11 May 2022
Marie Rippingale
Job Title
Image © calipso88 / Adobe Stock
Allergies are commonly seen in equine patients.
This article will look at two of the main respiratory and skin allergies that affect horses, and investigate how the RVN can assist the vet with the diagnosis and treatment of these disorders.
Equine asthma (EA) is one of the most common respiratory diseases of modern-day equids (Gough, 2021).
EA is a term used to describe a syndrome of chronic allergic airway inflammation that varies in clinical presentation, disease severity and, importantly, reversibility (Gough, 2021).
EA is caused by an immune-mediated inflammatory response to aeroallergens – such as bacterial and fungal endotoxins and exotoxins, dust mites, and ammonia (Gough, 2021).
Within the EA syndrome are three primary presentations:
It is now common to apply mild, moderate and severe classifications into the EA spectrum. Clinically, horses with EA, irrespective of severity, develop lower airway inflammatory changes that include aberrations to the bronchoalveolar lavage fluid (BALF) leukocyte profile, altered respiratory function and varying degrees of poor performance associated with exercise intolerance (Gough, 2021).
Bronchoalveolar lavage and assessment of the cytological profile of the BALF is a common diagnostic tool associated with EA. RVNs can assist with this procedure by making sure all the required equipment is set up and prepared correctly beforehand (Slater and Knowles, 2012). The RVN will also ensure the horse is handled and restrained correctly during the procedure.
It is essential the patient is calm and relaxed at all times – even if sedation is to be administered. The RVN should ensure adequate methods of restraint are available, and used with skill and caution. The patient should be kept calm by the RVN talking calmly and gently stroking the patient to provide reassurance. It is far better to make the experience a calm and positive one for the horse, as this will make further procedures safer and easier for all involved.
The RVN can administer the IV sedation to the horse based on the dose determined by the case vet. The RVN can help to pass the endoscope under the direction of the vet. The samples must also be handled and labelled correctly. The samples should also be packaged for transport for an external laboratory if required, which is also something the RVN could assist with.
The treatment of choice for cases of EA often involves the administration of corticosteroids and bronchodilators (Gough, 2021). Both corticosteroids and bronchodilators can be administered using a nebuliser (Slater and Knowles, 2012).
The treatment of EA requires the owner to get familiar with unusual medical equipment – for example, a nebuliser – and requires the owner to make significant changes to their management practices. If an owner feels overwhelmed, they will be less likely to carry out the necessary changes, and, ultimately, the patient will suffer (Gerrard, 2015).
It is best not to make any assumptions about the level of the owners’ health literacy. It has been estimated less than half of the information clients are given during each visit to the vet is retained (Kessels, 2003). Therefore, during the discharge process, the amount of information given to the owner should be limited by using clear, simple language and keep a slow pace to allow the owner the time to absorb the information (Gerrard, 2015).
The RVN could assist with this, making sure that time is taken to ensure the owner understands the condition and the treatment plan moving forwards. The RVN could also demonstrate how to use the nebuliser, and discuss the care and cleaning of it with the owner.
Although the administration of medication is important in the treatment of EA, methods of prevention are essential. The mainstay of prevention is ensuring horses are exposed to minimal amounts of dust in their environment, which requires ensuring good ventilation to the stable, provision of low-dust stable bedding, feeding low-dust feeds or dampening feeds to reduce aerosolisation of any dust present (Gough, 2021).
Horses prone to EA should be worked on a low-dust surface or not directly behind other horses. Additional practices that can help with reducing exposure to aeroallergens include removing the horse from the stable prior to mucking out/turning over the stable, spraying the bedding down with water twice daily to settle dust during periods of hot weather, steaming hay to reduce dust within the feed and wetting feed down (Gough, 2021).
The RVN could assist with educating the owner regarding the management changes required. A follow-up visit could be booked and the RVN could go out on a visit to meet the owner, assess the yard set up and collaborate with them regarding management changes.
Collaborative planning helps to increase owner concordance (Gerrard, 2015). Compromises can be discussed and put in place to ensure the management changes take place and the patient receives the best possible aftercare. Owners may be more likely to speak to an RVN as they do not want to bother the vet (Gerrard, 2015).
This puts RVNs in a unique position to be able to go out on an ambulatory basis and offer aftercare support to clients.
Culicoides hypersensitivity (CH), also known as sweet itch, is the most common allergic condition in horses that affects the skin (Fettelschoss-Gabriel et al, 2021). Clinical signs result from a hypersensitivity reaction to the saliva of the Culicoides midge, and include redness of the skin, and pruritus along the mane and tail, which can become severe (Slater and Knowles, 2012).
Horses with CH rub at these regions, causing self-inflicted damage and hair loss (Slater and Knowles, 2012). CH presents a significant welfare issue for affected horses.
CH management lacks reliable, sensitive, specific and easy-to-measure diagnostic tools (Fettelschoss-Gabriel et al, 2021). Diagnosis is usually based on clinical signs and patient history.
Local or systemic antihistamines and corticosteroids are often used in the treatment of CH. Antihistamines are often ineffective, and corticosteroids can cause adverse effects (Fettelschoss-Gabriel et al, 2021). If medications have been prescribed by the vet, the RVN can help to educate the owner about how to administer the medication and how to identify the signs of an adverse reaction. An off-licence vaccination is now available for the treatment of CH – the RVN could help to educate the owner about this also.
No cure for CH exists and treatment is based mostly on management changes. These changes can be time-consuming and cumbersome for horse owners, which could present a compliance issue. Management changes include:
These management strategies may be overwhelming to many owners, and this would present a good opportunity for the RVN to arrange a follow-up appointment at the yard. The RVN could visit the yard, meet the owner and discuss how the suggested management strategies could realistically be implemented.
If limiting factors are identified, compromises can be put in place to ensure that the patient receives consistent, ongoing care. This is also a good way to increase owner concordance through collaborative planning (Gerrard, 2015).
Although the case vet would be updated and remain involved with the process, the RVN could be the main point of contact for the owner. The RVN could coordinate regular updates with the owner and carry out further follow up visits if required.
Building a professional relationship of trust and understanding with the owner would help to raise awareness and public perception of the role of the RVN in equine practice.
RVNs can play a significant role in supporting the vet to diagnose and treat allergies that affect the respiratory system and the skin in horses. They can also assist the case vet with diagnostic procedures, including correctly and safely restraining the patient.
RVNs can also prepare and provide the correct equipment for the diagnostic procedure required. They can administer treatment and monitor the patient for progress.
The role of owner education should not be overlooked. RVNs can advise owners on the use of medication and assist the owners to implement new management strategies.
A role clearly exists for RVNs to support owners on an ambulatory basis, booking follow-up visits to go out and assist owners out on the yard. This not only allows them to use their expertise, but also helps raise public awareness of the role of the RVN in equine practice.
