infection with salmonella bacteria. Trail-feeding grain in the same area can lead to a build up of faeces and result in disease, especially if sheep are under nutritional stress or subject to adverse weather. Summer storms may wash large quantities of faeces into water supplies leading to salmonellosis.

Signs

• Scouring, high temperature, lethargy, death.

• Abortion in pregnant ewes.

Control

• Prevent faecal contamination of feed and water.

• Change trail-feeding sites regularly.

• Withhold sheep from affected mobs from slaughter until the outbreak is over.

Hydatids

Hydatid disease is caused by the tapeworm Echinococcus granulosus which lives in the intestines of dogs, foxes and dingoes. The tapeworm eggs pass onto the ground in the dog faeces where they may be ingested by grazing animals. These eggs then develop into multiple cysts within the liver and lungs and will result in condemnation of the carcase at abattoirs.

Hydatid disease is a major human health hazard. Dog tapeworm eggs ingested by humans develop into cysts that can only be treated surgically.

Signs

• Infected sheep show no external symptoms.

• Autopsy reveals multiple fluid-filled cysts in the liver, lung and occasionally the brain.

• Dogs infected with E. granulosus show no signs of a problem.

Control

• Treat dogs every two months with the drug praziquantel.

• Do not feed dogs raw meat or offal. Prevent access to any carcases on the farm (including kangaroo,wallaby and pig). Burn carcases as soon as possible.

• Control fox and dingo populations.

Sheep Measles

As with hydatid disease, sheep measles is the intermediate stage of a dog and fox tapeworm called Taenia ovis. Eggs on pastures picked up by sheep develop into small cysts in the muscles and heart. Old cysts become hard, fibrous and sometimes gritty, and are known as “measles”. Infected carcases are rejected at abattoirs.

Signs

Severe infection may cause production losses.

• There are no other external signs of infection in sheep.

• Carcases show small cysts in the heart, diaphragm and meat.

• Dogs infected with T. ovis may pass segments in faeces resembling grains of rice.

Control

• As for hydatid disease.

Annual Ryegrass

Annual Ryegrass Toxicity

Seed heads of annual ryegrass infected with the nematode Anguina funesta and the associated bacterium Clavibacter, become toxic to livestock. The danger period starts after flowering in spring and lasts while infected heads remain in the paddock. The infection can be transferred to new areas by contaminated machinery and hay.

Signs

Disturbance of the nervous system.Collapse,convulsing and then apparent recovery after driving is common. Animals may have a stiff-legged gait.

• Seriously affected sheep will remain down until they die.

• Pregnant ewes may abort.

• Mild cases can recover with rest.

Control

Use of the twist fungus on pastures.

• Reduce reliance on annual ryegrass as major pasture species.

• Seed set control in early spring by heavy grazing or chemical application.

• Autumn burn of affected paddocks.

Other disease conditions

Other common conditions that can affect lambs include trace element deficiencies, weaner ill-thrift, perennial ryegrass staggers, toxic algae, hypocalcaemia, hypothermia, foot abscess, Eperythrozoonosis (E. Ovis) and photosensitivity.

Water requirements

The provision of adequate supplies of good quality water is important. The consumption of water increases as the concentration of salt in the water increases. Therefore, it is essential to monitor the quality of the water and to ensure that the supply can meet the expected demand.

Lambs can only tolerate water with about half the total salts that can be used by adult sheep (1100 compared to 1650 to 2200 milliSiemens per metre).

Weaners grazed on feeds with a high content of solubleprotein during summer, can drink large quantities of water (up to 9 litres per head per day).

Grown sheep can drink even more water than this. This reinforces the need to have a plentiful supply of good quality water for sheep grazed on these feeds. Similarly, supplementary fed sheep need a good supply of water.