Arthritis / Polyarthritis
- Arthritis is inflammation of the joints, usually in the legs, and leads to permanent changes within the joints.
- When multiple joints are affected, the condition is referred to as polyarthritis.
- Arthritis is estimated to cost the sheep industry $39 million a year due to poor growth rates and deaths on farm, plus losses at abattoirs due to trimming and condemnations.
- Arthritis affects 2% lambs/weaners and 1% adult sheep.
- Inflamed joints can be damaged by infection, often from skin wounds.
- Numerous different types of bacteria can cause arthritis in sheep. The bacteria gain access to the body, circulate in the blood stream, settle out and multiply in the joints.
- Bacterial arthritis occurs when lambs have a break in their skin, which becomes infected. They then get septicaemia, or blood poisoning, and blood-borne bacteria lodge in a joint
- Often seen in lambs prior to weaning (lamb marking wound infections), but also in older sheep (shearing wound infections).
- Short tail docking has been linked to bacterial arthritis in lambs.
- First signs are heat and swelling around one or more joints.
- Large joints (such as the knee and hock) are the most commonly affected.
- Movement of affected joints is restricted and painful and lambs are obviously lame.
- The heat and most of the swelling subsides over a few days but slight swelling, restricted movement and a mild lameness often remain permanently.
- Examining the joints for swelling and heat.
- On post mortem there is often bone damage in the joints, the joint fluid becomes thicker and fibrous, the tissues around the joint are thickened and there can be pus within the joint.
- Arthritis is often not seen in live animals and only discovered in meat processing plants leading to losses due to downgrading, trimming, or condemnation. The average loss per carcase from arthritis = 3kg.
- Early antibiotic treatment can reduce the extent of joint damage.
- A vaccination called Eryvac is available for the prevention of arthritis due to one of the most common bacteria and is given to ewes 4 weeks prior to lambing.
- Keep stress at lamb marking to a minimum by choosing a warm sunny day, keeping droving to a minimum before and after marking and allowing the lambs to mother up as soon as possible.
- Maintain good hygiene at marking.
- Tails should never be docked higher than the third palpable joint.
- Do not move sheep immediately after shearing, until wounds are healed.