Diagnosing the Setback: Indonesia Rapidly Adapts LF Surveillance Strategy Towards Elimination
Protecting 108 million Indonesians from a disfiguring disease called lymphatic filariasis (LF) faced a significant setback in 2021: disease experts confirmed that the rapid diagnostic test used to detect one of the parasites that cause the disease wasn’t working.
LF is a neglected tropical disease (NTD) caused by three species of parasitic worms transmitted by mosquitoes which can cause severe swelling in the lymphatic system, leading to profoundly disfiguring swelling in arms, legs, and reproductive organs. The disease causes permanent disability which can also lead to mental health issues and social stigma. LF elimination programs traditionally used two different rapid diagnostic tests to find people with LF caused by the various species. In Indonesia—the only country where all three species are endemic—the rapid test commonly used to detect antibodies to Brugia malayi and Brugia timori species was found to be no longer working. This meant communities didn’t have an accurate picture of their risk of LF infection.
Quickly adapting to address this diagnostic dilemma, the Indonesian Ministry of Health (MOH) collaborated with the University of Indonesia’s Parasitology Laboratory, USAID’s Act to End NTDs | East, led by RTI International, the World Health Organization (WHO), and The Task Force for Global Health, keeping LF elimination on track.
The team developed a new survey methodology called the Brugia Impact Survey (BIS) tailored to the logistical context of Brugia-endemic areas, like those in Indonesia. BIS used a tried-and-true diagnostic technique of examining fingerpick blood samples on slides under a microscope for traces of microfilaria, or baby worms.
The catch? These baby worms have evolved to be most active in the peripheral bloodstreams of infected people at night, the same time that mosquitoes are biting. Additionally, blood must be collected from a random sample of people, requiring survey teams to approach specific individuals across many households in the middle of the night.
“Given the presence of all three LF parasites, the MOH and local universities have relied more than most countries on night blood testing for microfilaria,” says Molly Brady, Senior NTD Advisor at RTI International on USAID’s Act to End NTDs | East project. “This put them in an excellent position to pivot to implementing BIS, as they already had significant capacity and systems to collect and read night blood slides.”
BIS teams work at night, moving through moonlit palm oil plantations by boat. The teams complete BIS by waking residents of randomly selected households to draw blood samples. Local health workers alert the selected households the day before and explain why their participation is needed. The whole BIS process, including planning and coordination, for one survey takes nearly a month to complete, twice as long as previous surveys, requiring more resources and dedication from the LF teams and communities.
Ultimately, rousing residents from their beds and taking blood samples in the dead of night isn’t the easiest public health campaign. However, to those involved, accurately knowing the risk of LF infection is worth the extra effort.
“Although the BIS survey is challenging, we are proud that we successfully implemented many pending surveys with this alternative methodology and very convinced with the outcomes. I am hopeful that the WHO can recommend the new rapid test diagnostic for Brugian area sooner rather than later", says Dr. Anas Ma’ruf, Acting CDC Director of MOH Indonesia.
These types of community surveys are an essential step after mass drug administration during which LF medicines are distributed to communities. The surveys confirm the level of infection rates and whether they are low enough to indicate that residents are no longer at risk for the disease and mass treatment can be stopped.
Thankfully, BIS is yielding results.
Between 2022 and 2024, the BIS protocol allowed for the completion of 43 surveys that otherwise would not have occurred, informing decisionmakers on whether continued treatment is needed in certain districts. Most districts surveyed showed infection rates below the WHO threshold for ending mass treatment and more than 76 million people in Indonesia are no longer at risk for LF, demonstrating the success of the public health effort and the country's tremendous progress towards elimination.
In the meantime, additional hope is on the horizon as WHO and partners work toward a long-term solution through the development of a new diagnostic test to detect Brugia species.