Direct exposure of carpets to sunlight can kill all mites

Tovey and Woolcock

REFERENCES 1. Simons FER, Simons KJ. Second-generati0n Hi-receptor antagonists. Ann Allergy 1991;66:5-16. 2. Seldane. In: Physicians' desk reference. 47th ed. Montvale, New Jersey: Medical Economics Corporation, 1993:1398. 3. Sklarew PR, Thrasher JB, Vaughan TR, Spaulding HS. The effect of terfenadine on urination [Abstract]. J ALL~t~G¥ CLZNIMMUNOI~1991;87:562.

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4. Jonides L, Dumont A, Rudy C, Walsh S. Urinary frequency in an adolescent female. J Pediatr Health Care 1993;7: 42,52. 5. Histamine and antihistamines. In: AMA drug evaluations. 6th ed. Chicago: American Medical Association, 1986: 1041-8.

Direct exposure of carpets to sunlight can kill all mites Euan R. Tovey, PhD, and Ann J. Woolcock, MD

C a r p e t s a r e a n i m p o r t a n t site for h o u s e d u s t m i t e c o l o n i z a t i o n a n d for t h e a c c u m u l a t i o n a n d dissemination of mite aeroallergens? Numerous m e t h o d s have b e e n u s e d to try to c o n t r o l m i t e p o p u l a t i o n s in c a r p e t s i n c l u d i n g acaricides, liquid n i t r o g e n , a n d w e t a n d d r y v a c u u m cleaning. E a c h of t h e s e m e t h o d s has p a r t i c u l a r p r o b l e m s including a l a c k o f effectiveness, safety, a n d cost1: and n o n e have g a i n e d w i d e a c c e p t a n c e . M i t e s a r e highly s u s c e p t i b l e to w a t e r loss, an effect t h a t i n c r e a s e s at h i g h e r t e m p e r a t u r e s . 2 P l a c i n g i t e m s in d i r e c t sunlight will s i m u l t a n e o u s l y dry t h e m a n d h e a t them, c r e a t i n g a mic r o c l i m a t e hostile to m i t e survival. A l t h o u g h " a i r ing" o f furnishings is w i d e l y p r a c t i c e d in s o m e c o u n t r i e s , its effects on m i t e s a n d a l l e r g e n s have not been determined. We report the preliminary results o f t h e effect o f e x p o s i n g c a r p e t s to t h e sun on m i t e s a n d t h e i r allergens.

METHODS Study design Four woollen carpets (approximately 2 × 3 m), all from the same house, were used. Before exposure, live mites were collecte d from the carpets with adhesive tape to estimate mite populations, and dust samples were collected for allergen assay. For solar exposure, two carpets were placed pile-side down (i.e., upside down) on a concrete slab in the direct summer sun in From the Department of Medicine, University of Sydney. Dr. Tovey is supported by the National Health and Medical Research Council of Australia. Reprint requests: Euan Tovey, PhD, Department of Medicine, DO6, University of Sydney, NSW 2006, Australia. J ALLERGYCLINIMMUNOL1994;93:1072-4. Copyright © 1994 by Mosby-Year Book, Inc. 0091-6749/94 $3.00 + 0 1/54/52811

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Sydn~Australia

Sydney, Australia. from 9:15 AM to 3:00 PM. Measurements of temperature and relative humidity underneath the carpets were made every 15 minutes, and mite collections were made from the carpet pile for each 30,minute period. The two control carpets remained inside a local house where temperature and relative humidity under them were monitored and a single collection of live mites was made during the exposure period. After exposure, live mite populations in each carpet were again estimated, and dust samples were collected for allergen assay. To check for survival of mites and eggs after exposure, 0.5 gm samples of the fine dust collected from all carpets were cultured at 25 ° C, 75% relative humidity for 4 weeks and then examined.

Live mite counts, dust collection, and allergen assay Live mite populations were estimated by counting mites collected on adhesive tape with a combination of modified "mobility" and "heat escape" methods? For the estimates made before and after exposure, two sections of Vibac adhesive tape (10 × 15 cm) (Vibac, Ticenito, Italy) were applied to the pile side of each carpet for 36 hours. During the exposure period similar sections of tape were applied to new areas for 30 minutes each. Mites were counted on 5 x 10 cm areas of the tape under 30× stereo magnification and categorized as "live" (white, mobile, and full-bodied) and "dead." Dead mites included those that were shrunken and fragmented and those that had distinctive brown shriveled bodies with fully intact setae. All were Derrnatophagoides pteronyssinus. The number of live mites collected in each half hour of the exposure period was expressed a s a percent of the total collected from that carpet over the 6-hour exposure period. Dust was collected with a modified hand-held vacuum cleaner, and mite allergen (Der p I per gram of fine dust) was measured by ELISA. 4

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FIG. 1. The temperature (°C) and relative humidity (%RH) under the carpets and live mites collected at 30-minute intervals during exposure to the sun. The mean percentage of live mites collected was calculated from the numbers collected from each carpet at 30-minute intervals expressed as a percentage of the total number collected from that carpet during the exposure period 9:15 AM tO 3:00 PM. The arrows show the maximum temperature and minimum humidity reached under the carpet.

Measurement of temperature and humidity Relative humidity and temperature were measured under the carpets with small electronic hygro-thermometers (model HT-201Y Jaycar Electronics, Concord, NSW, Australia), claimed to be accurate to 5%. Temperatures greater than 35° C were measured with mercury bulb thermometers.

RESULTS The collection of live mites, together with the microclimate conditions that occurred under the carpets when they were exposed to the sun, are shown in Fig. 1. The first hour of exposure had little apparent effect on mite mobility, despite the developing adverse microclimate. Over the next 90 minutes, a massive migration of mites occurred. Many of the mites a p p e a r e d to be very dehydrated. For the last 3 hours, no live mites were collected, but there was a 10-fold increase in the numbers of dead mites collected from the carpet surface (data not shown). Almost all of the latter dead mites were of distinctive appearance with fully intact setae and were completely dehydrated. Toward the end of the exposure period the t e m p e r a t u r e and humidity under the carpets were 55 ° C and 24% relative humidity, whereas condi-

tions inside the carpet pile would have been more extreme. U n d e r the two control carpets kept indoors during the same period, the indoor temperature and humidity remained between 25 ° C and 26 ° C with 69% to 74% relative humidity. Before exposure, the estimated m e a n population density of live mites per unit area (50 cm 2) as determined by the "mobility m e t h o d " was 408 and 13 for the two treated carpets and 586 and 71 for the controls. The total n u m b e r collected by the " h e a t escape" method from the same size area during the treatment period was 1628 and 50 for the two treated carpets and 55 and 20 for the two control carpets, respectively. No live mites were collected on tape from either of the treated carpets in the 36 hours after sun exposure, whereas 764 and 126 live mites per unit area were collected from the controls. A month later, 12 and 7 live mites per unit area were collected from the treated carpets and 487 and 56 live mites per unit area were collected from the control carpets. In the dust collected from the carpets after treatment, which was set up in culture, no mites were present in the dust from the exposed carpets, whereas the dust from the untreated carpets was heavily infested (not counted). T h e r e was no trend or significant difference in

Rolla, Bucca, and Brussino

the allergen concentration of dust samples collected before and after sun exposure with either the treated or control carpets.

DISCUSSION These preliminary experiments demonstrate that exposure of carpets to direct sunlight created a microenvironment of low humidity and high temperature that was lethal to mites. These observations are consistent with the heat escape method of measuring mite populations, 3 known humidity requirements,: and the thermal death point of mites, s The failure of mites to grow in the cultures of the dust collected from the exposed carpets suggests that eggs and mites in quiescent stages were also killed, although this is not proven. There was no effect on mite allergen Der p I concentration, suggesting that the allergen is stable when dry. Although the precise time required to kill all mites would vary depending on the solar intensity, carpet thickness, and other factors, these preliminary experiments establish a precedent for using sunlight to kill mites. Direct strong sunlight is readily available, and its peak intensity often coincides with the season of highest mite growth. Indeed, the indoor conditions at the time of the study were optimum for

J ALLERGYCLIN rMMUNOL JUNE 1994

mite culture. The treatment is simple, safe, free, and highly effective; and it is suitable for many living conditions where alternative methods of mite control are not available. These studies suggest that where carpets are desired, they should be loosely fitted so that they can be regularly treated in this way. We thank Jeffery Jones for technical assistance in performing the experiments and Dr. Guy Marks for advice on statistical analysis. REFERENCES 1. Colloff M J, Ayres J, Carswell F, et al. The control of allergens of dust mites and domestic pets: a position paper. Clin Exp Allergy 1992;22:1-28. 2. Arlian LG. Water balance and humidity requirements of house dust mites. Exp Appl Acarol 1992;16:15-35. 3. Bischoff ERC, Fischer A, Liebenberg B. Assessment of mite numbers: new methods and results. Exp Appl Acarol 1992;16:1-14. 4. Luczynska CL, Karla-Arrauda L, Platts-Mills TAE, Miller JD, Lopez M, Chapman MD. A two-site monoclonal antibody ELISA for the quantification of the major Dermatophagoides spp. allergens, Der p I and Der f I. J Immunol Methods 1989;118:227-35. 5. Kinnaird CH. Thermal death point of Dermatophagoides pteronyssinus (Trouessart, 1897) (Astigmata, Pyroglyphidae), the house dust mite. Acarologia 1974;16:340-2.

Systemic reactions to intravenous iron therapy in patients receiving angiotensin converting enzyme inhibitor Giovanni Rolla, MD, Caterina Bucca, MD, and Luisa Brussino, MD Torino, Italy

Intravenous administration of iron may cause systemic reactions characterized by fever, arthralgia, myalgia, hypotension, nausea, and vomiting. The incidence of all adverse reactions, including From the Department of Scienze Biomediche e Oncologia Umana, University of Torino, Torino, Italy. Supported by a grant from the Italian Ministry of University and Scientific Research. Reprint requests: Giovanni Rolla, MD, Dipartimento di Scienze Biomediche e Oncologia Umana, Universita' di Torino, via Genova 3, 10126 Torino, Italy. J ALLERGYCLIN IMMUNOL1994;93:1074-5. Copyright © 1994 by Mosby-Year Book, Inc. 0091-6749/94 $3.00 + 0 1/54/52810

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Abbreviation used ACE: Angiotensin converting enzyme

the mild ones, has been reported to occur in 26% of 481 patients treated. 1 Of these patients, 0.6% had a life-threatening anaphylactoid reaction. The pathogenesis of such reactions may depend on iron-catalyzed generation of toxic free radicals, which are believed to oxidize membrane lipids, and on the consequent release of inflammatory mediators? Angiotensin converting enzyme (ACE) inhibitors cause decreased break-