Bulletin Penelitian Kesehatan Vol. VII No. 2 Health Studies in Indonesia 1979 THE CONDITIONS OF MALARIA TRANSMISSION IN DISTRICT, AND THE RESIDUAL EFFECTS OF SUMITHION, DDT AND MALATHION

Jeffrey L.K. HII' , Michael ~acdonald~

During 1976 - 1977, the Sabah Malaria Control Programme carried out an extended field trial com- paring the residual effects of summithiona, DDT and Malathion b against the primary vector of Sabah, An. balabacensis balabacensis Baisas in . In the courseof this work and continuiting into 1978, a study was made of the conditions of increased malaria transmission in 3 areas four month after residual applications of Sumithion, DDT and Malathion. Since the findings relate to the south- western part of Sabah which suffers annual anticipated seasonal outbreaks of malaria they are of parti- cular epidemiological interest

A detailed description of the area in which nozzle tips. By using the three insecticides the insecticide trial was carried out is given in the from of emulsion (5%) it was hoped to in the earlier paper (Farid and Hii, in press) obtain a better response from the inhabitants and is therefore not repeated here. The plan and achieve a good coverage. No insecticide of the trial area is shown in figure 1. Table 1 was applied after the second cycle in Area I shows the arrangement of the sprayed areas and I1 (after July, 1977) and after the third in terms of population distribution, the num- cycle in Area 111 (after September, 1977) ber of kampungs (villages) and sprayable due to an unseasonably dry weather which structures (houses and sulapsc), entomologi- makes resumption of spraying impossible cal indicator stations and district dispensa- until May, 1978. ries. Data on the incidence and prevalence of The experimental area was divided into malaria was obtained from a longitudinal three parts: a Sumithion test area (Area I), study of persons of all age groups from 1976 a DDT test area (Area 11) and a Malathion through 1978. A general reduction in the test area (Area 111) where Sumithion SO%, number of P. falciparum cases by quarterly DDT 25% and Malathion 84% emulsifiable periods was seen in all areas. In area I1 the concentrates were all used at a target dose of drop in falciparum incidence was more pro- 2 g/m2 of the technical grade. The insecti- nounced and steady, a result that was not cides were all applied using 3 US gallons Hud- noticed in the other two areas. The decrease son X-pert sprayers fitted with 8002 HSS was noticeable in the third and fourth quarters of 1977 when transmission was expected to 1 Medical Entomologist, Vector Control Unit, De- be higher. In the fourth quarter of 1977, partment of Medical Services, , Sa- bah. P. falciparum cases reappeared in this area while the other two areas showed some improvement. 2 Senior Malaria Technician/Peace Corps Volunteer, Department of Medical Services, Malaria Contrdl By the end of 1977, the total falciparum Programme, Kuala Penyu, Sabah, . incidence in areas I, I1 and 111 were 32.6%, JEFFREY L.K. HI1 ET AL.

a. 0,O-dimethyl 0-4 Nitro-meta-tolyl, phosphothio- walled with sagolkajang branches; they are usually ate (or fenitrothion) situated on hill slopes and are close to the b 0,O-dimethyl phosphorodithioate fringe of the jungle forest or plantations of rubber. c temporary farm huts which are built before har- vesting or planting of hill rice and are usually made of local nipah attap roof and partially

Figure 1 Map of Kuala Penyu showing the insecticide trial area. (Areas 1,2 and 3 are sprayed with sumithion, DDT and malathion respectively)

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Table 1 General reconnaissance data, population and house and sulap .census for each spray area in Kuala Penyu district, December 1976

> No. of Structures Insecticide Entomology Area Population Kampongs . Dispensary Houses Sulaps Used Station

I 5524 10 1080 25 Sumithion Kiaru Kuala Penyu I I 3637 7 671 62 D.D.T. Menunggang - 111 3273 17 626 75 Malathion Menumbok Darat

13.5% and 53.9% respectively. Area 11 showed saries figure 1. a dramatic drop change in the parasite formula Case investigations were done by malaria for P. alcipamm (63.1% drop) followed by technicians and their reports were revised and area 1 (44.8% drop) one year after the trial. analyzed by the authors at Headquarters Area 111 did not show much change. No in- and district office and during monthly visits. fants were found infected in Area 11, whereas Contact surveys were also carried out at the two and three were found in qrea 1 and I11 time of case investigations. All persons with respectively. Mixed infections were more malaria were given radical treatment in accor- common in area 111 than areas I and 11. dance with age. Most of the cases were treated in the two dispensaries as inpatients, however some P. vivax and a very small number of P. falcipamm cases continued their treatment EPJDEMIOLOGJCAL INVESTJGATJONS at home. AND RESULTS Although it was considered that the trans- mission is all year round but at higher levels from August to December 1977 it was de- Surveillance and case detection tected, further transmission mainly in area Surveillance include both ACD and PCD. I from January to March 1978 when the rain- ACD was assigned to and carried out by four fall was very low (total for 3 months = 4.88 junior canvassers and they visited each house in), figure 1. During this dry season five positive within their assigned area on a monthly sche- slides were found in the examination of 70 dule. When they found anyone with fever, newhorn infants in area I table 2. No infants chills or other symptoms suggestive of mala- were found infected in areas I1 and 111. The ria, they took a blood sinear and adminis- results are shown in table 3. Investigations of tered presumptive treatment. Each canvasser these infants with positive Mood slides showed covered each of the operational areas while that one (vicax infection) was infected in mid the fourth canvasser rotated from one area January, one in early Februaru (mixed falci- to another accelerating ACD in an area report- pamm and vivax infection) and two (vivax ing a high number of malaria cases. They also and falciparum) in early March respectively. carried out follow ups of confirmed malaria The other infant (falcipamm) was an imported cases monthly and to collect as many slides case found on 7 January, 1978. The mothers as possible from fever cases. PCD was based of four of these infants were asked whether on malaria microscopy and treatment cen- they had ever taken them away from the home tres in Kuala Penyu and Nenumbok dispen- kampung only one admitted having done Table 2 Result of malaria case detection activities showing P. falciparum ratio, indigenous cases and number of heavy infections and affected age groups from July 1977 to June 1978, Kuala Penyu.

Spraying Rainfall No. of P. falciparum Indigenous Heavy infections Mixed Age groups status and Test P. falci- ration (%) cases of P. falciparum infec- quarter area parum (no. slides examined) (no.falciparum & P. vivax tions 0-1 1 1-9 10 of year cases cases)- (total infected mths Yrs yrs Onset of 19.8" I 23 57.5 (989) 23 (10) 4 (40) 0 0 12 28 second cycle (inter-monsoon) I1 0 0 (769) 10 (0) 2 (14) - 0 0 8 6 in areas I July-September I11 36 51.4 (983) 49 (24) 8 (70) 2 1 34 35 + and I1 tY '7 -l Onset of 26.9" I 23 31.5 (829) 60 (19) 25 (73) 0 0 31 42 ff .c: second cycle (northeast LI 5 29.4 (551) 12 (1) 2 (17) 0 0 10 r in area III monsson raihs) X October-Decem- I11 20 50.0 (651) 30 (40) 11 (40) 0 0 11 29g ber 1977 3 P Post spray 4.88" I 95 44.8 (1840) 169 (73) 60 (212) 3 5 87 120 (dry season) I1 19 26.0 (792) 64 (19) 15 (73) 0 0 33 40 January-March I11 23 60.5 (492) 33 (16) 7 (38) 0 0 14 24 1978

------Onset of 25.5" I 69 41.6 (1341) 118 (44) 29 (166) 2 3 53 110 third cycle (southwest mon in areas I soon rains) I1 37 15.3 (1571) 219 (33) ,52 (242) 0 11 84 147 and 11; fourth April-June I11 26 35.6 (514) 64 (25) 9 (73) 0 1 35 37 cycle in area I11 1978 THE CONDITIONS OF MALARIA TRANSMISSION

Table 3 Results of ovarian dissections parous rate 1 probability of daily survival2 and estimated life expectancy of An balabacensis balabacensis 3 from July 1977 to June 1978

Sumithion (I). . I DDT 11) Malathion (111). . Month % parous p3 O/o parous p3 % parous p3

July 1977 August September October November December January 1978 February March April May June

Life expectancy (in days)

Month Area I Area I1 Area 111 July-September 1977 5.68 8.81 7.36 October-December 5.81 24.24 5.23

January-March 1978 18.69 - - April-June 1978 7.62 13.91 5.00

Monthly samples with less than 40 mos- of balabacensis is 3 days; probabi- quitoes are not included; lities were derived from HGarrett- Jones (I 964). 2p3 = probability of daily survival with the power of 3; and gonotrophic cycle ( ) Figures in parenthesis indicate total number of balabacensis dissected.

so and she had visited another village in the I1 followed by area I and area 111. During DDT treated area (Area 11). All the five posi- the second quarter of 1978, April to June, tive cases were evenly situated in five seriously nine infants (one falcipamm and eight v9vax affected foci in area I. The possibility of infections) were found to have contracted congenital malaria was considered but no indigenous malaria in three serious foci (Ke- infant under the age of 1 month was found rukan, Menunggang and Mansud). One vivav to have a positive blood slide. case was a relapse. The indigenous cases were Continuing transmission occured in all infected from as early as late April to mid three test areas after the rains in April and June. An additional three infants were also May 1978, the highest rate occurring in area found infected in area I (one mixed falci- parum anci vivax indigenous, one vivax relapse sampling huts. However, previous data before and one jalciparum relapse). In area 111, one the trial revealed that both species prevail vivax infant case was found only. during different parts of the year, An. sun- The average age at which an infant living daicus being the predominant coastal species in area I first gave a positive blood slide during from February to June and An. Ealabacensis January to March 1978 was determined as 22 balabacensis from Aplil to llecember. It will weeks; for the DDT test area 11, the compa- be seen that rainfall has more influence on rable Figure was 33.6 weeks. Thus infants tlie balahaccnsis population during different in the test area I1 were on average 11.6 weeks parts of the year and this seasonal pattern older than those in area I when the first po- probably depends on the presence of suitable sitive blood slides were obtained. This would habitats for breeding. It is known that bala- appear to indicate that sumithion and DDT, barensis breeds in shaded pools, ground see- by reducing the mosquito population, reduced pages, wells, hoof prints; during the dry the inoculation rate and thereby affected weather these pools usually disappear and from the age at which infants were first infected. April to Juni suitable conditions usually occur It may therefore be possible to use the age for breeding. Heavy rains commenced in the at wldcl~ infants first give positive slides as third week of April (the first heavy rain in an indication of the efficacy of an insecticide. 1878 was on 17 April); by the end of May all This point would open tlic scope of carrying the wells and water pools were filled up and out longitudinal infant studies on an area basis production of iSalabacensis increased. during minor and major transmission periods. Throughout 1877 to 1978, the fall in telnpe- ratures and humidities was not significant enough to allow for the densities of 'lala- Entomological investigations. baccrzsis to drop. as these climatological va- riables did not fluctuate greatly month by The densities of ,411. balubaco~sis baluhu- mon tli. Both sunduicus and bulabarensis ccnsis were dete~niinedin splayed experinien- transmit malaria in this area and it will be tal hutb and outdoors by human bait catches seen that either one or both of them occur from 2100 to 2400 hours and 1800 to 2400 throughout the year. hours respectively. The huts were pait~cularly suitable foi the use of this method of sampling Longevity and survival rate of An. bal. bala- . as they were of the louvre-type and had two bacerzsis. window traps attached to opposite sides of Simple- age-grading using the Deteniova the walls. Indoor man-biting catches were technique of exanlining ovarian tracheation made two to five times a month while out- was used on samples of Aalabacensis popu- door catches were made two to nine times lation niontl~ly throughout the year in all a month The collected anopllelines weie iden- three test areas, table 3 summarises the re- tified as to species and classified according to sults obtained. the stage of ovarian development by ovary During the period April to Juni 1978 when dissections for parity. Exit window-trap collec- transmission was taking place at a high rate tions were also made each morning after in- by An. balabacensis balabaccrzsis the pro- door collections. Dissections fro physiological portion of parous mosquitoes in the samples age were confined to balabarensis only with dissected was 0.67, 0.80 and 0.55 in areas the ovarian developn~ent of Christopher's I, 11, and 111 respectively. On the assumption Stage 111. that balabacensis have a gonotrophic cycle Figure 2 shows the period of abundance, of three days duling this period, the proba- indoor hut and outdoor man-biting densities bility of survival through one day (p) is given of bulacacensis. No such data is available by the formula : for An. sundaicus at the respective entomo- logical stations, due to the location of the P = proportion parous THE CONDITIONS OF MALARIA TRANSMISSION

Figure 2. Graph showing epidemiological, entomological and spraying data in Area I, (Sumithion), I1 (DDT) and I11 (Malathion) in Kuala Penyu district. Sabah. JEFFREY L.K. HI1 ET AL.

Thus, from the present results, p for bala- was near 35 : 65 (309 balabacensis exami bacensis were 0.877, 0.931, and 0.819 respec- ned). This shows that, during the rainy months, tively for areas I, I1 and 111, i.e., the survival less mosquitoes leave the huts than would be rates per day were 87.7%, 93.1% and 81.9% normal solely for the accomplishment of the respectively. gonotrophic cycle These mosquitoes usually leave early for outdoor vegetation where humi- Behaviour patterns after residual spraying dity is high and temperature is low and op- timal. An. sundaicus is an early biter (1800-2000 hours) but An. balabacensis balabacensis Transmission during the dry season January is a late biter (2100-0200 hours). Spraying has to March 1978 little effect in reducing outdoor densities. At the end of the year 1977 it was postu- Both species were found to be biting outdoors lated that transmission in the trial area would when baits were present outdoors. However, be seasonal i.e. during and after the rains, as there were very few people sleeping out- and that during the dry season transmission doors at any time of the year, outdoor trans- would occur only in very few localities with mission by both vectors may not be signifi- permanent water wells, brackish streams or cant. seepage streams so that the vector mosquitoes After spraying a considerable drop in the would survive the dry spell. This view was based lethal effect of sumithion and malathion on the belief that the extreme dryness of the was observed for as long as four and three weather, especially in January to February months respectively (Hii and Chin, in press). 1978 which seriously affected the water-table As balabacensis rarely remained in huts long and ground wells, would provide an atmosphere after feeding, it might be thought that resi- whose humidity was too low for mosquitoes dual insecticides would have little effect on to survive long enough to play their part in it, but in was found that for at least two the transmission cycle. However this was not months, a high proportion (80%) that left the case. the sumithion-sprayed hut soon died. This Assuming that the rainfall in Kuala Penyu phenomenon in conjunction with a reduction was representative for all three test areas it in the biting rate, resulting in an increased was noted that transmission reaches a peak number of unfeds leaving the huts showed in January 1978 in areas I and I1 and then that presumably short contacts with the in- decreases steadily after as the rainfall increases; secticide are sufficient for effective control secondly, transmission appears to be con of balabacensis. The reduction in feeding, centratid within area I in the dry season and due to the irritability of DDT and the air- area I1 during the wet season. The last DDT borne effects of sumithion and malathion and sumithon spraying was in June to July might, in themselves, contribute to a decline 1977. The investigations during the trial led in malaria transmission from January to De- to conclusion that these insecticides could cember 1977. The repellent action of DDT have exerted little influence on the mosquito was demonstrated by the smaller numbers population after the end of December 1977. of adults obtained from indoor sprayed huts On epidemiological grounds sumithion can than from control huts (Hii and Chin, in exert good control of malaria for as long as press). four months, DDT for five months and ma- Classification of the abdominal stages of lathion three months under the prevailing con- An. balabacensis balabacensis collected in the ditions of the trial area. window exit traps during the morning catch The majority of cases during January to showed that, during the dry months of 1977 March 1978 originated from certain sections to 1978, the ratio of fed to unfed mosqui- of the western coastal areas where possible toes was about 50 : 50 (65 balabacensis exa- breeding sites of An. snrzdaicus were found. mined), whereas during the rainy months, it In Tenambak which lies north-west from THE CONDITIONS OF MALARIA TRANSMISSION

Kuala Penyu town, a village of some 650 population 208, which is 3.5 miles south of people, 207 blood slides from all age groups Kilugus figure 1, 45 indigenous cases were were examined at the Kuala Penyu dispensary found in the dry season including one vivax- during this period; 21 indigenous cases were infected infant in early March; heavy infec- found but from April to June, 15 such cases tions accounted for 19 cases but this dropped out of 214 slides were positive for malaria. down to 6 after the dry season. No mosquito Indoor and outdoor biting catches in kampung catches were done but heavy An. sundaicus houses were made in February and the man- breeding was found in brackishwater streams biting density was 0.37 sundaicus per man- and rivers in the latter part of the dry period. hour indoors and 1.15 per man-hour out- In Menunggang, population 1480, trans- doors. No balabacensis were caught. One infant mission started in early January in two wet (falcipanrm) was discovered in early March sago areas where An. balabacensis balabacen- and the number of heavy infections during sis was still found breeding during the dry and after the dry season were about equal. period. Vector density collected outdoor In Kiaru, population 480, which lies midway ranged from 0.07 to 0.35 per man-hour; no between Kuala Penyu town and Tenambak vectors were caught in indoor experimental one positive infant-blood slide falcipamm) huts. During the dry period there were 42 was obtained among 40 indigenous cases indigenous cases from 427 blood slides includ- during the dry season, Nine of these cases ing 10 heavy infections. had heavy infections including the infant. In area 111, malaria transmission was main- After the dry season 23 indigenous oases and tained at a low level during the dry season 4 heavy infections were found, a drop of (33 indigenous cases from January to March 42.5% and 55.6% respectively. Monthly indoor 1978) and no infected infants were found. hut catches were carried out in an entomolo- Slide collection was relatively low compared gical station (experimental hut was sprayed to that in areas I and 11. on 23 June 1977) at regular intervals and bet- ween January and March 1978 only one ba- Transmission during the wet season April to labacensis was found in 6 night hut cathes June 1978 giving a man-biting density of 0.02 per man After the dry season, several residual pa- hour. Three night indoor catches in kampung rasite pools were concentrated along the coastal houses revealed no biting mosquitoes. By the to inland areas (Tempurong - Mansud) and end of January 1978, airborne bioassays of in the central wet sago areas of Menunggang sumithion hut gave 0% 12-hour knockdown figure 2. However, when the soyth west man- rate and 0% mortality after 24 hours. Window soon rains began in April., a buildup of bala- trap mortality on 23 January 1978 in this bacensis population occured. Coinciding with hut also gave 0% mortality after 24 hours. this increase of vector density, a large scale The last contact biossay on 9 December 1977 transmission of vivax malaria occured in pre- gave 42% mortality. Thus it was concluded viously non-malarious areas which were kept that there was hardly any residual insecticidal under good control during the spraying phase potency of sumithion after January 1978. in 1976-1977. By the end of June 1978 In Kilugus, population 943, 34 indigenous spraying operations were almost completed, cases (including one mixed-infection infant) but this not significantly affect the epidemio- were found during the dry season in 361 logical picture during the wet period. Out of blood films collected; 9 heavy infection of 612 slides collected in Menungang during brackish pools at the mouths of four small this period there were 93 indigenous cases streams revealed heavy breeding of An. sun- amongst which four infants (3 vivax and 1 daicus close to the seashore. Previous man- falcipanrm) were found infected. There were biting density was 0.2 sundaicus per man- also 24 heavy infections. Vector density in- Nour outdoois in 'this area. In Tempurong, creased rapidly after the rains. In another JEF1:REY L.K. HI1 KT AL.

focus, Kerukan, 97 indigenous cases (in 592 the primary vector during the dry period blood slides) were found including five infants did not contribute to a high transmission (4 viva 1 falciparum); in Mansud (pupula- in the badly affected localities in area I tion: 500) there were 30 indigenous cases (in (sumithion) but high densities were mainly 275 blood slides) including one-viva-infected responsible for persistent transmission at infant. In areas I and 111 resumption of mala- the onset of monsoon rains; ria transmission was seen but at a less in- (d) recovery of vector populations after the tense magnitude compared to that in area monsoon rains following delay of spraying 11. operations was dramatic and reached a peak of 6 balabacensis per man-hour; CONCLUSIONS (e) for good control of malaria caused by balabacensis, it is advisable to spray re- Conclusions based on the results obtained sidual insecticided regularly, viz. every from this study are: four months for sumithion and DDT and every three months for malathion. (a) The residual effectiveness of sumithion was estimated to be four months after the second spraying round based on epi- demiological and entomological observa- AKCNOWLEDGMENTS tions; whereas that of DDT was four to five months and malathion three months under the prevailing local conditions: The authors wish to thank the Director (b) monthly ACD and PCD surveillance of Medical Services Dr. Mechiel K.C. Chan definitely show the pers;stence of ma- for permission to publish tlus paper Sincere laria transmission; thanks and appreciation are expressed also (c) during the dry period, secondary trans- to Professor C.Y. Chow, Dr. W.J.O.M. van Dijk, mission appeared to be caused by An. Dr. C.T. Chen, Dr. G. Farid, Dr. E.S. Theva- sundaicus in four discrete coastal areas sagayam and Mr. Y.K. Chen for their advice when indoor An. balabacensis balaba- and assistance. Our appreciation to Sumi- censis populations were as low as 0.04 tom0 Chemical Company, Japan for pro- per man-hour and outdoor man-biting viding sumithion 50% emulsifiable concentrate density were 0.1 (DDT station), 0.4 insecticides for the trial. Our thanks to Puan (sumithion station) and 0.8 (malathion Theresa Chong for her excellent typing of the station) per man-hour. These densities of manuscript.

REFERENCES;

Farid, G. and HII, J.L.K. (1978). Compa- Field experiments on the behaviour rative evaluation of sumuthion, DDT of Anopheles balabacensis balabacen- and malathion for the control of mala- sis in huts sprayed with sumithion, ria in Kuala Penyu district, Sabah. Acta DDT and malathion in Kuala Penyu Tropica (in press). district, Sabah, Malaysia. Bulletin of HII, J.L.K. and Chin Kui Foh. (1978). the Public Health Society (in press).