Risk of exposure of a selected rural population in South Poland to allergenic mites. Part II: acarofauna of farm buildings

Exposure to mite allergens, especially from storage and dust mites, has been recognized as a risk factor for sensitization and allergy symptoms that could develop into asthma. The aim of this study was to investigate the occurrence of mites in debris and litter from selected farm buildings of the Małopolskie province, South Poland, with particular reference to allergenic and/or parasitic species as a potential risk factor of diseases among farmers. Sixty samples of various materials (organic dust, litter, debris and residues) from farm buildings (cowsheds, barns, chaff-cutter buildings, pigsties and poultry houses) were subjected to acarological examination. The samples were collected in Lachowice and Kurów (Suski district, Małopolskie). A total of 16,719 mites were isolated including specimens from the cohort Astigmatina (27 species) which comprised species considered as allergenic (e.g., Acarus siro complex, Tyrophagus putrescentiae, Lepidoglyphus destructor, Glycyphagus domesticus, Chortoglyphus arcuatus and Gymnoglyphus longior). Species of the families Acaridae (A. siro, A. farris and A. immobilis), Glycyphagidae (G. domesticus, L. destructor and L. michaeli) and Chortoglyphidae (C. arcuatus) have been found as numerically dominant among astigmatid mites. The majority of mites were found in cowsheds (approx. 32%) and in pigsties (25.9%). The remaining mites were found in barns (19.6%), chaff-cutter buildings (13.9%) and poultry houses (8.8%). The results suggest that the allergenic mites may constitute an occupational hazard for agricultural workers in all farming environments examined.


Introduction
Storage mites, especially several species from the families Acaridae, Glycyphagidae and Chortoglyphidae (Acari: Sarcoptiformes, Astigmatina), are commonly found in stored food products, hay, straw, granaries, barns and other farming and occupational environments, in dust from railway freight wagons, as well as in samples of house dust. The most abundant mites are Acarus siro, Acarus farris, Tyrophagus longior and Tyrophagus putrescentiae from Acaridae, Lepidoglyphus destructor and Glycyphagus domesticus from Glycyphagidae and Chortoglyphus arcuatus from Chortoglyphidae (Boström et al. 1997;Franz et al. 1997;Mehl 1998;Sánchez-Ramos et al. 2004Pike and Wickens 2008;Wong et al. 2011;Solarz 2012). These mites were identified as a source of clinically important allergens, causing occupational allergy (known as allergy to storage mites) among farmers, grain-storage workers and other agricultural workers (Fain et al. 1990;Revsbech and Dueholm 1990;van Hage-Hamsten and Johansson 1998). These mites cause IgE-mediated sensitization among the above-mentioned occupational populations, who develop asthma, rhinitis and conjunctivitis when exposed to organic dust containing mite allergens (Arlian 2002;Sánchez-Ramos et al. 2004;Berger et al. 2005;Solarz 2012).
The aim of this study was to investigate the occurrence of mites in debris and litter from selected farms of the Małopolskie province, South Poland, with particular reference to allergenic and/or parasitic species as a potential risk factor of diseases among farmers.

Materials and methods
The study was carried out from May 2011 to September 2012. A total of 60 samples of materials collected from four farms in two locations (Lachowice and Kurów) on the territory of the Suski district (Stryszawa and vicinity, Małopolskie) were examined as the potential sources of the allergenic and/or parasitic mites in the farming environments (Table 1). All samples were collected into plastic bags of 1 l capacity. These samples were sweepings containing organic dust, litter, debris, residues and other materials from certain farming environments. Generally 12 cowsheds, barns, pigsties, chaff-cutter buildings and poultry houses were analyzed for the occurrence of mites, including allergenic and/or parasitic taxa (Table 1). The mites were extracted using the Berlese method and preserved in 75% ethanol. For identification, all mites were mounted in Faure's medium on microscope slides, with the aid of the Olympus Europe Highlight 2100 stereomicroscope. All mite specimens collected were examined using differential interference contrast (Nomarski  Hughes (1976), Baker (1999), Zhang and Fan (2005), Fan and Zhang (2007), Colloff (2009), Krantz and Walter (2009) and Solarz (2012). The results were expressed as the number of mites per g of sample (wet weight). Mite abundance was also calculated as the number of specimens per sample. Data were analyzed using χ 2 tests in CSS-STATISTICA for Windows v.12 (α = 0.05).

Abundance of mites in the examined farm buildings
The mean number of all mites collected per g of sample constituted 17.55. The number of mites per g sample was varied considerably among mite species and among particular types of farm buildings (Table 4). The most abundant species were A. siro (especially in cowsheds, barns and pigsties), A. farris (in barns) and L. destructor (mainly in pigsties) ( Table 4). The total number of mites per sample constituted 278.65 (on average 111.5). The number of mites per sample was highest for cowsheds (198.0) and lowest for poultry houses (48.8) and chaff-cutter buildings (77.4) ( Table 4). The most abundant species of mites per sample were A. siro (especially in cowsheds and barns), A. farris (in barns and pigsties), L. destructor (mainly in pigsties) and G. domesticus (mainly in barns). The remaining allergenic mites were distinctly less abundant both per sample and per g (Table 4).

Discussion
Agricultural work is considered to be a major risk factor for occupational diseases (Berger et al. 2005). All mites should be regarded as a potential source of mite allergens in environments associated with activity of man, not only in dwellings (Fain et al. 1990;Solarz 2006;Stejskal and Hubert 2008;Colloff 2009). So far, many groups of mites were not reported as occupational biohazards for humans (Arlian 2002). The greatest exposure to storage mites usually occurs in an agricultural setting where allergies to these mites are of major importance Arlian 2002;Cichecka et al. 2006). For the urban population, sensitivity to particular species of storage mites and their cross-reactivity with pyroglyphid dust mites is usually not important. Generally, the exposure of city people to storage mites is minimal (Solarz 2010). For farmers and other agricultural workers both storage and house dust mites may act as inhalant allergens. Therefore, for people living in (sub)agricultural settlements, sensitivity to various species of domestic and storage mites and cross-reactivity between species may be of clinical significance (Arlian 2002;Cichecka et al. 2006). On the other hand, sensitization to storage mites in urban dwellers has been reported in Spain, Denmark, Germany, Croatia, Poland and USA (Ebner et al. 1994;Garcia-Robaina et al. 1996;Macan et al. 1998;Gislason and Gislason 1999;Kanceljak-Macan et al. 2000;Arlian 2002;Solarz et al. 2008). Sensitization to T. putrescentiae and L. destructor is present in the urban population of Upper Silesia in similar proportions as to the Dermatophagoides spp. (Szilman et al. 2004;Cichecka et al. 2006;Solarz et al. 2008;Asman et al. 2009). Our previous studies suggest that allergenic mites belonging 1 3 to the Acaridae, Glycyphagidae and Chortoglyphidae should be considered in Poland as potential occupational risk factors contributing to the occurrence of respiratory and dermal diseases among workers of zoos, coal-miners, bird breeders and farmers (Solarz and Solarz 1995;Solarz et al. 2004aSolarz et al. , b, 1997Cichecka et al. 2006).
The natural sources of allergenic mites in stores are still not well known. It has been suggested that the majority of the mite population is brought from the cultivated field into the stores, and that the open field is the main source of storage mites (Hallas and Iversen 1996), whereas bird nests are less important (Solarz et al. 2007).
The stated prevalence of cheyletids and glycyphagids in the farming environment is not in accordance with earlier data by Hallas (1981), Terho et al. (1982) and Solarz et al. (1997). The abundance of acarids was distinctly higher than that found in Solarnia (Lubliniec vicinity), in the vicinity of Kokotek and in Lesko (Krosno province) (Solarz et al. 1997), and it was similar as the abundance in dust samples from byres, hay and grain stores of 11 farms in Eastern Finland (Terho et al. 1982(Terho et al. , 1985 and in samples of dust and organic debris from coal mines in Upper Silesia (Solarz and Solarz 1995) or in storage facilities in Iran (de Saint Georges-Gridelet et al. 2003). The number of astigmatid mite species found in this study was higher than in farming environments in Finland (Terho et al. 1982) and Iceland (Hallas 1981;Hallas and Gudmundsson 1985) or in coal mines in Poland (Solarz and Solarz 1995), and it was similar as in farm buildings examined earlier in Poland (Solarz et al. 1997;Solarz 2012) or in Iran (de Saint Georges-Gridelet et al. 2003). Some species of the family Pyroglyphidae (G. longior, H. chelidonis and Dermatophagoides farinae) have been found in farming environments in UK, Switzerland, Israel, Iran, USA, Canada (Hughes 1976;Fain et al. 1990;Mumcuoglu and Lutsky 1990;de Saint;Georges-Gridelet et al. 2003) and also in Poland (Solarz et al. 1997;Solarz 2012).
The present results confirm the occurrence of allergenic mites in cowsheds, barns, chaffcutter buildings and poultry houses (Hughes 1976;Terho et al. 1982;Fain et al. 1990;Mumcuoglu and Lutsky 1990;Solarz et al. 1997;Stejskal and Hubert 2008), and reveal the occurrence of these mites in pigsties. Thus, all these locations should be regarded as a potential source of storage mite allergens in the farming environment. As the occurrence and concentration of mites in samples from different farm buildings may vary to a considerable extent, further studies are highly desirable.