Background
Buruli ulcer (BU) is an emerging skin disease caused by an infection with
Mycobacterium ulcerans [
1‐
4]
. BU represents the third most common mycobacterial disease after tuberculosis and leprosy in immunocompetent hosts. Infection with
M. ulcerans often leads to extensive destruction of skin and soft tissue with the formation of large ulcers, commonly on limbs. About 60% of lesions occur on the lower limbs, 30% on the upper limbs and 10% on the rest of the body. Although the rate of mortality of Buruli ulcer is low, the serious morbidity caused by the disease includes functional disabilities that may result in permanent social, economic and developmental problems. At least 50% of those affected by BU are children aged < 15 years. Rate of infections among males and females are equal [
1‐
5]. To date, BU cases have been reported in over 30 countries, particularly in tropical and subtropical climate regions but also in temperate climate zones such as Japan and southern Australia [
1‐
5]. BU is a neglected tropical disease (NTD) with a poorly known global prevalence and mainly affects remote rural African communities [
6]. According to the WHO, from an estimated 7000 BU cases reported annually (2016) worldwide and more than 4000 cases occurred in Sub-Saharan Africa. The largest numbers of reported BU cases were from West African countries, particularly from Ivory Coast (about 2000 cases annually), Benin and Ghana as well, each of which reported about 1000 cases a year (2016) [
1‐
6].
In Togo, the first cases of BU have been described in 1996 by Portaels et al. [
7]. From 1996 to 2004, more than 100 cases were clinically diagnosed [
8,
9]. Between 2007 through 2010 [
9], a joint research project between the German Leprosy and Tuberculosis Relief Organization in Togo (DAHWT) and the Department for Infectious Diseases and Tropical Medicine, University Hospital, Ludwig Maximilians-University, Munich, (Germany) allowed the first systematic study of laboratory confirmed BU cases from Togo and established prevalence of BU in the Maritime Region of south Togo. Since 2011, within the frame of the European Community funded research project “BuruliVac”, a National Reference Laboratory for BU (NRL-UB) was established at the Institut National d’Hygiène (INH) and all BU cases notified were confirmed by IS
2404 PCR [
10].
Previous case-control studies [
11‐
15] have reported a high risk of contracting Buruli ulcer by swimming in or wading through a river. Residence near marshy areas with stagnant or slow-flowing water bodies and farming activities near rivers were additionally described as risk factors [
11‐
15]. Several epidemiologic studies in Africa [
16‐
19] and Australia [
20,
21] have identified aquatic sources as possible reservoirs of
M. ulcerans by detecting DNA of the pathogen in water filtrant and in a range of environmental samples. All these findings used PCR methodology which does not provide definitive proof for the presence of intact bacteria in a matrix. More recently, results from laboratory experiments [
22‐
25] have suggested a new hypothesis that aquatic insects, fish, plants and terrestrial mammals may be reservoirs for
M. ulcerans and that insect may be even involved in transmission to humans. In addition, the successful culture of
M. ulcerans from an aquatic water bug collected in Benin [
26] provides definitive evidence for the presence of
M. ulcerans in an aquatic invertebrate as possible reservoirs or vectors of
M. ulcerans.This considerable achievement showed that the
M. ulcerans is present in the environment and that transmission to humans might occur through contact with water or environmental samples contaminated with or harboring the mycobacteria [
27]. Inoculation of this pathogen into the subcutaneous tissue could occur when the exposed skin is traumatized. However, the exact mechanism of transmission of the bacterium remains unclear [
27].
Human-linked changes in the aquatic environment such as dam constructions on rivers, deforestation, agriculture and mining have led to environmental disturbance and may contribute to the spread of
M. ulcerans [
28,
29]
. This could increase the incidence of Buruli ulcer cases in endemic areas and lead to the emergence of
M. ulcerans in areas where the pathogen was previously absent [
28]. Some studies, mainly clinical [
7‐
10,
30‐
32], were carried out in Togo on BU but little were focused on socio-demographic, environmental or behavioral factors. We conducted this study to determine such risk factors for
M. ulcerans infection in the Zio and Yoto Districts in the Maritime Region.
Results
Clinical diagnosis, laboratory confirmation and characteristics of BU cases.
During the study period, 129 probable cases were observed (Table
1). ZN microscopy confirmed the presence of acid-fast bacilli (AFB) in 67 (52%) among probable cases while PCR detected
M. ulcerans DNA in 91 cases (71%). The two techniques were both positive in 58 cases (44.5%) and no AFB were detected from any of the PCR negative lesions (Table
1). Of all confirmed cases, lesions were mainly ulcers (41.7%), nodules (27.5%) and plaques (19.8%) (Table
2). Most of these lesions were found on the lower (40%) and the upper limbs (45%). The rest of lesions were localized on the buttocks, abdomen, back and head. Of 91confirmed cases, 83 (91%) responded to the questionnaire. The remaining 8 cases were absent at the time of the survey. Therefore, the case-control study was carried out with 83 cases and 128 control subjects. The socio-demographic characteristics of the participants are presented in Table
3.
Table 1
Yearly distribution of clinically suspected BU cases, laboratory tests used for confirmation and positive BU cases detected in Zio and Yoto Districts of Maritime Region, Togo, March 2013 to April 2015
Yearly distribution of BU suspected cases |
2013 (March to December) | 31 |
2014 | 63 |
2015 (January to April) | 35 |
Total | 129 |
Laboratory confirmation tests | Positive BU Cases, n (%) |
Ziehl-Neelsen microscopy (129 cases analyzed) | 67 (51.9) |
PCR technique (129 cases analyzed) | 91 (70.5) |
ZN microscopy and IS2404 PCR | 58 (44.4) |
Table 2
Type and localization of observed lesions in 91 BU cases in Zio and Yoto Districts of Maritime Region, Togo, March 2013–May 2015
Type of lesions |
Edema | 10 (10.9) |
Nodule | 25 (27.5) |
Plaque | 18 (19.8) |
Ulcer | 38 (41.7) |
Total |
91(100.0)
|
Localization of lesions |
Abdomen | 3 (3.0) |
Back | 2 (2.5) |
Buttocks | 3 (3.0) |
Head | 2 (2.5) |
Lower limbs | 37 (40.6) |
Upper limbs | 44 (48.3) |
Total |
91 (100.0)
|
Table 3
Socio-demographic characteristics of the participants of the case-control study in Zio and Yoto Districts of the Maritime Region, Togo, May 19–30, 2015
Number of participants | 83 (39.3) | 128 (60.7) | 211 | |
Sex | | | | 0.32 |
Female | 50 (60.2) | 68 (53.1) | 118 (55.9) | |
Male | 33 (39.8) | 60 (46.9) | 93 (44.1) | |
Age |
Median (range in years) | 11 (3–65) | 19 (8–60) | 15 (3–65) |
0.001
|
< 10 | 39 (47.0) | 15 (11.7) | 54 (25.6) | 0.01 |
11–14 | 16 (19.3) | 19 (14.8) | 35 (16.6) | 0.03 |
15–24 | 13 (15.7) | 47 (36.7) | 60 (28.4) | 0.76 |
> = 25 | 15 (18.1) | 47 (36.7) | 62 (29.4) | |
District of residence | | | | 0.75 |
Zio | 62 (74.7) | 98 (76.6) | 160 (75.8) | |
Yoto | 21 (25.3) | 30 (23.4) | 51 (24.2) | |
Education level | | | |
0.03
|
None | 19 (22.9) | 36 (28.1) | 55 (26.1) | |
Primary school | 57 (68.7) | 67 (52.3) | 124 (58.8) | |
Secondary school | 7 (8.4) | 25 (19.5) | 32 (15.2) | |
Ethnicity | | | | 0.48 |
Ewe | 76 (96.2) | 110 (97.3) | 186 (96.9) | |
Other (Lamba. Moba et Peulh) | 3 (3.8) | 3 (2.7) | 6 (3.1) | |
Number of people in household | | | | 0.58 |
Median (range) | 8.5 (2–40) | 8.0 (3–40) | 8.0 (2–40) | |
Univariate analysis
Socio-demographic characteristics of the participants
Most of BU patients (66%) were under 15 years of age and were significantly younger (median age = 11 years) compared to controls (median age = 19 years with 73% of who aged more than 15 years) (
p = 0.001) (Table
3). The primary school educational level was more frequent (59%) (
p = 0.03) in children aged ≤10 years (28.2%) while the secondary school educational level was associated with the 15–24 age groups (56.2%) (
p = 0.007) (Table
3). Among cases, women (60%) were more frequently affected than men (40%) (
p = 0.01). There was no significant difference in the number of people living per household between cases and controls (
p = 0.58) (Table
3).
Environmental factors
We found that drinking or washing clothes with water taken from rivers (
p = 0.95), open boreholes (
p = 0.98) and boreholes with pump (
p = 0.49) were not associated with an increased risk of contracting Buruli ulcer (Table
4). However, bathing with water from an open borehole was associated with higher risk of contracting BU (OR = 5.07, 95% CI =1.33–19.31) (Table
4). The frequent use of soap while bathing was not associated with reduced risk of BU (
p = 0.69). In contrary, a significant decrease of risk of
M. ulcerans infection was observed when using detergents for washing clothes or dishes (OR = 0.38, 95% CI = 0.32–0.45) (Table
4). Walking in stagnant water or wading in mud did not significantly increase risk of
M. ulcerans infection (
p = 0.72). However, frequently crossing a river (OR = 1.93, 95% CI = 1.09–3.39) or swimming (OR = 1.98, 95% CI = 1.11–3.52) in a river were associated with an increased risk of BU. Receiving cuts or scratches (OR = 1.88, 95% = 1.06–3.36) near rivers represented an additional increasing risk for contracting BU (Table
4).
Table 4
Univariate analysis of risk factors for Buruli ulcer disease in Zio and Yoto districts of Maritime Region, Togo, May 19–30, 2015
Farming | 77 (92.8) | 120 (93.8) | 0.86 (0.29–2.56) | 0.78 |
Farming activities |
Plowing | 79 (83.1) | 117 (91.4) | 0.46 (0.19–1.01) | 0.07 |
Sowing | 73 (88.0) | 123 (96.1) | 0.29 (0.09–0.90) |
0.03
|
Harvesting | 74 (89.2) | 125 (97.7) | 0.19 (0.05–0.75) |
0.01
|
Exposure to water |
Primary source of drinking water |
River or stream | 38 (45.8) | 58 (45.3) | 1.02 (0.58–1.77) | 0.95 |
Open borehole | 15 (18.1) | 23 (18.0) | 1.0 (0.49–2.01) | 0.98 |
Borehole with pump | 75 (90.4) | 119 (93.0) | 0.71 (0.26–1.92) | 0.49 |
Primary source of washing water |
River or stream | 42 (50.6) | 60 (46.9) | 1.16 (0.68–2.02) | 0.59 |
Open borehole | 21 (25.3) | 28 (21.9) | 1.21 (0.63–2.31) | 0.56 |
Borehole with pump | 73 (88.0) | 116 (90.6) | 0.75 (0.31–1.83) | 0.54 |
Bathing with a water from an open borehole | 9 (10.8) | 3 (2.3) | 5.07 (1.33–19.31) |
0.01
|
Standing water in house | 10 (12.0) | 18 (14.1) | 0.86 (0.38–1.97) | 0.72 |
Swam, waded or bathed in a river or stream | 37 (44.6) | 37 (28.9) | 1.98 (1.11–3.52) |
0.02
|
Crossed a body of water | 48 (57.8) | 55 (43.0) | 1.93 (1.09–3.39) |
0.02
|
Received cuts, scratches and thorn pricks near a river | 49 (62.8) | 60 (47.2) | 1.88 (1.06–3.36) |
0.03
|
Exposure to insect bite |
Received insect bite near a river | 50 (64.9) | 59 (46.5) | 2.13 (1.19–3.83) |
0.01
|
location of insect bite on the body |
Head | 48 (57.8) | 56 (43.8) | 1.76 (1.01–3.08) | 0.05 |
Forearms | 50 (60.2) | 57 (44.5) | 1.88 (1.08–3.31) |
0.03
|
Arms | 50 (60.2) | 59 (46.1) | 1.77 (1.01–3.10) |
0.04
|
Hands | 49 (59.0) | 57 (44.5) | 1.79 (1.03–3.14) |
0.04
|
trunk | 48 (57.8) | 57 (44.5) | 1.70 (0.98–2.98) | 0.06 |
thigh | 48 (57.8) | 56 (43.8) | 1.76 (1.01–3.08) | 0.05 |
Legs | 48 (57.8) | 57 (44.5) | 1.70 (0.98–2.98) | 0.06 |
Feet | 48 (57.8) | 57 (44.5) | 1.70 (0.98–2.98) | 0.06 |
Mosquito bite in house | 75 (90.4) | 124 (96.9) | 0.95 (0.48–1.89) | 0.90 |
Exposure to animals |
Owned livestock or pets | 60 (77.9) | 100 (78.7) | 0.95 (0.48–1.89) | 0.89 |
Handled livestock or pets | 12 (15.6) | 26 (20.6) | 0.71 (0.33–1.50) | 0.37 |
Share indoor living space with livestock or pets | 24 (32.4) | 37 (29.4) | 1.15 (0.62–2.14) | 0.65 |
Bitten or scratched by animals | 5 (6.7) | 10 (7.8) | 0.84 (0.27–2.56) | 0.76 |
Exposure to infectious agents |
BCG vaccination | 41 (51.2) | 64 (50.4) | 1.03 (0.59–1.181) | 0.90 |
Soap use while bathing |
Sometimes | 5 (6.4) | 10 (7.9) | 1 | |
Always | 73 (93.6) | 117 (92.1) | 0.80 (0.26–2.43) | 0.69 |
Soap use while washing |
Sometimes | 5 (6.0) | 0 (0.0) | 1 | |
Always | 78 (94.0) | 128 (100.0) | 0.38 (0.32–0.45) |
0.01
|
Clothing worn while farming |
Trousers | 40 (48.2) | 92 (71.9) | 0.36 (0.20–0.65) |
0.001
|
Top shirt | 76 (91.6) | 120 (93.8) | 0.72 (0.25–2.01) | 0.55 |
Closed shoes | 9 (10.8) | 26 (20.3) | 0.48 (0.21–1.08) | 0.07 |
Dress | 34 (41.0) | 48 (37.5) | 1.16 (0.66–2.03) | 0.61 |
Open shoes | 73 (88.0) | 110 (85.9) | 1.19 (0.522–2.73) | 0.67 |
Hat | 6 (7.2) | 35 (27.3) | 0.21 (0.08–0.52) |
0.001
|
Clothing worn in non-farming activity |
Trousers | 33 (39.8) | 61 (47.7) | 0.72 (0.41–1.27) | 0.26 |
Top shirt | 73 (88.0) | 118 (92.2) | 0.62 (0.25–1.56) | 0.31 |
Closed shoes | 4 (4.8) | 5 (3.9) | 1.25 (0.32–4.78) | 0.74 |
Dress | 33 (39.8) | 54 (42.2) | 0.90 (0.51–1.59) | 0.73 |
Open shoes | 72 (86.7) | 114 (89.1) | 0.80 (0.35–1.87) | 0.61 |
Hat | 1 (1.2) | 7 (5.5) | 0.21 (0.25–1.75) | 0.15 |
Insect protection products use |
Sometimes | 74 (96.1) | 118 (92.2) | 1 | 0.27 |
Always | 3 (3.9) | 10 (7.8) | 0.59 (0.22–1.64) | |
Bednets use |
Sometimes | 40 (51.3) | 76 (59.4) | 1 | |
Always | 38 (48.7) | 52 (40.6) | 0.72 (0.41–1.27) | 0.26 |
Perception and etiology of the BUD | 68 (88.3) | 113 (88.3) | 1.00 (0.42–2.42) | 0.99 |
Behavior and beliefs |
Poor hygiene cause Buruli ulcer | 57 (81.4) | 116 (91.3) | 0.42 (0.17–0.99) |
0.04
|
Seeking treatment with plants | 4 (5.3) | 10 (7.9) | 0.64 (0.19–2.12) | 0.47 |
Exposure to insects
Our study showed that receiving insect bites near a river was significantly increase risk of
M. ulcerans infection (OR = 2.13, 95% CI = 1.19–3.83) (Table
4). This risk was higher when it occurred on the forearm (OR = 1.88, 95% CI = 1.08–3.31), the arm (OR = 1.77, 95% CI = 1.01–3.10) and the hands (OR = 1.79, 95% CI = 1.03–3.14) compared to the other parts of the body. We found that mosquito bites at home were not associated with an increased risk of
M. ulcerans infection (
p = 0.90) (Table
4). The use of mosquito coils (
p = 0.27) or bednets (
p = 0.26) did not provide any significant reduction in the risk of contracting BU (Table
4).
Farming activities
Farming (93.8%) was the main activity of the participants of the study. However, there was no significant difference in practicing this activity between patients and controls (
p = 0.78) (Table
4). In addition, some tasks such as sowing (OR = 0.29, 95% CI = 0.09–0.90) or harvesting (OR = 0.19, 95% CI = 0.05–0.75) during farming showed significant decrease in the risk of contracting BU (Table
4). Frequently wearing trousers (OR = 0.36, 95% CI = 0.20–0.65) or a hat (OR = 0.21, 95% CI = 0.08–0.52) while performing farming activities provided significant reduction in the risk. However, wearing clothes at home or in non-farming activities did not provided any significant reduction in the risk of BU disease (Table
4).
Exposure to animals
In our study, we found that living with (
p = 0.89) or sharing indoor living space with livestock (
p = 0.37) did not represent a significant increase in the risk of
M. ulcerans infection neither did incurring bites or scratches from (
p = 0.76) (Table
4). Also, hunting or handling of wild animals (
p = 0.65) was not significantly associated with an increasing risk of BU infection.
BCG vaccination
Most of participants showed BCG vaccine scars and there was no significant difference between cases and controls (
p = 0.90) (Table
4).
Attitude, behavior and beliefs of BUD
Of the participants interviewed, 88.3% were familiar with BU symptoms and this attitude was similar between BU cases and controls (
p = 0.99). Regarding treatment behaviors, most of cases (83.5%) indicated seeking help from hospital while 5.3% believed in herbal treatment as the first preferred treatment option (Table
4). Considering the hygiene practice, BU cases as well as controls thought that personal poor hygiene and dirty surroundings could increase the risk of contracting BU (Table
4).
Multivariate analysis
After adjustment for potential confounders, we found that factors such as age (< 10 years (aOR = 11.48, 95% CI = 3.72–35. 43) and 10 to 14 years (aOR = 3.63, 95% CI = 1.22–10.83)), receiving insect bites near a river in children aged 10 to14 years (aOR = 7.8, 95% CI = (1.48–41.24)) and bathing with water from open borehole (aOR = 5.77, 95% CI = 1.11–29.27) (Table
5) remain as potential factors of increasing risk of
M. ulcerans infection.
Table 5
Multivariate model for risk factors of Buruli ulcer disease in Zio and Yoto Districts of the Maritime Region, Togo, May 19–30, 2015
Age (Years) |
< 10 | 11.48 (3.72–35.43) |
0.001
|
11–14 | 3.63 (1.22–10.83) |
0.02
|
15–24 | 1.07 (0.39–2.97) | 0.88 |
> 25 | 1 | |
Receiving insect bites near a river (Yes/No) |
< 10 (years) | 3.29 (0.77–14.04) | 0.11 |
11–14 (Years) |
7.80 (1.48–41.21)
|
0.016
|
15–24 (Years) | 3.05 (0.71–12.99) | 0.13 |
> 25 (Years) | 1.76 (0.48–6.45) | 0.39 |
Bathing with water from open borehole | 5.77 (1.11–29.27) |
0.03
|
Discussion
The objective of this study was to identify risk factors for Buruli ulcer in the two endemic districts of Zio and Yoto of the Maritime region. This is the first study that has investigated these factors in Togo. In general, socio-demographic, behavioral or environmental factors have been considered as important risk factors for M. ulcerans infection.
Socio-demographic factors
The present study showed that children under 15 years of age were at higher risk of contracting Buruli ulcer than adults. This result is in accordance with other studies conducted in Benin [
11] and Ivory Coast [
13] as well as WHO reports [
37]. Indeed, in this age group children appeared to be often less protected especially at the head and feet [
11]. Also, children’s behavior is usually driven by their parents’ activities as they accompanied them to the river for washing and for farming where they were highly exposed to aquatic areas that are associated with an increasing risk of BU infection.
Environmental factors
We found that bathing with water from an open borehole was associated with higher risk of contracting BU. Similar results were found in Ghana [
38], Ivory Coast [
39] and Cameroon [
14]. Indeed, other studies [
6,
28,
40] have also shown that using unprotected water sources for bathing was associated with
M. ulcerans infection. It has also been observed that even when used with soap, unprotected water sources constitute an increased risk of
M. ulcerans infection [
37]. However, Raghunathan et al. [
38] in Ghana found that using a detergent while bathing provides significant reduction in Buruli ulcer risk. This difference could be explained by the antibacterial power of the soap used. Besides, in our study people from villages commonly used the local soap. On the other hand, we found that using soap to wash clothes or dishes was reducing the risk. This time, the type of the soap used for the laundry is provided from commercial brands which are strongly enriched in detergents and acids. Our study also identified other water sources of
M. ulcerans infection such as swimming in a river, frequently crossing a river, receiving insect bites or injuries of cuts near rivers. However, after adjustment for potential confounders, only receiving insect bites near a river remained as an independent predictor of acquiring BU infection. Similar results were found in Ghana [
38] but in Ivory Coast [
13] and in other study [
12], it was found that swimming or wading in water did significantly increase the risk of BU infection. To explore the difference of our finding with other studies, we looked to determine any potential age confounding or effect modification. Therefore, we found that insect bites increase the risk of BU only in 101-14 years age group (aOR = 7.80, 95%CI = 1.48–41.21). Though, other studies did not determine in which age group swimming or wading in water significantly increased the risk of BU, we could explain the difference between these studies by the age of BU cases. Further, in our study, 63% of BU cases were aged < 15 years while in Ivory Coast, 75% of cases were aged more than 15 years who are able to swim or wad in a river.
Most of the people surveyed were perform agricultural activities. However, we did not find any significant association with the risk of contracting BU. Among agricultural activities, planting and harvesting activities were associated with decrease risk of
M. ulcerans infection. Similar results were found in Cameroon [
14]. We observed that wearing a long-sleeved shirt or a long dress while performing agricultural activities did not provide significant reduction of the risk of contracting of Buruli ulcer. This observation is in accordance with the study conducted in Cameroon [
14]. On the other hand, we found that wearing pants or hats is associated with reduction in the risk of mycobacterial infection. This would explain the low frequency of wounds on head and legs observed in our investigation. These results are consistent with those found in Ghana [
12,
38] and Ivory Coast [
13].
In Australia, Lavender et al. [
20] showed that mosquito bites were significantly associated with Buruli ulcer. However, we did not find any risk of
M. ulcerans infection associated to mosquito bites in Togo. In general, results of studies on mosquito bites associated with the use of mosquito coils or bednets during
M. ulcerans infection are often contradictory [
11,
14,
38,
39,
41].
Some studies [
12,
13,
42] have shown that animals such as chickens, goats, cats and pigs could harbour
M. ulcerans and exposure to these animals may increase the risk of contracting BU disease. During this study, we did not observe significant increase in risk of contracting BU associated with contact with domestic animals.
BCG vaccine is delivered against a mycobacterium. This vaccination could therefore provide a cross-protection against
M. ulcerans infection [
43]. In our study, we did not observe any significant difference in the percentage of BCG vaccination scar between patients and controls. The lack of a significant association with BCG vaccination with
M. ulcerans infection has been also described in the literature [
12,
16,
43]. However, data from Benin [
11], Ivory Coast [
13] and Cameroon [
14] showed negative correlation between BCG vaccination and BU. Studies conducted to explore this possible cross-protection have often led to contradictory results. Indeed, a multicenter study [
44] conducted in the DR Congo, Ghana and Togo did not reveal any significant association between BCG vaccination and BU disease.
Attitude, behavior and belief on BU
The attitude of the participants interviewed has considerably improved with their capacity to recognize some BU symptoms and their ability to refer suspected cases to medical treatment compared to the situation 5 years before [
33]. This finding could be attributable to several awareness campaigns in the community that had influenced their behavior toward this disease [
33]. However, there remains some effort to help recognizing early symptoms by the community as well as the herbalists because 5.3% of BU patients continue to believe in herbal treatment as the first preferred treatment option. Poor individual hygiene and dirty surrounding were recognized as a potential risk factor for participants in the present study. The impact of poor hygiene and its possible role as a risk factor has been underlined in studies in Benin [
11,
45] and Ghana [
12].
This study had some limitation. We did not reach all participants especially some BU cases due to their unavailability during the survey time. The sample size was calculated based on the proportion of households using water from unprotected sources which was higher than the prevalence of BU. The number of newly confirmed BU cases in Togo every year is low and varies from 30 to 65 patients. During the study period, we found 91 BU cases but 8 patients were not available at the survey time. The main concern with the limit number of controls was due to the fact that in many households, there were often two to three patients and exceptionally in one house up to six. In those households, it was difficult to enroll two folds of controls. Moreover, as 47% of BU patients were under 10 years, it was difficult to interview children who were not capable to describe their activities which are driven by their parent’s duties. The reason we had decided to use their parents as controls sometimes.
Acknowledgements
We would like sincerely to thank the Institut National d’Hygiène through its Director for supporting financially this study and ensuring the logistic of the investigation. We also express our acknowledgments to the National Program for the Control of Buruli Ulcer, Leprosy and Pian through its Coordinator for authorizing the survey. Many thanks to the CNTR-UB and PNLU-LP focal points.