# Equine Headshaking Syndrome: Triggers, Seasonality, and Treatment Efficacy in Australia

## TL;DR

This study explores equine headshaking syndrome in Australian horses, finding that bright light, wind, and pollen are common triggers, and that treatments are often ineffective.

## Contribution

The study provides new insights into the triggers and treatment efficacy of equine headshaking syndrome in the Southern Hemisphere.

## Key findings

- Geldings are more commonly affected and develop symptoms later than mares.
- Bright sunlight, wind, and high pollen are the most reported triggers.
- Most treatments are ineffective when used alone, and symptoms often occur seasonally.

## Abstract

Equine headshaking syndrome is a painful condition causing the horse to shake or flick its head violently without any obvious reason. Treatments for the condition are poorly effective and information on the condition in Australian horses is lacking. An online survey was sent to owners of headshaking horses in Australia to gather more information on when headshaking occurs and what treatments have been used to address it. The results showed that more geldings were affected than mares, and geldings were older when they first started headshaking compared to mares. Bright sunlight, wind, and high pollen count were the most reported triggers, and more than half of the owners reported that headshaking occurred in a specific season each year. Most owners had used more than two types of treatment, but few treatments were reported effective when used alone. The finding that a large proportion of horses start headshaking in spring and summer, combined with owner reports that light-blocking masks do not work well as a treatment, suggests that day length rather than brightness should be considered as an important factor in headshaking. This study provides new information on the causes and treatments of headshaking in horses in Australia.

Equine headshaking syndrome is a poorly understood neuropathic pain condition presenting as uncontrollable shaking, flicking, or striking of the head. Therapeutic options are limited, and treatments are only partially successful. Currently, epidemiological information on headshaking in the Southern Hemisphere is lacking. An online survey was circulated to Australian owners of headshaking horses to collect information on triggers, symptoms, seasonality, treatments, and perceived treatment efficacy. The responses (n = 216) showed the mean age at symptom onset as 9.6 (±4.7) years. More geldings were affected than mares (76% vs. 24%), and symptom onset occurred later in geldings compared to mares (10.1 ± 4.7 vs. 7.9 ± 4.0 years; p < 0.01). Bright sunlight, wind, and high pollen were the most commonly reported triggers (61%, 46% and 40%, respectively), and seasonal onset of symptoms was reported by 54% of respondents. In total, 71% of respondents reported using two or more treatments. The most common treatments were supplements (68%), nose nets (63%), light-blocking masks (48%), bodywork (48%) and pharmaceutical compounds (38%). Overall, treatments were considered ineffective by 33% of respondents. The findings were in agreement with surveys from the Northern Hemisphere. Of note was the perception of bright light as a primary trigger, alongside the reported low treatment efficacy of light-blocking masks. Seasonal intensification of symptoms and its relationship to day length merits further exploration.