[SurveilLance on filariasis after its basic elimination in Hunan Province]

Abstract

Aim: To explore the fluctuation pattern of prevalence and to detect the residual infection in Hunan Province where filariasis had been basically eliminated since 1986.

Methods: Longitudinal surveillance and cross-sectional surveillance were extensively carried out by using parasitological, entomological and serological methods in areas previously endemic for filariasis.

Results: In 55 counties, cross-sectional surveillance on filariasis had been executed for 11-19 years. The results showed that microfilaria cases had not been found for 4 years, and filaria larvae had failed to be detected from mosquito vectors for 12 years. Serological surveillance in the population revealed that the mean positive rate of IFAT had dropped from 13.15% in 1987 to 1.06% in 1996, the latter rate being similar to that of the nonendemic area. 6 longitudinal surveillance spots in 5 counties (cities) had been observed for 10-17 years. Annual quantitative blood examination of 11 microfilariemia cases showed that 10 cases became negative in 1-10 years, and the remaining 1 case remained positive at the 14th year. A. sinensis were dissected with no filaria larvae found in 2 surveillance spots of malayan filariasis. Culex quinquefasciatus were dissected with filaria larvae found only in the first to third year, the natural infection rates were 0.38%-1.98% in 4 surveillance spots of bancroftian filariasis.

Conclusion: Since the basic elimination of filariasis in Hunan Province in 1986, the number of residual microfilariemia cases decreased year after year, suggesting that the transmission of filariasis has been interrupted.