Relentless rain can soon attack a horse’s natural defences, while boggy conditions underfoot can create a multitude of health
hazards. Roger Lee MRCVS offers advice on surviving the current deluge

Waterlogged fields, flood warnings and mud everywhere — parts of the UK have had the wettest January since records began and now, into February, still the rain keeps falling. But how does all this wet weather affect our horses’ health?

For many owners, the choice is between keeping horses stabled for 23hr a day or turning them out into paddocks that resemble ploughed fields. For horses turned out, particularly those wintering outside, problems tend to occur in the areas most exposed to the continuous wet — the coat and the feet.

Rain scald is the name given to the bacterial skin infection that can occur when the coat is wet for prolonged periods. The hairs become clumped together and eventually large, matted areas can lift off to reveal raw patches of skin.

This condition typically affects the back and quarters, with the affected area often mirroring the pattern of water running off the horse’s back and down its sides. The bacteria responsible, Dermatophilus congolensis, is one of a group of organisms also responsible for mud fever.

Horses wintering without rugs are most at risk, although rain scald can occur on the neck and face of rugged horses and even the body of those rugged up when still wet. The most important part of any treatment is to keep the horse stabled and dry. The scabs will eventually brush out or lift off, but antibiotics may be necessary in severe cases.

Fighting fungus

Horses’ hooves have evolved for hard, dry conditions, so it is no surprise that constantly wet feet are prone to problems. Foot abscesses are particularly common in wet weather, especially if a horse is unshod.

Small cracks in the hoof wall that developed in dry weather widen and become packed with mud. Such cracks gradually work their way deeper into the hoof until reaching the sensitive tissues — where an abscess forms.

The white line is the name given to the area where the horn of the hoof wall joins that of the sole. Like any join or seam, it is a weak spot.

White line disease is a bacterial or fungal infection that attacks the white line when it is further weakened by prolonged soaking. The hoof wall then separates from the horn underneath, creating a gap that is filled with white, crumbly material. When this happens at the front of the hoof wall, it is called seedy toe.

Mild cases of white line disease don’t cause lameness, but if the hoof wall separation extends higher it can reach sensitive areas.

The treatment is to cut away the affected hoof wall and treat the horn underneath with dilute iodine or a sugar and pevidine mix; something to dry it out and kill any bacteria. Affected horses need to be stabled on a dry surface during treatment.

Thrush can occur when the feet are kept continuously wet, either because of muddy fields or damp bedding. The condition is another infection, causing a black, unpleasant-smelling discharge in the clefts of the frog — particularly the central one. It is more common in horses with narrow heels and deep clefts, especially if the feet are not regularly picked out.

Like white line disease, thrush rarely causes lameness unless it is severe. Treatment involves bringing the horse in to stand on a dry surface, cutting away any diseased frog and keeping the feet clean. Dilute iodine can be painted on to the frog, or an antiseptic spray can also be used.

Slippery when wet

Wet ground or not, horses still like to gallop. They don’t always realise, however, that it may be harder to pull up on slippery ground. Injuries from skids and falls are common in the mud, and horses can slide into wire or even flip over a paddock fence.

When hacking off-road, and particularly when hunting, very soft ground brings its own injury risks. Jumps with boggy landings are dangerous because a horse may be unable to “unstick” his front legs in time, and his own momentum can bring him down.

Soft ground generally means lower speeds, with less concussion on joints, but very “holding” ground can lead to check ligament or suspensory damage as horses struggle to maintain their balance. Tiredness and muscle fatigue are major contributing factors to injury, and horses have to work much harder in soft going. It is important to slow your speed and to keep your hunting day shorter.

Although it might be fun to gallop through puddles and standing water, if you can’t see what is lurking under the surface you can’t avoid it either. Always proceed with great care.

Horses can successfully winter outside, even without rugs, but in persistently wet weather they lose weight easily. A wet coat loses its insulating properties and if it is also cold, a horse has to use much more energy keeping warm. To counter this, try to provide a field shelter with a dry floor, ensure adequate feeding and check the coat and feet regularly.

Liver fluke: the wet weather worm

The parasitic flatworm liver fluke affects mainly sheep and cattle, especially on wet or boggy pasture.

The liver fluke eggs hatch out in water and the larvae live first inside small water snails. They then hatch out again before crawling up grass stems, ready to be eaten by the grazing animals. Once swallowed, the fluke burrow through the gut wall and eat their way into the liver, causing serious damage and even death.

Mild and wet winters such as this one increase the number of snails and provide ideal conditions for liver fluke, which is especially common in Scotland and the west of England.

It is known that horses are more resistant than livestock to fluke, but it is hard to tell how many could still be carrying a low level of infection. This is chiefly because there is no reliable way of identifying liver fluke in horses — the flukes only rarely produce eggs and signs of infection are often vague. These signs include anaemia (a lower than normal level of red blood cells), dullness and possibly soft droppings. Liver enzymes, as measured by a blood test, are also likely to be higher than normal.

Infection is unlikely unless a horse is sharing pasture with livestock. If fluke infection is suspected, horses can be treated with the same “anti-fluke” drug as cattle and sheep, but always discuss with your vet first as these medications are not licensed for use in horses.

‘We didn’t know what was wrong’

Unexplained weight loss coupled with diarrhoea, lethargy and a lack of appetite were the worrying signs that all was not well with thoroughbred mare Poppy.

“A blood sample revealed an abnormal white blood cell count and a raised level of gamma-GT liver enzymes,” explained her owner, Kate Hewetson, who first noticed problems with Poppy back in October 2012.

“Poppy regained her appetite once she was put on a course of antibiotics and a low-protein diet, but her liver enzymes remained high.

“We were advised to see whether the liver, given time, would repair itself, but by February she was no better and was referred to hospital.”

Liver scans and biopsies shed no further light on the cause, but it was a chance meeting between Kate’s own vet and another that raised the possibility of liver fluke, especially as livestock grazed nearby. Testing returned a positive diagnosis.

“One of my other two horses also tested positive, although he showed no signs of illness,” said Kate. “All three were dosed with Fasinex [a farm animal liver fluke treatment].” A month later, Poppy’s blood tests showed an improvement.

“It took 10 months for Poppy’s liver to recover fully,” added Kate. “She later took part in The Showing Register masterclass at Horse of the Year Show — a fairy-tale end to a difficult year.”