MDA is needed to reduce infection in the community to levels below a threshold at which mosquitoes are unable to continue spreading the parasites from person to person, and new infections are prevented. WHO recommends the transmission assessment survey (TAS) to determine when infections have been reduced below these target thresholds and MDA can stop. Once MDA has stopped, TAS is used as a surveillance tool to determine that infection levels are sustained below target thresholds.
© WHO / Aya Yajima
The province of New Ireland in Papua New Guinea has successfully reduced the level of transmission of lymphatic filariasis (LF) among its inhabitants, despite disruptions caused by the COVID-19 pandemic and other challenges.
This achievement, enabled through large-scale treatment programmes, or mass drug administration (MDA), makes New Ireland the first province in the country to reach this milestone and free its inhabitants from further large-scale treatment.1 It means that mosquitoes infected with microfilariae – which happens when they ingest blood from an infected host – are unable to continue spreading the parasite that causes LF.
"This is a great achievement as the province of New Ireland is the first to enter a post-MDA surveillance phase and is now on track towards eliminating LF," said Dr Osborne Liko, Papua New Guinea's Secretary for Health. "It has been a long winding journey, and despite numerous challenges, including COVID-19, we look forward to continuing our collaboration with partners to scale up LF elimination efforts until we achieve similar results across other provinces."
LF challenges in an island setting
Papua New Guinea has one of the highest burdens of LF. The disease is known to be prevalent in 14 out of the country's 21 provinces, with prevalence rates ranging up to 70% in some areas.
As the world's third largest island country and being predominantly rural, Papua New Guinea faces multiple challenges, such as:
- geographically challenging terrains with multiple islands and jungles;
- frequent natural disasters;
- limited health system capacity, human resources and basic infrastructure to reach remote communities; and
- high operational costs, insecurity and staff turnover within the health system.
Until recently, all of these challenges have deterred major donors and partners from supporting programmes for neglected tropical diseases (NTDs) in Papua New Guinea.
© Japan International Cooperation Agency
Tackling LF
Despite multiple challenges, the Government of Papua New Guinea has continued to progress its efforts to eliminate LF step by step.
In 2011, the National Department of Health (NDoH) conducted a baseline survey in New Ireland Province. This survey found a 15–17% antigenaemia prevalence using an immunochromatographic test in the 2 districts.
In 2014, the NDoH implemented its first MDA using the conventional 2-drug therapy in New Ireland Province, with support from the United States Agency for International Development (USAID), FHI 360 and the World Health Organization (WHO). This achieved coverage of 78%.
The second and third rounds of MDA using 2-drug therapy in New Ireland Province was implemented in 2015 and 2016, with support from WHO. These achieved coverage of 87% and 78% respectively.
In 2017, WHO supported an LF mid-term survey in New Ireland Province that found an overall antigenemia prevalence as low as 0.3% using an immunochromatographic test.
© Japan International Cooperation Agency
In November 2017, WHO issued a new recommendation on triple-drug therapy – a combination of albendazole, DEC and ivermectin, called IDA – because clinical studies showed that this regimen – a combination of albendazole and DEC or albendazole and ivermectin – is more effective than the conventional 2-drug therapy. IDA has an impact on adult worms living in the human body and requires no more than 2 rounds of MDA to interrupt transmission.
Soon after, a decision was made to introduce IDA in New Ireland Province through the fourth round of MDA. The first MDA using IDA strategy in Papua New Guinea was implemented in December 2018, with support from WHO and the Japan International Cooperation Agency (JICA).
This MDA campaign was seriously challenged by a polio outbreak and subsequent roll-out of a national polio mass vaccination campaign, at the same time as the planned MDA campaign. Those implementing the NTD programme had to coordinate closely with the polio team to carry out the MDA campaign in between polio vaccination campaigns. Finally, the MDA campaign started just before Christmas. Despite these challenges, the MDA campaign was able to achieve coverage of 67.1%.
The success in New Ireland Province inspired the expansion to East New Britain Province. The MDA campaign with the IDA triple therapy was scaled up here in November 2019, again with support from WHO and JICA. The first campaign was implemented successfully, achieving 82.2% treatment coverage.
The first transmission assessment survey (TAS-1) in New Ireland Province and the second round of MDA in East New Britain Province were planned for 2020. But the COVID-19 pandemic disrupted the schedule, meaning all activities had to be postponed.
In April 2021, implementation of TAS-1 finally began through the NDoH and New Ireland Provincial team, with support from WHO, JICA and the Papua New Guinea Institute of Medical Research. The survey was completed and data analysed in September 2021. A team of global LF experts reviewed the data and subsequently recommended that New Ireland Province stop MDA and move into the post-MDA surveillance phase.
"We are proud to be the first province in our country to achieve this historical milestone and come very close to getting rid of this terrible disease," said Dr Joachim Taulo, Acting Chief Executive Officer of the New Ireland Provincial Health Authority. "We are determined to continue robust surveillance until we are officially validated for elimination of LF in our country. We very much appreciate the support provided by the relevant development partners in our efforts to implement MDA since 2014, as well as our current work on TAS. We wholeheartedly thank our partners for their assistance, which has enabled us to reach this milestone."
© Japan International Cooperation Agency
New partners to sustain progress
Despite recurrent challenges, Papua New Guinea is demonstrating its progress towards LF elimination, motivated by strong partnerships with the NDoH, provincial health authorities, JICA, WHO and pharmaceutical donors such as Eisai, GSK and the Mectizan Donation Program.
Recent achievements through local efforts have also managed to introduce a new funding partner. Bridges to Development has joined the fight, pledging to support Papua New Guinea to further expand efforts to eliminate NTDs through integrated MDA, as well as health system strengthening targeted at multiple NTDs in the West New Britain Province. Efforts have also seen renewed support from USAID to eliminate LF starting this year.
"We are excited to be part of a strong partnership to support national and provincial governments in controlling and eliminating this antient and disfiguring disease in Papua New Guinea," said Anna Alexandra Maalsen, acting WHO Representative in Papua New Guinea. "With commitment and steady progress on LF elimination efforts, donor and partner support for the NDoH is expanding to tackle not just LF but all NTDs in Papua New Guinea."
The disease
Lymphatic filariasis is a mosquito borne NTD. It is caused by 3 parasites: Wuchereria bancrofti, Brugia malayi and Brugia timori – all of which are transmitted between humans by mosquitoes. In the most severe cases, LF may cause swollen limbs or thickening of the skin (known as elephantiasis), which typically inhibits mobility.
Beyond the pain and disability, people affected by the disease are frequently ostracized in their communities, as they are often unable to work and eventually sink into poverty.
1 MDA is needed to reduce infection in the community to levels below a threshold at which mosquitoes are unable to continue spreading the parasites from person to person, and new infections are prevented. WHO recommends the transmission assessment survey (TAS) to determine when infections have been reduced below these target thresholds and MDA can stop. Once MDA has stopped, TAS is used as a surveillance tool to determine that infection levels are sustained below target thresholds.
