Spatial Dynamics and Bioclimatic Drivers of Airborne Cladosporium Spores: A Comparative Aerobiological Study Across Three Strategic Agricultural Regions of Madagascar

Abstract

Spores of the genus Cladosporium are among the major biological components of the atmosphere and represent both a source of phytopathogenic inoculum and an important factor in respiratory allergies. The aim of this study was to analyse the spatial variability of biological pollution by Cladosporium spores in three agricultural areas of Madagascar: Ambatondrazaka, Amparafaravola, and Betafo. Aeropalynological monitoring was conducted from April 1 to September 30, 2023, using Hirst-type volumetric traps (Lanzoni). Spores were identified under a light microscope at ×400 magnification, and results were expressed as daily concentrations (spores m⁻³) and as a Seasonal Fungal Index (SFI). Differences among the sites were analysed using non-parametric tests, geographic correlations, and hierarchical clustering. Mean daily concentrations ranged from 11 spores m⁻³ in Amparafaravola to 187 spores m⁻³ in Ambatondrazaka. The total seasonal spore count (SFI) ranged from 1,956 in Amparafaravola to 34,165 in Ambatondrazaka, while intermediate values were observed in Betafo (3,000–4,000 spores). The operational benchmark of 80 spores m⁻³ was exceeded for 8 to 58 days depending on the site. Maximum concentrations ranged from 139 spores m⁻³ in Amparafaravola to 2,295 spores m⁻³ in Ambatondrazaka. The timing of the seasonal peak showed a positive correlation with latitude, indicating a north–south gradient in seasonal dynamics. Hierarchical clustering identified groups of sites with similar seasonal profiles, regardless of their geographic proximity. This study represents the first comparative spatial analysis of Cladosporium spores in agricultural areas of Madagascar and highlights a strong geographic heterogeneity in atmospheric biological pollution.