This week we continue looking at two frustrating conditions for horses and their owners: mud fever and rain scald. Last week covered what the conditions were and the clinical signs, so now we finish by discussing diagnosis, treatment and prevention.
Diagnosis of either condition is usually provisionally done by clinical examination, taking into account the distribution of the lesions and the appearance of the skin. If a definitive diagnosis is needed something called an impression smear of the pus or crushed scabs can be used. This involves directly getting the bacteria onto a glass slide which can then be specially stained and studied under a microscope to identify the type of bacteria involved. Occasionally a sample of infected material can be sent to a laboratory to try to grow the bacteria but this is usually unnecessary.
The condition is usually self-limiting, so will go away on its own if the factors that have caused the problem can be removed. However, this is rarely practical given the facilities most owners have.
In an ideal world this would mean confining the animal to clean, dry places by housing the horse inside and removing rugs so they cannot get sweated up and air can get to the affected areas (while also keeping them warm enough if they are used to being rugged). More practically, this means bringing them in out of the mud as much as possible and giving them time with rugs off. Moving them into better drained, less muddy paddocks out of poached or flooded ones will also help, as may turning them out some of the time in an arena if it is dry. Ironically, if rain scald is the problem and they are kept outside without rugs, using a rug to prevent further damage (as long as it’s not causing excessive sweating) may help.
Topical antibacterial treatments directly onto the affected areas will help reduce the number of bacteria, and these include chlorhexidine washes, povidone iodine washes and various shampoos that may contain tar and sulphur or potash aluminium.
Your vet may have their own special concoction made up with a variety of the above and extras that they find is most effective. Some people advocate removing as many scabs as possible before using the topical treatment and certainly this can be helpful when managing mud fever, but care should be taken as this can be very painful to the horse and is not always needed.
Once the topical treatment has been applied (usually twice daily) to the affected areas, it is left on for a certain length of time (dependent on the product used) before being totally rinsed off and then very thoroughly dried. It’s important it is totally dry before the next step of applying a barrier cream, otherwise you run the risk of sealing moisture in.
The cream will, hopefully, reduce the amount of further wetting of the area. Numerous barrier creams are available and each vet/horse owner who has battled the problem will probably have their own opinion as to which works best!
The fact that every vet I know has a slightly different way of approaching the problem shows that no one topical system is vastly superior to another, and each individual horse may respond better to one than another.
In severe cases and cases that have become resistant to topical treatment, systemic antibiotics (injection or oral) and sometimes Bute for pain relief may be required. Recovery of normal cases usually occurs within three weeks if strictly managed and the underlying cause can at least be substantially reduced, but having the problem once will not make a horse resistant to it.
In terms of prevention, it’s important to try to stop contamination from one infected horse to others by direct contact or indirect contact (shared grooming equipment, boots, bandages and numnahs, for example). Although near impossible to completely stop it happening, anything that reduces the amount of time the lower legs and back are kept wet will also help.