Which strategy for malaria control in Africa?

Letters 5 Snow. R.W. and Marsh. K. (I 995) PnrasttoL Today I I, 188-190 6 Trape,J-F.and Rogier,C. (1996) Parasltol. Today 12, 236-240 7 Curtis, C,F. (I 996) l~'0p.A4ed.Int. Health I, 137-13~ 8 Trape,J-F.etaL(1987) Trans.RSoc. Trop. Meal. Hyg. 8! (Suppl. 2), 34~.2

9 Snc.~v.,:LV\Lec al (I 984) Acta Trap.57. 289-30zj 10 Lenoaeler,C. et ,:!1.{ 1995) Parclsltol Today I i. 425 I I Greenwood, B.M. et uL ( 1991) Paras~toi.Today 7. 277-281 12 Unes.J. andArmstrong. J.R-M(1992) Para.tcl "today 8, 381 .-383

A Call for Integrated Approaches to Controlling Malaria Jean-Franqo~sF,'ape is to be congratulated on yet another outstanding large-scale population-based study on malaria epidemiology I. Such information helps to ~-ationalize data From numepous studies and helps focus on real issues concerning malaria control. Hi.= analysis of the situation in Senegal, companng the pro_valence of illness and severe disease under differing conditions of entomological inocu!alic,n rates, draws attention to two f"~c~'s.Fir,t, the epidemiology of severe malaria along with incidence of clinical conditions is complex, and is dependent upon intrinsic and extrinsic n'lechanisms aff'ecting humans and mosquitoes. Second, although there is implication of a ~,'ooleapproach to malana control, etTect~vecontrol of malaria cannot depend on a monob'pic "-t:~eg'/. It ~sthis second point I would ',ike to emphasize. There is a dan~er in focusins on a monotypi~ approach. Cleady, reducing tran~nlission in reriain situations, as a result of sporadic and short-term interventior,~ using ir,secticide-impregnaL~.d bednets (IBNs), has caused reduction in many indicators of ma!ana disease, )ut r,~ euede~ whether Iong-teFm effe~s would be

:ustainable, bearing in mine the changing immunological patterns in tile human population that may result from r.'ducing transmisslon. Ar important conclusion From his work is that control of this disease should now pass from the expenmer~tai to the functional; instead of being ~n the hands of agencies and organlzations with numerous scientific agendds, it should move to a stage of national planning in those endemic countqes wher~ malaria cor, trol ,s a h~gh pnorlb,. The proce.~s should become a national concern. Those of us who have run ;.0tional pr-_gmmmcs know that there musL be a plan of operations based on demographic. epidemiolo~:r~l and economic conditions. and the com~onents of the intervention must combine e~'~c~tivecase detectloq and treab~ent with vc,:~r co~rol and reduction of t~nsmisslon. To find evidence of programmes that involved vector control and effective treatment, and data on their successes one should look into the past to see U-,e long-term effec:s of such integrated activities. Apar~ From many other parts of •~he world, malaria has been effect~veiy

Which Strategy for Malaria Control in Africaf Can malaria mortality be decreased in tropical Africa by vector contr~,, • -~? Th e answe~ is 'yes' il we consider tne short-term impact on mortality of direct intervent, ions, such as ilouse spraying or i,-npregnated bednets, which have decreased malaria transmi~ic~n I-I~wo,,~. :~ ~he answer is 'no' if we consider the results oFepidemiological studies which have c,)mpared malaria mortality rates between populations exposed to significantly difl'erent intensities of transmission. My belief is that the conb'adiction is only appa,~, t, each approach revealing dilTe~nt but complementary aspects of the complex host/vee:or/paras~te relation! hip in malaria, arid that intervention tr, als p,: ~cipally measure a short-term effect, :vhereas epidemioiogicat studies better reflec the equilibnum that results from the Parasito;o~ Today. vat 13. no. 2 I ~97

devaiopm~'qt of pren,un,t,on'. S,nce fluctuations of U~nsmission rem~ir, associated with fluctuations of mo/oidlty and mortality whatever the epidemiolog~ca~ context,, the short-torah Follow-up of interventions that ciccrease transmission d-'_cc ~:.:t 7.c.,-~.~itthe pred,~ inn of" the future evolution of mortality, whereas epidemiological analysis does pen'nit prediction of the ~rong trends nf this evo!utlon. In most epidem~o!oglca! contexts oLse~ed in tropical Afnca, even a substantial reduction in transmission cannot significantly reduce the burde~ at ma!3da For the who!e community I. NeveI~hei~ss, can impregnated bednets contribute to malana control in Afnca! Br,~,~ Greenwood (th~s issue:) present°, a series of a~gumen[S in Favour of cont:n:;in~ impregnated bednet programmes.

U m ~ r t o ID'Ai~J~..'~h'o Mare Co~:~rn~ns Depan.,,'aentof Paras,!4,1oEy Pr:ns Leopoid Institut voor TI-O~_~sche C,eneeskurde Nat~0nalestraa~ B-20OOAntwetp Be;g~um

controlled in numerous African countries, For example (among oth~.~3'/Swaziland, Ea.~tem Transvaal, Zimbabwe, Zambia and Zanzibar• The programmes u~.ilizedboth arms of the ~ntervention and were considerably., uccessrul. Thus, as transmission pattems declined and when clinical cases became evident, adequate drug suppl:c~ were available in rura; c!inics. and chemotherapy prevented an upsurge in severe, malada. Many such orogrammcs are still in force, o~ers w~.re, disbanded because of co~; however, they demonstrate that the concerns raised by Trope ~ can be surr4ou~ted it, :~ nationally planned, integrated strate~f. We ~,hould be careful ~o consider his excellent present~t,on of data is it should be seen, a call for integrated approaches to controlling malaria, and not as one may fear. ~mmunition for those who consider diagnosis and b-eatmefit as the main vehicle for malatia con*o~l and may propose, heaven forbid, a decli;~e back to tactical variant no. I of the W H O (1974), I~efe~m:es

I -I~pe, j-F.and Regier.C. ( 19961P~,as~.o! ;ada/ 12, 236-240 ¢llve S ~ I f f School c' Hygiene and Public H~.alth jo~'nsH.- pk~n:.Unlver~P,y 615 Notch WO;/~:Street, Bal*imore MD 21205• USA

t iL'ewise. C,~ris'tian Lengeler e.' aL (above), and Umberto D'Alessa'~d,:~ 2nr~ Marc Coosemans (above) believe that the evidence accumulated so lar s nCt su~cient to wan~nt aDandonlng tiyese plo~lJn~r4es. Their a,~uments have welght: t~-,e irr.mediate benefit is ndisputable, some medium- or long-ten:, beneh~ • ,-:main possible. Vane could refuse to try to save the iives of 5 0 0 0 ~ African children ea~, year=? Idea!!y, any strategy of malaria centre! must aim at optimizing a series of actions co.'ceming: (I) patient care (health education at the comm~,n~y level for a suitable a~itude tow~.-d disease: network of" health structbres: availabii~ty of personnel, equipment ar.d drugs; adequate decision making and therapeutic schemes): and (2) disease preven.~ion, of vJhlch vector control is on~ of the major components. Theore~ic.ail)',tnes~~.vo cateo~o,'iesof measures are ccmpl~mentary, ~r~d they slner~:.ize ~n are.o cf :n~abi,." ~ ~laria Hnwevel. in the context. 3i t,opical A~,6ca, 12S

Letters where malaria is stable and resources are limited, we believe that a choice has to be made, because the pctent,al b~nc.£t~ ~ these b,~'o categories of measures ai'e [oo different to justify the dissipation of effort. In tropical Afd~a. child mortality ha~ decreased considerably over the past 30 years. At the beginn~n~ of the 1960s. neady four children out often died before their fi,~h birthday: Nowadays, )n most of Africa, eight or nine children out of ten r'each the age of five years. The building of dispensaries, and the availability of vaccination, health education and schoollng are the main reasons for thi~ rapid progress in the space of only one generation. Thus, in tht 1°80s malaria mortality was almost totally supp~vssea in entire regions of the Congo ~ s Kenya% Senegal ~ and pnabably of numerous other countries of tropical Africa. This was airnost entirely due to the widespread use of chioroquine for treatment c4 fever ca~es, in particular by sel~.rr~atrr, enL There was no reduction of mal~,la transmission levels. Ev~;- if. at present, malana mo~ta!ity is gceatly increasing because of drub resistance (J-F. Trape et a;.. unpub!ished), in my view this cleady shows tha~ in a,~as o( stable malada, action against human-vector contact could have only a minor effect ':omoared ~o that of patient health care. In a recent vaccine thai in The Gambia e. biweekly home visits for clinical monitoring have probably reduced child mortaEty b;* >90% despite the lack of efficacy of" [he

tested ', accine. No particular medical follow, up was planned for most bednet tff2!.~, but the occasiona! r, re~encc o; me,bile research teams may have saved many children. Since Ross and Gray,i, it has been demonstrated many d~,e~ that using a bednet could p~ 3toct !:,eeple against malaria infection. Yet, except in China, ~his effective to~,l of individual protect,on has never been able to constitute an el~cient tool of malaria centre! at the community level, even in areas of instable malaria where the use o1" bednets would have rapidly reduced the human vector contact to a level lower than the crucial threshold of malaria transmission As stressed by Clive Sh,ff (above), in areas of instable malana of Europe, Asia, Amenca and southern and northern Aflica, it is inte~rateci conlrol that has pertained the suppression or s~gnificant re_dJction in t'~,e burden of malana 9. Vector control was only one componenl, arid not always an essentiel one. It was malnly basec" on house spraying (and initia!ly on a v:,rlety of measures such as larviciding, elimination of b'eeding olaces, and improvement of hou~.ing), and not on bednets. In these regions, imprc,wng conditions of diz~ct treat ment of c inical cases has pem~itted the ¢ontinuin~ reduction in nlalai-ia morality, despite the rapid development of high levels of dP..;~ resisidnce. Unfortunately, the e
inapplicable until new control tools and economic development cur,verge. For the i~:t ",or;t, '~¢~. must make the best of the limited res~,rces that ,:an be obtained for

malaria control. To p:ornote the use of impregnated bednets would requ.-e, without any clear expectation l'or long-ten'n efficacy, a considerab!e effect aimed at radically and clurably changing the behaviour and daily practices of African people in a domain where no major or immedi:.~e stake is generai!y felt by these popu!atlc, ns. We believe that the search for efficacy requires us to give up this dubious , ".mbat, and ,nstead concentr-ate all ouF efk,;*,~ , ~ ,mp*c,,4,;g mecical care for p:ltlents.

References I Trape. I-F. and Rogle,-. C. (1996) P(~r~s,ml Todnv 12.236 ~40 2 Anon. (1996) TDR New:, 50, 1 2 3 Carme. B. et ¢II. (1954) ~dl ~oc P~ilhol Exot. 77, 104 114 4 Trape, J-F. el ~J! (1987) Trot:s, R. S0c. TIop IVied. Hy 2 81 (5uDpl. 2). 34 42 5 Carme, B. (1996) P~Ic~sR01.Todc~y 12. 200 208 6 5p~i~cer, HC. et n,' (1987) .Ann. Trap. iVied. Pnms~toL 81 (Suppl. I). 36.45 7 Pison, G el al. (i993) Int.j Epiden!~ol. 22. 72-80 8 D'Alessandro. LJ. et ~ (1995) L~mcet 34& 4e2--467 9 Coiuzz,. M. (I 992) Fclras,~r¢ Ys:/,~y8. I 13 I 18

Jeen-Franfols Trope Laboratoi,e de Paludologie, ORSTOM 8P 1386 Dakac. Senegal

The IDRC/TDR 1997 Award cm Gender and TropicaJ Disease,s Call for Entries on 'Gender Issues kl the Operationalization uf Bed.et Use' This CSS000 award is jointly spor~mred by Canada's Internadoral Development Research C~nrre (IDCR) &~d the WHO's TDR. C ~ - ~ , as d|~lnct from 'sex', refers t~ the socioculmral aspec~ of ~ ..n~in-female dichotomy, whereas sex ~e¢,oces its biological IP-~i,. G ~ l e r r ~ . ~ to qualities, behaviour~ and roles ascribed I~ ,lllferent societies ~o women and to men, Pyredvold-~ted bednets prevent s~eepir~ children from beitlg bitten by mosqu~oes, resulting in a dramatic reduction ;n deaths from malaria in children unge; five years old (by one.third In Kenya and by one-sixth in Ghana). There i_• a need now to ~plore d ~ be~ n~hods for i ~ t i n g wtdespre~ .~nd effective use of hc~ets under different socioeconomic conditions, and guaramentn¢ I ~ p t e r m ir~,k~tenp.~ce. Gender issu~ will be an important factor in thi~, including: • i-lous~,.~ld Info~rn~,~. ~h~r~n~~a~ur t~e positive aq~--~ of b ~ m ~ use, • P~ re~fions influ~cing deci:~on.mak~ng on purchase, dlpptt~ and net rnalntenance. • P r ~ v e dfects of bedn~. ~me for pr~nanc w o ~ . •~ of L ~ r differences in th~ control Of hou.~eh~ld ir~:o,-~e ~nd in the u,Jlizadon of bednets within the household. (NB ~xcitil~ r~N contributions on issues of sex that rela~ to the topic are also acceptable, providin~ these have clear implications Pa~rs ~dlou!:loErer a critical re~ew of current kav.-wled~: on the chosen t~ic~ and should focus on practical disease-control iUu.~. They must be orkjinal (le. not ~ l l t , hed elsewbe~a), may b~ I ~ on ~:ond~ry s o u r c e s o r original research, and will provide a basis for future research ~at could be supported by t~e IDRC or the TDR. .P~I~.~s may have more than one author, and wevk~s winne~ =-fan IDRC/TDK A~rard are not eligible. Entries (in English, Sp~.nlsi~ or French. Of no¢ more than 30 paps ~( A4. double.-~F~ced type) should be submitted by 30 September 1997 to: Dr Carol Vlassoff, Hanaxer, Gender and T,ml,~al C~lsec%~sTask Force, TDR/WHO. 12 ! I Gepav~ 27, Switzerland. (k would be helpful tf luchors pl~i~l~ to ~ i t a ll~,~er would inforn'~ Dr .~ssoff w~gl in advance of the deadline.) The ~ n n e ~ wtil ~ announced in November 15"97

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