Wet Weather Ailments

Preparing Your Horse for Severe Wet Weather: What to Expect and How to Respond

Heavy rain brings numerous health hazards: flooded paddocks, horses cut off from each other or trapped in floodwaters, loss of shelter, contaminated drinking water, downed fences and tangled wire, an increase in biting insects, and skin problems. These conditions create significant demands and stress for both our horses and ourselves. Let's explore some of these hazards and ways to mitigate them.

Skin problems
Rainrot or rainscald produces distinctive gray/white scabs with tufts of matted hair on top and yellow-green pus underneath. This condition can be transmitted through contact and flies, spreading from horse to horse and even to people. Horses sharing paddocks with sheep or cattle are at a higher risk of developing rain scald and greasy heel. Additionally, horses with white socks are particularly susceptible due to the increased sunlight sensitivity of non-pigmented skin, which worsens the reaction.

Treatment
The first priority for treatment is to dry the hair and skin if the weather permits. Benzoyl peroxide (commonly used for human acne) and chlorhexidine are often effective treatments, as staphylococcus bacteria ('Staphs') are commonly involved. For stubborn heel infections, coconut oil, Vaseline, and zinc oxide can help remove scabs and repel moisture. If the skin condition hasn't cleared up within a week, it's important to call your vet, as the infection may become 'mixed,' progressing to cellulitis and requiring stronger medication.

Hooves and Feet
Horse hooves absorb water quickly, making soft soles vulnerable to bruising and penetrating injuries. These wounds can be fatal if the coffin joint, navicular bursa, or tendon sheath become infected. Early treatment is crucial for the best outcome. Ensuring paddocks and yards are free of debris like fencing wire off-cuts, broken bottles, and roofing nails is essential preparation for wet times. In wet conditions, horses often pull their shoes, leaving toe clips and nails as potential foreign bodies that can penetrate the sole. Removing shoes, regularly checking your horse’s feet, and seeking prompt vet and farrier attention for any abnormalities are good management practices during wet conditions.

Common Hoof Issues
Thrush, hoof cracks, white line disease, and hoof abscesses are especially prevalent during wet weather. If possible, create a clean and dry space for horses to retreat to. Be aware of the signs of hoof problems, such as a strong unpleasant smell, discharge, or acute lameness, and seek immediate inspection by your vet or farrier if you notice anything unusual. For all wounds, consult your local veterinarian for advice on the appropriate dressings and bandaging techniques for different types of wounds and injuries. Zinc and castor oil mixtures can help protect the skin and promote healing.

Wet/Dry Cycles
Hooves adapt well to consistently dry or damp conditions, but fluctuating between wet and dry stresses them. Like a sponge, the hoof wall absorbs and releases moisture quickly. Repeated wet/dry cycles exacerbate chronic dryness, causing nails to loosen and making it difficult for horses to keep shoes on. Discuss hoof dressing options with your farrier or veterinarian to mitigate the effects of these cycles, as they have experience with local conditions.

Oils and Omega Fatty Acids
Oils and fatty acids play a crucial role in hoof structure and integrity. Together with phosphorus, they form phospholipid compounds that both repel and attract water, helping to maintain the correct moisture balance. This is essential for combating both wet and dry conditions, building healthy, resilient hooves that are less likely to become damaged or cracked. Linseed meal is an excellent source of Omega-3 fatty acids and provides good levels of phospholipids, which is especially beneficial if your horse has limited access to fresh grass. Horses with pasture access usually get enough essential fatty acids, including Omegas 3, 6, and 9, in their diet if they are not in work. Older horses and those with arthritis, skin, and hoof problems often benefit from supplementation with flaxseed, flax, canola, or other oils rich in Omega-3 fatty acids.

Stocking-Up
Stocking-up occurs when fluid accumulates in two or all four lower legs overnight and goes away once your horse starts moving. This swelling is common and usually happens when horses move less than normal. The swellings are typically about the same size in all affected legs, may extend the length of the cannon bone, and are cool and nonpainful, with the horse otherwise appearing fine.

To determine if the swelling is stocking-up, apply pressure with your fingers over a swollen area to produce pits in the skin (hence the term 'pitting oedema'). It shouldn't cause pain, and the pits will slowly refill over 30 to 60 seconds. If inactivity is the cause, the swelling should resolve completely after 10-15 minutes of gentle exercise. Compression or stable bandages can help minimize fluid accumulation, but only use this solution if you're sure there isn't another cause for your horse's swollen leg(s).

Swelling in One Leg
Swelling in one leg is a basic symptom of inflammation, along with heat and pain. Common causes include injuries and infections. Sudden swelling in a single leg could indicate cellulitis, an allergy, or a venomous bite and needs prompt investigation and treatment.

Skin Swellings
In wet environments, the skin of horses is continuously exposed to moisture, allowing organisms normally found on the skin to invade the weakened barrier and establish infections. Fungi and mites can also contribute. Mild infections like pastern dermatitis, 'scratches,' greasy heel, or mud fever can spread into deeper layers, leading to cellulitis or lymphangitis. Muddy conditions aren't always necessary; wounds or grazes can also allow bacteria to penetrate.

Pastern dermatitis is more common on white legs with pink skin. In severe cases, the entire lower leg can swell and become very painful and hot. All participants (bacteria, fungi, mites) must be treated early for the best outcome. Check the lower legs carefully for any signs of the condition, as early treatment will hopefully deliver a speedier resolution. If the condition doesn't respond to treatment within a few days, continues to spread, or is painful to the horse, contact your vet. Calling a vet in more serious cases gives you the best chance of getting on top of the problem, as they come armed with sedatives.

Cellulitis and Lymphangitis
Leg swelling caused by cellulitis or lymphangitis can follow a break in the skin’s protective barrier, allowing bacteria to enter the body and infect deeper layers. If the infection progresses to involve the lymphatic system, it becomes lymphangitis. These are both very serious and potentially life-threatening diseases that need to be addressed as soon as possible. Although commonly due to cuts and puncture wounds, cellulitis or lymphangitis can also follow spider or insect bites, and some cases are linked to specific diseases like purpura haemorrhagica, a complication of strangles. Most of the time, the actual cause of lymphangitis is difficult to determine because the leg has already swollen significantly by the time the problem is recognised, making it hard to find wounds.

Lymphangitis presents with varying amounts of swelling, from foot to fetlock level or as a 'fat-leg' extending far above the hock or knee. It is acutely painful, and horses may be subdued, distressed, off their food, show colic signs, sweat, and have a fever, though some horses may appear fine. In very severe cases or those left untreated, the pressure build-up within the lymphatic vessels can lead to leakage of serum (straw-brown coloured fluid) from the skin, appearing as crusting and oozing areas (ulcerative lymphangitis). Treatment of lymphangitis is always necessary and must be started quickly and continued until the condition resolves.

Biting Insects
Biting insects like flies and ticks breed rapidly in wet weather, causing skin irritation, sleeplessness, and weight loss in horses. They can also carry viruses, infect wounds with worm larvae, and cause allergies such as 'sweet itch,' 'summer itch,' and 'Queensland itch.' Midges often feed on the neck and tail area, leading horses to rub against fences and trees, while others target the chest or belly, causing ventral midline dermatitis. Larval cattle ticks can cause acute dermatitis, especially around the horse’s face and lower legs, leading to severe skin damage and bacterial infections as horses chew their skin to relieve the pain and itch.

Biting flies can carry Habronema larvae from the horse’s manure. The larvae develop in maggots and then transfer to adult flies, which deposit the larvae into wounds while feeding on raw surfaces. The resulting sores, known as Summer Sores, can be enormous and are often confused with Swamp Cancers, a distressing fungal growth caused by the soil organism Pythium insidiosum. Pythiosis can cause rapidly growing, itchy, foul, oozing sores anywhere on the horse’s body. Prompt veterinary treatment within two weeks of infection, including surgical and antibiotic options, as well as immunotherapy via a vaccine, can be highly effective.

Infections
Ross River virus, Kunjin virus, and melioidosis are some of the more serious challenges, especially in tropical and subtropical regions, including northern Australia.

• Ross River Virus: This mosquito-borne virus causes Ross River fever, leading to joint pain, fever, rash, and fatigue.

• Kunjin Virus: A subtype of West Nile virus, Kunjin virus can cause symptoms ranging from mild fever and headache to severe encephalitis.

• Melioidosis: Caused by the bacterium Burkholderia pseudomallei, melioidosis is most likely to occur following heavy rainfall and affects many animals, including horses and humans. Signs of infection include depression, weight loss, lameness, swollen joints, mild colic, diarrhea, coughing, nasal discharge, and fever.

• Importantly, these signs also occur with Hendra virus. Any horse with a fever, especially in Queensland and northern NSW, has the potential to be infected with the deadly Hendra virus if not vaccinated

Finally, if you have a horse or livestock caught in floodwater, call the SES, state agriculture department or local veterinarian. Specialised equipment is often required to rescue them. Keep safe.

Dr Jennifer Stewart
BVSc BSc PhD Equine Veterinarian and Consultant Nutritionist