Introduction : Lymphatic filariasis (LF) is one of the neglected tropical diseases targeted for elimination as a public health issue in the world by 2020. To achieve this goal, one of the strategies is interruption of transmission using chemotherapy (mass drug administration). Burkina Faso in west Africa, an endemic country, has endorsed this resolution. In 2000, all Sanitary Districts (SD) in the country were endemic, and then a national elimination program has made it possible to stop mass treatment in 45 out of 70 SD over 12 years. Sixteen years later, 13 other SD were re eligible for Transmission Assessment Surveys (TAS) . This study aimed to determine the current level of the Mass drugs Administration (MDA) impact indicators in these 13 targeted SD in order to decide whether we need to continue MDA. Method : It was a descriptive study that took place from June to September 2017 in 13 SD regrouped into 7 Evaluation Units (EU). The population of the study was 6 to 7 years old children. The community-based cluster survey method was used. The diagnostic test used to detect Wuchereria bancrofti ’ s circulating antigen (W. bancrofti) is the F i lariasis Test Strip (FTS). The critical threshold of positivity was set at 18 positive subjects per EU. Results: We sampled a total of 12 , 060 children, 48.9% were female and 51.1% male. In the 7 EU, 13 children were positive to W. bancrofti test. The average antigenic prevalence was 0.11% (13/12 , 060). In all EU, the number of positive subjects was below the critical threshold. Conclusion: At the end of this evaluation of the transmission of lymphatic filariasis in 13 SD of Burkina Faso, we can tell the MDA could be stopped in these areas without risk of resurgence of the disease, according to the current recommendations of WHO. This can be possible by setting up post-TMM surveillance, considering migratory flows, and including villages where positive cases were found to search possible residual transmission zones.
Lymphatic Filariasis (LF) is a neglected tropical disease with vector-borne transmission. It is one of the diseases targeted by the World Health Organization (WHO) for elimination as a public health problem in the world by 2020. LF is endemic in 73 countries and about 1.39 billion people are at risk of infestation [
The interruption of transmission involves four steps: mapping, MDA, post-MDA monitoring, and checking of elimination by Transmission Assessment Surveys (TAS) [
Burkina Faso, in West Africa, a LF endemic country, has endorsed this elimination resolution. In 2000, a map showed endemicity of all Sanitary Districts (SD) in the country. A national elimination program was then implemented in 2001. Since then, over 124,911,968 million treatments have been administered to the population and that enabled the discontinuation of MDA in 45 out of 70 SD in 12 years [
We carried out a descriptive cross-sectional study that ran from June to September 2017 in 13 SD of the country that met the eligibility criteria of the WHO transmission assessment.
The requirements for inclusion of the SD and establishment of the evaluation units (EU) were:
− To have completed at least 5 rounds of MDA with coverage rates greater (≥) than 65%. The epidemiological coverage of medicines is the proportion of inhabitants of the evaluation unit (EU) who ingested the drugs on the total population of the evaluation unit.
− To have a prevalence of microfilaraemia (Mf) less than 1% or a prevalence of filarial antigenemia (Ag) less than 2% after the last effective MDA session for each sentinel site and point control site. The sentinel site and the control site must have Mf < 1% or Ag < 2% prevalence at all sites after the last successful MDA round. Plus, at least six months should have been elapsed since the last MDA.
The 13 SD have been regrouped into 7 Evaluation Units (EU) to meet the WHO criteria for evaluation below. All areas of an EU must share the same epidemiological features and a similar dynamic of LF transmission (epidemiological drug coverage, baseline prevalence, Mf or Ag prevalence at sentinel sites, point control sites, major LF parasites, and vector abundance). The population of the EU must not exceed two million inhabitants.
The study population was 6 to 7 years-old children living in these EU. These children was born when MDA where already established. The positivity of the
EU | Mapping prevalence in 2000 | Baseline Microfilaremia Prevalence | Mid-term microfilaremia Prevalence | Pre-TAS Prevalence | Number of actual MDA rounds |
---|---|---|---|---|---|
EU1: Bogandé-Manni | 52% | 23.90% | 1.80% | 0.86% | 13 |
EU2: Gayéri-Pama | 56% | 23.90% | 1.80% | 0.60% | 13 |
EU3: Garango-Pouytenga | 58% | 12.70% | 0.80% | 0.80% | 14 |
EU4: Centre 3 | 60% | 3.80% | 0.80% | 0% | 11 |
EU5: Sebba | 60% | 4.80% | 2.60% | 0.30% | 11 |
EU6: Kombissiri | 52% | 13.27% | 3.8% | 0.98% | 13 |
EU7: Manga | 46% | 16.80% | 8.80% | 0.30% | 13 |
antigen test would be more indicative of a recent transmission of filarial infection than in adults who had previously been exposed to infection during their lifetime. Recruitment could be done in schools if the net school enrollment rate is higher than 75%, if not, it should be done in the community. Due to the low rate of schooling (<75%) in all evaluation units, we have recruited children in the community [
The enumeration areas (EA) from the last general population and housing census were retained as clusters. The Microsoft Excel Computer Tool, Survey Sample Builder (SSB) was used to randomly generate numbers for the chosen clusters of EA in the selected EA. SSB isused to automate the calculations for determining the appropriate clusters [
All the households in the selected EAs were enumerated and numbered by the head nurses of the corresponding health facilities in a census book. Only households with numbers corresponding to the numbers provided by the SSB tool were surveyed.
All children aged 6 to 7 present in the selected household and living in the region for at least 6 months were recruited in the study. They were subjected to a blood test for filarial antigenemia. The qualitative detection of circulating antigen of W. bancrofti was performed on a blood sample using the Filariasis Test Strip (FTS), which is recommended by WHO for its better sensitivity [
Data collection was ensured in each EU by a team of 4 investigators including a biomedical technician. Investigators were first trained in the use of the data collection tool and the technicians were trained to use the FTS tape.
The data collection was done by a survey, including socio-demographic and biological items of the children. Additional information (length of stay in the region and level of schooling) was collected from children with a positive result.
The data were entered with the Epi Info Version 7.2 software and analyzed by IBM SPSS Statistic software version 22.
During implementation, the teams were supervised on the spot with a supervision tool [
The threshold value is the infestation prevalence threshold below which it is considered that transmission cannot be continued and upsurge is unlikely even in without of MDA. This value is expressed in number of positive cases for antigens or antibodies:
− If the number of positive cases is equal or lower than to the set threshold, the EU fulfills the terms and the public authorities can decide to stop the MDA.
− If the number of positive cases is greater than the set threshold, at least two additional rounds of MDA should be performed.
The SSB tool was used to select the threshold value of 18 positive cases for each EU in this study [
The study protocol was submitted and approved by the ethics committee of the Ministry of Health. Consent was required from parents or the responsible adult before the inclusion of children in the study. Treatment with ivermectin and albendazole was administered free of charge to the children who were positive and to their immediate entourage.
The 13 SD selected to participate to this study were Bogandé, Manni, Gayéri, Pama, Center 3 (regrouping the rural parts of SD of Boulmiougou, Nongre Massom and Signoghin), Garango, Pouytenga, Sebba, Kombissiri, Saponé, and Manga.
These SD were divided into seven evaluation units (
A total of 12,060 children from 6 to 7 years were recruited (
In all 7 EU, 13 children were tested positive on 12060 children, that means an average of 0.11% for filarial antigen prevalence of children born during MDA. The number of children tested positive was below the critical threshold (18 positives) in each EU.
Among the 13 children tested positive, 6 were female, 7 were 6 years old. Eight out of 13 children were not in school yet (
Characteristics | Size n Percentage (%) |
---|---|
Sex | |
F | 5902 (48.9) |
M | 6158 (51.1) |
Age | |
6 | 5902 (48.9) |
7 | 6158 (51.1) |
Treated before | |
Yes | 9395 (77.9) |
No | 2614 (21.7) |
Unknown | 51 (0.4) |
EU | Size | Positive | Prevalence (%) |
---|---|---|---|
EU1 | 1864 | 0 | 0 |
EU2 | 1572 | 2 | 0.13 |
EU3 | 1702 | 2 | 0.12 |
EU4 | 1835 | 3 | 0.16 |
EU5 | 1795 | 0 | 0.00 |
EU6 | 1604 | 2 | 0.12 |
EU7 | 1688 | 4 | 0.24 |
Total | 12,060 | 13 | 0.11 |
specifications | Effectif (n/13) |
---|---|
Sex | |
F | 6 |
M | 7 |
Age | |
6 | 7 |
7 | 6 |
Treated before | |
Yes | 9 |
No | 4 |
School | |
Yes | 5 |
No | 8 |
This evaluation, carried out in 13 SD (regrouped in 7 EU) of Burkina Faso, shows an average filarial antigenic prevalence of children born during MDA of 0.11%. The number of children tested positive, was below the critical threshold (18 positive) in each of the 7 EU, which is consistent with the forecasts of the Neglected Tropical Diseases National Program. Actually, the results of the mid-term and pre-TAS surveys were very conclusive compared to the baseline prevalence (
These results show the progress made in the interruption of transmission component and then, in the elimination of LF in Burkina Faso: the number of SD to be excluded from MDA in 2018 should be increased to 60 out of the total 70 SD in the country, which represent 88.7% of the country’s population [
For the post-MDA period, the other possibility is a resurgence of the disease in these supposedly controlled zones. These resurgences could come from imported cases (migration), or residual foci of transmission of the disease [
In the EU where positive cases were reported, 2 children (out of the 13) were immigrants from Côte d’Ivoire, a neighbouring country of Burkina Faso. This raises problems of migration, one of the factors that can threaten the success of lymphatic filariasis control activities [
− migration from endemic areas to non-endemic areas (rural or urban),
− migration from endemic areas to areas that have controlled the disease
− cross-border migration.
The last two cases are the ones concerning us: Migration from an endemic area to an area that controlled the disease within the country, and cross-border migration.
Burkina Faso is a migration country, the rural exodus towards the big cities, or more recently towards the mining zones. Thus, a migration of the endemic zones towards controlled areas is to consider because that could reintroduce the disease into these cleaned areas and the NTD program must be vigilant.
About cross-border migration, the first destination for Burkinabe immigrants is Côte d’Ivoire and also in the opposite direction, from Côte d’Ivoire to Burkina and is not only limited to border areas. The role of migrants in reintroducing transmission in “cleaned” areas would depend on several factors (climate, level of development of the country, etc.) [
If the migrant arrives in an area where the vector cannot survive, the transmission is interrupted. The Persian Gulf countries are the destination of millions of workers from South and Southeast Asian countries, a very endemic region of the LF. The antigenemic prevalence of LF in immigrant workers in Kuwait is 18% to 20% and the prevalence of microfilariae is 3%. However, there has been no evidence of infection of indigenous people [
The SD of Gayeri and Pama, bordering Niger and Sebba bordering Togo and Benin have however registered no positive cases. This brings the thought that the border zone can be used as transit for the migrant, who does not always settle there.
The implementation of an LF elimination program as well as intensive monitoring and evaluation between the two countries is needed. Particular focus is needed in coordinating programs with health authorities of neighboring countries for better efficiency on both sides. The zones of high migration and the one that hosts the most population returning from endemic areas should be targeted, for a more regular control. We can work to make drugs available to migrants before entering in Burkina Faso.
The implementations of adequate post-MDA surveillance as well as the reinforcement of morbidity management in the concerned SD are the immediate challenges to be meet. Considering the villages that have recorded positive cases in the next surveys for the transmission of LF in these EU, will allow assessing the impact of the treatment of the positive cases and their entourage. It will also determine the existence of a residual focus of transmission.
At the end of this evaluation study of the transmission of lymphatic filariasis in 13 SD of Burkina Faso, we can affirm that the MDA can be interrupted in these zones without risk of resurgence of the disease, according to the current recommendations of WHO. That can be possible by setting up post-MDA surveillance, considering migratory flows, and including villages where positive cases were found to search for any residual transmission focus.
We thank the actors of Regionals Directions and Sanitary districts of Health Ministry, the investigators, Helen Keller International through the project End NTD’s in Africa. Great thank to Serme Mamadou, the data manager.
The authors declare no conflicts of interest regarding the publication of this paper.
Ouedraogo, N.A., Ouedraogo, S.M., Tapsoba, G.P., Bougma, W.R., Serme, M., Kima, A., Kaboret, N., Sangare, I., Bougouma, C. and Drabo, F. (2018) Evaluation of Mass Drug Administration Impact on Transmission of Lymphatic Filariasis in 13 Sanitary Districts in Burkina Faso. Journal of Cosmetics, Dermatological Sciences and Applications, 8, 185-194. https://doi.org/10.4236/jcdsa.2018.84020