Berman, D.

Jooma, O.F.

Manjra, A.I.

Potter, P.C.

Weinberg, E.G.

English

AJOL - African Journals Online

Accumulation of house-dust mite (Der-p-1) levelson mattress coversO. F. Jooma, E. G. Weinberg, D. Berman,A. I. Manjra, P. C. PotterMattresses serve as a large reservoir for house-dust miteantigens and harbour the highest mite levels within thehousehold. Mite reduction measures have previously beenshown to be unsuccessful. The effect of mattress coversand acaracides on Der-p-1 levels in the mattresses of 60patients with mite-allergic asthma was studied. Der-p-1levels were measured using monoclonal antibodies (ELlSAmethod). Baseline levels were recorded and re-assessedat 8-week intervals over a 6-month period. Patients wererandomised into three equal groups. In group Amattresses were treated with Metsan (Snowchem) andbenzylbenzoate only; group C had their mattressescovered with mattress covers (Allergy Control Products).Group B was the control group.We were unable to demonstrate any 'reduction of mitelevels in the beds of all 3 groups. In fact all 3 groupsdemonstrated an increase in Der-p-1 levels over the studyperiod, viz. group A (mean pre: 14,28, post: 34,18 ~g/gdust); group C (mean pre: 8,26, post: 20,80 ~g/g dust) andgroup B (mean pre: 18,21, post 38,47 ~g/g dust). However,12 patients in group C had their mattress covers washedin hot water at weekly intervals over a 5-week period atthe end of the study. The results demonstrated asignificant reduction in mite levels (mean pre: 41,95, post:26,2 ~g/g dust; P =0,027).We therefore conclude that the use of mattress coversper se does not reduce Der-p-1 levels. The regularapplication of benzylbenzoate and Metsan does notprevent the accumulation of Der-p-1 on mattresses either.Hot water washing of mattress covers, if possible, willreduce Der-p-1 levels and must be performed regularly.S Afr Med J 1995; 85: 1002-1005.Allergy Clinic, Red Cross War Memorial Children's Hospital andInstitute of Child Health, University of Cape TownO. F. Jooma. M.B. CH.B., ~C.P. (SA)E. G. Weinberg, M.B. CH.B.. ~C.P. (SA)D. Sennan. BA, DIP. MED. TECH.A. I. Manjra, M.B. CH.B., ~C.P. (SA), D.e.H. (SA)Allergology Unit, Department of Clinical Science and Immunol09Y,Groote Schuur Hospital, Cape TownP. C. Potter, M.D.. ~e.p. (SA), D.C.H. (SA)Inhalent allergens play a major role in the pathogenesis ofasthma and allergic rhinitis in children and the house-dustmites, Dermatophagoides pteronyssinus (Der-p-1) andDermatophagoides farinae (Der-f-1), are the predominantinhalent allergens in most South African coastal cities.' Sincethe level of exposure to Der-p-1 antigen has been directlyrelated to the severity of symptoms, it is important toattempt to reduce the level of Der-p-1 and Der-f-1 antigensin the bedrooms of mite-allergic patients!The efficacy of house-dust mite avoidance measuresusing acaricides such as tannic acid and benzylbenzoatehas been well documented in clinical studies of patients whohave moved to mite-free environments. These patient? ,havedemonstrated both an improvement of asthma and adecrease in bronchial hyperreactivity.3.' Mattress covers havelong been advised in the management of house-dust allergy,but these encasings vary in type, and feiN studies of theireffectiveness have been undertaken.5.• Our previou!! study'showed that a single application of benzylbenzoatEl'significantly reduced Der-p-1 levels in bedroom carpets inthe Cape Town area, but had no effect on Der-p-1 levels onmattresses. In this study, we investigated the abilitY of acommercial mattress cover (Allergy Control Products,Ridgefield, USA) and repeated applications ofbenzylbenzoate and a tannic acid solution to reduce Der-p-1levels on mattress surfaces of asthmatic children.Material and methodsSixty children aged 6 - 14 years, with mild to moderateasthma and allergy to Der-p-1 (on skin-prick testing orRASTS) but negative to other aero-allergens, were includedin this study. Patients were randomised into 3 groups (A, B,C) by means of a system of random numbers. Patients werestudied for 6 months and their homes were visited by thesame investigator, who collected the dust samples frommattresses and carpets and applied the acaricide treatment.At the beginning of the study, 'baseline' bronchialhyperreactivity was determined in each child by means of ahistamine challenge test, and baseline dust samples werecollected from the mattresses and carpets of the child'sbedroom. Dust samples were collected 4 times at 8-weeklyintervals. At the end of the study all patients underwent arepeat histamine challenge test. The 3 patient groups, eachcomprising 20 patients, were studied as follows.Group AThis group had Metsan (Snowchem) with benzylbenzoateapplied to both the carpets and the mattresses. The activeingredient of Metsan is bromopol, a detergent. Acombination of Metsan and benzylbenzoate was preparedfor this study. After the first dust sampling it was applied tothe carpets and mattresses. The carpets were vacuumed 24hours later to remove the residue. This procedure wasrepeated every 8 weeks until the end of the study.Group BThis was the control group. Dust samples were collected at8-weekly intervals from the mattresses and carpets but noacaricides were applied to the bedding or the carpets. Nomattress covers were used in this group.1002 Volume 85 No, 10 October 1995 SAMJ-SAMJARTICLES80,..------------------------,70 f--------------------1Fig. 1. Mean Der-p-1 levels on mattresses (lIg/g dust ± SEM)(group A .; control group B • ; group C (mattress covers) D .24 Weeks16 WeeksTime8 WeeksBaselineDerpluglg dustshowed a significant increase in dust levels at the secondsampling. The levels fell marginally in the 16-week and24-week samples. Der-p-1 levels were extremely high onthe mattress surfaces in all 3 groups (A: 34,2 ~g/g dust; B:38,5 ~g/g dust; C: 20,9 ~g/g dust) at the end of the study.There was no statistically significant difference betweenthe levels obtained in the 3 groups at each sampling timepoint.Der-p-1 determinationDust samples were obtained with a Vorwerk vacuum cleanerwith a disposable bag. This was done according to astandardised protocol7 which included vacuuming 1 m2 ofthe carpet for 2 minutes and 2 m2 of the mattress for 2minutes. Each dust bag was sealed and the samples storedat -20°C. Der-p-1 levels were quantitated by means of anELlSA technique with monoclonal antibodies obtained fromDr M. Chapman (University of Virginia, Charlottesville, USA).Group CThis was the second test group. After baseline sampleswere collected, their mattresses and pillows were encased inmattress and pillow covers. These are zippered cottonmattress covers that are laminated on the inner surface.They are impermeable to particulate matter but permeableto water vapour. They are therefore more comfortable thanpreviously recommended plastic covers. Three per centtannic acid was applied to the carpets. In the subsequent 8-weekly visits we repeated dust sampling, taking samplesfrom the surface of the mattresses. The 3% tannic acidsolution was sprayed on the carpets at 8-week intervals.The 3% tannic acid solution was also supplied by AllergyControl Products. Mattress covers were not washed duringthe study period.Bronchial hyperreactivityThis was assessed by means of the histamine challenge testdescribed by Yan et al. 8 This test was carried out at thebeginning of the study and repeated at the end of the study.Children discontinUed antihistamines and anti-inflammatoryinhalant for at least 48 hours and bronchodilators for 24hours prior to the test. Patients on steroids were notstudied. Cromoglycate was discontinued 24 hours beforethe challenge.Der-p-1 levels on carpetsMean baseline Der-p-1 levels were 7,5, 13,1 and 4,8 ~g/gdust for groups A, Band C respectively (Fig. 2). SUbsequentsamplings from carpets in groups A and B did not show asignificant change in the levels. By contrast group C showeda sharp rise at the second sampling and the carpet levels ir;lgroup C remained higher than in the other 2 groups for theremainder of the stUdy.Fig. 2. Mean Der-p-1 levels on floors (lIglg dust ± SEM)(group A .; control group B. ;group C (mattress covers) D .Effect on bronchial hyperreactivityDifferences between the mean bronchial hyper-responsiveness (PC,.,) levels at the beginning and at the endof the study were determined. Paired t-tests were used tocompare the mean differences in the 3 groups. The meandifference for group A was 1,257, for group B, 0,134 and forgroup C, 1,206. No significant change in the PC20 was foundin any of the groups.Effect of washing mattress covers inhot waterAt the end of the 24-week study period, the effect ofwashing of mattress covers in hot water was investigated in12 homes. These covers came from patients in group C whohad the highest levels of Der-p-1. Mattress covers werewashed once weekly for 5 consecutive weeks in hot soapywater at > 70°C for 30 minutes. Following this, Der-p-1levels were determined in dust samples obtained from thesurface of mattresses at the end of 5 weeks.In order to exclude a possible seasonal variation in thelevels of house-dust mites during the study period, dustsamples were taken monthly from March to November fromthe carpets and mattress surfaces of 4 patients in thecontrol group. Mite antigen levels were determined bymeans of the Der-p-1 EL/SA.ResultsDer-p-1 levels on mattressesMean baseline Der-p-1 levels ranged from 8,3 ~g/g dust ingroup A to 19,2 ~g/g dust in group C (Fig. 1). All 3 groups504030Der p Iuglg dust2010Baseline 8 WeeksTime16 Weeks 24 WeeksSAMJ Volume 85 No. 10 October 1995 1003201-----------------i25,----------------------,~ ~ MQ J~ J~ ~ ~ ~ ~ ~MonthMetsan to the mattresses in group A did not prevent theaccumulation of Der-p-1 antigens. Also the application of abenzylbenzoate-Metsan combination or 3% tannic acid tothe carpets was totally ineffective in achieving a reduction inmite antigen levels. These findings clearly show theresistance of house-dust mite to conventional controlmeasures.There are several possible explanations for theineffectiveness of mattress covers in our patients. In the firstinstance, house-dust mite levels are known to be high in ourarea. In areas where mite levels are high, there is a largereservoir of live mites which continue to proliferate on .bedroom furnishings, bedding and carpets. As these . ;become airborne during normal activities in the room, theywill settle onto the bedding and ultimately onto the mattressor mattress covers. Thus, unless there is elaborate reductionin the pool of mites from·other sources in the room. thesemites will soon find their way to the ideal environm~nt of themattress surfaces. ~The mean baseline Der-p-1 levels on mattresses were veryhigh, and since no improvement in mite levels was,1chieved,the absence of any improvement in the PC20 of the'patientswas expected. A closer look at our results shows that theDer-p-1 accumulation.in the beds of patients with mattresscovers in the first 4 weeks after application of the coversinitially exceeded the Der-p-1 accumulation in the controlgroup (Fig. 1). It is likely that blankets and duvets also carrya significant pool of live mites which then deposit on themattress surfaces. In the past, scant attention has beengiven to eradication of mites from this obvious source (e.g.by hot washing (> 70°C)). There was a dramatic increase inmite levels on carpets from 4,8 ~g/g to 25,4 ~g/g in group Bin the first 8 weeks of the study. It is likely that these mitescame from the patients' bedding or mattress covers whenthe beds were made up.Our study suggests that covering of mattresses makesabsolutely no difference to mite-sensitive patients if mattresscovers are not also frequently washed in hot water. Althoughwe have also shown that regular hot water washing ofmattress covers known to be colonised with mites will resultin a significant reduction of these mites, the reductionachieved did not approach acceptable levels (less than 1,0I-Ig/g dust). It would therefore seem necessary to treat otherpotential sources of mites such as blankets and duvetsbefore mattress covers are introduced.The seasonal variation of mites in 4 patients from thecontrol group over a 10-month period confirmed high levelsof Der-p-1 antigen on mattresses and carpets throughoutthis period. The highest levels were observed in Novemberand December. Our main study was conducted betweenApril and October.As far as can be determined, only one other study hasinvestigated the efficacy of mattress covers manufacturedby Allergy Control Products.· This study demonstrated asignificant clinical improvement in the encasing regimengroup after 8 months. The manufacturers only recommend6-monthly washing 'of their mattress covers. This is not .appropriate in our area and will result in an unacceptablyhigh accumulation of Der-p-1 antigen on the mattresssurfaces.The reduction of the Der-p-1 allergen pool, especially thefaecal pellets and dead mites, remains largely unresolved.- -- - -it151-----------------;10 h-c,---------j l=--------jDerplug/g dust10506020Effect'of washing of mattress covers inhot waterThe mean levels of Der-p-1 antigen on the 12 mattresscovers at the end of the 24-week study period prior towashing was 41 ,95 ~g/g dust and, after 5 weeks of regularwashing, 26,2 ~g/g dust (P = 0,027).M~ ~ M~ ~e J~ ~ ~ ~ ~ ~MonthFig. 3. Seasonal variation of arithmetic mean (D ) and geometricmean (. ) Der-p-1 levels on carpets (lJglg dust).Derpl40ug/g dust 3070Seasonal variation of house-dust mitelevelsArithmetic and geometric mean levels in carpets andmattress covers in the 4 control homes over the 10-monthperiod studied are shown in Figs 3 and 4 respectively. Inboth groups peak levels were observed in November andDecember, but very high levels were also observed on themattresses between May and August, the wettest months inCape Town.Fig. 4. Seasonal variation of arithmetic mean (D ) and geometricmean (. ) Der-p-1 levels on mattress covers (1J91g dust).DiscussionThis study has shown that covering the mattresses of CapeTown asthmatic children with a commercial mattress coverresulted in a significant accumulation of mites in the 24-week period studied. The study was conducted during thewinter months when the proliferation of house-dust mites isknown to increase because of increased indoor humidity.We also found that the application of benzylbenzoate and1004 Volume 85 No. 10 October 1995 SAMJ-Reduction of indoor humidity9 appears to be an effectivemeans of controlling the mite population in the household;however, this is not affordable and practical for mostpatients. Washing of the bedding is effective at temperaturesgreater that 70°C and may be more appropriate here.Removal of carpets, heavy fabrics and soft toys is stronglyadvised and acaricides may help to destroy any remainingmites. ,aIn conclusion, control of exposure to dust mites remains alargely unresolved problem. It is clear that the use of onlyone method of control, Le. special mattress covers,acaricides, or hot washing of fabrics, will only partiallyalleviate the problem. A comprehensive strategy to utilise allavailable methods known to be effective in reducing dustmites should be used. Further studies are required todetermine whether the application of all known controlmeasures will achieve optimal levels in areas of high miteprevalence. We also need to know what level of reduction ofDer-p-1 is required to produce an improvement in thepatient's condition.The authors wish to thank Tony Cawood (Vorwerk (Pty) Ltd)for assistance with the collection of the dust samples, AnnToerien and Bev Peper for helping with the patientinvestigations, Varina Stevens for typing the manuscript, EleanorGouws of the Department of Biostatistics of the MRC (Natal)who analysed the data, and Annette Miller of Allergy ControlProducts for supplying the mattress covers and pillow covers.REFERENCES1. Voorhorst R, Spieksma PM, Lenpen MJ, Lyklema AW. The house dust mite andthe allergens it produces. Identity with the house dust allergen. J ANergy 1967;39: 325.2. Murray AB, Ferguson AG. Dust-free bedrooms in the treatment of asthmaticchildren with house dust or house dust mite allergy: a controlled trial. Pediatrics1983; 71: 418-422.3. Platt-Mills TAE. Reduction of bronchial hyperreactivity during prolonged allergenavoidance. Lancet 1982; 2: 675- 678.4. Morrow Brown H, Merrett TG. Effectiveness of an acaricide in management ofhouse dust mite allergy. Allergy 199f; 67: 25-31.5. O.wen S, Morganstem M, Hepworth J, Woodcock A. Control of house dust mite inbedding. Lancet 1990; 335: 396-397.6. Ehnert B, Lau Schadendorf MO, Weber At Buettner P, Schou C, Wahn U.Reducing domestic exposure to dust mite allergen reduces bronchialhyperreactivity in sensitive children with asthma. J Allergy Clin Immunol 1992; 90:135-138.7. Manjra A. Berman D. Toerien A, Weinberg EG, Potter PC. The effects of a singletreatment of an acaricide, Acarosan, and a detergent, Metsan. on Der-p-lallergen levels in the carpets and mattresses of asthmatic children. S Afr Med J1994; 84: 278-280.8. Van K, Salome C. Woolcock AJ. Rapid method for measurement of bronchialresponsiveness. Thorax 1983; 38: 760-765.9. Korsgaard J. House dust mites and absolute indoor humidity. Allergy 1993; 38:85-92.10. Lan-Schodendorf 5, Ausche AF, Weber AK, Buettnner-Gaetz, Wahn U. Short-termeffect of solidified benzyl benzoate on mite allergen concentration in house dust.J Allergy Clin Immunol 1991; 87: 41-47.Accepted 2 Mar 1994.SAMJARTICLESReasons for failure toadminister antenatalcorticosteroids in pretermlabourD. E. Ballot, N. S. Ballot, A. D. RothbergA retrospective review of 101 preterm infants deliveredat Johannesburg Hospital was conducted to determinethe use of antenatal corticosteroids (ACs). Overall therewere 38 opportunities for the use of ACs of which 18were missed. Of the remaining mothers, 32 presentedin advanced labour, 22 presented with obstetricemergencies and 6 were managed as inevitableabortions. There was a signficant association betweenlack of antenatal care and presentation in advancedlabour. Therefore, although only 20% of mothersreceived ACs, there was no opportunity for their use inthe majority of patients. The use of a safe and cost-effective measure such as ACs should not be ignoredin a country with limited health resources. Betterantenatal care as well as increased awareness amongobstetricians is required to improve the situation.S Afr Med J 1995; 85: 1005-1007.The administration of antenatal corticosteroids (ACs) hasbeen shown significantly to reduce complications ofpremature birth, including hyaline membrane disease,bronchopulmonary dysplasia, patent ductus arteriosus,necrotising enterocolitis and intraventricular haemorrhage. '·5Failure to use ACs in appropriate circumstances thereforeadversely affects neonatal outcome. It is our impression thatACs are used only infrequently in the mothers of preterminfants admitted to our neonatal unit. Reasons may includelack of awareness by the attending obstetrician, or clinicalcircumstances that preclude the use of ACs. In order toestablish the frequency of AC administration in our unit,reasons for failure to do so, and whether there were anymissed opportunities for the use of ACs, we reviewed themanagement of pregnancies that resulted in the birth ofpreterm infants requiring admission to the neonatal unit.Subjects and methodsThe maternal records of all neonates with a birth weight< 1 500 g and/or gestational age < 32 weeks admitted toDepartments of Paediatrics and Child Health and Obstetrics andGynaecology, Johannesburg Hospital and University of theWitwatersrand, JohannesburgD. E. Ballot PHD., F.G.P. (PAED.)N. S. Ballot, F.G.C.G.A. D. Rothberg, PHD., F.G.f' (PAED.)SAMJ Volume 85 No.10 October 1995 1005

Accumulation of housedust mite (Der-p-1) levels on mattress covers

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Accumulation of housedust mite (Der-p-1) levels on mattress covers

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