ABSTRACT
Environmental allergy is characterized by great diversity in clinical properties and inciting factors such as house dust. House dust samples were obtained from 120 homes in Benin City by vacuum cleaning between Oct.1997 - Sept. 1998 for determination of moisture content, house dust mites (HDM) counts, total protein and carbohydrate contents, and for microbiological and heavy metal analyses. Samples were examined for mites using the suspension technique. Protein in dust was extracted by dissolving 1.0 g of sieved sample in 10.0 ml (1:10 w/v) 5% NaOH, stirred mechanically for 5 min and allowed to stand for 10 min. The solution was filtered and the extract measured by Lowry’s method. Total carbohydrate was determined by the phenol– sulphuric acid method. House dust fungi and bacteria were determined using plate count method, while air-borne fungi and bacteria were determined using settle plate method. Dust samples were plated on MacConkey, nutrient and tryptone soya agar for bacterial isolates while potato dextrose and malt extract agar amended with a mixture of streptomycin and penicillin were used to isolate fungi. The concentration of heavy metals in house dust was analysed using an atomic adsorption spectrophotometer. Albino rabbits (Oryctolagus cunniculus) were grouped (4/ cage) and immunized intravenously using 1.0 ml of protein extract at concentrations of 10, 20 and 30 mg/ml. Booster doses of 0.5 ml were given weekly. Biochemical parameters and liver enzymes were analyzed as a batch using the Biochemistry Analyser while haematological parameters were determined by standard methods. Mean total protein and carbohydrate concentrations of pooled dust sample were 32.0 ± 1.20 mg/ml and 31.92 ± 0.25 g/% respectively. The identified fungal genera in indoor air included Aspergillus niger, Penicillium oxalicum Fusarium oxysporium,Rhizopus nigricans and Candida albicans. In the dry season, the predominant indoor aerofungi included Aspergillus spp (65.9 %), P. oxalicum (19.0 %), and Cladosporium herbarium (6.1 %), while in the rainy season Aspergillus spp (66.7 %), P. oxalicum (22.2 %) and Cladosporium herbarium (5.43 %) predominated. Viable dust bound fungi included Aspergillus, Penicillium, Alternaria, Fusarium and Cladosporium spp. There was a higher (p< 0.05) geometric mean fungal concentration in high-density areas (HDA) than in low-density areas (LDA) (602 cfu and 214 cfu, respectively). Mean bacterial count in settled floor dust and indoor air were 102 - 107 cfu/g of dust sample and 102 - 105 cfu/m3 air. The microbial genera; Bacillus, Staphylococcus, Enterococcus, Micrococcus, Pseudomonas, Corynebacterium, Klebsiella, Streptomyces were identified in the dust and air samples. The concentration of heavy metals was as follows: iron 3288.77±124.6, magnesium 2269 ± 737.01, lead 153.46 ± 30.3, nickel 40.8 ± 24.95 and cadmium 5.93 ± 1.53 μg/g. Rabbits immunized with 30 mg/ml of protein had significantly lower ( p< 0.05 ) mean body weight of 1.4 ± 0.12 kg compared to that of the control animals ( 2.0 ± 1.0 kg ). Packed cell volumes (PCV) of immunized rabbits were higher than control. There were increased concentrations of serum electrolyte (Na+, K+, Ca++ and Cl-) and reduction in liver enzymes in immunized rabbits compared with the control. The spleen of immunized rabbits had mild hyperplasia of the lymphoid follicles (B cell domain) and periarteriolar tissue (T cell domain), while their lungs showed severe interstitial pneumonitis. The results show the severe health effects of house dust exposure and the microbial content of domestic indoor airspora. Therefore, environmental control measures must become an integral part of the overall management of allergic individuals.
