Progress from morbidity control to elimination as a public health problem of schistosomiasis and the status of soil-transmitted helminth infection in Togo: a second impact assessment after ten rounds of mass drug administration.

BACKGROUND: Due to the burden of schistosomiasis (SCH) and soil-transmitted helminths (STH), Togo Ministry of Health launched a program for Preventive Chemotherapy Neglected Tropical Diseases (PC-NTDs) in 2009, initiating integrated mass drug administration (MDA) the following year for the three PC-NTDs: SCH, STH and onchocerciasis. Significant reduction of infection across the country was noted in 2015 during the first impact assessment, following 5 years of high-coverage MDA implemented at the sub-district level for SCH and district level for STH. After another 5 years of effective MDA, a second survey was conducted in 2021 to re-evaluate the situation of SCH and STH. METHODS: A cross-section of school-aged children was taken across ten districts of Togo. A total of 302 schools in 92 sub-districts were sampled, with 24 school-aged children per school resulting in 7248 children surveyed. Urine samples were tested by haemastix® for Schistosoma haematobium, with urine filtration for the presence of eggs conducted on haematuria-positive samples. Stool samples were collected in a subset of 34 sub-districts in seven out of the ten surveyed districts, where STH and Schistosoma mansoni endemicity was high during the 2015 impact assessment. Duplicate (two) Kato-Katz analysis was performed for each stool sample. Sociodemographic and school-level water, sanitation and hygiene information was also collected. RESULTS: Overall, SCH prevalence was 5.90% (95% CI: 5.4-6.5), with 5.09% (95% CI: 4.64-5.67) for S. haematobium and 2.56% (95% CI: 1.98-3.29) for S. mansoni. STH prevalence was 19.7% (95% CI: 18.2-21.4), with 19.6% (95% CI: 18.1-21.3) hookworm, 0.08% (95% CI: 2.2-5.8) Trichuris trichiura and 0.04% (95% CI: 0.01-0.33) Ascaris lumbricoides. Compared to baseline, a significant reduction in both SCH (22.2% to 5.90%) and STH (29.2% t0 19.7%) prevalence was observed. Children aged 5-9 years were less infected than older peers aged 10-14 years: 4.76% vs. 7.53% (P < 0.01) for SCH and 17.2% vs. 23.0% (P < 0.01) for STH. CONCLUSIONS: After 10 years of high coverage integrated MDA, Togo has achieved low prevalence SCH infection through the sub-district MDA implementation with considerable infection heterogeneity within sub-districts. As STH infection has not reached a level where the infections are not a public health problem, the sub-district treatment strategy could also be adopted in addition to improvement of treatment coverage among preschool age children and hygiene and sanitation practices.

The elimination of trachoma as a public health problem in Togo: Successes and challenges.

BACKGROUND: As of May 2022, 15 countries have declared that they have reached their trachoma elimination targets, but only 13 of them, including Togo, have been validated by the World Health Organization as having eliminated the disease as a public health problem. The aim of this study was to describe the broad interventions that have supported the elimination of trachoma as a public health problem in Togo from its inception in 2006 to the validation of its elimination in 2022. METHOD: A review and compilation of data and information contained in the country's submission to World Health Organization for validation of trachoma elimination as a public health problem was conducted. Data from national and local surveillance systems and reports on actions taken after achieving the elimination target were also included. RESULTS: Togo has achieved the elimination of trachoma as a public health problem by 2022. The prevalence of follicular trachoma among children aged 1-9 years is <5% in all nationally defined administrative units suspected of having trachoma after stopping mass treatment for at least 2 years. The prevalence of trichiasis among persons aged 15 years and older is less than 0.2% in all administrative units previously endemic for trachoma and evidence of the ability to manage incident cases of emerging trichiasis in the community has been demonstrated. The key of the success in the elimination process was primarily the political commitment of the health authorities with financial and technical support from various international organizations. CONCLUSION: The elimination of trachoma as a public health problem in Togo is a real success story that can serve as an example for the elimination of other neglected tropical diseases in Africa. But regular monitoring and surveillance is essential to avoid the re-emergence of such disease in the country.

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

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.

Impact of community-based integrated mass drug administration on schistosomiasis and soil-transmitted helminth prevalence in Togo.

BACKGROUND: Togo has conducted annual, integrated, community-based mass drug administration (MDA) for soil-transmitted helminths (STH) and schistosomiasis since 2010. Treatment frequency and target populations are determined by disease prevalence, as measured by baseline surveys in 2007 and 2009, and WHO guidelines. Reported programmatic treatment coverage has averaged over 94%. Togo conducted a cross-sectional survey in 2015 to assess the impact of four to five years of MDA on these diseases. METHODOLOGY/PRINCIPAL FINDINGS: In every sub-district in the country outside the capital, the same schools were visited as at baseline and a sample of fifteen children age 6 to 9 years old was drawn. Each child submitted urine and a stool sample. Urine samples were tested by dipstick for the presence of blood as a proxy measure of Schistosoma haematobium infection. Stool samples were analyzed by the Kato-Katz method for STH and Schistosoma mansoni. At baseline, 17,100 children were enrolled at 1,129 schools in 562 sub-districts; in 2015, 16,890 children were enrolled at the same schools. The overall prevalence of both STH and schistosomiasis declined significantly, from 31.5% to 11.6% for STH and from 23.5% to 5.0% for schistosomiasis (p<0.001 in both instances). Egg counts from both years were available only for hookworm and S. mansoni; intensity of infection decreased significantly for both infections from 2009 to 2015 (p<0.001 for both infections). In areas with high baseline prevalence, rebound of hookworm infection was noted in children who had not received albendazole in the past 6 months. CONCLUSIONS/SIGNIFICANCE: After four to five years of MDA in Togo, the prevalence and intensity of STH and schistosomiasis infection were significantly reduced compared to baseline. Data on STH indicate that stopping MDA in areas with high baseline prevalence may result in significant rebound of infection. Togo's findings may help refine treatment recommendations for these diseases.

Surveillance for lymphatic filariasis after stopping mass drug administration in endemic districts of Togo, 2010-2015.

BACKGROUND: Togo is a country previously endemic for lymphatic filariasis (LF). In 2010, following nine years of mass drug administration (MDA) for LF, the country established a post-treatment surveillance (PTS) system. We present here the results of these PTS activities, carried out from 2010 to 2015, as well as the findings of follow-up investigations in 2016 to confirm the absence of infection in previously infected individuals. METHODS: The routine surveillance established in 2010 consisted of a network of 47 laboratories, which searched for Wuchereria bancrofti microfilaria on nocturnal blood smears collected for malaria diagnosis and an additional network of 20 peripheral health facilities, which collected dried blood spots and tested them for Og4C3 antigen. Two transmission assessment surveys (TAS) were also undertaken, as recommended by WHO, in 2012 and 2015. Any positive case identified through any surveillance activity was immediately retested by nocturnal smear and confirmed cases were immediately investigated by screening family members and neighboring household members. In 2016, 32 of the 40 positive cases detected during TAS or laboratory and health facility network activities were traced and whether confirmed positive by nocturnal smear or not were tested again simultaneously by filariasis test strip (FTS), Og4C3 and a nocturnal blood smear to rule out any active infection. RESULTS: From 2010 to 2015, the laboratory network identified one microfilaria-positive individual (0.0% of 26,584 persons tested) and the peripheral health facility network detected 19 Og4C3-positive individuals (0.28% of 6788 persons tested). All 19 Og4C3 cases were negative for microfilaremia by nocturnal blood smear. In the 2012 and 2015 TAS, thirteen and six ICT/FTS positive cases, respectively, were identified, which were significantly below the critical cut-off (18-20 cases) across all evaluation units. Three of the six ICT/FTS-positive cases from the 2015 TAS were positive by nocturnal smear; immediate investigation identified one additional microfilaria-positive individual. Epidemiological investigation revealed that four of the five cases of microfilaremia were imported from another country in the region. In 2016, 32 of the 40 positive cases detected by at least one test during all surveillance activities were traced: four (12.5%) individuals were still positive by FTS but all 32 individuals were negative for microfilaremia and Og4C3 antigen. CONCLUSION: The results of post-treatment surveillance in Togo have demonstrated that W. bancrofti filariasis is no longer of public health concern in Togo, more than six years after stopping MDA. Every possible effort should be made to maintain surveillance in order to promptly detect any resurgence and preserve this achievement.

Molecular xenomonitoring for post-validation surveillance of lymphatic filariasis in Togo: no evidence for active transmission.

BACKGROUND: Lymphatic filariasis (LF) is a mosquito-borne filarial disease targeted for elimination by the year 2020. The Republic of Togo undertook mass treatment of entire endemic communities from 2000 to 2009 to eliminate the transmission of the disease and is currently the first sub-Saharan African country to be validated by WHO for the elimination of LF as a public health problem. However, post-validation surveillance activities are required to ensure the gains achieved are sustained. This survey assessed the mosquito vectors of the disease and determined the presence of infection in these vectors, testing the hypothesis that transmission has already been interrupted in Togo. METHOD: Mosquitoes were collected from 37 villages located in three districts in one of four evaluation units in the country. In each district, 30 villages were selected based on probability proportionate to size; eight villages (including one of the 30 villages already selected) where microfilaremia-positive cases had been identified during post-treatment surveillance activities were intentionally sampled. Mosquitoes were collected using pyrethrum spray collections (PSC) in households randomly selected in all villages for five months. In the purposefully selected communities, mosquitoes were also collected using human landing collections (HLC) and exit traps (ET). Collected mosquitoes were identified morphologically, and the identification of Wuchereria bancrofti DNA in the mosquitoes was based on the pool screening method, using the LAMP assay. RESULTS: A total of 15,539 mosquitoes were collected during the study. Anopheles gambiae (72.6%) was the predominant LF vector collected using PSC. Pool screen analysis of 9191 An. gambiae in 629 pools revealed no mosquitoes infected with W. bancrofti (0%; CI: 0-0.021). CONCLUSIONS: These results confirm the findings of epidemiological transmission assessment surveys conducted in 2012 and 2015, which demonstrated the absence of LF transmission in Togo. The challenges of implementing molecular xenomonitoring are further discussed.