Progress and impact of 20 years of a lymphatic filariasis elimination programme in South-East Asia.

BACKGROUND: The South-East Asia regional programme to eliminate lymphatic filariasis (LF) was launched in 2000. This study presents the progress and impact of the programme in the region. METHODS: Mass drug administration (MDA) and morbidity management data were accessed from the WHO preventive chemotherapy databank. The status of the programme in the nine South-East Asia countries was reviewed and progress was assessed. The impact of the programme on LF disease burden was estimated on the basis of the effectiveness of the MDA drugs against microfilaraemia and chronic disease. RESULTS: Under the MDA programme, 8.1 billion treatments were delivered in nine countries and 5.7 billion treatments were consumed by the target population during 2001-2018. Three of nine countries eliminated LF. Bangladesh is poised to reach its elimination goal by 2021. In the other five countries, 38-76% of intervention units completed intervention and surveillance is in progress. The MDA programme prevented or cured 74.9 million infections, equivalent to an 84.2% reduction. Close to 1 million lymphoedema patients and 0.5 million hydrocele patients were reported and are being provided with the minimum package of care. CONCLUSIONS: The South-East Asia region's LF elimination programme reduced the burden of LF appreciably and is moving towards achieving the elimination goal in the next 8-10 y.

Elimination of lymphatic filariasis as a public health problem from Tonga.

BACKGROUND: Tonga was highly endemic for lymphatic filariasis (LF) caused by diurnally sub-periodic Wuchereria bancrofti transmitted by Aedes vector species. LF prevalence declined very appreciably as a result of chemotherapeutic intervention measures implemented in 1977, but low levels of infection persisted. Along with other Pacific Island countries and in partnership with the Pacific Programme to Eliminate LF (PacELF), Tonga implemented a programme to eliminate LF as a public health problem. METHODS: On the basis of historical data and baseline survey, all the divisions of the country were declared as endemic. Five to six consecutive rounds of effective MDA were implemented in all the divisions during 2001-2006. The impact of MDA was assessed through interim and post-MDA antigen (Ag) detection surveys among adults and transmission assessment surveys among children. The chronic disease burden was assessed by health workers through observation. RESULTS: The base-line Ag prevalence was 2.70%. The treatment coverage was > 80% in all MDA rounds. The mid-term surveys showed an Ag prevalence of 2.46%. The pre-stop MDA Ag survey revealed an Ag prevalence of 0.34%. The stop MDA survey and transmission assessment surveys among children showed Ag prevalence at < 0.05%, indicating transmission is negligible. Health workers concluded that filarial lymphedema or hydrocele condition in the communities is absent or very rare. CONCLUSION: Tonga had successfully met the criteria for elimination of LF as a public health problem. The accomplishment was acknowledged by the WHO in 2017. Tonga looks forward to work with stakeholders to eliminate transmission of LF and achieve zero incidence of infection.

Elimination of lymphatic filariasis as a public health problem from the Cook Islands.

BACKGROUND: The Cook Islands has a long history of high-endemicity lymphatic filariasis (LF) transmitted by Aedes vector mosquitoes. Though the infection prevalence had declined between 1975 and 1999 following episodic treatment activities, still infection was widespread with pockets of persistent infection. Beginning in 1999, the Cook Islands embarked on a national program, in partnership with Pacific Programme to Eliminate LF (PacELF), to eliminate LF as a public health problem. METHODS: All 12 inhabited islands were identified as endemic, and six rounds of mass drug administration (MDA) with once-yearly, single-dose albendazole plus diethylcarbamazine (DEC) were implemented during 2000-2006 to interrupt transmission of LF. Surveys carried out at the baseline, mid-term, stop-MDA, and post-MDA periods assessed LF antigen (Ag) prevalence in children and adults. Historical data, health workers' observations, and hospital records were used to assess the trend and burden of chronic disease. RESULTS: The baseline Ag prevalence (1999) ranged from 2.0% in Manihiki to > 18.0% in Aitutaki, Mitiaro, and Pukapuka, and the national average Ag prevalence was 8.6%. MDA, carried out with a national treatment coverage over six annual rounds of MDA ranging from 63.5 to 96.7% in different years, was stopped in 2007. By then, the national Ag prevalence had declined to 0.27%. The post-MDA surveillance survey results (2013-2014) showed that Ag prevalence had fallen to 0% in 11/12 islands, and the national prevalence was only 0.03%. Chronic filarial disease had almost entirely disappeared. CONCLUSION: The Cook Islands met all the criteria required for the World Health Organization (WHO) to acknowledge elimination of LF as a public health problem, as it did officially in 2016. This success also confirms that LF, even when transmitted by Aedes mosquitoes that are recognized to be more efficient than other vector species, can be eliminated as a public health problem by six rounds of MDA.