There is increasing concern about the exposure to fungal aerosols in occupational environments and associated respiratory allergic diseases and asthma. A large number of farmers work in paddy field around the world, suffering from asthma, allergy and systemic mycosis; however, it appears that adequate information on the fungal aerosols from the paddy field of 24-Parganas (North) are largely lacking.
The aim of the study was to assess the concentration of the major airborne pathogenic fungal spore over paddy field and to check their allergenic potential causing respiratory allergy in agricultural workers.
Methods:
Volumetric assessment of airborne culturable and nonculturable fungal spores was performed in the experimental site (North 24 Parganas, West Bengal, India) for 2 consecutive years (November 2011–October 2013). An aerobiological survey was performed to assess the concentration of pathogenic fungal spore load by an Andersen Two Stage volumetric sampler used for sampling culturable fungi using Czapec-Dox agar medium/MEA medium and a Burkard Personal Slide Sampler used to collect the total airborne fungal spores including both the culturable and non-culturable types. Culturable fungal spores found in Anderson volumetric sampler were sub-cultured separately for isolating individual species. Extraction of individual fungal protein was performed using Y-cell lysis reagent (buffer) at pH 7.4. Skin-prick tests were performed with antigenic extracts prepared from the mass culture of fungi on people who were either occupationally involved or used to visit the places.
Results:
A total of 34 spore types and 24 types of viable colony-forming units were recorded. Average concentration range of total fungal spores was 233-2985/m3 and concentration of viable colony-forming units ranged between 165 and 2225 CFU/m3. The major perennial fungal spore types included Aspergilli group, Fusarium sp., Cladosporium sp., Nigrospora sp., Helminthosporium sp., Alternaria sp., Drechslerasp. etc. showed higher reactivity in skin prick test. Among these fungal spores Aspergilli group showed highest (23.7%) reactivity in skin prick test carried out in 214 adult agricultural field workers with respiratory disorders living inside the study area. The meteorological factors responsible for the frequency of fungal spore types and their concentrations were analyzed.
Conclusions:
Higher concentration levels of airborne total and culturable fungal spores were recorded during the months of November through February (winter) and June through September (late summer and rainy season). Meteorological factors were found to play a significant role on fungal spore release and dispersal. The study revealed high prevalence of predominantly allergenic fungal spores in the paddy fields.