Fungal Aerosol In Rabbit Houses And Its Spread To The Environment

The breeding environment is an important source of fungal aerosol, which can cause a variety of fungal diseases of livestock and poultry, and their universal presence has posed a huge threat to livestock and poultry industry. China has become the biggest rabbit raising country in the world, but the literature and systemic study on composition and concentration change of airborne fungi in rabbit raising environment are very little. It is well known that the polluted air in livestock farms is often associated with the outbreak of the epidemic diseases and environmental problems. Many airborne pathogen microbes, including viruses, fungi and bacteria, can spread over a large area through the air. Bioaerosol disseminated from animal houses to their environments has been studied with an emphasis on total bacterium amount, pathogenic bacteria and antibiotic resistances of the bacteria in animal houses and their ambient air. But it is difficult to differentiate between two strains that have very close genetic relationship using traditional taxonomy, and can not get the enough evidence to prove the transmission of microbes from animal houses to their sorroudings. Therefore, a one-year sampling from June 2007 to May 2008 was conducted in an enclosed rabbit house and a semi-closed one by Andersen–6 sampler, (1) to detect composition, particle size distribution, and predominant genera features of airborne fungi; (2) to analyze and compare the composition and concentrations of airborne fungi in an enclosed rabbit house and a semi-closed rabbit one using ERIC-PCR; (3) Based on ITS sequence specificity, to identify homology of fungal pathogens with different sources; (4) to accurately quantify airborne Aspergillus fumigatus by means of fluorescence quantitative PCR .1. Composition, concentration changes and predominant genera of airborne fungi in different structured rabbit housesA one-year sampling from June 2007 to May 2008 was conducted in an enclosed rabbit house and a semi-closed one by Andersen–6 sampler, using Sabouraud culture medium as sampling medium. The results showed that: (1) the concentrations of fungal aerosol in rabbit houses were higher than in the normal environment, and the aerodynamic diameters of most particulate matter (PM) were very small (<2.5μm). Therefore, these PM can penetrate into the lower respiratory tract easily. Though the health status of animals and farm workers could not be investigated, the health of them would be damaged, and living in this environment can cause many subclinical symptoms; (2) the concentrations of airborne fungi were characterized with the maximum level in October and the minimum level in January. Within one day, it had the maximum level at 09:00 and its concentration changes were characterized as 09:00>17:00>13:00. (3) Through detection and analysis of 12 months, 6523 fungal colonies were obtained; through identification, they belonged to 17 genera and 36 species, of which the predominant genera included Cladosporium, Penicillium, Aspergillus, and Altemaria. (4) The higher the animal raising density is, the heavier the airborne fungal concentration is. Fungal particles were easily inhaled into deep respiratory tract than those of bacteria. The fungal particle concentrations with 0.65-2.1μm in diameter in rabbit house were much higher than in other sampling environments. The proportion of Aspergillus correlated with human and animal health was very high among the identified fungal genera. The airborne fungi in animal raising environments have become an important contamination, implying that they should be given an enough importance for their possible damage to human and animal health.2. Compare composition of airborne fungi in different structured rabbit houses using ERIC-PCRIn this study, air samples were collected from 9 enclosed rabbit houses and 8 semi-closed rabbit houses by the AGI-30 sampler, and then the total DNA of samples were directly extracted without culture. Comparison of the composition and concentration in two different structured rabbit houses was made by the use of ERIC-PCR method and computer software. Results suggested that: compared with semi-closed rabbit houses, the enclosed rabbit houses had more kinds of airborne fungi; meanwhile, the airborne fungal similarity of the semi-closed rabbit houses was higher than that of the enclosed rabbit houses. Long-time exposure to high fungal concentration, the chronic subclinic symptoms might occur in the rabbit houses,such as anorexia, slow growth, and failure of immunity. Similar cases had been found in the sampling enclosed rabbit houses, alarming us that more attention should be paid to the harm of airborne fungi and mycotoxins on health.3. Predict the spread of airborne Trichophyton mentagrophytes in rabbit houses by means of ITS sequenceTrichophyton mentagrophytes originating from feeders, rabbits, and air were collected. On the basis of the morphological identification, the homology of these Trichophyton mentagrophytes was compared using the sequence results of ITS, assessing the spreading model of this airborne pathogen. The results revealed that: Trichophyton mentagrophytes of feeders and rabbits were derived from the same origin, i.e., Trichophyton mentagrophytes of rabbits can aerosolize and infect persons through air; it also could be concluded that indoor microbiological aerosol aerosols in indoor air of animal houses could transmit to their surroundings via air exchange and cause microbiological contamination. 4. Quantification of airborne Aspergillus fumigatus concentrations in rabbit houses usingquantitative fluorescent PCRTo obtain the accurate airborne Aspergillus fumigatus concentrations in the environmentsof rabbit houses, and evaluate the health risk, rabbit houses were used as subjects in thisexperiment. Air samples were collected by AGI-30 sampler, and the quantitative fluorescentPCR and the culture counting method were used to determine the airborne Aspergillusfumigatus concentrations.The results showed that, of the three closed rabbit houses (A, B, andC), the average airborne Aspergillus fumigatus concentrations determined by the fluorescencequantitative PCR were 3.0×10~3, 3.0×10~3, and 1.5×10~3 (spores/m~3 air), respectively, whilethose determined by the culture counting method were 2.5×10~2, 2.8×10~2, and 1.1×10~2 ColonyForming Unit/m3 air (CFU/m~3 air), respectively; i.e., the concentrations of Aspergillusfumigatus determined by the fluorescence quantitative PCR were 12-14 times higher thanthose determined by the culture counting method. From those results, it is clear that theconventional culture counting method underestimated the concentrations of airborne fungi.Therefore, it is insufficient to determine the microbial aerosol concentration and evaluate thehealth risk only by culture counting method.