WORLD HEALTH ORGANIZATION
ORGANISATION MONDIALE , DE LA SANTE
REGIONAL OFFICE FOR THE WESTERN PACIFIC BUREAU REGIONAL DU PACIFIOUE OCCIDENTAL
UGIOlW. COMMITTEE
WPR/RC3l/26 30 June 1980 ORIGINAL: ENGLISH
Thirty-first session Manila 9-15 September 1980 Provisional agenda item 26
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CONTROL OF MALARIA IN THE WESTERN PACIFIC REGION WITH SPECIAL REFERENCE TO THE MALARIA RISK FOR INTERNATIONAL TRAVELLERS
C0ntrel of malaria was placed on the provisional agenda of the Regienal Committee at the request of the Government of New Zealand in view .f the increasing number of travellers in the Regi,n exposed t. the disease. A decument describing the present situation has been prepared by the Secretariat. In a large part of the Pacific area, malaria has never been endemic. The disease is no longer endemic in six countries or areas of the Region. Elsewhere it is still endemic to a varying degree. Where malaria was never endemic, control can be restricted tQ (1) measures preventing the establishment of a vecter population; (2) provision of proper diagnosis and treatment facilities for imported cases; and (3) advice on prophylaxis to international travellers. Where"malaria is no longer endemic, a competent malaria vigilance organization is required, to institute apprepriate measures to prevent re-establishment of the disease. Where malaria is still endemic (1) the overall risk can be reduced through the acceleration .f antimalaria programmes; (2) the risk for international travellers can be minimized through c •• rdination of antimalaria operations along common borders; and (3) protective measures can be introduced in high risk areas, for example in development projects employing imp~rted manpower. The changing distribution of malaria throughout the world and the steadily increasing occurrence of chloroquine-resistant strains of P. falciparum, make it necessary to continue the dissemination of up-to-date information throughout the Region.
WPR/RC3l/26 page 2
1.
INTRODUCTION
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Because of the increase in international travel to and from malarious areas and the occurrence of strains of P. falciparum resistant to a variety of antimalarials, notably to the 4-aminoquinolines, necessitating changes in the drugs used, the distribution of malaria has become of increasing global importance. Up to date information on the malaria situation, published regularly in the WHO Weekly Epidemiological Record, includes special information on malaria risk for international travellers. The situation, particularly in relation to the spread of drug-resistant malaria, is constantly changing. The most recent information available is provided below.
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2.
DISTRIBUTION OF MALARIA IN THE WESTERN PACIFIC REGION
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2.1
Countries or areas where malaria was never endemic
Sixteen countries or areas of the Region have never been malarious because of the absence of anopheline vectors. They are included in the list of malaria-free countries or areas regularly published in the WHO Weekly Epidemiological Record. They comprise New Zealand, the island groups commonly known as Micronesia and Polynesia, the Melanesian islands to the south and east of New Hebrides, and a few isolated islands in the Indian Ocean, with a total population of about 6 million. 2.2 Countries or areas where malaria is no longer endemic
Malaria has been eradicated from Australia, Brunei, Hong Kong, Japan, Macao and Singapore. An estimated 13 million people now live in the originally malarious districts. Although an indigenous case of malaria has occasionally been encountered, no serious difficulties have been experienced in preventing re-establishment of the disease, despite high receptivity (potential degree of transmission) and/or vulnerability to i~po~ted parasite carriers in some places. Malaria vigilance operations are a routine activity of the general health services, in some instances in cooperation with other departments. In general, a special unit exists to provide technical guidance and as,sistance in, for eX,1lmple, the continuous assessment of the malaria situation. epidemiological investigations and the application of remedial trteal!lures.
WPR/RC3l/26 page 3
2.3
Countries where malaria is still endemic
In the remaining 10 countries or areas of the Region malaria is still endemic to a greater or lesser extent. In the Republic of Korea, the risk is minimal and is limited to a remote rural area in the north-eastern part of the country, where only P. vivax transmission occurs during a short transmission season. In large parts of China, peninsular Malaysia, Sarawak (Malaysia) and the northern provinces of Viet Nam, there exists an acceptable degree of control. While the overall risk is low, practically nil in urban areas, some high-risk areas or foci may still exist, usually in the remote rural areas. Similarly, parts of other countries may be enjoying a relatively low endemicity or absence of transmission. In the Philippines, for instance, urban centres and major tourist areas are virtually, without exception, malaria-free. 2.4 Origin of imported cases of malaria
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Detailed information on the origin of imported cases is available from countries or areas in the maintenance phase, and from some projects at an advanced stage of development (see Annex 1). An analysis of the data reveals that the majority of imported cases originate in neighbouring countries and are due to border crossings for family reasons or because of better job opportunities. The latter in particular give rise to extensive movement of labour well beyond neighbouring countries; Singapore, for instance, has a large number of imported cases originating in India. The massive movement of labourers across Asia to countries in the Eastern Mediterranean Region may be mentioned in this context, although the malaria situation in the Western Pacific Region does not appear to have been affected. Other particularly vulnerable groups are the experts, students and imported workers engaged in rural development projects in malarious areas, including agriculture, the forestry and timber industry and road construction, and the more adventurous tourists. 2.5 Implications of P. falciparum resistance to the 4-aminoquinolines
P. falciparum strains resistant to the 4-aminoquinolines, commonly referred to as chloroquine resistance, were first discovered in South America (Colombia) and at about the same time in South-East Asia (Thailand). Some isolated cases have recently been confirmed in Africa, but the main foci today are the north-western part of South America and what is known as the South-East Asian focus, which extends as far west as Bangladesh and the eastern parts of India (with imported cases into Nepal) and as far east as the Western Province of Solomon Islands. This means that, in the Western Pacific Region, the phenomenon has been identified in all countries or areas where P. falciparum is still endemic, with the exception of New Hebrides. Imported resistant cases have been reported in recent years from Australia, Japan and Singapore.
WPR/RC31/26 page 4
This situation has necessitated a review of the use of antimalarial drugs. A completely revised edition of the WHO monograph on Chemotherapy of malarial is expected to be issued this year. In the meantime, the table attached as Annex 2, taken from the report of a workshop on drug-resistant malaria,2 held in Manila in 1978, may serve as a guide to the chemoprophylaxis and chemotherapy of malaria under the changed circumstances. 3. PREVENTIVE AND REMEDIAL MEASURES
3.1
Countries or areas where malaria was never endemic
In countries or areas where malaria was never endemic, the main concern is to prevent the introduction of vectors and to provide proper diagnosis and treatment of imported cases. In the broader context of vector control, anti-mosquito measures need to be instituted at international ports and airports, as well as the disinsection of aircraft on international flights. In Guam and some adjacent islands of Trust Territories of the Pacific Islands a number of anopheline species have been identified during recent years, indicating that the establishment of a malaria vector population on at least some of the islands of the non-malarious Pacific area is a real possibility. More specifically, members of the medical profession need to be brought constantly up to date in the diagnosis, prophylaxis and treatment of malaria, to enable them to deal with imported cases among visitors or returning residents and to give proper advice to outgoing residents. For the same reason, malaria should remain as a subject on the curricula of medical schools and allied training institutions. Various agencies involved in international travel could play an important role in briefing travellers on the malaria risk. 3.2 Countries or areas where malaria is no longer endemic
In countries or areas where malaria has been eradicated, preventive and remedial measures have the additional objective of preventing the re-establishment of malaria. WHO has been cooperating with Member States in maintaining adequate vigilance organizations, including the orientation of key general health services staff through their participation in
lGeneva, World Health Organization, 1955 (Monograph Series, No. 27) (second edition in press). 2World Health Organization Regional Office for the Western Pacific. Final report of the Workshop on Drug-Resistant Malaria, Manila, 23 May - 2 June 1978.
WPR/RC3l/24 page 5/6
regional group educational activities, in providing information on malaria through dissemination of relevant documentation, in the assessment of vigilance organizations, as and when required, and in the promotion of intercountry arrangements for reducing vulnerability to malaria in receptive areas. At the request of governments, WHO will undertake to certify the achievement of malaria eradication. Such a request was received in 1979 from the Australian authorities. A special evaluation team visited Australia early in 1980 to confirm the absence of indigenous malaria in recent years and the existence of a vigilance machinery capable of maintaining the malaria-free status. 3.3 Countries where malaria is still endemic
In countries where malaria is still endemic, the risk is of course related to the original endemicity and the degree of control attained in the various parts of the countries. With regard to the malaria risk for visitors to such countries, there is an obvious case for coordination of antimalaria operations along common borders. This kind of cooperation has been established between several countries of the Region and coordination meetings have been held between the countries or areas of the South-West Pacific, between Malaysia and Thailand, and between Indonesia, Malaysia and Singapore. The other particularly vulnerable groups identified in paragraph 2.4 above should be provided, wherever feasible, with information on malaria and the means of protection. The provision of adequate protection against malaria in development projects in high-risk areas would, in general, require a negligible budgetary outlay and should be made an integral part of such projects.
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wPR/aC3l/26 page 7/8
ANNEX 1
IMPORTED CASES OF MALARIA DURING 1979 AS REPORTED BY SOME COUNTRIES OR AREAS OF THE WESTERN PACIFIC REGION
Australia
Total imported cases Papua New Guinea Indonesia Solomon Islands India Others Total imported cases Sarawak (Malaysia) India Sabah (Malaysia) Total imported cases India China African countries Refugees Others Total imported cases Western Pacific countries South-East Asian countries African countries Unspecified No cases reported Total imported cases India Indonesia Others Total imported cases Thailand Indonesia Refugees India Sabah, Sarawak (Malaysia) Papua New Guinea Total imported cases Indonesia Sabah Peninsular Malaysia Refugees Africa
443 251 46 24 23 99 14 9 4 1
(57%) (10%) ( 5%) ( 5%)
Brunei
Hong Kong
39 22 5 3 6 3
Japan
23 5 8
4 6
Macao Singapore
202 87 (43%) 75 (37%) 40 (20%) 200 92 (46%) 39 (20%) 28 (14%) 23 (12%) 15 3
Peninsular Malaysia
Sarawak, Malaysia
333 166 (55%) 114 (38%) 15 7
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SUGGESTED USE OF ANTIMALARIALS IN AREAS WITH OR WITHOUT DRUG RESISTANCE (ADULT DOSE, TO BE ADJUSTED TO AGE) Areas Where chlorquineresistant P. falciparum is well established Areas seriously exposed to potential spread of chloroquineresistant P. falciparum/resistance occurring in limited foci A or B depending on the area A B Areas without chloroquineresistant P. falciparum not seriously threatened by its potential spread Chloroquine ) or ) 600 mg base Amodiaquine ) +
Type
0
f t rea tmen t
Presumptive treatment (Single dose) (all species)
SuI fadoxine ) 1. 0 ) 1.5 g or ) Sulfalene +
pyrimethamine 50-75 mg +
Primaquine 45 mg base
Primaquine 45 mg base Mass dru~ administration (Single dose monthly) (all species) Radical cure P. falciparum (0 Uncomplicated (and P. malariae) (2) Acute, complicated (3)
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(4)
Recrudescence after (1) Recrudescence after (3)
Sulfadoxine or Sulfalene 1.5g + pyrimethamine 75 mg + Primaquine 45 mg Quinine Sulphate 2g/day p.o. x 3-7 days or 20-30 mg/kg/day i.v. as indicated + (1) Quinine Sulphate 2g/day p.o. x 3 days + (1) Quinine Sulphate 2g/day p.o. x 3 days + Tetracycline 19/day/p.o. x 7 days (1)
(i)
Chloroquine) 1.5 g base or ) in 3 days Amodiaquine ) +
(H)
Primaquine 45 mg base x 1 Quinine Sulphate Lv. 20-30 mg/kg/day as indicated + (1)
P. vivax (and P. ovale)
( 2)
Chloroquine or Amodiaquine - 1.5 g base in 3 days + Primaquine 15 mg/day x 14 days (or 22.5 mg/day if indicated) In certain G6PD deficient individuals: Chloroquine or Amodiaquine 450 mg base, once weekly for 8-12 weeks + Primaquine 45 mg base (1)
Proph~laxis
for non-immunes (all species)
Sulfadoxine or Sulfalene 0.5 g once weekly + Pyrimethamine 25 mg (not recommended for prolonged use)
(2) (3)
Chloroquine or Amodiaquine 300 mg base once weekly, or pyrimethamine 25 mg once weekly, or Proguanil 100 mg daily (2) and (3) if there is no local resistance to these compounds
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