econ.1997.binka.healthpolicy.the cost effectiveness of permethrin impregnated bednets in preventing...

8/14/2019 Econ.1997.Binka.healthPolicy.the Cost Effectiveness of Permethrin Impregnated Bednets in Preventing Child Mortality in Kassena Nankana District of Norther

1/11

ELSEVIER Health Policy41 (1997) 229-239

The cost-effectiveness of permethrin impregnatedbednets in preventing child mortality inKassena-Nankana district of Northern GhanaFred N. Binka a,b,*,Omer A. Mensah , Anne Mills d

a Navrongo Health Research Centre, Ministry of Health, PO Box 114, Navrongo, Ghanab Swiss Tropical Institute, Basel, Switzerland

Centre Regional pour le Developement et la Sante, Cotonou, Benin Health Economics and Financing Programme, London School of Hygiene and Tropical Medicine,

London, UK

Received17 April 1997;accepted6 May 1997

AbstractPermethrin impregnated bednets are now being widely promoted BSan effective means ofprotecting African children against malaria, but there is little evidence of their cost-effective-ness. The impact on child mortality of introducing permethrin impregnated bednets wasevaluated in a rural district of northern Ghana in a controlled trial. The cost-effectiveness ofthe intervention is reported in this paper. The total cost of the intervention over the 2 yearsof follow-up was US $148 245. Cost per impregnated bednet per year and per person protectedper year was US $2.4 and 1.2, respective ly. Approximately 16 800 child years were protectedand 74 child deaths avertefl at fn estimated cos t of US $8.8 per chi ld year protected and US$2003 per death aver&@ In this rural community, where life expectancy at the mean age ofdeath of trial children was 57.5 years, the estimated cost per discounted healthy life-year gainedwas US $73.5. Sensitivity ana lysis suggested that this cost-effectiveness atio might be reducedsubstantially by feasible changes in programme implementation. This study supports theargument that the cost-ef fectiveness of bednet impregnation is sufficiently att ractive to makeit part of a package of high priority interventions for children. Issues of how to finance theprovis ion of nets and insectic ide, and especially the relative contribution of governments,households and donors, need urgently to be addressed. 0 1997 Elsevier Science reland Ltd.* Correspondingauthor.

0168-8510/97/$17.00 1997 ElsevierSciencereland Ltd. A ll rights reserved.PIISOl68-8510(97)00035-3


2/11

23 0 F.N. Binko rr al. / Hmlth Policy 41 (1997) X9- 2.19Keywords: Malaria control; Insec ticide impregnated bednets; Ghana

1. IntroductionMalaria continues to be a major public health problem in Africa, with only 7%of the population living in areas with negligible risk or no risk of getting malaria[I]. It is also the most important cause of disability-adjusted life years lost insub-Saharan Africa [2] and particularly affects children. Due to poor levels of socialand infrastructural development, high transmission, and financial and managerial

problems, control programmes on the continent have not achieved the desiredimpact in controlling malaria. Currently, the global strategy for the control ofmalaria is aimed at reducing morbidity by using early case detection and treatmentas well as targeted vector control [3]. Implementation of this strategy in mostAfrican countries is faced not only with poor access to health care, but also withgrossly inadequate resources for health, from both government and donor agencies.Any new control strategies, to have a chance of acceptance, need to be shown tohave levels of cost-effectiveness similar to those of existing strategies for childsurvival, such as the expanded programme on immunisation (EPI). Studies inseveral countries in Africa have shown that the use of insecticide impregnatedbednets (IIBN) is a simple and effective means of reducing child morbidity andmortality [4-81. The promotion of IIBN and their incorporation into malariacontrol programmes in Africa has recently been advocated by WHO [l]. Reportsfrom The Gambia have indicated that this intervention is as cost-effective asexisting interventions targeted at children [9,10]. However the special context of TheGambia, most notably the seasonal nature of transmission and the high levels ofbednet ownership, require that this conclusion be validated elsewhere. We reporthere the cost-effectiveness of IIBN in a controlled trial in northern Ghana, wherebednets and insecticide were introduced into local communities and provided freeof charge.

2. Methods

2.1. Study areaThe study was carried out in the Kassena-Nankana district of northern Ghanawhich covers an area of 1675 km2. The population of the distr ict is estimated at175 000 with two main ethnic groups, the Kassena and Nankana. The population isrural, and lives in dispersed settlements which consist of compounds containinghouses made mainly of mud, with mud, thatch and occasionally zinc roofs. They


3/11

F.N. Binka et al. /Health Policy 41 (1997) 229-239 231

are surrounded by farming land. There are two main seasons. The wet season isshort, with an average annual rainfall of 850-950 mm, most of which fallsbetween June and September. The people are subsistence farmers growing millet,sorghum and groundnuts. Malaria is endemic and occurs throughout the yearbut with marked seasonal variation [ll]. Transmission is high with a mean of300 infective bites per person per year [12]. Health facilities in the area are few,fees are charged and settlements are scattered, hence utilisation levels are low.Prior to the trial, there was no tradition of bednet use in the area.

2.2. InterventionThe details of the intervention are reported elsewhere [8] and summarised here.

A census of the study area was conducted and all members of the 11733compounds enumerated. The area was divided into 96 clusters (or villages) ofgeographically contiguous compounds with an average of 120 compounds (about1400 persons) per cluster. Basic information on the type of house, number ofbeds, educational status, age, sex and relationships of the residents within eachcompound were recorded. Meetings were held in each of the 10 paramountchiefdoms which comprised the study area to explain the design of the study andto demonstrate the use of the bednets to the community. The chiefs, elders andthe general members of the community were present at 21 such meetings held allover the distr ict. Open ballots were conducted to randomly select the clusters toreceive impregnated bednets.

The nets which were brown, rectangular in shape and of four sizes (single,double, family and extra large) were prepackaged for each compound, based onthe number of sleeping rooms, women of child bearing age and children under10 years of age. Init ially nets were not provided for men, but this was laterfound to be necessary to ensure nets were not diverted to male use. The commu-nity provided volunteers to carry the bales of bednets from one compound toanother as well as clean buckets of water for the impregnation. The bednetswere handed over to each adult member of a compound in the area randomisedto receive bednets. A field worker measured 15 ml of permethrin (50% EC,Zeneca, UK) into a plastic bowl and added 500 ml of water per bednet to attaina target dose of 500 mg/m2. The impregnation of the bednets was carried out byeach bednet recipient, and the field worker demonstrated the proper hanging ofat least one bednet in each compound. Re-impregnation of the bednets wascarried out every 6 months at three subsequent vis its to each compound. A totalof 31 100 bednets and 2065 1 of insecticide were provided free to all participantsover the 2-year period of the trial. A randomly selected 5% sub-sample of thecompounds were visited at night to monitor the correct use of the bednets. Nofurther health education messages were provided during the trial on how to usethe bednets.


4/11

232 F.N. Binka et al. /Health Policy 41 (1997) 229.. 239

2.3. Costs

The costing of the intervention was carried out under three main activi tysub-heads: community mobilisation, bednet distribution and initial impregnation,and re-impregnation [13]. Research costs were excluded. Each activity had a leaderwho kept a log of each person, his grade and the amount of time spent each dayon specific tasks. Project staff costs were calculated based on gross salaries (whichincluded social security contributions by the employer). The number of volunteerman-days was assessed on the basis of the average number of compounds each fieldworker covered in a day. Total volunteer man-days were valued by applying theaverage daily national minimum wage for the period. The distance covered byvehicles was recorded on specially designed forms and the total cost at theNavrongo Centres prevailing (cost-covering) rental rates calculated. These ratescovered vehicle costs, maintenance, drivers salary, fuel and overhead costs. Othersupplies and services such as paper, duplicating of forms, public address system,computer time, soap and communication were recorded and charged appropriatelyto each activity.The Ghanaian economy is open, with a freely floating exchange rate. Hence thecost of the imported bednets and insecticide were converted to local currency usingthe average exchange rate for the year of purchase. Bednets were treated as acapital item and converted to an annual equivalent assuming a j-year life span and3% discount rate. The latter was chosen in conformity with recent economicevaluation practice in low income countries [2] and in the absence of any widelyaccepted alternative Ghanaian rate. Project costs were calculated in financial terms,to show the magnitude of funds required to implement the intervention, and thenexpressed as economic (opportunity) costs to permit calculation of cost-effective-ness ratios. Since effectiveness was assessed over a 2-year period to obtain asufficiently large sample size, costs (expressed in 1993/1994 prices) were similarlysummed for the 2 years.2.4. Effectiveness

Each compound was visited every 3 months to update the current status of eachresident, recording in and out migrants, deaths and births. New compounds thathad been built since the last visit were also recorded. A total of 120 key informantswere recruited from members of the study community and paid to record allpregnancies, births and child deaths in their local area. These data augmented thedemographic data collected every 3 months and facilitated checks for completenessof event reporting. The overall population, total number of deaths observed by ageand intervention group and the person years of follow-up over the 2-year periodwere calculated from the demographic surveillance system [8]. The number ofdeaths prevented by the use of the IIBNs was the difference in the observed deathrates in the intervention and control areas summed for the 2-years of the interven-tion. Discounted healthy l ife years gained were estimated by applying the locallife-expectancy at mean age of death to deaths averted.


5/11


6/11

234 F.N. Binka et al. /Health Policy 41 (1997) 229-239

GDP deflator prior to being converted to Cedis at the 1993/1994 rate of exchange.The total cost of the intervention including bednets and other capital items (whoselife extended beyond the period of the intervention), four rounds of bednetimpregnation with insecticides, and delivery to the community was Cedis139 709 382. Of the total cost of the intervention, 87% was made up by insecticidesand bednets, with bednets contributing 60% and insecticide 27%. Transportation,mainly 4-wheel drive Landrovers, contributed 6% of the costs. An average of 64project staff were engaged in the distribution of the bednets and insecticide every 6months and for a period of 2 weeks during the months of July 1993, January andJuly 1994 and January 1995. About 100 community volunteers were also involved,especially during the init ial distribution of the nets. Personnel costs made up thenext 5% of the total financial cost of the intervention. The per capita financial costwas Cedis 2275 (US $3.77).The distribution of economic cost by activ ity, for the 2-year period and in USdollars, is shown in Table 2. Economic costs are based on financial costs, but withlocal costs converted into US dollars at the prevailing rate of exchange and deflatedto 1993/1994 values by the US GDP deflator. The imputed value of communitylabour is included. The total economic cost of the intervention was US $148 245. Ofthis cost, 2% was contributed by community mobilisation, 60% by bednet distribu-tion and initial impregnation, and 38% by the three rounds of re-impregnation.Bednets absorbed US $58436 (39%) and insecticide US $63 107 (43%) of theeconomic costs.Table 3 shows the cost-effectiveness ratios. Approximately 60000 persons (chil-dren and adults) were protected by the intervention at an estimated economic costof US $1.2 per person protected per year. Among children aged 6-59 months whowere the main target of the intervention, 16 841 child years of protection wereachieved at an estimated cost of US $8.8 per child year protected. A total of 74child deaths were prevented by the use of insecticide impregnated bednets (a 17%)reduction in all cause mortality in children aged 6-59 months; RR = 0.83; 9S/oCI = 0.69,1 .OO;P = 0.05) [S] at an estimated cost of US $2003 per death averted. Onthe basis of the estimated local li fe expectancy of 57.5 years at the mean age ofdeath (1.24 years) of trial children, and applying a discount rate of 3%, each deathprevented was equivalent to 27.24 discounted healthy life-years (DHLY) gained,giving an estimated cost of US $73.5 per DHLY gained.The results of the sensitivity analysis are shown in Table 4. Increasing thediscount rate applied to costs, from 3 to 6 and lo%, would increase the total costof the intervention by about 3.6% (to US$ 153 513) and 8.4% (to US$ 160 637)respectively, increasing the cost per child death averted to US $2075 and US $2171.Reducing the frequency of net re-impregnation to once a year, at the beginning ofthe rainy season, would have very little impact on mortality reduction in the area[8] but would have reduced the number of bednet re-impregnations by 50% over the2 years, and reduced the total cost of the intervention by 25% to US $111003,giving a cost per child death averted of US $1500. Insecticide cost could further bereduced by the use of alternative insecticides, such as alphamethrin anddeltamethrin, which are both cheaper and longer lasting [14]. For example, a


7/11

F.N. B inka et al. /Health Policy 41 (1997) 2 29-239 235

Table 2Econ omic costs by activity

Activity 1993-1995 (US $) Cost profile (%)(1) Community mobilizatio n

CapitalOffice equipment

RecurrentStaff salariesVehicle chargesOther

Subtotal

61 0828

204150

2919

102

(II) Distribution and initial impregnationCapital

BednetsImplementsStoreOther

RecurrentInsecticideStaff salariesCommunity labourVehicle and motor-bike chargesOffice rentalStaff trainingOther

Subtotal

58 436 3943 058 0

4 0

18 886373215925660

48287485

89 231

1334000

60(III) Re-impregnation (3 rounds)

CapitalImplementsStoreOther

RecurrentInsecticideStaff salariesCommunity labourVehicle chargesOffice rentalOther

Subtotal

78 076 012 0

442215165

28 66011

418 2

56 035

300400

38Total 148 245 100

reduction in the cost of insecticide by 50% would on its own improve the cost perchild death averted to US $1579, and much greater reductions in insecticide cost areplausible. Costs could have been further reduced by delivering the bednets andinsecticide to central points in each village instead of door to door, and by usingless expensive means of transport. However, since these costs made up a relativelysmall proportion of total costs, these changes would have had little impact on totalcosts.


8/11

23 6 F.N. Binka et al. /Health Policy 41 (1997) 229-2 39Table 3Cost-effectiven ess ratios of permethrin impregnated bednets (July 19933June 1995)Total implementation cost over 2 years $148 245Numbe r of impregnated bednets 31 100Cost per impregnated bednet per year $ 2.4Total nu mber of people protected 61 415Cost per person protected per year $ 1.2Child-years protected 16 841Cost per child-year protected $ 8.8Numbe r of deaths averted (children 6-59m) 14Cost per death averted $ 2003Life expectan cy at mean age of death 57.5Discounted Healthy Life-years (DHLY) gained 27.24Cost per DHLY gained $ 73.5

It is important to note that the intervention cost included nets sufficient toprotect ail family members. This proved to be necessary to ensure children hadaccess to a net, elsewhere families may be more prepared to give priority tochildren. If nets were provided only to mothers and children, the total cost wouldbe reduced to US $107486, the cost per death averted to US $1453 and the cost perdiscounted healthy life year to US $53.If all the cost reducing measures are taken together-fewer nets, lower insecticidecost, and impregnation once a year-the effect is substantial. The cost per deathaverted would be US $941 and the cost per healthy life year gained, US $35.

4. DiscussionThe cost and effectiveness results were obtained under trial conditions whichsought to ensure high coverage of bednets and insecticide. For example bednets and

Table 4Sensit ivity analysesParameter change Cos t per death averted ($) Cos t per discounted l i fe

year gainedDiscount rate6%10%Net impregnation once a yearCost of insecticide reduced by50%Nets for mothers and childrenonlyNos. 2, 3,4

2075 762171 801500 551579 581453 5394 1 35


9/11


insecticide were provided free, enough nets were provided to families to ensureeveryone had access to a net, and re-impregnation was done twice a year using adoor to door delivery service. This approach to the intervention is likely to haveresulted in costs and effectiveness that were both higher than under routineprogramme conditions.Any substantial reductions in the total cost of the intervention would have to bedirected at reducing the costs of either bednets or insecticides. The sensitivityanalysis was based on assumptions that costs might be reduced in several wayswhich might not affect impact. The intervention was implemented by a researchcentre and thus was not integrated with routine health service delivery. Howeversince nets and insecticides make up such a high proportion of total costs, changesin delivery strategies would not greatly affect costs.Benefits higher than those which might be achieved in routine programmeconditions are likely to have resulted from the high coverage and compliance levelsachieved [8]. Al l compounds were provided with nets, including new ones builtduring the trial. Around 80% of nets were reimpregnated in each round. Compli-ance with using nets was high in the wet, cold season (97 and 72% of nets used theprevious night in randomly selected households visited in the first and second yearsof the trial, respectively, and 65 and 50% in the hot, dry season).Only benefits accruing to children aged 6-59 months over the 2 years of the trialand in the form of averted deaths were taken into account. Health benefits to adultswere ignored, since their nature and magnitude are not known. In this area,children are at greatest risk of malaria, and adults are likely to benefit not so muchin terms of health as in terms of protection from the nuisance of night-bitinginsects. This benefit could in future studies be included by estimating a willingnessto pay value.Because of the tria ls design, impact on morbidity could not be included as abenefit. Simi larly, the effects of the trial on reducing government and householdexpenditure on treatment, and reducing the costs of caring for sick children, couldnot be studied. Such benefits, if included, would make the intervention even morecost-effective. However, savings in direct treatment costs are likely to have beenrelatively small because of the poor access to health services in the area.Only two other cost-effectiveness studies of insecticide treated bednets areavailable for comparison, both from the Gambia. The circumstances of TheGambia are rather different because nets are widely owned and used, and the focusof the intervention was on ensuring impregnation. The most recent study, anevaluation of a national programme to introduce IIBNs, found a cost per child(under 10 years) death averted of US $1500 (including an allowance for the cost ofthe nets) [lo]. The earlier study, a much smaller scale trial, found an estimated costper child (l-4 years) death averted of US $245 including the estimated cost ofimported nets [9]. The extremely low cost-effectiveness ratio was largely explainedby the 63% fall in child mortality resulting from the trial.Further comparisons of relative cost-effectiveness are hampered by the lack ofsimilar studies of other evaluations targeted at children. Jamison [15] and the WorldDevelopment Report 1993 [2] provide a source of extensive comparisons, though


10/11

238 F.N. Binka et al. /Heulth Policy 41 (1997) 229 -239

they use the Disabili ty Adjusted Life Year (DALY) as the unit of outcome whichincludes weighting for disability and age preference as well as assuming a standardlife expectancy in the absence of disease of 84 years. Since morbidity was notassessed and the desirabil ity of age weighting is disputed [16], the DHLY calculatedhere is adjusted only for a life expectancy of 84 years. Using this life expectancy, thecost per DHLY of impregnated bednets is US $66. A recently suggested rule ofthumb is that any intervention that costs less than US $25-30 per DALY avertedin low income countries is highly attractive, and that anything that costs less thanUS $1.50 is attractive [17]. Hence this intervention as implemented, and even moreso with plausible adaptations, ranks amongst the interventions most worth promot-ing.Given the relative attractiveness of this intervention in efficiency terms, andapparent popularity amongst users, attention needs to focus on issues of financingand affordability. Bednets were not tradit ionally used in these communities prior tothe trial, but proved highly acceptable. However, purchasing power is very low, andrequiring people to pay the full cost would undoubtedly result in low coverage. Theaverage financial cost of the bednet alone (with an estimated length of life of 5years) in this study was $4.5, with $0.52 per net required for the insecticide for eachimpregnation. Total per capita expenditure on government health services in Ghanain 1996 was $6.4 [18], and a similar sum in most sub-Saharan African countries. Wesuggest that money spent on IIBNs wil l be a good use of government and donorresources. The scientific evidence currently available makes it one of the mosteffective strategies available in Africa to supplement the global effort to promoteearly diagnosis and treatment for malaria. Several options should be examined tomake the use of IIBNs affordable to most governments and the public, including:subsidised nets and insecticide; provision of IIBNs free for the most vulnerable,children and pregnant women; providing insecticide free to populations whoalready use bednets; and finally starting the programme in phases but coveringareas with highest incidence of malaria and gradually extending to cover the wholecountry.

AcknowledgementsWe wish to thank the following people, who al l helped to make this workpossible: the District Chief Executive, chiefs and people of the Kassena-Nankana

District for their enthusiastic participation in the study; the field, administrative andcomputer staff of the Navrongo Health Research Centre for the implementationand collection of the data; Dr. Moses Aik ins for his invaluable contribution inorganizing and checking the data; Messier Everest Derry and Sixtus Apaliya, theaccounting staff, for their excellent accounting records and Professor MarcelTanner and Dr Christian Lengeler for their comments on earlier drafts of the paper.This study received financial support from the UNDP/World Bank. Special Pro-gramme for Research and Training in Tropical Diseases, The International Devel-opment Research Centre (Canada), The Rockefeller Foundation, UNICEF


11/11


(Ghana) and the UK Overseas Development Administration through its grant tothe Health Economics and Financing Programme.

References[I] World Health Organisation, World malaria situation in 1993. Weekly Epide miologic al Report,

1996.[2] World Bank, Investing in Health. World Development Report. 0xford:Oxford University Press,

1993.[3] World Health Organisation, The Global strategy for malaria control. Geneva:WHO, 1993.[4] Alonso PL, Linsay SW, Armstrong JRM, Conteh M, Hill AG, David PH, Fegdn G, De Francisco

A, Hall AJ, Shenton FC, Cham K, Greenwood BM. The effect of insecticide-treated bed nets onmortality of Gambian children. Lancet 1991;337:1499 %502.

[5] DAlessandro U, Olaleye BO, McGuire W, Langerock P, Bennett S, Aikins MK, Thompson MC,Cham MK, Cham BA, Greenwood BM. Mortality and morbidity from malaria in Gambianchildren after introduction of an impregnated bednet programme. Lancet 1995;345 :479983.

[6] Choi HW, Brem an JG, Teutsch SM, Liu S, Hightower AW, Sexton JD. The effectiveness ofinsecticide-impregnated bed nets in reducing cases of malaria infection: A meta-analysis of pub-lished results. American Journal of Tropical Medicine and Hygiene 1995;52:377-82.

[7] Nevill CG, Some ES, Munga la VO, Mutemi W, New L, Marsh K, Lengeler C. Snow RW.Insecticide-treated bednets reduce mortality and severe morbidity from malaria amo ng children onthe Kenyan coast. Tropical Medicine and International Health 1996;1:13 9946.

[S] Binka FN, Kubaje A, Adjuik M, Wil l iams LA, Lengeler C, Maude GH, Armah GE, Kdjihara B.Adiam ah JH, Smith PG. Impact of permethrin impregnated bednets on child mortality inKassena-Nankana district, Ghana: A randomised controlled trial. Tropical Medicine and Interna-tional Health 1996;1:147-54.

[9] Picard J, Aikins M, Alonso PL, Schellenberg JRMA, Greenwood BM, Mills A. A malaria controltrial using insecticide-treated bednets and targeted chemoprophylaxis in a rural area of TheGambia, West Africa 8. Cost-effectiveness of bed net impregnatio n alone or combined withchemoprophylaxis in preventing mortality and morbidity from malaria in Gambian children.Transactions of the Royal Society of Tropical Medicine and Hygiene 1993:87:53-57.

[IO] Aikins MK, Cost-effectiveness analysis of insecticide-impregnated mosquito nets (bednets) used asa malaria control measure: a study from the Gambia. University of London PhD thesis, 1995.

[I I] Binka FN, Morris SS, Ross DA, Arthur P, Aryeetey ME, Patterns of malaria morbidity andmortality in children in northern Ghana., Transactions of the Royal Society of Tropical Medicineand Hygiene 1983;88:381-385.

[I21 Armah GE, Adiam ah JH, Binka FN, Adjuik M, The effect of permethrin impregnated bednets onthe activity of malaria vectors in the Kassena-Nankana district of the Upper East Region of Ghana.Medical and Veterinary Entomolog y (in press)

[I31 Phillip s M, Mills A , Dye C, Guidelines for cost-effectiveness analysis of vector control. PE EMguidelines no 3, Geneva:WHO, 1993.

[I41 Dapeng L, Deling L, Renguo Y, Peng L, Xueguang H, Aimin L, Lei W, Changyin G. Shaowen Z,Hongru H, Leyuan S, Alphametrin-im pregnated bed nets for malaria and mosquito control inChina. Transactions of the Royal Society of Tropical Medicine and Hygiene 1994;88:625-628

[I51 Jamison DT, Disease control priorities in developing countries: An overview. In: Jamison DT,Mosley W H, Measham AR, Boba dilla JL, editors. Disease Control Priorities in DevelopingCountr ies. 0xford:Oxford University Press, 1993

[I61 Anand S, Hanson K, Disability-adjusted life years: a critical review. Harvard Center for Popula tionand Development Studies, Working Paper Series no 95.06, 1993

[I71 Ad Hoc Comm mittee on Health Research Relating to Future Intervention Options, Investing inhealth research and development. Geneva:World Health Organisation, 1996.

[I81 Ministry of Health, Ghana, Health sector 5 year programme of work. Unpublished, 1996.

econ.1997.binka.healthpolicy.the cost effectiveness of permethrin impregnated bednets in preventing...

Documents