Monitoring migrant groups as a post-validation surveillance approach to contain the potential reemergence of lymphatic filariasis in Togo

Abstract

Background In March 2017, Togo was declared the first country in sub-Saharan Africa to eliminate lymphatic filariasis as a public health problem, but post-validation surveillance has been lacking. In some areas of the country, migrant groups from neighboring countries that are still endemic for LF pose a risk of reintroduction of LF to Togo. The objective of this study was to identify the risk posed by migrant groups by measuring their prevalence of LF infection and investigating any positive case using Togo’s case investigation algorithm to prevent resurgence of LF and sustain Togo’s elimination success. Method A cross-sectional study was conducted in 2018 in the northernmost region of the country. Three migrant populations were identified: (i) nomadic Peuhls, (ii) Togolese members of local communities who migrate annually to neighboring countries for seasonal labor, and (iii) refugees from Ghana who came to Togo because of a communal conflict in Ghana. A questionnaire was designed to collect data on demographics and history of LF and MDA; all participants were tested for circulating filariasis antigen (CFA) using the filariasis test strip (FTS). Any CFA-positive case was confirmed with nocturnal microfilaremia. Results Refugees, seasonal economic migrants and nomadic Peuhls represented 42.1%, 31.4% and 26.5% of the study participants, respectively. The overall prevalence of CFA was 4.2% (58/1391) with the highest prevalence in the nomadic Peuhl group (11.9%), but only one of them (0.07%) was confirmed positive with nocturnal microfilaremia. Using the case investigation algorithm, no other positive case was identified in the positive case’s surroundings. Conclusion This study demonstrates that nomadic Peuhls, with a CFA prevalence of 11.9%, pose a potential risk for reintroduction of LF into Togo while Ghanaian refugees and seasonal economic migrants do not appear to pose a significant risk. Periodic monitoring of migrants, especially the nomadic Peuhl population, is a potential post-validation surveillance approach that could be used to promptly detect any LF cluster that may arise.

Leaving no one behind: targeting mobile and migrant populations with health interventions for disease elimination—a descriptive systematic review

“…Many reviewed studies reported MMPs being missing or underrepresented in service delivery programs [ 28 , 29 , 31 , 34 , 35 , 37 – 39 , 41 , 51 , 54 , 56 , 57 , 60 , 67 , 69 – 71 ]. This underserved status, it is argued, is important to resolve to address both equity concerns and modeling evidence indicating that focus disease control and elimination efforts cannot be successful without adequate intervention coverage among MMPs.…”

“…This discrepancy in coverage is further concerning when noting that mobility may increase transmission dynamics and affect resource allocation at and between both sending (the location of origin for migrant flows) and receiving (destination locations) areas that may have varying endemicity statuses. In a study on the potential risk of re-infection of LF in Togo, a country with documented LF elimination, Dorenkoo et al surveyed multiple MMP groups from neighboring countries with known travel routes through Togo [ 37 ]. They concluded that the nomadic Peuhls, with an LF prevalence rate of 11.9%, pose a risk of potentially reintroducing LF into Togo.…”

“…This review provides foundational information to the NTD community as programs investigate whether MMPs do in fact contribute to and could be the reason for persistent transmission of NTDs in certain geographic areas. The published literature on NTDs in MMPs suggests movement could possibly (re)establish foci of transmission in the destination upon arrival or in place of origin upon return if population movement is occurring in endemic areas [ 26 , 27 , 37 , 38 , 41 , 43 , 45 , 47 , 56 ]. Movement can also impact population’s knowledge about disease risk [ 15 , 44 ].…”