aoo JounuL oF THE AMERTCANMosqurro CoNrnor. AssocrluoN Vor,. B, No. 3

MALARIA CONTROL IN -PRESENT AND FUTURE

M. ZAIM

Department of Medical Entomology,Schaol of Public Health, P. O. Bot 6446-14155,Teheran, Iran

ABSTRACT. The malaria eradicatio-ncampaign in Iran, which started in 19b8,has not been able to achieve-its goals. final The technical, adminisirative, socio-economicand financiaiobstacles i"uof""a in this unfrnished task are mentioned and the-present status ofmalaria in the country ls discussed.ttis grged-that eradication policy, presently used, be substituted by malaria coniroi ptog.u*, as denned by The World Health.Organization. This would serveas a prerequisite for eventual u.u-ai"uii"" "i;;i;rii from.th^e country, in the future. Within such agreemeni,the improuement of basic freaftft servicesani searchfor better technical meansof controlling the transmission of the i"J""iio" ".. "-ptr".ir"a ". "ii"i to-achieve this goal.Intensive training of experiencedstaff, in tran, for stimulatlo" u"a p.o-oiio"-oi relevant researchand training activities in milaria control is highly iecommended.

INTRODUCTION (Dr. Gh. Eddrissian, School of Public Health, Teheran; personnal communication) Malaria is still the most important parasitic makes it apparent that more technical problems have to diseasein Iran. Annual prevalencerates average be faced in the near future. 30 to 40 thousandcases with 80 to 85% of the casesoccurring in the south and southeastern parts of the country,bounded by Jiroft ( PRESENT STATE OF MALARIA AND Province), (Hormozgan Province) and MALARIA CONTROL IN IRAN Baluchistan(Sistan and BaluchistanProvince). Iran entered the world malaria eradication Iran is an arid land of 1.6 million square campaign in 1958. The attack phase covered kilometers,extending north to the USSR and 50% of the population by 1961 and 90% of it the CaspianSea, to Afghanistanand Pakistan had entered the consolidationphase by 1963; in the east,to the PersianGulf and Seaof however, the south and southeastern parts of in the south and bordered by Turkey and Iraq the country had to be put under reinforcedat- in the west. Mountains spread in a gigantic V- tack in 1967.Since then one or two rounds of shapeover the nation. Between these rangeslies indoor-residualspraying of human and animal a high plateau where flowing waters from the dwellingsper annum, accompaniedby larvicid- mountains disappear into desert sand. The ing and active and passive case findings have mountain ranges divide the country into three continued. separateclimatic and biotic regions:the Caspian Certainly technical factors such as resistance Sealittoral; the central plateau; and the Persian of anophelinevectors to insecticidesand exo- gulf littoral and the Khuzistan plain. philic habits of someof the vectors,as well as a The CaspianSea littoral comprisesthe north- number of factors related to human ecologysuch ern slopes of the Alborz mountains and the as outdoor sleepingcustoms of people,relative Caspian plain, a narrow strip of land, forest inaccessability of some localities, reluctance of covered. with Mediterranean climate. The av- somecommunities to havetheir housessprayed eragetemperature ranges between 10'and 35'C and movementsof human populations(e.g., ref- and the average relative humidity between 70 ugees,nomads, seasonallabor forces, etc.) have andt00Vo.Water sourcesare abundant, keeping interferedwith antimalaria activities.However, the regiongreen throughout the year. inadequacy of planning, administrative short- The central plateau, situated between the AI- comings,financial stringency;especially in the borz and Zagors ranges of mountains, is very areas of training and research, shortage of mountainousin the northwestwhere the ranges trained manpower,a sharp decline in the atten- originate and is a somewhat lower desert in the tion devoted to malaria control by the govern- east. The climate is dry, with averagetempera- ment (other health problemshave seemed more tures between0' and 40'C, with hot, dry sum- urgent and more interesting and there has been mers and cold, snow-boundwinters. The few a great setback in training and recruiting young rivers originate on the southern slopes of the malariologists), and various logistic difficulties, Alborz mountains, and these, together with suchas transportation,have been equally, ifnot "ganats" (underground water sources) and more, responsiblefor not achievingbetter con- springs,provide potable and irrigation water. trol. The littoral and Khuzistan plain, The resurgenceof chloroquineresistance in to the south of the foothills of the Zagrosmoun- Plasrnodium falciparum in Baluchistan, Iran tains, has a tropical climate. The averagetem- SoprnNasnn1987 Mnllnn CoNrnor, rN Inen 393 peratureranges between 12' and 50'C. The av- Table 1. Status of insecticide resistance in eragerelative humidities range between 40 and anopheline vectors of malaria in Iran. 80%,the highest values being along the coastal Species DDT Dieldrin* Malathion plain. The coastal plains becomebroader as the ZagtosMountains lose height towards Pakistan. An. culicifacies T An. dthnli l f Recently, malaria control in most of the An. fluuiatilis northern parts of the Zagrosrange of mountains An. maculipennis + with a population of about 35 million, is in the An. sacharoui T consolidationphase. From March 1985through An, stephensi T f March 1986, out of 1,042,727slides actively or An. superpictus I passively collected and tested for the presence * Use of dieldrin in intradomiciliarysprays was of malaria parasites, in the area under consoli- phasedout duringthe 1970sand is no longerrecom- dation phase, 5,246 were positive (Pl. uiuax mended. tt 95.I%; Pl.falciparums.4Vo; Pl. malariaeI% and Verificationis required. mixed 0.5%). About 87% of these caseshave been imported into this area (Malaria Eradica- tion Unit, Ministry of Health and Medical Ed- housespraying was discontinuedfrom 1961until ucation, annual report, 1986). The area under 1967. Malathion house spraying, using 50% consolidation phase remains under entomologi- water-dispersible powder, 2g/m", was imple- cal and parasitological surveillance since the mented one to two rounds per year, starting in danger of returning malaria from in and/or out- 1968.However, in 1976 resistanceto malathion side country's endemic foci are still very great. was also noticed (Manouchehri et al. 1976). Anopheles maculipennis Meigen is the major Since 1978,the more expensivecarbamate in- vector of malaria in the Caspian Sealittoral and secticide,propoxur, has been used.It is interest- An. sacharouiFavre and An. superpictusGrassi ing that resistance to malathion in adult An. are considered as the principal vectors in the stephensidid not decreasethe susceptibility of central plateau. the larvae to malathion and temephos (Abate). The southern parts of the Zagros range of The latter compound is presently used along mountains are still under the attack phase of with oil for larviciding of anophelinepopulations malaria control. This area, with a population of in the country. about 13 million can be roughly divided into two From March 1985through March 1986,783 sections. One with a population of about 9.7 tons of propoxur were applied in one or two million wheretransmission of malaria has been rounds of indoor residual spraying per year, substantially reduced;and the other with a pop- mostly in the southern part ofthe country (cov- ulation of about 3.3 million (2.2 rutal and 1.1 ering populationof about 3.7million) to combat urban) where malaria transmission still occurs anophelinevectors of malaria.Two hundredand with varying degrees.Many of the villageswhich eighty-nine tons of DDT were also used,mostly are located in the latter area are small, well in the central and western states (coveringa scattered and relatively inaccessible with low total population of about 1.3 million), where populations. From March 1985 through March DDT resistanceis not yet a problem (e.g.,in An. 1986,out of 1,670,980blood smearstested for superpictus).Malathion (4 tons) was only used malaria parasitesin the areaunder attack phase, in northwesternIran (Moghan,East Azerbaijan a total of 20,400were positive (82.2VoPl. uiuax; Province)where An. sacharouiis responsiblefor l6.9VoPl. falciparum and 09% mixed) (Malaria maintaininga relativelysmall malariatransmis- Eradication Unit, Ministry of Health and Med- sion focus close to the USSR border. ical Education; annual report, 1986).Anopheles A total of 4,401,910liters of oil and 12,187 steph.ensiListon is the chief vector of malaria in liters of temephoswere usedin larviciding pro- the Khuzistan Plain and Persian Gulf littoral. grams in areasunder attack phaseas opposedto Anopheles dthali Patton, An. fluuiatilis James, 4,712,476liters of oil and 19,459liters of teme- and An. superpicttts are secondary vectors of phos usedin areasunder consolidationphase. malaria in this part of the country. Anophelcs culicifaciesGiles is regardedas the chief vector FUTURE OF MALARIA CONTROL IN of malaria in the southeasterncorner of Iran. IRAN The status of insecticide resistance in an- opheline vectors of malaria in Iran is given in The advent of DDT in 1943 made it possible Table 1. Anophelesstephensi was first recorded to undertakethe control of anophelinemosqui- resistant to DDT in 1957 (Mofidi et al. 1958) toes on a scale sufficiently large that it led to a and to dieldrin in 1960 (Mofidi and Samimi malaria eradication campaign on a global basis 1960).Due to this double resistance,residual in 1955.The program was definedas an opera- 394 JouRNlr, oF rHE AMERTcANMoseurro CoNrnol AssoclATroN VoL.3,No.3 tion aimed at cessationof transmissionof ma- near future due to mosquito resistance. The laria and elimination of the reservoir of infected continuation of the control program then re- casesin a campaign limited in time and canied quires new substitutes, which of course have out to such as degreeof perfection that, when it recently been very slow in coming. comes to an end, there is no resumption of Environmental management measures and transmission.The programis usuallycanied out reduction of mosquito breedingsites is of course, over eight or more years,in four phases;prepar- in the long term, the best way to control vectors atory, attack, consolidation, and maintenance of malaria. However, the high capital cost, the phases.Today, after three decadesofthis unique length of time required for completion, as well international endeavor in the field of public as the complexity of important works which health, the overall results are of great interest; require resources beyond those of mosquito- they justify the original concept and yet show borne disease control programs make these that under someconditions it cannot be put into measuresimpracticable in the present situation practice. The latter situation was re-examined of the country. Small scaleoperations, however, at the 31st World Health Assembly,meeting in are feasible and should be incorporated in con- 1978,where a revised strategy of malaria control trol strategiesand applied in combination with with four tactical variants of it were recom- other methods of malaria control. mended.These tactics ranged from reduction of In the area of biological control of anopheline malaria mortality to a comprehensivecountry- vectors certain improvements have been made wide antimalaria program. in the past 10 years. However, we are still trail- Although malaria eradication should remain ing a long way behind the progress made in the final aim in Iran due to its overall impact biological control of agricultural pests. As Bay on health and its socio-economicbenefits. the et al. (1976) and Service (1983) have already existing serioustechnical problems and admin- discussed,there are reasonsfor this. These are istrative limitations justify the replacement of mainly: eradication strategy, presently used, with that 1. The diversity "antimalaria of mosquito habitats: some of control programs". This, of mosquito larvae inhabit a variety of breeding course, would form a transitional stage toward sites at a given location, so that an effective the future launching of an eradication program. predator in one of thesebreeding sites might not Improvementsof basichealth services,promot- have a noticeable effect on the adult mosquito ing community participation, as well as finding populationas a whole. better meansof controlling the transmissionof 2. Lawal habitats are very unstable ecosys- the infection are vital in such programs. Inte- tems. This makes the study of population dy- gration of specific curvative and preventive namics of mosquitoesvery difficult. Permanent measuresof malaria control in the frameworh water constitutes only a fraction of the available of primary health care at the community level mosquito breeding sites in many localities, and may be of great value in achievingthis goal. This in those areas where water is relatively perma- can only be done if appropriate ways of manag- nent many larvae breed in side-pocketsof shal- ing control strategiesthrough the involvement low waters. of the community is properly studied and inten- 3. Mosquitoes generally have high fecundity, sive training of medical and health personnei short generation time and high dispersalpoten- are properly done. tial and not only have most establishedbiocon- Our technicalmeans of controllinganopheline trol agents little chanceto discover and respond "instantaneous" vectors of malaria are still inadequate.Vector to such mosquito breeding,but control basedon chemical insecticideshas al- man even has less time to mobilize for mass waysbeen a major techniqueto combat malaria releasethose parasitesor predators that he may in many parts of the world as well as in Iran. be successfulin rearing. However,the emergenceand spreadof insecti- 4. In generalmosquitoes are efficient coloniz- cide resistance,along with the high cost of new ers, types of chemical insecticidesand concern with 5. Mosquitoes can experience large natural environmentalpollution, makesit apparentthat mortalities. However they are very resilient and vector control can no longer be solely dependent can quickly recoverfrom such population reduc- on the use of chemicals.and alternative methods tions. Natural mortalities of immature mosqui- of control have to be developed.As was men- toes may commonly be 95% of more, yet the tioned earlier,An. stephensithe chief vector o1' number of emerging adults may still constitute malaria in is resistant to DDT, a problem. dieldrin and malathion, and the expensivecar- These life history strategies are not very im- bamate insecticide, propoxur, has been used portant in insecticidal control, but they can against it since 1978. It is expectedthat this createdifficulties with biologicalcontrol. insecticidewould also becomeobsol-ete in the Biological control tends to have been prac- SEPTEMBER1987 Mlr,lnu CoNrRol tN IRnl 395 ticed on a trial and error basis (Service1985). releasesfor immediate control. I believe this Failure to understand the complex ecology and nematodewill be of limited use in antimalaria population dynamics of pests is an important campaignsin southernIran, basedon our knowl- reason why many projects have failed or have edgeat this time. only been partially successful.So we have to go It is noteworthy that the larvivorous fish, back and start to examinethe biology and gather Gambusiaaffinis, native of the Mississippi Val- more rigorous information on population dy- Iey, was brought to Iran for malaria control in namics of our vectors before conducting a sound 1928,where it was successfullybred, introduced biological control study. These kinds of studies and establishedin many anophelinebreeding have always been neglected in the past due to sites. However, with the introduction of fast the presenceof cheap and effective insecticides. actinginsecticides the useof this biologicalcon- Of courseecological studies like thesenot only trol agentbecame of secondaryimportance and take a long time, but they also haveto be tailored was almost neglected. Although many credits to the specific local area of concern. Lack of have been given to the efficiency and adaptabil- trained manpower,especially in the area of vec- ity of this species in the past, it has its own tor ecology, in Iran (as well as many other limitations (Motabar 1978),mainly: 1) they are developing countries) make such studies very handicappedby matted vegetation at the water difficult to conduct. surface;2) it is often impossibleto maintain Researchin the area of biological control of effective numbers of Gatnbusiain running water; anophelinevectors of malaria has receiveda top and 3) some vectors breed in such temporary priority by the Ministry of Health and Medical and small bodies of water that breeding of Gam- Education in Iran, in the past few years. While busiais impossible. the study on the potential use of the larvivorous This specieswas consideredof limited use by fish, Aphnnius dispar is under planning, a rela- The World Health Organization(1985) due to tively great amount of research has been done its effects on nontarget organisms, and is no with the bacterium, Bacillus thuringiensis (H- Iongerrecommended. 14), and the parasitic nematode,Rotnanornermis Integrated Pest Management (IPM) which is culiciuorax-the two better known biological based on ecological principles and integrates control agents. multidisciplinary methodologies in developing The most famous biocontrol agent for mos- ecosystemmanagement strategies that are prac- quitoes,B. thuringiensis (H-14), is actually a tical, effective,economic, and protectiveofboth microbial insecticideacting as a stomachpoison. public health and the environment(Axtell 1979) This is one of the better new insecticidesthough is believed to be the best approach to vector it is not without its limitations. It has been used control in the future. However, it should be against certain anopheline vectors in southern realizedthat IPM is the reductionofpest prob- Iran with a very high percentageoflarval control Iems by actions selectedafter life systemsof the (Ladoni et al. 1986,Motabar et al. 1987).The vector are understood and the ecologic as well effectivenessof B. thuringiensis in reducing the as economicconsequences of theseactions have adult population, as a whole, and hence,bringing been predicted,as accuratelyas possible.Inte- down the number of malaria casesis presently grated pest management is not merely the use under investigation in lran, by using a locally of severalcontrol methodologies,but the judi- producedB. thuringiensis (H-14). cious meshingof disciplinesand control meth- Rornanomerrnis culiciuorax was also tested ods to maximize the results. So, in order to against some of the anopheline mosquitoes in accomplish this, mosquito management pro- southern Iran (Zaim et al., unpublished data). grams have to be more firmly groundedon more However: 1) the average parasitism was only sophisticated mosquito, weather and habitat 60Vo;2)the levelofparasitism fluctuated greatly monitoring and on the prediction of mathemat- between sites and treatments; and 3) it was ical models of mosquito population dynamics establishedin releasesites but causedonly mi- and the effectsof implementingvarious actions. nor reductionsin anophelinelarval populations. As a result, until more reliable. uniform and In many locations whereAn. stephensibreeds in standardsampling and monitoring methodsare water of high salinity, this parasitic nematodeis devised, it is doubtful whether much progress of no use. We concluded that although R. culi- can be made in understandingthe population ciuorax.has a role in biological control of an- dynamicsof mosquitoesand henceimplement- ophelinemosquitoes in southern lran, effective ing IPM programs.Once more, the future role long term control levels are not likely to persist and contribution of vector ecologists in such from a few artificially createdepizootics. On the programshas to be emphasized,and training of other hand, the technicalprocedures of produc- young vector ecologistshas to receive a top tion, storageand transportation ofthe nematode priority. make it costly to use for periodic innundative In conclusion.we haveto admit that we have 396 JouRNlr, oF THE AunRrceN Moseurro CourRor, Assocrerro^l Vor,.3, No. 3 not developedthe technolosicalmeans to con- erinary pests. pp. 457-479.In: C. B. Huffaker and trol malaria in all circumsta.tces.As Bruce- P. S. Messenger(Eds). Theory and practice "With of bio- Chwatt (1980)so aptly states, the general logical control. Academic Press,New york. recognition of the magnitude of our unfinished Bruce-Chwatt, L. J. 1980.Essential malariology. Wil- task,comes the understandingof pressingneeds liam Heinemann Medical Books Ltd., London, Bb4 pp. for further research into methods of malaria Ladoni, H., M. Zaim and M. control and a return to the provision Motabar. 1986.The effect of adequate of Bacillus thuingiensis on the anopheline information on many rnosqui- essentialaspects of para- toes in southern Iran. J. Entomol. Soc. Iran g: sitology,entomology, epidemiology, prevention, 45-52. treatment and control of malaria". Manouchehri, A. V., B. Djanbakhsh and R. Rohani. It is a fact that there is an acute shortage of 1976. Studies on the resistance of Anopheles ste- experiencedstaff for stimulationand promJtion phensi to malathion in , Iran. Mosq. of relevant training and research activities in News36:320-332. malaria control in Iran and in view of this, Mofidi, Ch. and B. Samimi. 1960. Resistanceof Anophelesstephensi par- training of different categoriesof medical and to dieldrin in lran. Inst. asitol. Malariol., Teheran, Iran. Publ. 6b0. health personnel and community workers is Mofidi, Ch.,B. Samimi,N. Eshghiand M. Ghiassedin. highly recommended. 1958.Further studiesof anophelinesusceptibility to insecticides in lran, result of Bosvine and Nash method. Inst. Parasitol. Malariol., Teheran, Iran. ACKNOWLEDGMENTS Publ. 585. Motabar, M. 1978. Larvivorous fish, Gambusin af- I would like to extend mv sincere thanks to f inis- A review. WHO/VBC/78-703. Dr. G. R. Shidrawi of the-Division of Vector Motabar, M., H. Ladoni, and M. Zaim. 1987.Lawici- Biology and Control, World Health Organiza- dal activity of Teknar on mosquito larvae in rice tion, Geneva,Switzerland, for critically review- fields of southern Iran. Iran. J. Publ. Health (In ing the manuscript and for his valuable com- press). ments. Service M. W. 1983. Biological control of mosqui- toes-Has it a future? Mosq.News 43:113-120. Service, M. W. 1985. Some ecologicalconsiderations REFERENCES CITED basic to the biocontrol of Culicidae and other med- ically important insects.pp. 9-30. In: M. Laird and Axtell, R. C. 1979. Principles of integrated pest man- J. W. Miles (Eds). Integrated mosquito control agement (IPM) in relation to mosquito control. methodologies.Vol. 2. AcademicPress, New York. Mosq. News 39:709-718. World Health Organization. 1985. Tropical Disease Bay, E. C., C. O. Berg, H. C. Chapman and E. F. ResearchSeventh Program Report. Biological con- Legner. 1976. Biological control ofmedical and vet- trol of vectors. 16 pp.