A Fungal Spore Calendar for England: Analysis of 13 years of Daily Concentrations at Leicester, UK

Background Fungal respiratory allergy is believed to affect up to 30% of hayfever sufferers and up to 70% of severe asthmatics in the UK, however trends in fungal spore seasonality are not well described. Information about seasonal trends would help allergists determine sources of fungal sensitisation and aid disease management. Method Daily monitoring was carried out at Leicester from 2007 to 2020 using a Burkard volumetric spore trap. Fungal spore concentrations were analysed by microscopy, identifying 23 morphologically distinct taxa. Daily average concentrations were calculated as spores/m 3 of air sampled and a 90% method used to determine the spore seasons. Results Thirteen years of data were used to develop a fungal spore calendar for the nine most abundant spore types identified; Alternaria, Cladosporium, Didymella, Leptosphaeria, Sporobolomyces, Tilletiopsis and Ustilago plus the wider groupings of Aspergillus / Penicillium type and coloured basidiospores. All have been implicated in fungal allergy. We observed long seasons for, Cladosporium, Sporobolomyces and Tilletiopsis , beginning in late spring and ending in late autumn. In contrast Ustilago and the highly allergenic Alternaria showed relatively short seasons, spanning summer and early autumn. Temperature and precipitation were the main meteorological factors related to spore concentration with wind speed appearing to have little influence. Over the study period, there was a reducing trend for total spore concentrations, driven by a reduction in “wet weather” spores, in line with a reduction in precipitation. Conversely, the “dry weather” spores of Alternaria and Cladosporium demonstrated an increasing trend. Conclusion We present an aeroallergen calendar to provide readily accessible information to patients, healthcare professionals and pharmaceutical companies on exposure concentrations over the year in central England and potentially more widely across the UK. More research on allergenic thresholds would enhance the clinical usefulness of aeroallergen calendars.