28 August 1998

Getting on top of sheep foot rot and scald

What can be done to control

and eradicate foot-rot and

scald in sheep flocks?

Sandy Clark, manager of

SACs vet lab in Thurso,

advises prompt action

FOOT lameness is one of the major welfare concerns in sheep flocks throughout the country.

There are two causes – foot-rot, which is highly infectious, and scald, which is initially due to mechanical damage or irritation. Both conditions can be controlled and possibly eradicated by careful management, leading to an overall improvement in flock health.

Foot-rot

Foot-rot is a flock problem and is spread from sheep to sheep via the ground or bedding. Bacteria causing disease are Fusobacterium necrophorum necrophorum and Dichelobacter nodosus.

These only survive on pasture or bedding for a maximum of 14 days and this is one key to controlling infection.

Foot-rot can be difficult to eradicate since a percentage of sheep become chronically infected and lame, and will never respond to treatment.

Disease spread is temperature and humidity dependant – warm, damp conditions are ideal for the organism to live on the ground and spread from chronically infected sheep to others. Conditions in sheep housing are often perfect for spread if bedding is damp or there are wet areas near water troughs.

All the feet of all sheep in a flock require close examination to determine whether foot-rot is present, and a turning crate is a great advantage for this.

Infection is found between the cleats and spreads to the area between the hoof and the skin. Eventually it invades the hoof, damaging the wall and sole. The disease causes a most unpleasant – but never forgotten – smell which is obvious when the foot is handled and pared.

Where sheep with foot-rot are not treated, the disease results in loss of weight and bodily condition, reduced milk production and possibly reduced fertility in affected rams. The bacteria can also cause navel ill and liver abscesses in young lambs, often leading to premature death of these animals.

But with careful management, foot-rot can be adequately controlled or eradicated from any flock.

A programme to deal with the disease is best carried out at colder times of the year when the bacteria do not live easily on pasture. All sheep on the farm must be examined within a short space of time, and placed on clean pasture after treatment.

Feet should be examined and animals divided into two groups – those with no evidence of disease and the other group of sheep to be treated.

All sheep should be treated in a footbath, preferably with zinc sulphate in 10% solution. This substance is better for treating foot-rot than other options such as formalin or copper sulphate, but sheep should be allowed to stand in the bath for at least 20 minutes. This lengthy treatment is easily achieved if a stand-in bath is used, and the next group of sheep have their feet examined and treated while the previous group is in the bath.

Sheep with foot-rot should have feet pared and treated topically with antibiotic spray. An injection of a penicillin/streptomycin product at 100mg/kg body weight should also be given, as directed by your vet.

Treated animals should be separated from unaffected sheep, and given footbath treatment last. The two groups should be kept strictly apart and moved to clean pasture where sheep have not been for at least 14 days. It is important to clean up properly after treatment, burning all foot trimmings and disposing of footbath liquid correctly.

The procedure should be repeated one to two weeks later. Residual cases in the treated group may be given one more opportunity of treatment. When there is no improvement in any member of this group they should be culled as chronically infected animals. After implementing this programme it is important to treat any new sheep brought into the flock as they may carry infection.

A foot-rot vaccination is available, but should not be seen as a method of avoiding foot paring. The vaccine will help control the disease but will not eliminate it from any flock, however, it is useful in preventing attacks of foot-rot, for example when sheep are housed.

Scald

Scald is an inflammatory disease of the skin between the toes which can be very painful. It is often caused by mechanical damage, for example long grass dragging between the cleats, particularly in lambs, or clay soil balling around the foot and between the toes.

A secondary bacterial infection often develops, and unless treated it may allow foot-rot to develop. In severe cases lambs may be unable to rise and ewes will be found walking on their knees. Many sheep can be affected in a flock at the same time and treatment should be given as soon as possible.

The whole flock should be footbathed in zinc sulphate 10% solution or formalin at 3%. However, formalin can make the foot harden and this may not be beneficial if future paring is needed. It is worth remembering that formalin at any greater strength can cause the condition rather than cure it.

Time should be taken to allow treatment to work – do not run sheep through a footbath. Not only is this totally ineffective against disease, but it can cause other damage due to splashes in eyes or mouths of both sheep and operators.

Where scald is caused by long grass, fields used for grazing should be topped to reduce grass height. This will also help with grazing since sheep prefer short grass.

There is no excuse for lameness in sheep since control methods and treatment are readily available. Investment in a stand-in footbath is well worthwhile and a turning crate can be invaluable. Foot-rot can be eradicated from a farm with a programme developed for all the sheep and cattle.

Further information on treatment and eradication should be gained from your vet.

FOOT-ROT CONTROL

* Treat in cooler weather

* Examine all sheep

* Treat promptly and properly

set in box please

SCALD CONTROL

* Inflammatory disease

* Possible secondary infection

* Adequate foot-bathing

Sheep should stand in footbath solution for at least 20 minutes to help treat foot-rot – this type of footbath makes the task easier.

FOOT-ROT CONTROL

&#8226 Treat in cooler weather

&#8226 Examine all sheep

&#8226 Treat promptly and properly

SCALD CONTROL

&#8226 Inflammatory disease

&#8226 Possible secondary infection

&#8226 Adequate foot-bathing