Insect Bite Hypersensitivity in Horses (an overview)

This was an excellent review of the current state of our knowledge on Insect Bite Hypersensitivity mainly emphasizing that there is no cure and management is time-consuming and can be expensive. There were a few new recommendations. One was a topical preparation that was effective at reducing symptoms in 95% of the horses tested:

A double-blinded, placebo-controlled, randomised cross-over Australian study evaluated the efficacy of a purpose-made herbal spray (Red Healer Equine and Canine Spray, NSW, Australia) containing various natural ingredients including Cinnamonum camphora (Camphor), Cymbopogon citratus (Lemongrass), Litsea cubeba (May Chang), Mentha piperita (Peppermint), and Pogostemon cablin (Patchouli) [42]. These essential oils are reported to have mast cell stabilisation, antipruritic, anti-inflammatory, analgesic and insect-repellent effects [42,58,59,60,61,62,63,64,65]. This study focused on evaluating changes in clinical signs (rather than the mechanism of action of the product) and an improvement in pruritus and disease severity was reported in 95% of treated horses [42].

If your horse suffers from this condition follow this link to the full article which is well worth reviewing https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10416928/ .
DrO

Insect Bite Hypersensitivity in Horses: Causes, Diagnosis, Scoring and New Therapies
Animals (Basel). 2023 Aug 4;13(15):2514. doi: 10.3390/ani13152514.
Authors
Abbey Cox 1 , Allison J Stewart 1
Affiliation

1 School of Veterinary Science, University of Queensland Gatton, 5391 Warrego Highway, Gatton, QLD 4343, Australia.

PMID: 37570323
DOI: 10.3390/ani13152514

Abstract

Insect Bite Hypersensitivity (IBH, Queensland itch, sweet itch, equine summer eczema) is the most common pruritic disease of horses. It is most often caused by sensitivity to the saliva of Culicoides spp. of biting midges; however, it can also be caused by hypersensitivity to other insect species. The prevalence of IBH in horses is reported to be as high as 60% in some parts of the world. Due to the severe pruritus and effects of secondary self-trauma, IBH has animal welfare concerns, and there is currently no cure. Management of this condition is life-long, time consuming and costly. New grading systems to document disease severity are being validated, which will allow the comparison of clinical trial results of new and existing therapies. Management involves the minimisation of insect bites by use of stabling, fans, rugs and repellents. Symptomatic therapy involves the administration of systemic or topical corticosteroids, systemic antihistamines, and creams and sprays to promote skin healing and decrease inflammation. New immune-mediated therapeutics including vaccines, in addition to desensitisation procedures, show promise at controlling hypersensitivity reactions. This article will review aetiologic agents, pathophysiology, scoring systems and current and new therapies.

Keywords: IBH; Queensland itch; allergy; dermatology; equine summer eczema; sweet itch.