In rural inland, south-eastern Australia, allergy to the fungus Alternaria is prevalent and an important risk factor for asthma. The aim of the thesis was to investigate the distribution and factors influencing allergens of Alternaria in the air. As airborne allergenic spores were thought to arise from harvesting of nearby crops, two towns with different agricultural practices were studied. Moree has two crop harvesting periods in summer and autumn whilst Wagga Wagga has one harvesting period in summer. Over two years, air was sampled daily in Wagga Wagga and Moree using Burkard traps. The reliability of measurements from a single site to represent the distribution of airborne concentrations of spores across each town was examined using data from three traps simultaneously, sited 2.0 to 4.9 km apart, over four weeks. Substantial intra-class correlation coefficients (ICC) were observed between the three sampling sites across both towns (ICC=0.52, 95% CI 0.30-0.71 to 0.76, 95% CI 0.61-0.87) when counts of Alternaria spores were relatively high. The correlation was poor when counts were low. Of more than 365 trap tapes examined, the two microscopic traverses strongly correlated for counts of Alternaria spores (ICC=0.95, 95% CI 0.94-0.96). Alternaria was detected in both towns throughout the two year period with peaks in spore concentrations reflecting the season of crop harvesting in each region. Individual exposure to spores was examined. Thirty three subjects (adults and children from nine families) wore nasal air samplers and personal air samplers both inside and outside their homes. The effects of activity, location, age on the inhalation of Alternaria spores and variation between individuals in the same environment were determined. Every subject inhaled Alternaria spores. Personal exposure to Alternaria in the home environment varied substantially between subjects. Levels of fungal spores inhaled were higher during periods of activity than during rest, and higher while subjects were outdoors than indoors. During outdoor activity, the number of Alternaria spores inhaled ranged from 4 to 794 (median 11) spores/hr. Sources of airborne spores was investigated by sampling air above wheat and cotton crops near the towns during harvesting and non-harvesting periods, in a grain and cotton seed storage shed, and a cotton gin. Substantially higher concentrations were detected above crops during harvesting periods compared to non-harvesting periods. Peaks were associated with harvesting and other activities where plants were manipulated. By regression analysis spore concentrations in both towns were modelled against those detected above crops and with weather variables. Only one crop sampling period (cotton harvest) independently correlated with concentrations in town. Analysis combining all data showed concentrations of spores above crops correlated with spore concentrations in the town when lagged by one day. Variables of rainfall and maximum temperature influenced concentrations in both towns, and wind direction in Wagga Wagga alone. Parents of asthmatic children were asked by questionnaire in which locations symptoms were provoked. Asthma was reported to be exacerbated at grain farms and with disturbance of local vegetation in town and home gardens. Nasal sampling confirmed that activities that disturbed dust or vegetation increased the inhalation of spores. The factors that release allergen from spores were determined in a modified Halogen immunoassay. Approximately 60% of spores released allergen, and the proportion was influenced by isolate, nutrient availability, viability, and not influenced by sunlight or culture age up to 21 days. Germinating the spores significantly increased the proportion that released total allergen and Alt a 1 (p<0.0001). Alt a 1 appears to be a minor contributor to the total allergen released from spores except when spores have germinated. Conclusions: People living in inland rural regions of Australia are exposed to substantial quantities of allergenic spores of Alternaria. Exposure is a highly personal event and is largely determined by disturbance of local vegetation releasing spores such as from nearby crops by wind, harvesting, slashing, transport and processing of produce, and from within town and home gardens. Most spores inhaled are likely to be allergenic, with potency potentially increasing with viability.
| Identifer | oai:union.ndltd.org:ADTP/215930 |
| Date | January 2001 |
| Creators | Mitakakis, Teresa Zinovia |
| Publisher | University of Sydney. Science. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English, en_AU |
| Detected Language | English |
| Rights | Copyright Mitakakis, Teresa Zinovia;http://www.library.usyd.edu.au/copyright.html |
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