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Objective To conduct a nationwide integrated neglected tropical disease (NTD) prevalence survey to define the need for public health interventions using an innovative mapping protocol.
Methods Two villages were selected in every peripheral health unit in endemic districts: 29 districts for schistosomiasis and STH, 15 of them for trachoma. In each village, 15 children aged 6–9 years at a randomly selected school were tested. An additional convenience sample of 35 children aged 1–5 years underwent an eye examination for trachoma. This integrated mapping was followed by a 20-cluster trachoma survey in each district that surpassed the WHO-defined threshold of 10% prevalence of trachomatous inflammation-follicular (TF).
Results A total of 1096 villages were surveyed in <6 weeks. The district prevalence of schistosomiasis ranged from 2 to 49% and of STH from 5 to 70%, with prevalence at the village level ranging from 0 to 100% for both diseases. Two districts passed the threshold of 10% for active trachoma, but the cluster survey indicated this was because of misclassification bias and that the real prevalence was <1%.
Conclusion Results of this mapping were used by the MoH and partners to plan integrated mass drug administration (MDA). Mass drug administration for trachoma was not implemented as no district passed the threshold requiring public health intervention.
Objectif: Mener une surveillance nationale intégrée de la prévalence des Maladies Tropicales Négligées (MTN) afin de définir les besoins d’interventions de santé publique, en utilisant un protocole de cartographie innovant.
Méthodes: Deux villages ont été sélectionnés dans chaque unité de santé périphérique dans les districts endémiques: 29 districts pour la schistosomiase et les géohelminthiases, 15 d’entre eux pour le trachome. Dans chaque village, 15 enfants âgés de 6 à 9 ans d’une école choisie aléatoirement ont été testés. Un échantillon de commodité supplémentaire de 35 enfants âgés de 1 à 5 ans a subi un examen ophtalmologique pour le trachome. Cette cartographie intégrée a été suivie par une enquête sur le trachome, dans 20 grappes dans chaque district qui a dépassé le seuil de l’OMS pour la prévalence de 10% d’inflammation folliculaire trachomateuse.
Résultats: 1096 villages ont été surveillés en moins de 6 semaines. La prévalence de la schistosomiase dans les districts variait de 2%à 49% et pour les géohelminthiases de 5%à 70%, avec une prévalence à l’échelle du village allant de 0%à 100% pour les deux maladies. Deux districts dépassaient le seuil de 10% pour le trachome actif, mais l’étude en grappes a indiqué que cela était dûà erreurs de classification et que la prévalence réelle était inférieure à 1%.
Conclusion: Les résultats de cette cartographie ont été utilisés par le Ministère de la Santé et les parties prenantes pour planifier l’Administration Massive intégrée de Médicaments (AMM). L’AMM pour le trachome n’a été implémentée comme aucun district n’avait dépassé le seuil nécessitant une intervention de santé publique.
Objetivo: Realizar un estudio integrado y a nivel nacional sobre la prevalencia de Enfermedades Tropicales Desatendidas (ETD), para definir, mediante el uso de un innovador protocolo de mapeo, la necesidad de intervenciones de salud pública.
Métodos: Se seleccionaron dos poblados de cada unidad sanitaria periférica en distritos endémicos: 29 distritos con esquistosomiasis y helmintos transmitidos por la tierra, 15 de ellos con presencia de tracoma. En cada poblado se realizaron pruebas a 15 niños con edades entre los 6 y 9 años, pertenecientes a un colegio seleccionado al azar. En una muestra adicional de 35 niños, con edades entre 1 y 5 años, se realizó una prueba ocular para tracoma. Este mapeo integrado fue seguido por un estudio de tracoma en 20 conglomerados en cada distrito que sobrepasaba el umbral de la OMS del 10% de prevalencia de inflamación folicular (IF) por tracoma.
Resultados: En menos de 6 semanas se incluyeron en el estudio 1096 poblados. La prevalencia distrital de esquistosomiasis estaba entre el 2% y el 49%, y la de helmintos transmitidos por la tierra entre el 5% y el 70%, con una prevalencia a nivel del poblado de entre el 0% y 100% para ambas enfermedades. Dos distritos sobrepasaban el umbral del 10% para tracoma activo, pero el estudio de conglomerados indicó que ello se debía a un sesgo por una mala clasificación, y que la prevalencia real era de menos del 1%.
Conclusión: Los resultados de este mapeo fueron utilizados por el Ministerio de Salud y sus socios para planear una administración masiva de medicación (AMM). La AMM para tracoma no fue implementada ya que ningún distrito pasó el umbral requerido para una intervención de salud pública.
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There is a growing international interest in scaling up integrated implementation of control and elimination programmes for neglected tropical diseases (NTDs) with preventive chemotherapy (PCT) (Molyneux et al. 2005). The integrated control of five NTDs (lymphatic filariasis (LF), schistosomiasis, onchocerciasis, soil-transmitted helminthes (STH) and trachoma) consists of the delivery of a package of services targeting the diseases endemic in the local communities by utilizing pooled financial and human resources (Brady et al. 2006). This integrated package consists of mass drug administration (MDA) to at-risk populations and related activities such as training, logistics, supervision and reporting at all levels of the health system. The first step in this process is to identify implementation units (I.U.) where the prevalence of each disease surpasses its respective threshold for public health intervention (Baker et al. 2010). If reliable current data are not available, field surveys to map the disease prevalence must be implemented.
In Togo, the Ministry of Health (MoH) has been implementing onchocerciasis control and LF elimination activities for many years. Togo started ivermectin MDA in 28 of the nation’s 35 districts at the end of the 1980s, and starting in 2000, albendazole was added in the seven districts where LF was endemic (MMWR, 2011). Aside from a countrywide mapping of schistosomiasis conducted in 1996, no control activities have been implemented for schistosomiasis (Agbo et al. 1999). Limited public health interventions, such as deworming for preschool-age children, have been conducted for STH, but no activities have been implemented for trachoma.
In 2003, the Ministry of Health of Togo, with technical assistance from the Centers for Disease Control and Prevention (CDC), launched an operational research project to integrate NTD control that included a novel strategy for the integrated mapping of schistosomiasis, STH and trachoma followed by appropriately targeted integrated MDA. The strategy was successfully piloted in the district of Binah. Building on this success, the Togo MoH, with the assistance of Health & Development International (HDI) and CDC, secured funding for nationwide scale-up of the pilot project through USAID (the United States Agency for International Development) and RTI (Research Triangle International, NC, USA). The first activity implemented with this grant was an integrated nationwide prevalence survey. This paper describes the innovative methods used, the results and the programmatic decisions taken.
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Togo is a West African country with a population of 6.1 million persons living in 35 districts (district population range, 40 802–369 653). Each of the more than 600 peripheral health units (PHU, population range, 438–90 333) has a dispensary with at least one nurse and provides services for 1–10 villages. Based on general knowledge and available data, the five urban districts in the capital Lomé were excluded from the NTD mapping because transmission of the targeted NTDs is low or non-existent. Additional areas were excluded from trachoma mapping: the two southern regions outside Lome, which were considered low risk for active trachoma based on the geographical conditions and local knowledge, and the district of Binah, where the integrated mapping protocol was previously piloted.
The sampling method and sample size were based on a new, integrated mapping methodology developed by CDC (Pelletreau et al. 2011). In each PHU, two villages were selected for testing: one village was randomly chosen, and the other was selected for suspected high S. haematobium prevalence based on a history of high haematuria prevalence or proximity to a body of water. This information was provided by the district medical team or the PHU nurse. In each village, a school was randomly selected or, if the village did not have a school, the nearest school attended by the children was chosen. At each school, a teacher selected a sample of 15 children aged 6–9 years old, with equal numbers of boys and girls; all were examined for trachoma, schistosomiasis and STH. Additionally, mothers with children aged 1–5 years were identified by word of mouth and asked to bring their children to the school; 35 of these children underwent an eye examination for trachoma.
To adhere to the drug donation guidelines from the International Trachoma Initiative, districts identified as possibly endemic for trachomatous inflammation-follicular (TF) (>10% prevalence of TF) were subsequently surveyed using the standard WHO-recommended cluster survey methodology (WHO 2006b). Clusters were selected using probability proportional to estimated size, and the houses were selected using the improved random walk. In small villages, all the houses were included. In each village, 70 children aged 1–9 years and 50 women aged >15 years were examined.
For each child whose guardian gave consent, the team recorded the name, age and gender, and urine and stool samples were collected. Only children who were able to provide both samples were included in the survey. Urine testing was conducted in the village using a urine dipstick to test for the presence of microhaematuria as the indicator of Schistosoma haematobium infection (WHO 1991). Stool testing for Schistosoma mansoni and STH was performed at the district laboratory using the Kato-Katz method (WHO 1991). The technicians determined intensity of infection by calculating the numbers of eggs per gram of faeces, but these results are not described in this study. The GPS coordinates for each village were recorded. For the integrated protocol, the presence of all stages of trachoma was assessed only in children; in the subsequent cluster survey, data were collected from children and women. Each consenting person underwent a non-invasive eye examination by an ophthalmologic technician. Signs of trachoma were noted using the WHO ‘Simplified Grading Scheme for Trachoma’ (WHO 2006b).
Team structure and training
For the integrated survey, there were ten teams, two for each of the five regions surveyed. Each team consisted of two laboratory technicians from the central level. In districts where trachoma was mapped, two ophthalmologic technicians (TSOs) joined the team. Two teams travelled in a single vehicle and visited two PHU (four villages) per day. The dispensary nurse for the PHU and the community health worker for each village were also engaged to assist with recruitment and enrolment. In most districts, the district laboratory technicians assisted in conducting the Kato-Katz reading.
The training for the integrated protocol covered sampling, questionnaires and informed consent. The laboratory technicians were experienced in the Kato-Katz method, and for this reason, no laboratory training was provided, but training in trachoma diagnosis was organised by an international trachoma expert. Owing to a lack of clinical cases identified for the training, we were not able to test the inter-rater agreement of the four TSOs (Thylefors et al. 1987). As a result of concerns of overdiagnosis of trachoma during the integrated survey, a rigorous 3-day training was organised by CDC before the cluster survey. Twelve TSOs were trained of whom six were selected for the survey based on their performance on a practical examination using 50 PowerPoint slides because again no active cases were identified for a field test.
Data were entered into a Microsoft Excel database and were analysed using Excel. For trachoma and STH, the average district prevalence was calculated. For schistosomiasis, a positive urine dipstick and/or Kato-Katz result was counted as a case. At the PHU level, the higher measured prevalence of the two villages surveyed was taken as the prevalence for the PHU and was used for programmatic decisions based on WHO-defined thresholds and guidelines (WHO 2006a) as shown in Table 1. The 95% confidence intervals were calculated for the trachoma probability survey but not for the prevalence figures obtained by the convenience sample. We used Arc View software (Esri, Redlands, CA, USA) to visualise the data points.
Table 1. WHO-determined threshold for programmatic interventions (WHO 2006a, 2006b)
|Disease||Indicator||Threshold for MDA, %||Target group of MDA|
|Trachoma||TF/TT||TF ≥10||Total population|
|Eggs in stool||≥50||Total population|
|STH||Eggs in stool||20–49||School-age children (once a year)|
|≥50||School-age children (twice a year)|
The study protocol was reviewed by the ethical committee from CDC and the Ministry of Health in Togo and was deemed by both to be a programme evaluation activity not involving human subject research. Written consent was obtained from all adults and from the parent or guardian of all children; school-age children additionally provided oral assent. All persons identified with active trachoma received two tubes of tetracycline ointment. For schistosomiasis and STH, the list of individuals tested and their test results were kept at the local dispensary, which provides primary health care to local residents. After the mapping, in PHUs where the prevalence of schistosomiasis or STH was not high enough to warrant MDA, the PHU nurse went to the homes of participants who tested positive and treated them for free. In areas eligible for MDA, the dispensary nurse verified that those who tested positive were successfully treated during the drug distribution.
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The integrated survey was conducted from October 28 through December 6, 2009. It covered 29 districts in five regions and included 549 PHU. A total of 1096 villages were surveyed. For schistosomiasis and STH, the team tested 16 440 school children aged 6–9 years. For trachoma, the team visited 250 PHU in 14 districts in the three northern regions of the country and examined 25 000 children aged 1–9 years.
The district prevalence of schistosomiasis ranged from 2 to 49% with prevalence at the village level ranging from 0 to 100% (Table 2, Figure 1). Schistosoma haematobium was endemic in every district with district prevalence ranging from 1 to 49%, while S. mansoni was only endemic in 18 of the 29 districts with district prevalence ranging from 1 to 13%. Using the prevalence at the PHU level for programmatic decision-making as defined above, no treatment was indicated in 34% of the 549 PHUs, treatment of school-age children was indicated in 41% of the PHUs, and treatment for the entire population was indicated for 25% of the PHUs (Table 3).
Table 2. Prevalence of schistosomiasis and STH, Togo, 2009
|Region||District||Number of PHU||Number of children surveyed for schistosomiasis and STH||Schistosomiasis||STH|
|Prevalence (%)||Prevalence range for villages in the district (%)||Prevalence of Schistosoma Haematobium (%)||Prevalence of Schistosoma mansoni (%)||Prevalence (%)||Prevalence range for villages in the district (%)||Prevalence of Ancylostoma species (%)||Prevalence of Ascaris lumbricoides (%)||Prevalence of Trichuris trichiura (%)|
|National average or total|| ||549||16440||22|| ||20.1||3.0||33|| ||32.9||0.4||0.2|
Figure 1. Village-level findings from the schistosomiasis mapping and the resulting public health intervention. Togo, 2009.
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Table 3. Planned MDA with praziquantel based on the mapping results, Togo
| || ||Number of PHU with given schistosomiasis prevalence|
|Region||District||PHU with <10%||PHU with 10–49%||PHU with ≥50%|
|Total|| ||186 (34%)||223 (41%)||140 (25%)|
The district prevalence of STH ranged from 5 to 70% with prevalence at the village level ranging from 0 to 100% (Table 2 and Figure 2). Ascaris lumbricoides was found in six of the 29 districts, and Trichuris trichiura was present in eight of the 29 districts.
The prevalence of trachomatous inflammation-follicular (TF) varied from 0.5 to 11.3% in the 14 districts; however, the cluster survey and interviews with the TSOs confirmed that misclassification in the first survey led to an overestimate of active trachoma. The TF prevalence for the 20-cluster surveys in Blitta (0.2%, 95% CI 0.0–0.4), Binah (0.2%, 95% CI 0.0–0.3) and Sotoboua (0.0%) indicated that the threshold for MDA was not reached (Table 4).
Table 4. Results from the trachoma cluster survey, Togo 2011
|District||Population sampled||Number examined||Per cent with each finding|
Based on the budget, we calculated that the average cost of the survey per district for 2–3 NTDs was $5506. The main cost for the integrated survey was the per diem pay (41%), 35% was for transport costs, 14% for supplies for testing and data collection and 6% for training.
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The MoH of Togo and its partners successfully mapped the nationwide distribution of three NTDs in a very short time span using a new, integrated protocol. The protocol, developed and implemented in the pilot district in Binah in 2007, was adapted based on lessons learned in Binah. The results confirmed the limited available data (Doumenge & Mott 1987, Sodahlon, personal communication). There are several innovative aspects to this protocol.
First, the protocol is closely linked with the implementation units (I.U.) selected by MoH for NTD programme implementation (WHO 2006a,b). The PHU was chosen as the I.U. for praziquantel instead of either the more traditional village or district level. This choice reflects the focal nature of schistosomiasis while maintaining an I.U. size that is feasible for implementation of a national MDA programme. This more focal targeting of schistosomiasis also reduces the required amount of praziquantel, which is costly and of limited availability. Had implementation been based on the district-level prevalence of schistosomiasis, six districts (87 PHUs) would have received no treatment, and 23 districts (462 PHUs) would have been targeted for treatment every 2 years. Consequently, many people would not receive treatment otherwise indicated by the PHU prevalence; 16 (18%) of the 87 PHUs in untreated districts would warrant treatment based on the local PHU prevalence, and 140 (30%) of the 462 PHUs receiving treatment every 2 years would warrant yearly treatment based on the PHU prevalence. Additionally, unnecessary treatments would be administered, and resources consumed in 115 (25%) of the 462 PHUs where district prevalence dictates treatment every 2 years but where the prevalence in the PHU is below 10%.
Second, the idea was to use integrated mapping as the first step to real NTD integration. By creating one protocol, one multidisciplinary team, and common logistics and data entry, the MoH and partners learned to work together and showcased the idea of integration to the districts. The team was initially hesitant to have only one car and an integrated team, but the field experience convinced the team members. The integrated mapping also enabled national staff with limited experience to learn from more experienced staff about the way such field surveys are organised.
Although resources were available, a national mapping is costly not only financially (mainly due to per diems), but also in resources such as personnel time and cars. For this reason, some decisions were made to avoid unnecessary use of resources. As recommended by WHO AFRO, available data were used to exclude certain areas from the mapping (AFRO NTD mapping manual, in draft). For this reason, the five districts in the Lome commune were excluded. Based on health system data, we expected that trachoma was not endemic and there would be no, or limited, azithromycin drug donation needs. For this reason, we decided it would be more cost effective to first use a less accurate methodology to assess where a more robust survey is needed instead of immediately conducting 14 resource intensive cluster surveys. This is concordant with WHO recommendations, which recommend rapid mapping to identify where cluster surveys are needed (Negrel & Mariotti 1999) although those methods are of course less accurate and often do not provide data on trichiasis. In contrast, we chose a more expensive approach to schistosomiasis mapping for the reasons mentioned above. Ascaris prevalence was lower than expected, which is probably a result of more than three decades of ivermectin MDA in all regions with the exception of Golfe and Lac. Trichuris is known to be less prevalent in Togo.
The sampling frame and sample size for trachoma were designed as a simple, inexpensive way to obtain an estimate of trachoma prevalence, rather than spend resources on a disease that was not thought to be highly endemic. Our experience in Mali, Senegal and CAR, where we compared the integrated methodology with the WHO-recommended protocol, indicates that the findings of both methods result in the same public health interventions (Pelletreau et al. 2011). Unexpectedly, the prevalence estimates obtained in two districts were over 10% and demonstrated an unusual TF/TI ratio for low prevalence areas. We followed our initial plan to validate the results with a 20-cluster survey although we simultaneously determined that this unexpected high prevalence was likely due to overdiagnosis of trachoma by some of the trachoma graders; they admitted after interviewing that they had overdiagnosed active trachoma by defining a person with inflamed follicles of any size or number in any area of the eyelid as a case of active trachoma. This confirms the general consensus among trachoma experts that one of the challenges the trachoma elimination programme faces is accurate diagnosis of active trachoma in low prevalence settings. Despite efforts to develop visual aids to improve the training of trachoma graders, these tools are not sufficient to ensure correct diagnosis in field settings. The training of the TSO for the second survey followed a more rigorous training protocol, and we clearly expressed to the trachoma graders that it was not a problem if no cases were diagnosed. The final results show that there is no need for trachoma MDA in Togo, but that trichiasis surgery needs to be conducted through routine eye care services.
Integrated mapping of schistosomiasis, soil-transmitted helminthiasis and trachoma prevalence proved to be feasible and affordable on a national scale as was demonstrated at the district level in the Binah pilot. The integrated approach makes efficient use of resources, saving time and money. Teams were small and required only one vehicle for transport, yet each team included at least one expert for each disease. Customary laboratory technician training in Togo includes all of the parasitological testing procedures employed, so both technicians on a team could perform all tasks. Issues of organisation and communication were simplified by using few teams, and few teams were needed because local staff was engaged at each recruitment site, which facilitated and expedited the field work. The village chief and community health worker also assisted in bringing participants to a central location for examination. Additionally, and importantly, effective utilisation of local staff both builds local capacity and generates spontaneous local advocacy for integrated NTD control.
Following this successful nationwide integrated mapping of three NTDs, the MoH of Togo and partners received funding to conduct integrated MDA for schistosomiasis, STH and onchocerciasis in the 15 northern regions of the country in July 2010. More than 1.2 million people were treated for at least one of these NTDs. MDA for these same three diseases was completed in all 30 endemic districts in September 2011, reaching and treating more than 3 million people.