When a horse is found to be hypersensitive to a particular allergen, regardless of whether this is found in culicoides saliva, lurking in a dusty feed bin or is airborne such as a grass pollen, the most logical solution to prevent the horse reacting to it is to avoid the allergen in question. This sounds great in theory but in reality can prove a little more challenging. The tips below are designed to offer some both strategic and practical ideas that horse owners can implement to reduce exposure and help control the clinical signs.
Insect bite hypersensitivity
Creating a physically barrier with fly-proof garments can be helpful. Knowing your enemy is beneficial here as certain insects will attack the belly or legs, whereas others target the ears or face. Within the culicoides species alone you find location preferences and variable clinical signs as a result. You can then provide strategic accessories to a fly rug such as ear nets, face masks, belly bands (to ensure the ventrum has no sneaky gaps) or tail covers. Make sure these fit properly as if too big or small they won’t work well and may rub, leading to additional problems. Face masks may need some tactical extra securement like attaching to the head collar (as long as this is safe to do). All garments should be changed frequently, hot weather combined with soiled material against the skin is a recipe for secondary infections.
Check that fly prevention products are true repellents (>2% permethrin if this is the active ingredient) not just insecticides and also what residual efficacy they have. How much does the product adhere to the skin and will rain, sweat or UV exposure render it much less effective? Frequent reapplication is normally required. Following the manufacturer’s instructions for general good coverage, also target in particular any areas especially relevant to the flies known to be a problem. For head shy animals, and to avoid direct contact with the eyes, squirt sprays onto a cloth before application or use roll on products or creams for the head and ears to ensure this area is also well covered.
Modify the horses turnout schedule to minimise exposure to the type of flies causing the problem. For culicoides this means stabling when they are most active (dusk and dawn) but other flies are most bothersome in broad daylight, such as Stomyxs calcitrans (stable fly) or Tabanidae spp. (horse fly). Avoid fields with standing, stagnant water (slow running streams or muddy banks count too) where flies are more likely to breed. If you are in a hilly area chose the highest windiest field!
You can improve the stabling environment by installing fine-mesh screens to keep insects out and also set up strong fans (if possible safely) in front of the stable, or entrance and exit points, as culicoides struggle to fly in wind. Turn lights off when possible at night as this will attract flies. Finally, consider sticky fly tape on the ceiling or fly traps which can also help you monitor the number currently hatched in your area.
General yard maintenance
General yard maintenance, such as removal of manure and also standing water when possible, disrupts insect breeding and will help reduce their numbers. Encouraging seasonal fly eating birds such as swallows and house martins is a novel approach!
Other environmental allergies
If indoor allergens are suspected turn the horse out as much as possible. Source good quality forage with minimal dust and mould. Feed forage from the ground so the inhaled particles drop downwards rather than into the airways. Haylage or bagged grass is usually a better option than hay, if only hay is available soaking or steaming it will help minimise the dust.
When stabling is necessary low dust bedding for the affected horses stable and all other stables within the same airspace is a good idea (ideally they should not be fed dusty hay either). Ensuring adequate ventilation is also very important.
For storage mites always empty the feed from the original packaging into resealable plastic containers discarding the dust at the bottom of the bag. Clean these plastic containers regularly, again discarding any dust at the bottom and always do this before adding new feed. Keep the feed in dry, cool conditions. Wipe the horses muzzle with a damp cloth after finishing hard feed to remove any food residues.
Dust mites can take up residence in horse rugs so it is advised, if these have been identified as an issue, to frequently wash and dry the rugs on a hot wash ideally drying them in the sun afterwards (not always easy in the UK in winter) as mites struggle in hot/dry conditions. Old rugs are believed to often house both live and dead mites so before putting them away for the summer clean thoroughly as previously described and store individually in either an airtight container or sealed plastic bag.
If a horse’s outdoor allergies are aggravated by the pollens of summer pastures, when the pollen count is high move the horse inside. Again the devil is in the detail, if you know what to avoid there may be certain hacks you can steer clear of while particular crops are in flower. Using a pollen net or face mask may be beneficial.
Check for concurrent allergies. It is now thought that the allergy threshold in usually made up of multiple different allergens rather than one single allergen. The more relevant allergens you tackle successfully the better the chance of getting below the threshold and the horse becoming asymptomatic. Avoidance and reduction of exposure to allergens, while playing an important role, is usually just part of the solution in helping control allergies in horses.
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