The control and surveillance of filariasis in Hainan Province, China.

Hainan is a single bancroftian filariasis endemic province where filariasis is prevalent in all 18 cities and counties. A program to control filariasis was started in 1953. The strategy of eliminating infection sources has been adopted as the principal intervention measure in filariasis control. Over 30 years, the sustained effort throughout the province reached the point of basic elimination of filariasis in 1987. After the basic elimination of filariasis, the patterns of filariasis transmission in residual microfilaremia cases in Hainan Province were studied so as to provide a scientific basis for formulating strategies to eliminate filariasis. According to the "Technical scheme for surveillance in areas where fialariasis has been basically eliminated" issued by the Ministry of Health, a longitudinal and cross-sectional and entomological surveillance of fialariasis was carried out using parasitological and entomological and serological methods in the whole province during 1983-2004. In the cross-sectional and entomological surveillances, the last microfilaremia case was found in 1999, no mosquitoes were found to be infected with filarial larvae. A total of 132 microfilaremia cases found in the longitudinal surveillance become negative by 10 years. Since 1997 no mosquitoes were found to be infected with filarial larvae in the longitudinal surveillance. Serological surveillance of the population showed the mean positive rate of IFAT dropped from 10.63% in 1990 to 0.28% in 2000, which being similar to that of nonendemic areas. The results show that residual sources of infection after basic elimination of filariasis were tending to be naturally eliminated and transmission of filariasis has been interrupted in Hainan Province.