The malaria situation in the People's Republic of China

Bulletin of the World Health Organization, 59 (6): 931-936 (1981) The malaria situation in the People's Republic of China ZHOU ZU-JIE' This report describes the measures being applied to control malaria in China and out- lines the present situation in the country. In the 1940s, it was estimated that approximately 350 million people were at risk of infection and that about 30 million cases of malaria occurred annually. In the last 30 years, large-scale antimalaria campaigns have been estab- lishedand have achieved much success. In 1979, there werejust over2 million reported cases ofmalaria and approximately 64% ofthepopulation now live in areas where the incidence is below S per 10 000. However, there are still several major difficulties to be overcome, and much work is needed before the ultimate goal ofcomplete eradication of malaria in China can be achieved. Because of its extensive distribution and because a large proportion of the population has been at risk, malaria has long been a constant menace to the people of China. In 1932, the lower part of the Chang Jiang (Yangtze) was flooded, and soon after, the malaria incidence rose to 60%7, causing 300 000 deaths. Before the foundation of the People's Republic in 1949, it was estimated that 30 million malaria cases occurred yearly, that 70% of the counties were endemic for malaria, and that about 350 million people were at risk of infection.' Since then, anti- malaria organizations for control and scientific research have been established, technical personnel carefully trained, and large-scale surveys and anti- malaria campaigns carried out. However, malaria is still one of the major parasitic diseases in China. MALARIA ZONES On the basis of information obtained from exten- sive epidemiological surveys, the country can be divided into four broad zones (Fig. 1). Zone I is the area south of latitude 25 °N where Anopheles minimus is the main vector. This zone covers the tropical and subtropical parts of China, including the southern part of Yunnan province, the greater part of Guangdong province, Guangxi auton- omous region, the south-east part of Fujian province, and the whole of Taiwan province, with a total popu- lation in 1953 of 63 million (this represented 10.7% of the total population in 1953). ' Vice-director, Institute of Parasitic Diseases, Chinese Academy of Medical Sciences, 207 Rui Jin Er Lu, Shanghai, China. ' The estimated total population in 1953 was 591 300 000. In this zone, malaria has a long transmission season, lasting 9- 12 months. Three species of human malaria parasite are present, with Plas- modium falciparum the predominant species. Mixed infections of P.falciparum and P.vivax are very common, and the distribution of P. malariae is patchy.b Malaria in mountainous and hilly districts is of the stable type; in addition to A. minimus, the main vector, A.jeyporiensis candidiensis is the secondary vector, with A. balabacensis balabacensis an impor- tant vector in the jungle areas of Hainan Island. In the plains, malaria transmission is of the unstable type. A. sinensis, although found in large numbers, is a rela- tively inefficient vector. Parasite rates vary according to topography, altitude, and latitude, and children generally have a higher parasite rate than do adults. On Hainan Island, the peak incidence of malaria occurs before the rainy season, from April to May, whereas on the mainland, it occurs after the rainy season, from August to October. Zone 2 lies between latitudes 25 ON and 33 ON with A. lesteri anthropophagus and A.sinensis as vectors. This zone includes the whole of Guizhou, Hunan, Jiangxi, Hubei, and Zhejiang provinces, Shanghai municipality, the greater part of Sichuan, Fujian, Anhui, and Jiangsu provinces, the northern part of Yunnan province, and parts of Xizang and Guangxi autonomous regions, and Guangdong, Gansu, Shanxi, and Henan provinces, with a population in 1953 of 295 million, i.e., 49.9% of the total population. The malaria transmission season lasts for 6-8 months, with the peak malaria incidence occurring from August to October. Usually, vivax malaria pre- b P. ovale was also suspected of being present along the south- west border of Yunnan province (unpublished observation. 1953). 4137 - 931 Z. J. ZHOU 330 N .250 N I I I / / WHO 81913 Fig. 1. The four epidemiological zones for malaria in China (for explanation, see text). 932 MALARIA IN CHINA vails, but falciparum malaria may also have a diffuse distribution. Malaria in both hilly and lowland regions is of the unstable type. A. lesteri anthropo- phagus and A.sinensis are the known vectors, although A. minimus may also play a role in some hilly districts. Under certain circumstances, P. vivax and P.falciparum may give rise to severe malaria out- breaks. The parasite rates in hilly districts are usually higher than those in the lowland areas. Zone 3 is the area north of latitude 33 ON with A.sinensis as vector. This zone covers the northern part of China, including the whole of Shandong, Liaoning, Jilin, and Heilongjiang provinces, Beijing and Tianjin municipalities, the greater part of Hebei and Shaanxi provinces, and parts of Shanxi, Henan, Jiangsu, and Anhui provinces, and Xinjiang auton- omous region, with a population in 1953 of 186 million (31.5%). The malaria transmission season lasts for 3 -6 months, with the peak incidence of malaria occurring from August to October. Only vivax infections are prevalent. (In Yili Valley in the north-west of the Xin- jiang autonomous region, falciparum infection was reported occasionally in the early 1950s). The endem- icity is moderate or low, and malaria in the region is generally of the unstable type. In certain circum- stances, such as unusual climatic conditions or floods, severe and important outbreaks may occur. A. sinensis is the chief vector in most of the zone, with A. messae being found in Yili Valley. The parasite rates are usually below 5% with very little difference between the various age groups. The malaria-free zone includes the cold, high alti- tude area in the south-west, dry desert in the north- west and north, the loess plateau in the north, and mountainous districts in the north-east of China, with an estimated population of 47 million in 1953, i.e., 7.9% of the total population. ANTIMALARIA ACTIVITIES Antimalaria campaigns were launched in 1950, under the leadership of the Sanitary and Anti- epidemic Bureau, Ministry of Public Health. The Institute of Parasitic Diseases of the Chinese Academy of Medical Sciences was in charge of applied field research and technical guidance for malaria control in the whole country. Each province, municipality, and autonomous region has a bureau of health to lead and organize the antimalaria activities. At the provincial level, the sanitary and antiepidemic station and/or the Institute of Parasitic Diseases are responsible for technical guidance, whereas the sanitary and antiepidemic stations, under the directorship of the Health Bureau, share this responsibility at the prefectural and county level. At the people's commune level, antimalaria operations are assigned to the health centres, with the production brigades and teams, "barefoot doctors", and health aides sharing responsibility for the antimalaria activities. At the national level, the departments of agriculture, water conservancy, commerce, and chemical industry work closely together to fight against malaria. In view of the diverse characteristics of the malaria zones in the country, the strategy adopted is to eradi- cate malaria through gradual control and elimination of the disease. Special emphasis has been placed on combined measures to meet the local conditions and to reflect the different phases and progress of the anti- malaria campaign. Different measures have been taken in the various zones, according to the chief vector of the disease. (a) In areas where A. minimus is the chief vector, control measures consist of indoor residual spraying, mass drug administration twice a year, mass chemo- prophylaxis during the transmission season, treat- ment of all clinical cases, and wide use of bed-nets and screens for personal protection. In addition, in the forested mountainous areas of Hainan Island, the shrubs within a radius of 300- 500 m of the residen- tial quarters and on both sides of the streams and brooks have been cleared, to control the breeding and resting places of A. b. balabacensis. (b) In the zone where A. lesteri anthropophagus is the chief vector, control is effected by indoor residual spraying once a year, treatment of clinical cases, anti- relapse treatment during the intertransmission period, and the use of bed-nets for personal protection. (c) In areas where A. sinensis is the chief vector, the basic measures for vector control vary according to the local conditions. In some areas, insecticides are used for livestock spraying, while elsewhere larvi- cides, cultivation of rice in mud, intermittent irri- gation, pisciculture in flooded rice-fields, and improvement of the environmental conditions for larva control are used, in combination with treatment of clinical cases, antirelapse treatment in the inter- transmission period, chemoprophylaxis during the transmission season, and individual protection measures. A county is considered to have eliminated malaria when its incidence has dropped below 5 cases per 10 000 population. Antimalaria measures then involve the timely detection of residual sources of infection, radical treatment of cases and their follow- up, residual focal spraying, prophylactic treatment, and application of personal protection measures. 933 934 Z. J. ZHOU Some examples Hainan Island in Guangdong province was origin- ally a hyper- and holoendemic area with A. minimus the main vector in the mountainous and hilly regions. Since 1958, an antimalaria campaign has been conducted, with residual spraying twice yearly, treatment of clinical cases, and mass chemo- prophylaxis during the transmission season. By 1965, the malaria incidence had dropped to 0.89%. During the following ten years the antimalaria campaign was greatly reduced and the incidence rose again to 1.55%N in 1970. The campaign was reorganized in 1977, and the malaria incidence again decreased to 0.66% in 1978 and 0.50% in 1979. Miaoxi people's commune, Wuxing county of Zhejiang province, was an area with unstable malaria, where mixed infections of P. vivax and P.falciparum occurred, with A. lesteri anthropophagus as the main vector. In 1963, prior to the antimalaria campaign, the clinical incidence of malaria was 27.50/o with a parasite rate of 20.8%o (P. vivax, 69.8%; P.falciparum, 30.2%). Combined antimalaria measures were carried out in 1964, involving indoor residual spraying once a year, mass antirelapse treatment during the intertransmission season, and treatment of all clinical cases. The malaria incidence dropped to 0.57% in 1965 and has remained at a low level since then. The adult vector density was 47.8 per 100 nets prior to the residual spraying, dropped to 3.7 per 100 nets soon after the application of the control measures, and is now almost zero. Kaili county of Guizhou province was a meso- endemic area with A. sinensis and A. minimus as vectors. In 1957, prior to the antimalaria campaign, the clinical incidence among the autochthonous popu- lation was 9.4q7o with a parasite rate of 11.2%o (P.vivax 78.9/o, P.falciparum 18.4%, and P.ma- lariae 2.7%). Control measures were initiated in 1957 with indoor residual spraying once a year, treatment of clinical cases, antirelapse treatment in the inter- transmission period, and mass treatment just before the peak of transmission. The malaria incidence was brought down to 0.01 o in 1965 and 0.00407o in 1979. Pintai people's commune in Henan province is situ- ated in the dry area of a vast plain between the Huanghe and Huaihe Rivers, and was a hypoendemic area with A.sinensis as the sole vector, and P. vivax malaria of the unstable type. Antimalarial measures were started in 1974, when the malaria incidence was 4.13%o with a parasite rate of 5.18%o. The main measures were: mass mobilization to improve environmental conditions, residual spraying of live- stock sheds, treatment of breeding places, antirelapse treatment during the intertransmission period, and treatment of all clinical cases. Through these measures, the malaria incidence decreased to 2.19% in 1975, 1.40% in 1976, 0.847o in 1977, and 0.42% in 1978. PRESENT STATUS OF MALARIA The status of malaria in China in 1979 is shown in Fig. 2. According to the statistics collected through the case reporting system, there were 2 384 543 malaria cases in 1979 in the whole country,C a morbidity rate of 0.246/o ; this figure is 22.99% lower than the 3 096 240 cases recorded in 1978. In the southern part of China, blood examinations carried out in 1979 in Guangdong, Fujian, and Guangxi indicated that P. vivax had become the predominant species (64.9%), P.falciparum was next in order (35.1 1o), while P. malariae accounted for only 0.02%. In the central and northern parts, P. vivax was the only species encountered. In 1979, there were 948 counties (40.7%), with a population of 284 859 000 (29.3%), that were malaria-free; 725 counties (31.20o), with a population of 341 524 000 (35.2%), where the malaria incidence was lower than 5 per 10 000; 523 counties (22.5%o), with a population of 270 104 000 (27.81o), where the malaria incidence was between 5 and 100 per 10 000, and 131 counties (5.6qo), with a population of 74 440 000 (7.7%), where there was a high malaria risk, with an incidence above 100 per 10 000. Of the total number of malaria cases reported, 76.11% occurred in the plain between the Huanghe and Huaihe Rivers and the plain between Chang Jiang and Hanshui Rivers, an area which includes Anhui, Jiangsu, Henan, Shangdong, and Hubei provinces. However, most of the formerly highly endemic areas in the south have been brought under control. There, the malaria incidence was 5.6 per 10 000 for Guang- dong, 4.4 per 10 000 for Guangxi, 4.1 per 10 000 for Fujian, and 4.5 per 10 000 for Guizhou. In Yunnan province, however, the incidence is still higher than 10 per 10 000. Major technical problems There are still several major obstacles to the control of malaria. - The widely distributed A.sinensis is difficult to control because of its exophilic habits. - A. b. balabacensis, the important vector in the persistent foci in the forested hill regions of Hainan Island, is difficult to control. - A simple and satisfactory method for the radical treatment of vivax malaria is not available. ' Excluding Taiwan province. MALARIA IN CHINA Annual incidence t- D O El C 0.05% E 0.05- 1.0% m >1% I I C' I -11womp- WHO 81912 Fig. 2. The annual incidence of malaria in China in 1979. 935 I Z. J. ZHOU - It is not possible to trace people infected with on Hainan Island and in the China- Burma border long-incubation vivax malaria, between transmission area of Yunnan province. seasons. Many difficulties have still to be overcome and - There is a need for a simple and efficient method Many i s havestittogbeove come to control and prevent the spread of malaria due to much work is needed before the ultimate goal of com- chloroquine-resistant strains of P.falciparum found plete eradication of malaria in China can be achieved RtSUMt SITUATION DU PALUDISME EN RtPUBLIQUE POPULAIRE DE CHINE Dans des annees 1940, on estimait que 30 millions de cas de paludisme se produisaient chaque ann&e et qu'environ 350 millions de personnes risquaient l'infection. Au cours des 30 dernieres ann&es, des dispositifs antipaludiques ont et crees et des campagnes a grandes 6chelles ont ete men&es. Les m6thodes employ6es 6taient dict&es par les conditions locales ainsi que par 1'espece du vecteur et le genre d'infec- tion palustre en cause. En regle gen6rale, toutefois, les mesures de lutte comprenaient quelques-unes ou la totalite des actions suivantes: pulv6risations a l'interieur des maisons d'insecticides a effet r6manent, chimiotherapie et chimioprophylaxie de masse, traitement de tous les cas cliniques, enfin recours a des moustiquaires et a des treillis de protection individuels. Dans quelques contrees, on a en outre table sur 1'epandage de produits antilarvaires et sur l'amelioration generale des conditions environnementales. Ces mesures ont et largement couronn&es de succ6s. En 1979, il subsistait a peine plus de 2 millions de cas d6clares de paludisme et l'on estime actuellement qu'environ 64% de la population vivent dans des r6gions oui l'incidence annuelle du paludisme est inferieure a 5 pour 10 000. Neanmoins, il reste plusieurs difficultes majeures a surmonter et beaucoup a faire avant qu'ait e atteint l'objectif ultime de l'eradi- cation integrale du paludisme en Chine. 936