J WORLD HEALTH ORGANIZATION ORGANISATION MONDIALE DE LA SANT'
REGIONAL OFFICE FOR THE WESTERN PACIFIC BUREAU R~GIONAL DU PACIFIQUE OCCIDENTAL
REGIONAL COMMI'ITEE
TECHNICAL DISCUSSIONS WPR/RC25/I'D3 1 July 19r4 ORIGINAL: gGLISH
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Twenty-fifth session Kuala u.unpur 2-10 September 1974
THE CONTROL OF AEI>E3 AEGYPTI WRING AN OUTBREAK l OF DENGUE HAEMoRRiiAGIc FEVER IN PENINSULAR MALAYSIA by Weng-Hooi. Cheong Senior Entomologist Institute for Medioal Researoh Kuala Lumpur. Malaysia
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~Ckground document tor reterenoe Wle at the Teohnical Disoussions on "Control of Vector Mosqui toea of Dengue Haemorrhagio Fever".
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CONTENTS
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1. 2.
INTROOOCTI ~ ••••
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PREV'IOtJS OtJ'I'BREAJ(S ............................................... .
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PRE::3E.:tIT <XJTBREA.K ....................................... ••••••••• MOOQl1I'rO SUR'VEY ............................................... .
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TIlE CONTROL PROGRAP-1ME .....................................................
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RE:FER.E:tlC.F::3 ................................................... ......... . TABLE 1 - REPORl'S RECEIVED OF DllNGUE AND DENGUE HAFlttORRHAGIC FEVER IN PENINSULAR MALAYSIA BY THE MINISTRY OF HEALTS 1 JANUARY 1973 - 31 DECEloIBER 1973 ••••••••••••
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TABLE 2 - DISTRIBUTI<li OF DENGUE AND DENGUE HAEMORRHAGIC FEVER BY MONTH IN 1973 IN PENINSULAR MALAYSIA ••••••• 11/12 TABLE
3 - AEDES AEGYPl'I LARVAL SURVEY IN PENINSULAR MALAYSIA FOR THE PERIOD FROM 1971 TO EARLY 1974 ••••••••••••• 13/14
TABLE 4 - COMPARISON OF EARLY AND REC.I!lIT SURVEYS OF AEDES AEGYPl'I (HOUSE INDEX. ~) IN PENINSULAR MALAYSIA ••••
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WPR/RC25/rD3 page 1 1. INTROOOCTION
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Ear17 surve7s on the prevalence of Aedes aegypti in Asia were not concerned with the role it pla7ed in the transmission of dengue viruses but as a vector of yellow fever and its possible spread to Asia. As ear17 as 19l5,Stanton (1920) surve7ed a number of ports in southeast-Asia and found Aedes aegypti breeding in most of them at ver7 low levels. Lamborn (1922) searched for them in the ports of China and Japan without finding any. However, by the end of the second World War, reports on the tinding of this mosquito came from as tar north as the Ryukyu Islands and as far south as the Pacific Islands and ports of Australia. 2. PREVIOUS Ot1l'BREAKS
The first report of dengue with severe haemorrhagic manifestations in Malaysia occurred in Penang in 1962 • 1974 (Rudnick et a1., 1965). Dengue fever i taelf has been endemic for years in this country but the haemorrhasic manifestations have only been seen sporadically since 1962 with a aall reported peak in 1969 (University of California - ICMRT Report, 1969).
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The outbreak which took place between May and September 1973 had a pattern similar to other outbreaks elsewhere in Asia as its occurrence was sudden and wide-spread. It was considered to be the first serious epidemic of dengue haemorrhagic fever for the country. There were reports of sporadic cases in the first quarter of the year from Johore in the south and a sudden explosion in May in Jinjang, Selangor. A total of 969 cases were reported with 54 deaths, a percentage mortality of 5.6 compared to 8.2 in the Penang outbreak, 50% of the cases were in the age group 0-14 years. Of the 969 cases, 595 were confirmed serologically as group B virus infection and 146 of these had haemorrhagic manifestations (Lim et al., 1974). The distribution of cases and death in the different states is-gi;;n in Table 1 and in different months in Table 2. 4. MOSQUITO SURVEY
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Macdonald (1956 a, b; 1957) made a series of studies on the distribution of Ae. aegypti and its control in Malaysia. A large number of towns and villages were covered during his survey, and the results were expressed in terms of "house index" - percentage of houses posi ti ve for the Ae. aegypti larvae.
WPR/RC25I1'D3 page 2 Reoently, the Institute for Medioal Research carried out an extensive survey whioh covered more than 150 towns and villages in 11 state.. In general. the figures showed a very high index for ~. aegypU throughout the whole oountry; that for Ae. albopictus and ~ fatigana was much lower. Table 3 shows the number of towns and villages surveyed and the averase house index. of Ae. aegypti for each of the 11 states during the period 1971 to early 1974. If one compares Macdonald's results of 17 to 18 years ago with the current survey (Table 4), it will be seen that there has been a tremendous shift to higher indices. Forty seven. or 81.1%, of the 58 towns surveyed by him now show an increase in index, some rather high indeed. Improved communications (road etc.), an increase in vehicle load and movement have resulted in the spread of the Aedes into more remote towns. Increasing urbanization throughout the country has produced many more potential breeding containera, especially in areaa where the poorer olasses live in very congested surroundings and were very often piped water is not readily available. In general, the highest number of cases ot dengue/dengue haemorrhagic tever has been reported from areas with high house indices of ~. aegypti, auch as in Johore Bahru (64%), Ponti an Kechil (80%), Kelapa Sawit (70%) and JinJang (71.9%).
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THE CONTROL PROGRAMME
As soon as the situation became explosive, an emergency programme was immediately instituted with the aim of breaking the chain of transmission by vector control. Swing fog machines were purchased with special funds from the Treasury (68 fogs by the Ministry of Health and 71 by the state governllenta and local authorities) and fogging was carried out in the worst-hit areas, portable machines were used indoors and the heavy machine mounted on a land rover, out of doors. Before the swing fogs were available, DDT spraying was used. It was always stressed, however, that fogging was essentially a temporary measure and that improvements in basic sanitation and the establishment of preventive measures against the breeding sites were the long-term solution. The insecticide used wu mainly Reslin which is basically bioresmethrin, a synthetic pyrethrin. Malathion was alao used for togging. Since this was the first _Jor outbreak ot its kind, it was thought that a fairly non-toxic insecticide should be selected as the handlers had no experience with the machines and it was important to prevent accidents. Ad hoo teams were set up to deal with the emergency. A spraying team comprIiied'& public health overseer and two labourers. and at least seven teams were needed to cover 5000 houaea in five days (143 houses/team/day) by tOSSing. The anti-larval team consiated of a public health 1napector
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WPR/Rc25/I'D3 page 3 or antima1aria inspector, a public health overseer and a labourer. The team covered 75 houses per day in a house-to-house campaign by treating water containers with Abate 1~ sand granules at 1 ppm. They also explained the problem to the householders and removed unwanted containers or turned over containers with collections of water. Technical assistance from WHO was requested for the emergency control of the outbreak. Advice was given on ultra-low-volume (ULV) ground or aerial spraying. Near the end of the peak in August 1973, a ULV spray rig was brought by the staff of the WHO Vector and Rodent Control Research Unit in Jakarta, and they assisted in undertaking the trial aerial spray. A Sikorsky helicopter made available from the Malaysian Air Force was used for the first time. The areas sprayed were Sentu1, Cheras, FUdu and Arnpang, covering about 8 km 2 with an estimated population of 100 000 people. The insecticide used was malathion 8~ E.C. at a dosage of 263 m1/hectare or 3 fl. oz./acre of technical malathion. (Self et al., 1974). It was not possible to assess the actual effectiveness of the ULV spray because of the emergency situation. However, bioassay assessment using blood-fed Ae. aegypti placed in cages indoors and out of doors in one area, Sentul, showed a mortality of 21.~ indoors and 9B.7~ out of doors. The control group in the laboratory had a mortality of 7.5~. Less than one mosquito per man hour was caught with human bait. Similarly, at ground level in Serdang Bahru. where 3% malathion was used as a fog along the road, the kills were 6~ indoors and 8~ out of doors, while the mortali ty of the control group was 5~. During the same period, O. 05~ Reslin was used as a fog at JinJang and gave rather poor results. In 1974 the dosage was increased to 0.1~.
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Clean-up campaigns, usually led by a prominent citizen like the Minister, the Mentri Besar or the District Officer in conjunction with the local authority, were conducted at the same time. In JinJang, prior to the programme, the house index was 71.9%, and after two clean up campaigns and two foggings, the indices were 52.l~ in August and 58.~ in October 1973. The following activities were undertaken in 1973 and strengthened in 1974: (a) (b) Mobile vehicles of the Department of Information were used to inform the public. Circulars were distributed to private doctors and hospitals with information on typical symptoms, the collection of paired sera and the way to notify the Ministry of Health. Thousands of pamphlets were printed and distributed to the public by the Ministry of Health and the Institute for Medical Research in different languages.
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wPR/RC25/I'D3 page 4 (d) (e) (f) The Ministry of Health organized talks over the radio and on television for the schools and the public. Exhibitions, depicting the disease, the vectors and methods for their control, were held in various institutions and schools. The press was utillzed to publlcize the symptoms of the disease, to urge parents to seek early medical advice and to inform the householders of the measures they should take to control the breeding of ~ in their own homes. At the same time it was stressed that the problem was essentially one for the people themselves. A plan of action was prepared by a conm1ttee and a crash training course was conducted for all medical officers of health and health inspectors from each state and local authority. This plan of action will be reviewed from time to time. A committee was set up to prepare guidelines for vector control activities at headquarters and state levels, and for the establishment of a vector control unit in the Ministry of Health. A WHO consultant is now assisting the committee. Research activities have been intensified at the Institute for Medical Researoh with a view to obtaining a better understanding of the vector species, with partioular attention to the possibility of there being a sylvatic cycle among monkeys. The use of ULV spraying maohines, which are thought to be better and more efficient, is being seriously considered by the Qovernment as a supplement to fogging. There are existing laws and by-laws, including sections on disease-carrying inseots, in the Malaria Eradication Act 1971 which could be applied but which were not enforced in the" last outbreak. The law provides for a fine of tt'!$ 500/ = or three montha' ja.1l if found guilty of harbouring these insecta. These inolude all premises including construction sites. The law will be enforced in the next outbreak.
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Some ot the ~ate problems when the 1973 epidemic ocourred were essentially those related to: (a) Funding. This falls under the sooial servioes provided by the Government and has no measurable retums. Funds were reserved mainly for the purohase of spraying maohines, vehicles, spares, insecticides, the payment of overtime and advanoes to staff being temporarily transferred fl'CIII one state to another on emergenoy ,duty. The majority of the looal authorities had not set funds aside for this purpose as the problem was new.
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WPR/RC25II'D3 page 5/6 There was a lack of personnel in general and especially of trained staff who could supervise teams working in the field at ground level. The ad !:!2£ organization of the control teams was found to be very unsatisfactory and gave rise to many problems.
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WPR/RC25/l'D3 page 7/8 REFERENCES
Lamborn, W.A. (1922) The mosquitoes of some ports of China and Japan. Bull. ent. Res., 12, 401 Lim, T.W., Wallace, H.G., Rudnick, A. and Cheong, W.H. (1974) dengue haemorrhagic fever in Malaysia. (In manuscript) The 1973
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Macdonald, W.W. (1956 a) Aedes aegypti in Malaya: Distribution and dispersal. Ann. trop. Med. Parasit., 50, 385-398 Macdonald, W.W. (1956 b) Aedes aegypti in Malaya: Larval and adult biology. Ann. trop. Med. Parasit., 50, 399-414 Macdonald, W.W. (1957) and eradication. Aedes aegypti 1n Malaya. Experiments on Control Ann. trop. Med. Parasit., 51, 175-186.
RUdnick, A., Tan, E.E., Lucas, J.K. and Mohamed B. Omar (1965) Mosquitoborne haemorrhagic fever in Malaya. Brit. med. J., !, 1269-1272 Self, L.S., Pant, C.P., Singh, I. and Raja Noordin (1974) Ultra-lowvolume applications of malathion from a large helicopter during an outbreak of dengue haemorrhagic fever in Malaysia. Unpublished dooument WHO/VEC/74.484 Stanton, A.T. (1920) The mosquitoes of Far Eastern Ports with special reference to the prevalence of Stegomyia fasciata. Bull. ent. Res., 10, 333-344
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wPR/Rc25/I'D3 page 9/10 Table 1 REPORTS RECEIVED OF DENGUE AND D:mGUE HAEMORRHAGIC FEVER IN PENINSULAR MALAYSIA BY THE MINISTRY OF HEALTH 1 JANUARY 1973 - 31 DEClOOlER 1973
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Perlis Kedah Penang Peru Se1angor N.
2 2 60
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3. 4. 5.
15 449 (20) * 131 ( 1) 39 221 (:'1) 9 ( 2) 39 2
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Sembllan
7. Ma1acca 8. Johore 9. 10. 11.
Pahang Trengganu Ke1antan TOTAL:
969 (54)
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Deaths
WPR/Rc25;TD3 page 11/12
Table 2 DISTRIBUTION OF DENGUE AND DENGUE HAEMORRHAGIC FEVER BY MONTH IN 19r'3 IN PENINSULAR MALAYSIA
Month -January February March April May June July August September October November December TorAL
Number of cases
Number of deaths 2 2 1
8 11 12
19 17 47 405
3 8 6 14
306 76
8 8 0 0 2 54
34 21
13 969
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WPR/RC25/'I'D3 page 13/14 Table 3 A.EIES AEGYPl'I LARVAL SURVEY IN PENINSULAR MALAYSIA
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FOR THE PERIOD FRC* 1971 TO EARLY 1974 Total number of towns and vill!1es surveyed 6 8 19 15 21 12 24 11
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State 1. 2. PerU. Ma1acca Johore Negri Sembllan Se1angor
Aver!Be houle index ~~) 73.4 67.0 65.3 55.5 53.2 51.2 49.6 49.0 44.3 41.5 29.4
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6. Kedah 7. Perak 8. Kelantan Pahang penang and P. Wellesley 11 • Trengganu 9. 10.
15 9 12
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WPR/Rc25!rD3 page 15 Table 4 COMPARISON OF EARLY AND RECENT SURVEYS OF AEDE'S AEGYPl'I (HOUSE INDEX. ~) IN PENINSULAR MAr.AYSIA
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1222 Perl1a Kedah Kangar Kul1m Baling Sunge1 Patan1 Alor Setar Kota Bahru Kuala Kera1 Gr1k P. Weld Taiping Telok Anson Sungkai Ipoh Kuala Kangsar Sungai Siput Tapah Bidor TanJ ong MaUm George Town Butterworth K. Trengganu Kota T1nggi Mersing Kluang
1971-1974 76.1 65.5 25.0 53.3 60.7
32 50 2_ 24 64 32 25 41.5 44 22 48 3.8 12 48 11 20 12 28 24 52 24 8 25 33 40 10 68 70 78
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Kelantan Peru
88 72 64 60 64 56 30
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40 40 48 44 44 41.3 60.0 72 52 52 60 78 72 64 64.3 72 80 65.7 68 80 20
(after floods)
Penang
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TrenHanu' Johore
Segamat Batu Pahat Johore Bahru Malaooa, Malaooa Town Kg. Morten Bt. China
Ne(!ir1 Sembllan Seramban Tamp1n Kg. Bahru Kg.
(New V111age
47 56 62 0
Tampin) Batu Belang (TamP1n) Rembau 20 40
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WPR/RC25JTD3 page 16 Table 4 (Cont'd)
!222 NeSiri Sembllan Pecias Nota Chengkau Port Dickson Pulau Sebang (slum house) Tampin Selangor K. Kubu Bahru Jeram Kapar KaJang Port Swettenham Klang Raub Kuala Lipis Tennerloh Mentakab Pekan Bentong Banta Kuantan TanJong Lumpur, Kuantan (Fishing Village) Beserah (Fishing Village) 0 0 5 56 61.5 6 70
1271-1274 56.5 60 48 75.0 56 48 40 20 48.6 62.0 44 48 64
56
38 56.5 48.7 56.8 66
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Pahang
53 48
0 0 47 57 50 62.5 31.3
44 40 60 64 52 56 4
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