Sessions at the current American Society of Tropical Medicine and Hygiene in Philadelphia have focused on progress in the global elimination of lymphatic filariasis (LF). Filariasis and malaria have some elements in common, such as some mosquito vectors, and possibly malaria elimination efforts could learn from LF elimination.
The duration of a typical filariasis elimination program might span around 10 years, much shorter than expected for malaria, where Roll Back Malaria has already been working hard for 13 years. Even with this difference LF elimination has important surveillance tools needed for the end game that can be adapted for malaria. As the figure here shows, the first step is mapping which can take at least a year.
Then there are at least five annual mass drug administrations (MDA) with ivermectin or DEC and albendazole.Â Monitoring goes along with distribution, and as pointed out at a panel presentation at ASTMH, determines whether the program can enter Step 3 (three rounds of annual surveillance) or complete a few more MDA rounds.Â Eventually the project site is certified as having eliminated filariasis.
An ASTMH symposium highlighted the challenges: “The decision to implement a mass drug administration (MDA) program for LF is based on convenience sampling to demonstrate that the prevalence of infection is greater than 1% in a selected district or implementation unit. Making the decision to stop MDA has been a challenge for countries,” when prevalence drops below 1%.
Fortunately those involved in LF have tools and guidelines to focus their efforts. These guide initial mapping and choice of diagnostic tools, ongoing program monitoring and endline Transmission Assessment Surveys (TAS)Â The purpose of the guidelines is …
“Effective monitoring, epidemiological assessment and evaluation are necessary to achieve the aim of interrupting LF transmission. Th is manual is designed to ensure that national elimination programmes have available the best information on methodologies and procedures for (i) monitoring MDA, (ii) appropriately assessing when infection has been reduced to levels where transmission is likely no longer sustainable, (iii) implementing adequate surveillance aft er MDA has ceased to determine whether recrudescence has occurred, and (iv) preparing for verifi cation of the absence of transmission.”
The guideline manual provides general guidance to national programmes but reminds program managers that each program is unique and may require further technical guidance.
Several countries, especially in the Asia-Pacific Region and Southern Africa are working toward malaria elimination. Such tools adapted to malaria program needs are required. One of the challenges for the TAS is that while countries have received donations of medicines to eliminate LF, they have found it harder to find or allocate funds to do the necessary surveillance to know when to stop interventions and verify elimination. This also rings true for malaria – donors and governments should not stop funding malaria elimination until certification has been achieved.