Summarizes recent advances in knowledge about lymphatic filariasis and the methods available for its diagnosis, treatment, and control. In view of the many perplexing complexities of this disease, the report makes a special effort to distinguish between research issues that have now been resolved and the many others requiring further study. Emphasis is placed on the lines of investigation needed to develop simple and cost-effective tools for control. Background information is provided in the opening section, which summarizes changes, by country and region, in the prevalence and distribution of Wuchereria and Brugia infections. The second section, devoted to clinical aspects, describes the wide range of clinical manifestations seen in bancroftian and brugian filariasis and discusses the signs and symptoms that can make differential diagnosis especially difficult. Further clinical information is provided in a section covering new diagnostic tools, including improved serodiagnostic tests and the use of lymphoscintigraphy to assess asymptomatic patients and persons at risk. A summary of advances in understanding the pathogenesis of the disease, its immunopathology, and the mechanisms responsible for protective immunity is also provided. Problems considered include the factors influencing the pathogenesis of tropical pulmonary eosinophilia and of renal lesions, the mechanisms involved in the parasite-specific hyporesponsiveness observed in many patients, and possible explanations for the distinctly different clinical and pathological responses seen in residents of endemic areas and in migrants to those areas. A section on vectors updates knowledge on the distribution and bionomics of the Culex, Aedes, Mansonia, and Anopheles vectors and describes the range of methods now available for control. A new definition of low-density microfilaraemia is presented in response to the need to reduce the number of microfilaria-negative recordings of microfilaria-positive cases and thus establish the true rate of infection in a community. The next section explains the ways in which five categories of epidemiological studies can be used to support control efforts. Emphasis is placed on the use of epidemiological modelling as a powerful tool for understanding disease transmission and formulating control strategies. Problems identified include the long duration of infection, the large number of infected yet asymptomatic and amicrofilaraemic persons, and the many carriers with false-negative results who escape treatment. Of particular practical value is a summary of experiences with different treatment options, including selective and mass chemotherapy with diethylcarbamazine citrate (DEC), the use of DEC-medicated salt, and trials of single oral doses of ivermectin. The remaining sections discuss human behavioural and socioeconomic aspects, and outline the training, resource, and organzational needs of control programmes.

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WHODOC

WHO monograph

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