Sustainability of pyrethroid-impregnated bednets for malaria control in Afghan communities

Between 1992 and 1995 a series of studies was undertaken to assess the long-term suitability of pyrethroid-impregnated bednets (PIBs) for malaria control in Afghan refugee communities in two villages in North-West Frontier Province, Pakistan. During 1992, 86% of bednet owners volunteered to have their bednets re-impregnated, and a further 15% of families purchased nets at two-thirds of cost price. From 1992 onwards, 27% of the villagers returned to Afghanistan, and annual house spraying campaigns were introduced to protect those still resident but sleeping without bednets. Within 3 years, these campaigns, together with PIBs, reduced the annual incidence of malaria by 87%, from 597 to 78 cases per 1000 population. Nevertheless, 65% of resident families continued to re-impregnate their nets annually with permethrin. To assess whether PIBs were still being used and were still protective, in view of these reduced transmission rates, we carried out a case--control study in 1994 on febrile or otherwise symptomatic patients presenting at village health centres. Comparison of the slide-positivity rates of PIB users and those without bednets showed that regular usage reduced the odds of contracting falciparum and vivax malaria to 0.22 (95% confidence interval (CI): 0.09-0.55) and 0.31 (95% CI: 0.19-0.51), respectively. There was no evidence of a sex- or age-bias in bednet use or in protective effect. The results indicate that a community-based PIB programme is an appropriate malaria control measure in areas where management or security problems make traditional house-spraying campaigns impossible. A relevant finding for those involved in the monitoring of bednet distribution projects is that the local coverage of bednets and the local impact on malaria, even when introduced to remote areas, can be estimated very cheaply by health centre microscopists who simply catalogue blood film diagnoses according to patients' bednet use practices.

Behaviour of Anopheles albimanus in relation to pyrethroid-treated bednets

Responses of the malaria vector Anopheles albimanus to pyrethroid impregnated bednets made of cotton or nylon, compared with untreated nets, were investigated in houses occupied by two people inside and/or outside two bednets, in coastal Chiapas, México. The pyrethroid used was lambdacyhalothrin 30 mg a.i./m2. Bioassay mortality rates of An.albimanus exposed to treated nets for 3 or 15 min, rose from 40-55% to 90-100% for nylon nets 3-19 weeks post-treatment, but were consistently lower for treated cotton nets. An.albimanus females (collected unfed on human bait) were released in houses surrounded by curtains for trapping mosquitoes that exited from the house. Floor sheets were used in and around each experimental house for retrieving any mosquitoes knocked-down and/or killed. During post-treatment assessment for 17 weeks, An.albimanus blood-feeding success rates were 23-24% with untreated nets, 14-18% with treated cotton nets and 8-15% with treated nylon nets, significantly reduced when both human baits were inside the treated bednets, but not when one or more baits were outside the treated bednet(s) within the house. Proportions of mosquitoes leaving houses < 3 h post-release were 53-59% from houses with untreated bednets versus 65-78% with treated bednets. Except in one case (when both humans were outside treated cotton nets), these increased early exit rates were significant, whether or not the human baits were inside the treated bednets indoors. Mortality rates of An.albimanus females exiting overnight (22.00-06.00 hours) averaged 15-39% from houses with treated cotton and 16-46% with treated nylon nets, very significantly greater than the control mean rates of 6-8% mortality with untreated nets. Observations on wild-caught An.albimanus females marked with fluorescent powder and released indoors revealed that few mosquitoes (3-11%) actually contacted the bednets unless both human baits remained under them - when contact rates were 22% on treated nylon, 23% on treated cotton and 42% on untreated nets (P approximately 0.05). The mean resting time was significantly longer on untreated (14.4 min) than on treated nylon (5.8 min) or cotton (9.5 min) bednets, whereas mean resting times on other surfaces indoors were 16.5-19.8 min. Proportions exiting within 2h of release were significantly more from houses with treated houses (33-35%) than with untreated nets (8%). However, mortality rates of mosquitoes that landed on treated nets were very significantly greater (90-100%) than after landing on untreated nets (10%). Thus, despite some excito-repellency, lambdacyhalothrin-impregnated bednets (especially made of nylon) proved to be effective as an alternative to house-spraying against An.albimanus.

Snoring and obstructive sleep apnea: does head posture play a role?

The aim of this article is to present scientific and clinical evidence to support the role of proper head and neck posture in the management of snoring and obstructive sleep apnea. Obstruction of the upper-airway during sleep is a serious medical condition often associated with severe daytime somnolence, morning headache, and a host of cardiopulmonary complications, including but not limited to systemic and pulmonary hypertension, nocturnal cardiac dysrhythmias, myocardial infarction, and stroke. Though anti-snoring pillows are occasionally mentioned in the literature, the role of proper head-neck support during sleep has been largely neglected. In this article the effect of head-neck position on upper-airway obstruction during sleep is discussed from the perspective of both causation and treatment. Based on the evidence presented by the author, it is recommended that the use of cervical-support pillows be considered as an adjunctive treatment modality in patients suffering from snoring and obstructive sleep apnea.

[Encasing evaluation: studies of dust retention and water permeability]

The use of allergenproof mattress casings for those allergic to house-dust mite is a vital component of therapeutic concepts concerning the avoidance of allergens. Encasings of different materials are available from a variety of manufacturers on the German market. The goal of this study was to investigate different encasing materials to test for their impermeability to dust and permeability to water vapour ("breathability"). Material samples from nine different manufacturers as well as one additional samples were tested by two independent institutes. The samples were coded with serial numbers and the product names and manufacturers were unknown to the testers. The degree to which particles could penetrate the materials (as a measure of dust penetration) was tested in two series of experiments using the naturally available ambient air and fine coaldust. A thermo-regulation model ("skin model") was used to test the materials for water vapour permeability. The results of three of the nine samples tested for particle penetration have to be considered unsatisfactory due to the number and size of the particles allowed to enter. Overall an additional synthetic layer appears to improve the materials capacity to prevent dust penetration. The water vapour permeability of three of the nine samples of encasing material must be classified as unsatisfactory with the consequence of possible sleep disturbance. From an allergological point of view, minimal particle penetration is an essential criteria. On the other hand, low water vapour transport properties can diminish the patients willingness to comply. The present study cannot be substituted for a clinical study of effectiveness but nonetheless reveals, in some cases, considerable differences in the physical properties of the various materials. It would be desirable for the individual product packaging to feature a declaration of the relevant test data, thus providing decision-making for those buying or prescribing.

Effects of community-wide use of lambdacyhalothrin-impregnated bednets on malaria vectors in rural Sierra Leone

The effect of community-wide use of bednets treated with lambdacyhalothrin 10 mg/m2 on the malaria vector Anopheles gambiae (forest form) was evaluated in Sierra Leone. Sixteen similar villages near the town of Bo were randomly allocated either to remain without nets or to receive treated bednets for all inhabitants, with effect from June 1992. Mosquitoes were sampled using human biting catches on verandas, light-trap catch (beside an occupied untreated bednet), window exit-trap catch and pyrethrum spray collections. During the first year of intervention (June 1992 to July 1993) the treated bednets provided personal protection for people sleeping under them, but had very little impact on densities of An.gambiae collected on human bait. The human blood index (HBI) of An.gambiae was not affected (HBI = 99% in villages with and without nets). An.gambiae parous rates were significantly reduced in all intervention villages, but malaria sporozoite rates fell in only some of the villages. These results are intermediate between those obtained from other projects in Tanzania and Burkina Faso, where treated bednets reduced man-biting, parity and sporozoite rates, versus The Gambia where treated bednets had no significant impact on any of these factors. Possible reasons for these contrasted findings are discussed.

Anopheles gambiae gonotrophic cycle duration, biting and exiting behaviour unaffected by permethrin-impregnated bednets in The Gambia

Permethrin-impregnated bednets protect children against malaria in The Gambia, where Anopheles gambiae complex mosquitoes are the main vectors of malaria. However, no effect has been found on mosquito density, parous rates or sporozoite rates in An.gambiae sensu lato populations; only a reduction in the numbers of mosquitoes resting indoors in rooms with treated bednets. A possible explanation for this paradox is that exposure to treated bednets leads to changed vector behaviour such as a shift in biting time, a diversion to biting outdoors instead of indoors, to biting animals instead of humans, or to increased duration of the gonotrophic cycle. To investigate these possibilities, we observed the biting and existing behaviour of An.gambiae in ten pairs of villages, in half of which the residents used permethrin-treated bednets. The possible influence of treated bednets on the gonotrophic cycle length was evaluated by mark-release-recapture experiment. No significant difference was found between villages with treated and untreated bednets in the indoor/outdoor ratio of human biting, in mean biting times or in human blood indices of An.gambiae females found resting indoors in the mornings. The proportions of unfed, fed or gravid An.gambiae females collected in exit traps, and the number of females exiting showed no significant differences between rooms with treated and untreated bednets. Indications for a gonotrophic cycle length of 2 days were found. No evidence for any change in duration of the gonotrophic cycle in relation to exposure to treated bednets was found, although the number of recaptures was low in the villages with treated bednets. Since equal numbers of infective An.gambiae were found in villages with treated or untreated bednets, and no changes in mosquito behaviour were detected, we cannot account for how children are protected against malaria by treated bednets. One possibility is that mosquitoes divert to bite other hosts, including adults.

Distribution and density of house dust mites Dermatophagoides spp. (Acarina:Pyroglypidae) in the mattresses of two areas of Rome, Italy

The distribution of Dermatophagoides farinae and D. pteronyssinus in two groups of houses in Rome was investigated by means of weekly sampling of dust on mattresses during the period of high mite density (May-July, 1994). All mattresses were infested; overall 4,179 live and dead mites were collected. In the two examined areas, a difference in species distribution was observed. D farinae was always the prevalent species, it was 94.7% in area A and 64.1% in area B; only in houses 9 and 10 D. pteronyssinus was the most abundant species (71.4% and 45.8%). Housekeeping practices were investigated by interviewing the tenants and relative humidily and indoor/outdoor temperature were measured during each weekly sampling. A correlation analysis revealed a significant relationship between housekeeping practices and mite density (r = 0.83). The poorest housekeeping practices produced the heaviest mite infestation, while good ones were associated with low densities.

Treatment of atopic dermatitis in children: the importance of skin care and environmental control

A 5-year-old female with severe atopic dermatitis with secondary bacterial infection is presented. The patient had been managed with topical steroids and anti-allergic drugs for several months prior to admission to the National Children's Hospital, Tokyo. This case is reported to emphasize that drugs alone are not sufficient in treating severe atopic dermatitis. Skin care and environmental control are equally important and should form a part in the management of the disease.

Laboratory evaluation on the toxic effects of bednets impregnated with permethrin against malaria mosquitos

In the laboratory, bednets impregnated with 250mg ai/m2 and 500mg ai/m2 permethrin caused respectively the mean mortalities of 86.6% within 13 months and 87.2% within 17 months on laboratory-bred An. sinensis, while they caused average mortalities of 58.3% within 4 months and 73.8% within 10 months on An. dirus respectively. The bioassay results of KT50 and LT50 on the two species showed that KT50 is shorter than LT50 after exposure to the treated bednets. The ratio is 1:2.16 - 1:3.05. It was observed Anopheles had obviously secondary knocked down after exposure to the treated bednets and there is obvious resurgent after Anopheles have been knocked down. When the temperature goes up the resurgence gets shorter, the resurgence rate gets higher and the mortality gets lower. It showed that permethrin has stronger knocking down effect than killing effect.

Deltamethrin-impregnated bednets as an operational tool for malaria control in a hyper-endemic region of Burundi: impact on vector population and malaria morbidity

Within the framework of the National Malaria Control Programme Burundi, impregnated bednets were promoted through health care facilities, schools and local administration in Nyanza Lac district. The decision to buy a bednet was left to the inhabitants and, as a result, coverage rates between 6 and 65% were observed at sub-district level. Three intervention regions were specified based on the intervention start date. From November 1992 until March 1995, bi-monthly parasitological and entomological surveys were carried out in two areas each of Region 1 and Region 2. After introduction of impregnated bednets in Region 1 the proportions of children under 5 with high parasitaemia were reduced by 42 and 53% in the 2 parasitological survey areas, where the average bednet coverages were 55 and 44% respectively. In the survey areas of Region 2 (control) no significant change occurred during the same period. During the second part of the intervention from September 1994, when intervention was also operational in Region 2, significant decreases in the proportion of high parasitaemia (63 and 42%) among children under 5 years were obtained in both parasitological survey areas of Region 2 (average coverages of 51 and 29%). The positive output of the intervention was maintained and even reinforced in the survey areas of Region 1. Bednets as a tool for malaria control entail specific problems such as coverage, daily use, reimpregnation, and renewal of old and torn nets. Further evaluation has to point out the possible shift of the clinical spectrum and the age-specific admission of malaria cases to assess the long-term benefit of this control method.

Are bedding and rebreathing suffocation a cause of SIDS?

Suffocation by bedclothes became a popular diagnosis in the 1940s but gradually became replaced with the diagnostic label of Sudden Infant Death Syndrome (SIDS). In 1991 a paper purported that, instead of SIDS, pillows filled with polystyrene beads had caused death by rebreathing suffocation; this conclusion was reached on the basis of experiments with anesthetized rabbits breathing through a doll's head that was placed face down on the pillow. Because of the anesthesia, rabbits could not change their face down position. The doll's nares could not collapse, which would have resulted in rapid death due to conventional suffocation. The rabbits required up to 3 hours or more to die of hypercarbia and hypoxia. Studies in normal infants revealed that they turned from the face-down position after only 2 minutes. (The only infant who retained CO2 soon died of a fatal neurologic disorder, with central hypoventilation). Using the rabbit/doll's head and mechanical models, a wide range of bedding was indicted, including cushions, sheepskins, pillows, comforters, foam mattresses, and even simple blankets and sheets as potentially causing fatal rebreathing. Except for the use of pillows in general, as well as mattresses filled with kapok and bark, there has been no epidemiologic support for these indictments. Although normal infants are unlikely to succumb to rebreathing suffocation, infants with blunted ventilatory responsiveness and delayed arousal due to prior hypoxia were hypothesized to be at increased risk. Support for this concept was found in the pathology of the brain stem in victims of SIDS that was attributed to prior hypoxic injury. In infants who survived prolonged apnea, less than 20% have demonstrated a diminished ventilatory responsiveness to hypercarbia, but, more significantly, none had an absent response. Arousal to hypercarbia, an abnormality which is crucial to the hypothesis of rebreathing suffocation, is regularly present in normal subjects, but the threshold is higher in near-SIDS infants; however, no instances of failure to arouse have been reported in near-SIDS. If the infant is placed on his or her back or side, the issue of bedding could become moot; unfortunately, a sizable percentage of infants are still being placed prone for sleep. Instead of confusing parents with an ever-expanding list of "dangerous bedding," the message "Back to Sleep" should be emphasized.

LIBERATION OF ORGANISMS FROM CONTAMINATED TEXTILES

By using a specially designed apparatus it was possible to study the yield of airborne organisms when various hospital textiles, artificially and naturally contaminated, were shaken under reproducible conditions. The results indicated that contaminant organisms are most effectively liberated when a textile is shaken in contact with a second fabric. The yield of airborne organisms was approximately doubled under the conditions used. Similarly, a 95 % removal of surface con taminants was also demonstrated by shaking in contact with a second textile, compared to 52 % removal when the textile was shaken alone.

These findings confirm those described in an earlier study of the spread of air borne organisms in a ward environment. It is suggested that this increase in aerial spread of infectious particles, previously referred to as a ‘counterpane effect’, is due to friction between the contaminated textile and its covering material.

Other points which emerged in the course of this work were the demonstration that cotton blankets tended to yield higher airborne counts than woollen ones and that the size distribution of bacterial particles dispersed by textiles is the same as that of the particles which contaminate the textiles.

It is with pleasure that we acknowledge the encouragement and advice of Prof. Walsh McDermott, in whose Department at the Cornell Medical College, New York, this work was carried out. We are also grateful to the National Institutes of Health, Bethesda, for financial support under Grant No. E-635(C 7).

Thermal stress, sleeping position, and the sudden infant death syndrome

We review the evidence than overheating or disordered thermoregulation may be responsible for some cases of the Sudden Infant Death Syndrome (SIDS). Possible mechanisms for an interaction of thermal stress and the prone position are discussed with an emphasis on heat production and loss via the infant head. After the reduction in the prevalence of the prone position following "Back to Sleep" campaigns, and the emergence of cigarette smoking as a key risk factor, the role of disordered thermoregulation continues to be important in many cases of SIDS.

Preventing skin breakdown: nursing practices, costs, and outcomes

The aims of this study were to identify patients at risk for skin breakdown, to describe nursing interventions associated with the prevention of skin breakdown, and to analyze the cost of supplies used to prevent skin breakdown. An evaluation of nursing interventions used at three hospitals revealed that nurses used a variety of strategies for preventing skin breakdown. However, greater expenditures on prevention strategies did not improve outcomes and overuse of some items increased the incidence of skin breakdown. Protocol-based preventive nursing interventions are necessary to provide a cost-effective approach to the maintenance of skin integrity.

Full body forced air warming: commercial blanket vs air delivery beneath bed sheets

PURPOSE

Single-use commercial forced air warming blankets serve only to distribute heated air from a blower. Standard bed sheets may be equally effective in delivering hot air within a lower body field and at lower cost.

METHODS

Heated forced air at 38 degrees and 43 degrees was delivered within a simulated full-body field beneath standard hospital bed sheets or via a BAIR Model 315 commercial blanket. The air temperatures maintained within, as well as the caloric uptake of standard bodies containing 1000 ml water, were studied under standard simulated operating room conditions. Thermal input was provided by one Bair Hugger Model 500 Warming Unit and hospital acquisition cost for materials were calculated.

RESULTS

Air temperatures measured within the full body field at the three test sites were as great or greater using bed sheets (33.4-35.8 degrees) as with the commercial blanket (31.1-33.9 degrees), in spite of the 5 degrees cooler outlet temperature air settings @ 38 degrees vs 43 degrees, respectively (P = 0.003). Forced air delivered beneath bed sheets heated standardized thermal bodies twice as effectively as commercial blankets using identically warmed (38 degrees) forced air and heated as well as, or better, at the 38 degrees setting than did the commercial blanket at the 43 degrees setting. Calculated acquisition costs for sheets vs commercial blankets were $0.76 vs $18.00 US, respectively.

CONCLUSION

The simplicity, efficacy and economy of containing 38 degrees warm air beneath bed-sheets offer several advantages over commercial blankets and warrant further study.

Effects of Microstop-treated anti-mite bedding on children with mite-sensitive asthma

Seventy-one children with mite-sensitive asthma were randomly divided into three groups. Group 1 was comprised of 28 patients who were provided with new Microstop-treated bedding including matresses, quilts, pillows, bed linens and quilt covers. The Microstop mattresses and pillows were made of impermeable Polyurethane coated nylon ticking. Group 2 included 28 patients who were provided with new, conventional, mat Polyurethane mattresses, quilts, pillows, bed linens and quilt covers made of cotton and polyester which had not been Microstop treated. Group 3 included 15 patients who used their old bedding. Mite counts were performed on samples of dust collected from the old mattresses, pillows and quilts before the bedding was changed. After changing the bedding, mite counts were performed on dust from the same three bed sites at the end of months 1, 2, 3, 6, 9, and 12. Morning and evening peak expiratory flow, asthma symptom scores, were recorded by each patient at least 1 month before entering the study and every month during the one-year study period. Mattress mite counts were significantly reduced in Group 1 but not in Groups 2 or 3. However, quilt mite counts were significantly reduced in both Group 1 and Group 2 throughout the 12-monthstudy while mite counts in Group 3 quilts remained unchanged. The results provide evidence that the PU-coated nylon material was effective in reducing house dust mites, but do not demonstrate that the Microstop treatment had an obvious anti-mite effect. One-year follow-up of asthma symptom scores showed significant improvement in Group 1, but not in Groups 2 or 3. This suggests that the Microstop-treated bedding, as a system, was effective in asthma prevention.

Antimicrobial acetate fibers: a step forward in health care textiles

Health care providers are constantly battling the microorganisms that cause disease and infection. New textile products give professionals another weapon against these microscopic enemies.

Field trial of permethrin impregnated sisal curtains in malaria control in western Kenya

A trial to determine the effectiveness of sisal eaves-curtains impregnated with permethrin for malaria control was conducted in the malaria holoendemic western Kenya between 1991 and 1993. Indoor resting densities of Anopheles gambiae s.l. and Anopheles funestus were reduced by 90.9% and 93.8% respectively in protected houses. The entomological inoculation rate (EIR) was reduced by 72% in the intervention village. There was no significant reduction in vector longevity or survival as shown by the sustained high sporozoite rates. Monthly bioassays for retained insecticidal potency of permethrin on the fibre indicated vector mortality rates above 95% over the period. Of 283 and 240 children followed up from the intervention and control villages, a mean malaria prevalence of 43.2% and 52.2% respectively was observed over the trial period (p < 0.01). The prevalence rose to 73.5% and 75.7% (p = 0.541) respectively after the removal of the curtains. No significant differences were observed in the mean parasite density between the groups or between the proportions with parasite density exceeding 2,500 per microliter and with or without fever. The prevalence of splenomegaly was significantly lower in the intervention group compared to the control, both during (p = 0.005) and after the intervention (p < 0.001). There was no significant difference in the mean change in haematocrit at the end of the intervention. We observe that permethrin impregnated sisal curtains effectively retain permethrin, alter favourably the indoor vector density and EIR, and could provide a reduction in malaria prevalence.

Metabolic rate of sleeping infants

AIM

To measure the sleeping metabolic rate (SMR) of healthy infants in the first year of life.

METHODS

The SMR was measured on 73 infants aged 1 to 12 months in a special nursery using indirect calorimetry. One hundred satisfactory observations were made. The room air and radiative temperatures, humidity, and amount of insulation were measured. Parents chose the clothing and bedding that they judged their infant needed.

RESULTS

The mean (SD) SMR was 2.4 (0.4) watts (W)/kg or 45 (10) W/m2. The mean SMR of infants aged 1-2 months was 38 compared with 44 W/m2 in infants of 8-12 months; the difference was not significant. There were no obvious differences in SMR between boys and girls. But there were wide differences in SMR between apparently similar infants, range 1.4 to 3.5 W/kg. Most parents selected insulation between 1 and 3 togs, and this was weakly negatively correlated with air temperature.

CONCLUSION

These wide variations in SMR mean that it is impossible to give specific guidelines on the amount of clothing and bedding a particular infant will need for thermal comfort in a given room temperature.