House-dust mite and cat allergens in the Antarctic

Cat, dog and house dust mite allergen levels on children's soft toys

OBJECTIVE

Children's soft toys are known to harbour house dust mite (HDM) allergens, but little is known whether they harbour cat or dog allergens. The objective of the study was to measure cat (Fel d 1), dog (Can f 1) and HDM allergens on children's soft toys.

METHODS

Dust was collected from 40 children's soft toys and their mattresses. Data were collected on pet ownership. Dust samples were analysed for Fel d 1, Can f 1, Der p 1 and Der f 1 by enzyme-linked immunosorbent assay (ELISA) and results are expressed as median levels with inter-quartile ranges.

RESULTS

Thirty-five (87.5%) soft toys had detectable Fel d 1 levels (median: 0.73 µg/g; inter-quartile range: 0.26-2.56 µg/g) while 34 (85%) had detectable Can f 1 levels (1.20 µg/g; 0.53-2.68). Correspondingly, 32 (80%) mattresses had detectable Fel d 1 levels (0.18 µg/g, 0.07-1.01) while 34 (85%) had detectable Can f 1 levels (0.50 µg/g; 0.33-1.06). All mattresses and soft toys had detectable HDM allergen (Der p 1 + Der f 1) levels with soft toys containing about three times higher levels than mattresses. In homes with cats (n = 10) Fel d 1 levels were higher on soft toys than homes without cats (2.49 versus 0.48 µg/g; p = 0.0009). In homes with dogs (n = 25) Can f 1 levels were generally higher on soft toys (1.38 versus 0.63 µg/g; p = 0.10).

CONCLUSIONS

This study has shown that soft toys can harbour cat and dog allergen as well as HDM allergens, some with very high levels. Cat and dog ownership resulted in higher Fel d 1 and Can f 1 levels on soft toys and mattresses. The levels of Fel d 1, Can f 1 and HDM allergens on soft toys could be of importance to sensitized asthmatic children.

Tokelau: a unique low allergen environment at sea level

BACKGROUND

Previous studies have shown that children in Tokelau have a lower prevalence of asthma and atopy compared to Tokelauan children resident in New Zealand. We hypothesized that the low asthma and atopy prevalence in Tokelau may be associated with low indoor allergen levels.

METHODS

Dust was collected from bedding and floors of 76 homes and four public buildings in Tokelau and from the homes of 30 Tokelauan families in Wellington, New Zealand. Dust samples were analysed for Der p 1, Der f 1, Can f 1, Fel d 1, Bla g 2 and Blo t 5 by ELISA, and for endotoxin by a kinetic amoebocyte lysate assay.

RESULTS

Der p 1 levels were over 1000-fold lower in Tokelau compared to New Zealand, geometric mean levels were 0.04 and 47.0 microg/g in beds and 0.04 and 44.7 microg/g on floors, respectively. Can f 1 and Fel d 1 levels were also significantly lower in Tokelau. Bed endotoxin levels were significantly higher in Tokelau, geometric mean: 26 736 EU (endotoxin units)/g, compared to 5181 EU/g in New Zealand. Floor endotoxin levels were similar between the two countries.

CONCLUSION

The very low indoor allergen levels in homes in Tokelau compared to much higher levels in New Zealand homes provides a logical explanation for the lower prevalence of asthma and atopy in Tokelau, compared to New Zealand.

Concentrations of cat and dust-mite allergens in dust samples from 92 large US office buildings from the BASE Study

The concentrations of cat (Fel d1) and dust-mite (Der f1 and Der p1) allergens were measured in 92 large office buildings in the US Environmental Protection Agency's Building Assessment Survey and Evaluation (BASE) Study (251 dust samples; one to four samples per building). Fel d1 was detected in almost all buildings and samples (91 buildings, 99%; 235 samples, 94%; range: <0.01-19 microg/g; median: 0.3 microg/g). Cat allergen exceeded 1 microg/g (a lower symptom threshold) in 56 samples (22%) from 45 buildings, but exceeded 8 microg/g (a sensitization threshold) in only two samples (1%) from two buildings. Der f1 or Der p1 was found in approximately half of all buildings and samples (63 and 70% of buildings; 45 and 51% of samples; range: <0.01-53 microg/g and <0.01-25 microg/g; median: <0.02 and 0.03 microg/g, respectively). Mite allergen exceeded 2 microg/g (a sensitization threshold) in seven samples (3%) from five buildings and exceeded 10 microg/g (a symptom threshold) in three samples (1%) from three buildings. Fel d1 concentration was significantly higher in samples collected in summer (June to September, 48 buildings), but cat allergen was not correlated with either mite allergen. Der f1, but not Der p1, concentration tended to be higher in samples collected in winter (December to April, 44 buildings), and the two mite allergens were significantly correlated only in winter. Cat and mite allergens were detected in 78% of representative US office buildings, but the concentrations seldom exceeded levels associated with sensitization or symptom provocation.

PRACTICAL IMPLICATIONS

The information on the concentrations of cat and dust-mite allergens in representative large US offices has expanded the baseline data available for interpretation of measurements from other building investigations. With suggested refinements, the BASE protocol for measurement of allergen concentrations in dust samples may serve as a guide to future studies of building characteristics, bioaerosol concentrations, and occupant perceptions of the indoor environment.

House dust-mite allergen and cat allergen variability within carpeted living room floors in domestic dwellings

Exposure to allergens from house dust-mites (Der p 1) and domestic cats (Fel d 1) is associated with symptom severity in atopic subjects with asthma and rhinitis. Assessment of allergen exposure in the domestic environment is normally determined by measurement from a single floor site. We determined the variability of these allergens and protein throughout the whole living room floor area. Dust samples were collected from 1 m2 areas from 16 carpeted living room floors in Wellington, New Zealand, and analyzed for concentrations of Der p 1 and Fel d 1. Mean coefficients of variation for Der p 1 and Fel d 1 were 53.1% (range: 28.5-136.8) and 65.6% (range: 28.5-131), respectively. This study has demonstrated a large variation of house dust-mite and cat allergens within living room floors and thus a single sampling site may not be representative for assessment of an individual's exposure risk. House dust-mite and cat allergen levels from the center of the room, in front of a couch or chair, or from a corner of the room are similar to mean levels from the whole room, these sites may thus be representative of the whole living room floor in large-scale epidemiological studies.

Direct on air sampling filter quantification of cat allergen

A direct on sampling filter in solution (DOSIS) method for quantification of airborne cat allergens has been developed. In this method, the allergens firmly adsorbed to a porous polytetrafluoroethylene filter are reacted with specific antibodies conjugated to alkaline phosphatase, generating a matrix-bound allergen-antibody-phosphatase complex. The treated filter is subsequently floated on a commercially available chemiluminescent phosphatase substrate solution. Aliquots of this solution are removed and analyzed luminometrically. The light intensity of the product is linearly related to the amount of allergen over a large mass range, 0-100 SQ units (1 SQ unit is about 146 pg of the allergenic protein Fel d 1). DOSIS demonstrated intra- and interassay precisions of 9% and 8% and 14% and 21% for the levels 4 and 20 SQ units per filter, respectively. The limit of quantification was estimated to 0.4 SQ units (58 pg Fel d 1) of cat allergen per filter. Application of DOSIS to analysis of cat allergen concentrations of indoor air in homes with and without cats revealed, on average, a six times higher concentration in the former (142 SQ units/m(3)) as compared to the latter (24 SQ units/m(3)). The recorded concentrations for airborne cat allergen in homes with cats are in accordance with previously reported figures. Allergen-specifically stained sampling filters revealed the particulate nature of airborne cat allergen which seemed predominantly to be carried by numerous large dust particles.