WORLD HEALTH ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE
REGIONAL OFFICE FOR THE WESTERN PACIFIC BUREAU R~GIONAL DU PACIFIQUE OCCIDENTAL
RIDIONAL COMMITTEE Seventeenth Session Manila 21-27 September 1966 Provisional agenda item 15
WPRjRC17/8 1 July 1966 . ORIGINAL: ENGLISH
THE EPIDEMIOLOOY OF FILARIASIS IN THE WESTERN PACIFIC RIDlON 1
IN'mODUCTION
Filariasis is a major public health problem in many countries 'With an estimated 200 million infected people throughout the world. In the Pacific areas the disease is common in all tropical and sub-tropical islands. Rapid urbanization has created favourable conditions for the breeding of Culex pipiens fatigans, the most 'Widely distributed vector of Wuchereria bancrofti. In developing countries, large-scale water development schemes are also likely to change environmental conditions and have considerable impact on diseases such as filariasis. Nocturnal periodic W. bancrofti is present in most of the countries reviewed below, except in the Pacific 'Where diurnal sub-periodic W. bancrofti is the usual form. The vector of nocturnal W. bancrofti in all such area·s is C. pipiens fatigans but anophelines are important vectors in rural areas, 'While in the Philippines, Aedes Finla a oecilus is also a vector. The diurnal form is transmitted principally by Ae. Stegomyia)eolynesiensis, and related species such as Ae. (F.) samoanus and Ae. fijiensis play an important part in some localities. Brugia. malay! is restricted to Asia and occurs also in two forms, the nocturnal periodic which is present in Japan, Malaysia and Republic of Korea, and the sub-periodic nocturnal, B. malsyi, 'Which is present in Malaysia and the Philippines. The vectors are usually the Mansonia speCies, but anophelines and Ae. (F.) togoi transmit the nocturnal periodic form in scme countries. 2 FILARIASIS IN THE WESTERN PACIFIC RIDlON
A brief review of filariasis in certain countries and territories in the Region is given below. 2.1 American Samoa Diurnal sub-periodic W. bancrofti is present. In 1948 a micro-filaria rate of ~ was found amongst 753 people examined. Control measures using drug treatment and insecticide spraying have been undertaken. /2.2 British
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WPR/RC17/8 page 2 2.2
British Solomon Islands Protectorate
Nocturnal periodic W. bancrofti is present. In 1965 the micro-filaria rate was 14~ amongst 475 persons examined in Guadalcanal. The vector is the Anopheles punctul.a.tus group. 2.3 China (Taiwan) W. bancrofti is endemic in China (Taiwan) but B. malali has not been tound amongst the native population. The micro-filaria rate of nocturnal periodic W. bancrofti was 3.~ amongst a total ot 85 817 people examined in the period 1951 to 1957.
2.4 Fiji The micro-filaria rate of diurnal sub-periodic W. bancrofti varies from
2 to
25~.
2.5 French Polynesia Diurnal sub-periodic W. bancrofti is present. Of 25 623 people examined in Tahiti in 1964, 6.8% were micro-filaria carriers. 2.6 Gilbert and Ellice Islands Nocturnal periodic W. bancrofti occurs in the Gilbert Islands, while sub-periodic W. bancrofti is present in the Ellice Islands. Of 3695 persons examined in the Ellice Islands in the period 1956 to 1960, 25~ were positive for micro-filaria. 2.7 Japan Filariasis has been known to exist in three of the four main islands. Nocturnal periodic W. bancrofti exists in most Of the areas, except in the Izu Islands, which is a small endemic area of nocturnal periodic B. malayL Out of a total of 1 401 250 persons examined in the period 1962 to 1965, 29 418 had micro-filaria. 2.8 Ma.laysia A lot of research work has been undertaken in Malaya, where filariasis is due mainly to B. malayi, while W. bancrofti is only of minor importance. It is estimated that 350 000 people live in B. malali endemic areas. Two forms of B. lII81ayi have been recognized in Malaya. A focus of the nocturnal sub-periodic form of B. malayi has been reported from Sabeh. 2.9 Philippines Nocturnal periodic W. bancrofti has been known to exist for many years but the occurrence of nocturnal sub-periodic B. malayi has only been recently confirmed in the Philippines. Amongst 247 823 persons examined in 1959, the average micrO-filaria rate of W. bancrofti was 4.4~. /2.10 Portuguese •••
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WPRjR C17/8 page 3 2.10 Portuguese Timor ~arbirostris
Of 3350 persons examined in 1956, 2<{o were positive with B. malay!. is suspected as a vector.
2.11 Republic of Korea Nocturnal periodic B. malayi is present, but there is no evidence of the occurrence of W. bancrofti. Amongst 2139 persons examined in Chejwao in the period 1964 to 1965, S.6% were found to be micro-filaria carriers. 2.12 Republic of Viet-Nam Nocturnal periodic W. bancrofti is endemic. 2.13 Ryukyu Islands Nocturnal periodic W. bancrofti is present. The average micro-filaria rate was 14<{o amongst 51 022 persons examined. The GovenllIlent started a. control project at the beginning of 1965 with the assistance of the GovernIt is reported that satisments of Japan and the United States of America. factory results have been obtained. 2.14 SingaPore Nocturnal periodic W. bancrofti is present to a small extent. 2.15 Territory of Papua and New GUinea Nocturnal periodic W. bancrofti is present. 2.16 Tonga Only diurnal sub-periodic W. bancrofti is present. vector. 2.17 Trust Territory of the Pacific Islands Nocturna.l periodic W. bancrofti is present. examined in Truk, the micro-filaria rate was 1410. 2.18 Western Samoa Diurnal sub-periodic W. bancrofti is present. Amongst 219 persons examined in the period May to June 1964, the micrO-filaria rate was 20<{0. A filariasiS control pilot project, with the assistance of WHO, UNICEF and the Phillips' Bequest of New Zealand, was started in July 1965; activities are based mainly on mass drug distribution. In 1965, of 600 persons Ae. tOngae is the
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CONCLUSION
WPRjRC17/8 page 4
3
CONCLUSION
Although studies on the epidemiology and distribution of filariasis have been undertaken for a considerably long period in many countries and territories in this region, control programmes are slow in developing. In November 1965, WHO sponsored an inter-regional seminar on filariasis in Manila in order to discuss the epidemiology, the methodology of epidemiological surveys, the various methods of' control avaiJ.able, the training of personnel, and the ways and means of achieving a better co-ordination of filariasis activities.
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