Weather and air quality patterns preceding equine grass sickness: indicators for a windborne nitrogen-fixing bacterial contribution fuelled by excess heavy metal availability

not-yet-known not-yet-known not-yet-known unknown Background Investigate and analyse the relationship between atmospheric patterns and Equine Grass Sickness (EGS) cases to determine the cause of the disease. Objectives 1. Build an atmospheric model that generalises the conditions prior to an EGS case. 2. Use the generalised model and existing knowledge to perform a focused review of prerequisite conditions. 3. Determine the root cause of Equine Grass Sickness, explaining why and how it happens. Study design Retrospective case series. Methods Quantitative and qualitive analysis of environmental data for 180 EGS cases covering a 13-week period (12-week pre and 1-week post-case). Using the principle of superposition, overlapping each cases data to produce a single generalised case. Results Significant correlation between the case dates and global maximums/minimums in atmospheric conditions, with notable periods of low rainfall, high pressure, and high nitrate levels in the days before the case date. Main limitations EGS location data limited to county level. EGS case date inaccuracies with 2–3-day drift. Case data only available from 2017. Unknown if all EGS cases within the analysed time period were reported. Conclusions Combining the superposition model with existing knowledge identified a desiccation resistant, nitrogen-fixing bacteria and elevated levels of iron (Fe), molybdenum (Mo) and vanadium (V), the heavy metals used in nitrogen fixation, as most likely contributors to the disease.