Filariasis and its control in Fujian, China

Epidemiological survey of filariasis in Fujian Province, China showed that malayan filariasis, transmitted by Anopheles lesteri anthropophagus was mainly distributed in the northwest part and bancrof­ tian filariasis with Culex quinquefasciatus as vector, in middle and south coastal regions. Both species of filariae showed typical nocturnal periodicity. Involvement of the extremities was not uncommon in mala­ yan filariasis. In contrast, hydrocele was often present in bancroftian filariasis, in which limb impairment did not appear so frequently as in the former. Hetrazan treatment was administered to the microfilaremia cases identified during blood examination surveys, which were integrated with indoor residual spraying of insecticides in endemic areas of malayan filariasis when the vector mosquito was discovered and with mass treatment with hetrazan medicated salt in endemic areas of bancroft ian filariasis. At the same time the habitation condition was improved. These factors facilitated the decrease in incidence. As a result malayan and bancroftian filariasis were proclaimed to have reached the criterion of basic elimination in 1985 and 1987 respectively. Surveillance was pursued thereafter and no signs of resurgence appeared. DISCOVER Y OF FILARIASIS Fujian Province is situated between II S050' to 120°43' E and 23°33' to 28°19' N, on the south­ east coast of China and belongs to the subtropics. The area is nearly 121 ,300km2, with 80 counties or cities subordinate to 9 regions. The population of Fujian was about 27,490,000 in 1987. From the 1950s a thorough investigation was made of the epidemiology of filariasis in the province, followed by mass treatment and by 1988 the disease had been basically eliminated in Fujian. Filiariasis in China was first discovered in Fujian. The first elephantiasis of the scrotum was reported by Manson (1872) in Xiamen, in the south of Fujian. In 1876 he found the micro filariae of Wuchereria ban ero/t i, the microfilarial sheath (Foster, 1956) and the mosquito intermediate host (Service, 1878), while in 1880 he also found the female adult of W banero/ti from the Iymphocyst in a patient. The following year he and Remine confirmed the nocturnal periodicity of microfilaria in Xiamen and Fuzhou (Rennie, 1881). In 1889 Manson carried out an autopsy of a person who had committed suicide and had a high density of microfilariae circulating in the blood at night time: he found I male and 16 female adult filariae in retroperitoneallymphocysts and a lot of micro­ filariae in pulmonary capillaries and glomeruli at 8.30 am (Sasa, 1976). The first Chinese patient with malayan filariasis who came from Zhejian province was reported by Feng (1933) in Xiamen. The Fujian malayan filariasis was found by H u (1937) in Fuzhou. In 1948 Chen also found malayan filariasis in Nanping in the north of Fujian (Chen, 1948). In 1953 pure malayan filariasis endemic areas were discovered by Tang et al (1956). In 1958 the distributions of the two types of filariasis were confirmed by thorough investigation. In the fifties it was confirmed that malayan filariasis only produced elephantiasis of the limbs, .especially the legs (Xia et at, 1960). The morbidity of malayan filariasis was higher than that of bancroftian filariasis and the clinical manifestations of the two filariases were different (Fujian Anti­ Epidemic Station, 1959a). The two kinds of micro­ filariae in Fujian exhibited nocturnal periodicity. It was confirmed that malayan filariasis was transmitted by Anopheles lesteri anthropophagus in the 1970s (Liu et aI, 1981). Vol 22 No 2 lune 1991 147 SOUTHEAST ASEAN ] TROP MED PUBLIC HEALTH GEOGRAPHICAL DISTRIBUTION There are thus two types of filariasis in Fujian province. In the hilly and mountainous regions such as Nanping, Shamming and Longyan, including 24 counties or cities, the northern and western parts of Fujian, malayan filariasis is widespread. The size of the region is 42.6% of the whole province and it has enormous areas of rice fields. Bancroftian filariasis is found in the plains of the coast, islands and other places less than 200 meters above sea level, including 27 counties or cities situated mainly in the central and southern parts of the province, the area of which is 11.4% of the province, but the population is concentrated. The other 29 counties comprising 45.2% of the area were found to have both types of filariasis and double infection was characteristic in people of some villages. There was no filariasis in Zherong county which is higher than 700 meters above sea level, nor in the region between the two types of filarial areas and south of the entrance of the Minjiang River. The size of these areas is only 0.8% of Fujian province. The distributive area of malayan filariasis is 70.4% of the whole province, but the bancroftian filariasis endemic area is in the high density population regions so the numbers of people threatened by the two types of filariasis are about equal.