Abstract
Background
Visceral leishmaniasis (VL) is a neglected tropical disease affecting vulnerable refugee populations, including refugees residing in camps in Ethiopia’s Gambella and Benishangul Gumuz regions. With refugees from VL-endemic areas, identifying key environmental, behavioral, and demographic risk factors is essential for effective prevention. This study addresses knowledge gaps on Leishmania infection determinants, supporting targeted interventions to enhance disease control and inform public health efforts in crisis-affected regions.
Methods
A matched case-control study was conducted from May-August 2023 included 336 participants from four refugee camps (Kule, Terkidi, Tsore, and Sherkole) in Ethiopia. Data on socio-demographic, behavioral, and environmental factors were collected through interviewer-administered questionnaires. Blood samples were tested for Leishmania detection using the direct agglutination test and real-time polymerase chain reaction. Chi-square tests and multivariable conditional logistic regression assessed associations between independent variables and Leishmania infection.
Results
A total of 336 participants, 252 controls and 84 cases, were enrolled from all selected refugee camps. The distribution of matching variables among cases and controls by age group, sex, and region of camp location showed that they were similarly distributed (p > 0.05). Significant risk factors included residing in the camp for less than five years (AOR = 1.76, 95% CI: 1.06–2.93, P = 0.028), sleeping outside during the daytime (AOR = 2.38, 95% CI: 1.46–3.89, P < 0.001) or nighttime (AOR = 1.68, 95% CI: 1.07–2.64, P = 0.025), and the presence of bushes around the house (AOR = 1.76; 95% CI: 1.12–2.77, P = 0.014). Other analyzed factors, including educational level, seasonal sleeping habits, and proximity to termite hills, were not statistically significant.
Conclusion
The study identifies key behavioral and environmental risk factors for Leishmania infection among refugees, emphasizing targeted vector control and community education. Urgent interventions are needed to reduce transmission, protect vulnerable populations, and improve health outcomes in refugee camps and local villages in Gambella and Benishangul Gumuz regions of Ethiopia.
Clinical trial
Not applicable.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12879-026-12647-6.
Keywords: Behavioral factors, Environmental factors, Epidemiology, Infectious diseases, Risk factors, Visceral leishmaniasis, Ethiopia
Background
Leishmaniasis represents a complex of diseases caused by protozoan parasites of the genus Leishmania and is spread through the bites of infected female sandflies [1, 2]. The disease is considered as one of the neglected tropical diseases (NTDs) that significantly affects health in poor, remote regions with limited access to healthcare [3]. The clinical presentation is classified as visceral and cutaneous leishmaniasis, depending on the manifestation of the disease [4]. Visceral leishmaniasis (VL), also known as Kala-azar, is of higher priority than cutaneous leishmaniasis as it is a fatal disease in the absence of treatment [2]. VL is endemic in 79 countries, with a global estimated cases of 50,000 to 90,000, 20,000 to 30,000 deaths per year, and 1 billion people at risk [5]. In East Africa, VL is mainly caused by Leishmania donovani species, a major public health challenge, with some of the highest case rates in the world, often resulting in outbreaks [6–9].
Several factors including environmental changes and population migration between affected and unaffected regions are thought to influence the spread of Leishmania infection. Additionally, the presence of drug-resistant parasite strains and weakened immunity often due to malnutrition or HIV co-infection play a significant role [6, 10]. Among these factors, population migration is particularly significant given the global scale of displacement reported by the United Nations High Commissioner for Refugees (UNHCR), that there are more than 122 million displaced populations; of these 37.4 million people are refugees across the globe in 2023 [11]. Refugees, due to their frequent movement, inadequate living conditions, and limited access to healthcare, are highly vulnerable to infectious diseases. Visceral leishmaniasis has occasionally been reported in refugee camps [7, 12]. There is also a report that showed a strong relationship between civil unrest and VL [13].
In this regard, the government of Ethiopia opens its borders for refugees, the majority originating from South Sudan, Somalia, Eritrea, and Sudan. Ethiopia hosts a large number of refugees, many of whom are located in camps in the Gambella and Benishangul Gumuz regions, situated in the western part of Ethiopia. A large number of refugees in these camps came from areas where VL is endemic. Moreover, Gambella and Benishangul Gumuz regions have been identified as at high risk of VL based on geographical and climatological features [14, 15]. Consequently, refugees could be at high risk of contracting and transmitting Leishmania parasites to the indigenous community and vice versa [14]. Studies conducted in East Africa have identified various exposure factors associated with VL infection across different study locations and population groups. For instance, sleeping under an acacia tree at night [15, 16], the presence of cracked walls, and living in large households have been highlighted as risk factors [15, 17, 18]. Similarly, findings from Kafta-Humera, a region in northern Ethiopia, indicate that among migrant agricultural workers, a lower level of education significantly increases the risk of infection [15]. On the other hand, the use of bed nets has been observed to have a protective effect for VL infection [15]. Broadly speaking, social and political influences, such as military activities and agricultural development projects, are major contributors to VL endemicity and outbreaks in both Sudan and Ethiopia [13]. Despite few reports showing the exposure factors of Leishmania infections in these areas, localized and current evidence on specific risk factors such as environmental exposures, behavioral practices, and demographic factors remain scarce in refugee populations. Without a clear understanding of these factors, interventions remain generalized and may fail to reduce the infection rates effectively. Generating evidence to address this knowledge gap is important for designing effective Leishmania infection prevention strategies in refugee camps.
This may also help policymakers, health authorities, and humanitarian organizations implement targeted interventions. Beyond immediate public health benefits, the study also contributes to the broader understanding of infectious disease epidemiology in crisis settings, offering a framework for similar displacement-affected regions. Thus, this study aimed to assess the risk factor of Leishmania infection among selected refugee camps in Gambella and Benishangul Gumuz regions using a matched case-control study design.
Methods
Study setting
This study was conducted in four purposely selected refugee camps (with opened date) as described by Belay et al., 2025 (publication under review): Kule (February 2014) and Terkidi (June 2014) in Gambella, and Tsore (January 2015) and Sherkole (January 2005) in the Benishangul Gumuz regional states of Ethiopia. These camps were chosen among a total of seven camps in Gambella and three in Benishangul Gumuz regional states. The refugee camps host large populations of South Sudanese and Sudanese refugees and are located bordering the countries of South Sudan and Sudan [19]. In addition, these refugee camps are located in Itang and Homosha districts of Gambella and Benishangul Gumuz regional states, respectively. Itang, west of the Gambella region, hosts the Terkidi and Kule camps, sheltering 125,396 refugees. Similarly, Homosha, located near Assosa, the capital city of the Benishangul Gumuz Gumuz region, is home to the Tsore and Sherkole camps, which hold a total of 58,681 refugees [19] (Fig. 1). The regions are characterized by hot, humid climates, proximity to rivers and forests. Healthcare services are provided by NGOs and the Ethiopian Ministry of Health, but diagnosis and treatment remain inadequate, leading to underreporting and delayed interventions. Moreover, these camps have ecological conditions conducive to sandfly survival, increasing the risk of VL transmission [20, 21].
Fig. 1.
Geographical location of selected refugee camps in Benishangul-Gumuz and Gambella regions, Ethiopia, and bordering South Sudan and Sudan, 2023
Study design and population
A matched case-control study design was derived from cross-sectional data that was collected from May to August 2023. The cross-sectional study provided a snapshot of exposures and outcomes during data collection. Cases were matched to controls based on predefined criteria (age, sex, and region of camp location) to control for confounding variables. The data collection occurred within a defined timeframe, ensuring consistency in exposure assessment and minimizing recall bias. The study captured exposure and outcome information simultaneously, allowing for an efficient analysis of associations while maintaining the advantages of a case-control approach.
The source population included all individuals living in the refugee camps in Gambella and Benishangul Gumuz regional states. The study participants were refugees (five years of age and older) living in the selected camps. Individuals living in the camp for at least six months and willing to provide assent and/or written informed consent were included in the study. Moreover, the study population consisted of cases and matched controls selected from the source population based on predefined eligibility criteria. This matching process helped reduce confounding and enhanced the validity of comparisons. Individuals who were unable to speak, listen, or assent and/or provide written informed consent and who declined to participate or provide blood samples were excluded from the study.
Cases were defined as participants testing positive for Leishmania by either DAT and/or rtPCR. Whereas controls were defined as individuals who tested negative for Leishmania by both the DAT and rtPCR methods. The DAT was carried out as previously described, with titers ≥ 1: 1600 considered to be positive [22, 23]. The overall test performance of sensitivity of the DAT was 95.3% for the diagnosis of VL in Ethiopia [24]. The KDNA-based PCR was conducted as described elsewhere [25]. The diagnostic sensitivity of rtPCR for the diagnosis of VL using peripheral blood as specimens was measured at 98.08% and 100.00% specificity [26].
Sample size determination
The sample size was calculated using the freely available statistical tool “(https://www.openepi.com/SampleSize/SSCC.htm)” based on the proportion of exposure and the odds of availability of bushes around the house. In the previous study conducted in Gedaref State, Sudan [16], it was revealed that the presence of bushes, including some acacia trees, was found to be a risk factor for VL. So that we used the following parameters to estimate the minimum sample size for the current study: 43.5% of the controls reported bushes around the house, odds ratio of 2.2, with 80% power and 95% CI, and 1:3 cases to control ratio, then the sample size was estimated to be 76 cases and 226 controls. Adding 10% non-response rate, the final sample size was 84 cases and 252 controls, with a minimum total sample size of 336.
Selection of cases and controls
Cases were recruited from the previously conducted cross-sectional prevalence study. All participants tested positive using direct agglutination test (DAT) with titer 1:1600 concentration [22, 23] and/or rtPCR were eligible for recruitment for the study. The cases were distributed in the four refugee camps: Kule, Terkidi, Tsore, and Sherkole. Controls were selected from the same dataset, considering a distribution of age groups, sex, and region of camp location with match tolerance factors of 2, 1, and 1, respectively. This means that cases and controls could differ by up to two years in age, but had to be identical in sex and camp location. Controls were also selected based on the negative test to DAT (agglutination < 1:1600) and rtPCR. Case-control matching was performed using in SPSS, with three controls selected percase according to predefined matching criteria.
Study variables
Dependent variable: Leishmania infection in the refugee camps.
Independent variables: stratified as socio-demographic, behavioral, environmental, and housing condition factors (Fig. 2).
Fig. 2.
Description of independent variables: stratified as socio-demographic, behavioral, environmental and housing condition factors in matched case-control study in refugee camps in Gambella and Benishangul-Gumuz regional states, Ethiopia, 2023
Data collection
A structured questionnaire (Supp_File), based on existing forms [15, 18, 22, 23, 27, 28], was designed and utilized to collect demographics and potential risk factors, such as socio-demography, environmental and behavioral factors from both Leishmania infected individuals and healthy controls in the selected refugee camps. Then, blood samples were collected and tested for Leishmania antibody and kDNA presence to categorize study participants as cases or controls. Cases were selected based on operational definitions as stated above from the list of participants. After identification of the cases, controls who lived in the same location (region), age group (5–14, 15–39, and ≥ 40 years), and sex comparable to cases were included.
Data processing and analysis
Data was cleaned for completeness and consistency, coded and entered into EpiInfo version 7.0. and exported into Microsoft office excel then to Statistical Package for the Social Sciences (SPSS) version 24 for further analysis. The results were organized, summarized, and presented using texts, tables, and graphs. Descriptive statistics were used to summarize characteristics of cases and controls. Chi-square tests were used to compare the percentages of cases and controls in terms of selected categorical variables. Bivariate conditional logistic regression was analyzed to examine the association between each independent variable and the outcome and to calculate unadjusted odds ratios with 95% confidence intervals. Independent variables that were statistically significant at p < 0.20 in the bivariate analysis were retained and included in the multivariable conditional logistic regression model. All the candidate variables were entered into a multivariable binary logistic regression model to identify the effects of independent variables on the outcome variable. The fitness of the model was checked by the Hosmer and Lemeshow goodness-of-fit test. Multi-collinearity effects among independent variables based on the assumption of the variance inflation factor (VIF) were checked. The level of significance was set at 0.05.
Results
Socio-demographic characteristics
A total of 336 participants, 252 controls and 84 cases, participated in all selected refugee camps. Among the cases, 12 tested positive by DAT only, 53 tested positive by rtPCR only, and 19 tested positive by both DAT and rtPCR. The majority of individuals in both groups were from refugee camps located in Benishangul Gumuz regional state (89.3% control, 89.3% cases). Females predominate in both groups (65.5% control, 65.5% cases). The average age of participants in both case and control groups was similar. Most participants reside in Tsore camp (78.6% control, 74.6% cases). In terms of level of education, a prominent portion in both groups had reported that grade one to eight (47.6% control, 53.6% cases). In marital status, married individuals were more common in both groups (64.3% control, 62.3% cases), followed by singles. On the other hand, the test of independence was conducted to measure the proportion distribution among variables of cases and control. As a result, the distribution of matching variables age group, sex, and region of camp location showed that they were similarly distributed (p > 0.05) (Table 1). The mean number of family members per household was found to be six individuals for both controls and cases. Camp duration was also reported to have a mean year of duration of 5.6 and 6.8 for the control and case groups, respectively (Supp_Table_1). See Supplementary Table 2 for the distribution of environmental and behavioral risk factors of Leishmania infection among participants.
Table 1.
Socio demographic characteristics of participants in matched case-control study in refugee camps in Gambella and Benishangul Gumuz regional States of Ethiopia, 2023
| Variables | Description | Case (%) | Control (%) | Total (%) | P value | |
|---|---|---|---|---|---|---|
| Region | Benishangul Gumuz | 75 (89.3) | 225 (89.3) | 300 (98.3) | 1.000 | |
| Gambella | 9 (10.7) | 27 (10.7) | 36 (10.7) | |||
| Gender | Male | 29 (34.5) | 87 (34.5) | 116 (34.5) | 1.000 | |
| Female | 55 (65.5) | 165 (65.5) | 220 (65.5) | |||
| Camp Name | Kule | 6 (7.1) | 21 (8.3) | 27 (8.0) | 0.729 | |
| Terkidi | 3 (3.6) | 6 (2.4) | 9 (2.7) | |||
| Tsore | 66 (78.6) | 188 (74.6) | 254 (75.6) | |||
| Sherkole | 9 (10.7) | 37 (14.7) | 46 (13.7) | |||
| Age Group in years | 5–14 | 18 (21.4) | 53 (21.0) | 71 (21.1) | 0.807 | |
| 15–39 | 56 (66.7) | 175 (69.4) | 231 (68.8) | |||
| ≥ 40 | 10 (11.9) | 24 (9.5) | 34 (10.1) | |||
| Country of Origin | South Sudan | 44 (52.4) | 116 (46.0) | 160 (47.6) | 0.313 | |
| Sudan | 40 (47.6) | 136 (54.0) | 176 (52.4) | |||
| Level of education | No formal education | 32 (38.1) | 77 (30.6) | 109 (32.4) | 0.163 | |
| Grade 1–8 | 40 (47.6) | 135 (53.6) | 175 (52.1) | |||
| Grade 9–12 | 11 (13.1) | 25 (9.9) | 36 (10.7) | |||
| College/university | 1 (1.2) | 15 (6.0) | 16 (4.8) | |||
| Marital Status | Married | 54 (64.3) | 157 (62.3) | 211 (62.8) | 0.745 | |
| Single | 30 (35.7) | 95 (37.7) | 125 (37.2) | |||
| Length of stay in the camp | ≤ 5 years | 60 (71.4) | 136 (54.0) | 196 (58.3) | 0.005 | |
| > 5 years | 24 (28.6) | 116 (46.0) | 140 (41.7) | |||
| Family Size (HH members) | ≤ 4 | 57 (67.9) | 151 (59.9) | 208 (61.9) | 0.195 | |
| > 4 | 27 (32.1) | 101 (40.1) | 128 (38.1) | |||
The distribution of case and control participants in terms of country of origin (South Sudan vs. Sudan) and their respective states where the refugees come from is depicted in supplementary Table 3. In South Sudan, the majority of the participants were from Upper Nile (32.9% control, 45.2% cases), followed by Jonglei (11.5% control, 4.8% cases) and Lakes (0.8% control, 2.4% cases). In Sudan, Blue Nile dominated (30.2% control, 40.5% cases), Khartoum (4.8% control, 3.6% cases), and North Darfur (4.0% control, 1.2% cases) states (Supp_Table_3).
Determinants of Leishmania infection
The bivariate analysis identified significant associated factors between sociodemographic, environmental, and housing conditions and behavioral risk factors with Leishmania infected cases as indicated in Table 2. Sleeping outside during daytime (COR = 2.78; 95%CI = 1.71–4.51, p < 0.001) and nighttime (COR: 1.65; 95%CI: 1.07–2.56; p = 0.024), bush presence around the house (COR: 1.81; 95%CI: 1.17–2.81; p = 0.008), and cracked house walls (COR = 1.82; 95%CI: 1.15–2.90; p = 0.011) were associated with increased unadjusted odds of cases of Leishmania infection. In addition, among the sociodemographic factors, Leishmania infected participants who lived less than five years in the camp were 1.91 times more exposed compared to those who lived more than five years in the camp (COR: 1.91; 95%CI: 1.16–3.15; p = 0.011). On the other hand, bed net use showed a protective trend (COR = 0.59, p = 0.096), termite hills near to sleeping place (COR = 1.60, p = 0.075), and always sleeping outside during the dry season (COR = 1.56, p = 0.093) had a higher risk of being infected with Leishmania, but the association was not statistically significant. Furthermore, factors including presence of cracked floors, and termite hills near the house were not statistically significantly associated with cases of Leishmania infection among study participants (Table 2).
Table 2.
The bivariate association between sociodemographic, environmental, and housing conditions and behavioral risk factors with Leishmania infected cases: a case-control study conducted in Gambella and Benishangul Gumuz regional states of Ethiopia, 2023
| Variables | Description | Case (%) | Control (%) | COR | P value | |
|---|---|---|---|---|---|---|
| Sociodemographic factors | ||||||
| Camp Name | Kule | 6 (7.1) | 21 (8.3) | 0.62 (0.14–2.85) | 0.541 | |
| Tsore | 66 (78.6) | 188 (74.6) | 1.37 (0.66–2.83) | 0.400 | ||
| Sherkole | 9 (10.7) | 37 (14.7) | Ref | |||
| Country of Origin | South Sudan | 44 (52.4) | 116 (46.0) | 1.26 (0.79–2.01 | 0.336 | |
| Sudan | 40 (47.6) | 136 (54.0) | Ref | |||
| Level of education | No formal education | 32 (38.1) | 77 (30.6) | 5.12 (0.68–38.65) | 0.113 | |
| Grade 1–8 | 40 (47.6) | 135 (53.6) | 3.90 (0.52–29.12) | 0.184 | ||
| Grade 9–12 | 11 (13.1) | 25 (9.9) | 5.22 (0.66–41.22) | 0.117 | ||
| College/university | 1 (1.2) | 15 (6.0) | Ref | |||
| Marital Status | Married | 54 (64.3) | 157 (62.3) | 1.09 (0.65–1.85) | 0.741 | |
| Single | 30 (35.7) | 95 (37.7) | Ref | |||
| Length of stay in the camp | ≤ 5 years | 60 (71.4) | 136 (54.0) | 1.91 (1.16–3.15)* | 0.011 | |
| > 5 years | 24 (28.6) | 116 (46.0) | Ref | |||
| Family Size (HH members) | ≤ 4 | 57 (67.9) | 151 (59.9) | Ref | ||
| > 4 | 27 (32.1) | 101 (40.1) | 1.31 (0.82–2.10) | 0.252 | ||
| Behavioral practice factors | ||||||
| Sleep during day time | Outside | 26 (31.0) | 24 (9.5) | 2.78 (1.71–4.51)** | < 0.001 | |
| Inside | 58 (69.0) | 228 (90.5) | Ref | |||
| sleep during night time | Outside | 38 (45.2) | 75 (29.8) | 1.65 (1.07–2.56)* | 0.024 | |
| Inside | 46 (54.8) | 177 (70.2) | Ref | |||
| Always use bed net while sleeping | Yes | 13 (15.5) | 64 (25.4) | 0.59 (0.32–1.10) | 0.096 | |
| No | 71 (84.5) | 188 (74.6) | Ref | |||
| Frequency of sleeping outside during dry season | Always | 39 (46.4) | 65 (25.8) | 1.56 (0.93–2.62) | 0.093 | |
| Sometimes | 20 (23.8) | 111 (44.0) | 0.62 (0.34–1.12) | 0.113 | ||
| Never | 25 (29.8) | 76 (30.2) | Ref | |||
| Environmental and housing conditions | ||||||
| Bushes available around the house | Yes | 38 (45.2) | 69 (27.4) | 1.81 (1.17–2.81)* | 0.008 | |
| No | 46 (54.8) | 183 (72.6) | Ref | |||
| Presence of cracked wall | Yes | 28 (33.3) | 46 (18.3) | 1.82 (1.15–2.90)* | 0.011 | |
| No | 56 (66.7) | 206 (81.7) | Ref | |||
| Presence of termite hills near house | Yes | 31 (36.9) | 70 (27.8) | 1.38 (0.88–2.17) | 0.164 | |
| No | 53 (63.1) | 182 (72.2) | Ref | |||
| Termite hills present near sleeping place < 5 m | Yes | 20 (23.8) | 36 (14.3) | 1.60 (0.95–2.67) | 0.075 | |
| No | 64 (76.2) | 216 (85.7) | Ref | |||
| Presence of cracked floor near to sleeping place | Yes | 15 (17.9) | 32 (12.7) | 1.35 (0.77–2.39) | 0.299 | |
| No | 69 (82.1) | 220 (87.3) | Ref | |||
*<5 m: less than five-meter distance; COR: Crude Odds Ratio; 95% CI: 95% Confidence Interval; Ref: Reference variable; *p-values less than 0.05; **p-values less than 0.001
The adjusted analysis examined various factors associated with the cases of Leishmania infection. Variables with < 0.20 p values in the bivariate analysis were entered into the multivariate model and analyzed using the backward step-wise conditional logistic regression method. Duration in the camp lower than five years were significantly associated with cases of Leishmania infection (AOR = 1.76, 95% CI: 1.06–2.93, P = 0.028). Sleeping outside during the daytime (AOR = 2.38, 95% CI: 1.46–3.89, P < 0.001) and nighttime (AOR = 1.68, 95% CI: 1.07–2.64, P = 0.025) increased odds, and bushes available around the house was found to be an exposure factor to increase the odds of a case infected with Leishmania (AOR = 1.76; 95% CI: 1.12–2.77, p = 0.014). On the other hand, other variables we analyzed in the conditional logistic regression model were not statistically significant: level of education, frequency of sleeping outside during dry season, either always or sometimes respondents, and presence of termite hills near sleeping place < 5 m (Table 3).
Table 3.
Results from multivariable conditional logistic regression model of the adjusted odds ratios, together with 95% CI, for the risk of Leishmania infection in refugee camps in Gambella and Benishangul Gumuz regional states in Ethiopia, 2023
| Description | Case (%) | Control (%) | AOR (95%CI) | P value |
|---|---|---|---|---|
| No formal education | 32 (38.1) | 77 (30.6) | 4.30 (0.48–38.76) | 0.190 |
| Education level: Grade 1–8 | 40 (47.6) | 135 (53.6) | 2.59 (0.30-22.42) | 0.390 |
| Education level: Grade 9–12 | 11 (13.1) | 25 (9.9) | 4.06 (0.41–39.74) | 0.230 |
| Education level: College/university | 1 (1.2) | 15 (6.0) | 1 | |
| Sleep outside the house during day | 26 (31.0) | 24 (9.5) | 2.38 (1.46–3.89)** | < 0.001 |
| Sleep inside the house during day (Ref) | 58 (69.0) | 228 (90.5) | 1 | |
| Sleep outside the house during night | 38 (45.2) | 75 (29.8) | 1.68 (1.07–2.64)* | 0.025 |
| Sleep inside the house during night (Ref) | 46 (54.8) | 177 (70.2) | 1 | |
| Bushes available around the house | 38 (45.2) | 69 (27.4) | 1.76 (1.12–2.77)* | 0.014 |
| Bushes not available around the house (Ref) | 46 (54.8) | 183 (72.6) | 1 | |
| Always sleeping outside during dry season | 39 (46.4) | 65 (25.8) | 1.19 (0.69–2.04) | 0.532 |
| Sometimes sleeping outside during dry season | 20 (23.8) | 111 (44.0) | 0.62 (0.34–1.14) | 0.125 |
| Never sleeping outside during dry season | 25 (29.8) | 76 (30.2) | 1 | |
| Termite hills present near to house | 31 (36.9) | 70 (27.8) | 1.26 (0.68–2.35) | 0.468 |
| Termite hills not present near to house (Ref) | 53 (63.1) | 182 (72.2) | 1 | |
| Length of stay in the camp ≤ 5 | 60 (71.4) | 136 (54.0) | 1.76 (1.06–2.93)* | 0.028 |
| Length of stay in the camp > 5 (Ref) | 24 (28.6) | 116 (46.0) | 1 |
AOR: Adjusted odds ratio; 95%CI: 95% confidence interval; *p-values less than 0.05; **p-values less than 0.001
Discussion
The current study assessed the behavioral, environmental, and socio-demographic factors associated with cases of Leishmania infection in refugee camp settings in Gambella and Benishangul Gumuz regions of Ethiopia. This study provided evidence to guide Leishmania control in refugee camps, where populations are vulnerable due to overcrowding, limited resources, and environmental degradation. By integrating behavioral, environmental, and socio-demographic strategies into camp management protocols, policymakers and humanitarian actors can mitigate transmission risks and improve health equity in these high-risk settings. Sustained investment in prevention, community engagement, and context-specific research will be critical to achieving long-term impact.
The finding that sleeping outside during both daytime and nighttime increases the risk of Leishmania infection highlights a critical behavioral practice risk factor in refugee camp settings. This was supported by previous reports from other parts of Ethiopia showing that sleeping outside the house at night was significantly associated with VL [15, 18, 29]. When sleeping outside during the daytime, certain sandfly species (Phlebotomus spp.) may bite outdoors during the daytime, especially in hot climates or densely vegetated environments [30]. A case-control study conducted in West Pokot County, Kenya, supported the current report that VL transmission occurs both peri-domestically at night and outdoors during the day, particularly when sandfly resting sites are disturbed [31]. This finding emphasizes daytime outdoor sleeping as a major modifiable risk factor for Leishmania infection in the camp settings. On the other hand, the strong association among sleeping outdoors, daytime and cases of Leishmania infection suggest that behavioral interventions to reduce daytime outdoor rest could significantly lower transmission risk. Future studies should validate these results with longitudinal designs and explore interactions between sandfly activity patterns, environmental conditions, and human behavior, particularly in humanitarian settings like refugee camps. Sleeping outside during the nighttime is strongly associated with Leishmania infection in refugee camps in Gambella and Benishangul Gumuz regions of Ethiopia. This was supported by studies conducted in Sudan [16] and Kenya [31]. While sandflies are most active during crepuscular hours (dawn/dusk), nocturnal species or adaptations may bite at night, particularly in areas with high human activity or poor vector control [32–34]. However, in this study, the term ‘nighttime’ includes dusk and dawn periods rather than being strictly defined by specific hours. This broader timeframe accounts for the possibility that Leishmania infected individuals may have been exposed to sandfly bites during these transitional periods. Cases who sleep outdoors at night may lack protection, increasing exposure to sandfly activity. Indoor sleeping environments typically offer structural barriers, including walls and roofs, and relatively better access to protective tools. Moreover, outdoor sleeping areas near vegetation or cracked floors could also serve as sandfly breeding sites.
Staying in the camp less than five years was significantly associated with cases of Leishmania infection. Longer stays may correlate with better adoption of protective measures or improved housing conditions. The practice and awareness of protective measures among cases and controls were not assessed in the current study; however, new residents might lack awareness of local risks or engage in high-exposure activities such as outdoor activities at dawn/dusk. Additionally, refugees may have acquired infection due to prior exposure in their areas of origin, such as Sudan or South Sudan, where visceral leishmaniasis is also endemic [35]. Alternatively, this association may reflect new infections occurring shortly after arrival among individuals who had not previously been exposed and thus lacked immunity, regardless of protective measures.
This finding is not supported by a study conducted in northern Ethiopia among farmland workers. The longer stay in the VL endemic area is a risk factor compared to the staying in shorter period of time, less than four years of stay in Humera [36]. This difference could be the study area well known to be VL endemic in the northern part of Ethiopia and contribute almost 60% of VL load in the country [21].
In addition, the availability of bushes around the house was also found to be an exposure factor to increase the odds of a case infected with Leishmania infection in the current study. This finding was in line with reports from East African region, including Kenya, Sudan, Somalia, and Ethiopia [16, 31, 37]. Bushes near houses may increase human-sandfly contact, particularly during crepuscular/nocturnal biting periods. Vegetation may act as a bridge between natural sandfly habitats (such as forests) and human settlements. Other systematic reviews and meta-analyses revealed that living with domestic animals and being male were identified as associated with Leishmania infection in different regions of Ethiopia [38]. These exposure factors were not assessed in the current study because the target population’s lifestyle differs. In this study, we focused on refugees with no gender-specific activities and without domestic animals.
For those who always use a bed net while sleeping, there was a decreased risk of Leishmania infection in the studied refugee camps in Gambella and Benishangul Gumuz regional states. This report is supported by a case control study conducted in Sudan and Kenya [16, 31]. On the other hand, this was in contrast with previous studies in Ethiopia [15, 18], which found that using a bed net was protective for VL infection. This difference may be due to the fact that refugee camps often have temporary shelters with gaps in walls/roofs, allowing sandfly entry even when nets are used. Contrast this with studies in solid housing structures where nets complement other barriers.
Our analysis revealed no statistically significant association between Leishmania infection and exposure factors such as education level, always or sometimes outdoor sleeping during the dry season, and the presence of termite hills within 5 m of sleeping areas. On the other hand, educational level significantly associated with Leishmania infection in studies conducted in Gedaref Sudan [16] and Kafta-Humera, Ethiopia [15]. In the current study, lack of association with education may reflect limited socioeconomic variation in the refugee camp population or the dominance of environmental over behavioral risk factors in this setting. Moreover, education might correlate with protective behaviors (bed net use) that were already adjusted for in the model. There was minimal proportion variability in the education levels among the individuals included in the study. We assessed the seasonal variation in outdoor sleeping practices during the dry season. Since sandflies in the area are likely active during crepuscular hours (dawn and dusk), individuals may spend these peak biting times indoors, potentially reducing the relevance of their sleeping location. The null finding for termite hills, and always sleeping outside during dry season also supported by findings from Sudan [16] but not study conducted in Ethiopia [15]. The termite hills often cited as sandfly breeding sites, could suggest that proximity alone does not amplify risk in this context, possibly due to widespread environmental sandfly presence overwhelming localized effects, or termite mounds serving as poor proxies for actual vector habitats. Moreover, these discrepancies may be explained by differences in population characteristics as well as environmental factors, such as vegetation cover and the type and abundance of termite hills, which in the present study area are predominantly eroded. A comparative analysis across refugee camps that have not yet been studied would help to clarify variations in sand fly distribution. Such studies could also provide valuable insights into the habitat preferences and biting behaviors of the vector in these settings, which are important considerations for future research.
In the current study, the presence of cracked walls did not remain an independent predictor in the multivariable model. This was largely because its effect was adjusted for the habit of always sleeping outside during the dry season, which appears to be a stronger behavioral risk factor influencing exposure to sand flies. Previous studies have reported mixed findings regarding cracked walls: some have suggested that they may serve as potential resting or breeding sites for sand flies, thereby increasing transmission risk [18], while others have not found a significant association [16]. Our findings are therefore consistent with the latter, suggesting that structural housing conditions alone may not sufficiently explain transmission dynamics in this setting, and that behavioral and environmental factors, such as outdoor sleeping, may play a more dominant role.
Key factors such as proximity to vector breeding sites (availability of bushes around the house), limited access to protective measures (e.g., bed nets), and behavioral practices (day and nighttime outdoor sleeping) emerged as strong predictors of cases of Leishmania infection. These findings highlight targets for control strategies, including enhanced vector control, community education on risk-reducing behaviors, and distribution of protective materials. While unmeasured variables like housing construction materials or nutritional status may contribute to risk in broader contexts, the identified factors remain pivotal for designing context-specific, feasible interventions in resource-constrained environments like refugee camps, where addressing modifiable exposures can yield immediate public health benefits.
Strengths and limitations of the study
The current study has several strengths when investigating risk factors for Leishmania infection in refugee camps, particularly when cases and controls were recruited prospectively, this would help to minimize recall and selection biases. Moreover, matching cases and controls on variables of age group, sex, and region of location of the camps helps to control confounding factors, improving the validity of comparisons. Several potential predictors, such as occupation, income, domestic animal ownership, VL/HIV co-infection and nutritional status, were not included in the analysis. This omission stemmed from the homogeneity of living conditions within the refugee population, which limited variability in these factors. Additionally, variables like nutritional status and domestic animal ownership are widely recognized as systemic challenges in refugee settings, where access to resources is often uniformly constrained. Nevertheless, the limitations outlined in our analysis identified robust and statistically significant associations between exposure variables and Leishmania infection risk, underscoring their critical role in informing targeted interventions in refugee camp settings.
Conclusion and recommendation
In conclusion, this study identified critical behavioral and environmental factors associated with Leishmania infection risk in refugee camp settings. Sleeping outdoors during both daytime and nighttime significantly increased Leishmania infection. The presence of bushes near households and the shorter duration of residence in the camp (less than five years) were associated with Leishmania infection in refugee camps. This indicates that recent arrivals may not have developed adaptive behaviors or acquired immunity over time. These findings underscore the urgency of prioritizing vector control measures, such as clearing vegetation near shelters, distributing insecticide-treated nets, and promoting community awareness about minimizing outdoor sleeping behaviors. Targeted interventions for newer residents, coupled with environmental management, could considerably reduce transmission and mitigate the burden of leishmaniasis in similar resource-constrained, high-risk settings.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
We thank Addis Ababa University for ethical approval and follow-up. We also acknowledge the RRS head and branch offices for facilitating camp entrance, refugee camp coordinators for their support during data collection, and local health facility, clinical, and public health officers, refugee camp community officers, and participants for their cooperation.
Abbreviations
- DAT
Direct agglutination test
- HH
Household
- NTD
Neglected tropical diseases
- PCR
Polymerase chain reaction
- RRS
Refugees and returnees service
- UNHCR
United nations high commissioner for refugees
- VL
Visceral leishmaniasis
- WHO
World Health Organization
Author contributions
HB, EA, AA, BA and BE designed the proposal. HB, BA, MB, and GT acquired and analyzed the data, and drafted the manuscript. All authors discussed the results and implications, contributed to the work, commented on the manuscript throughout, and approved the final version.
Funding
No specific fund available.
Data availability
Data is provided within the manuscript or supplementary information files.
Declarations
Ethical approval and consent to participate
The study was conducted in accordance with the national ethical guidelines and received approval from the Aklilu Lemma Institute of Health Research-Institutional Research Ethics Review Committee (ALIPB-IRERC) prior to data collection (Ref. No.: ALIPB IRERC/112/2015/23). A permission letter was obtained from the Federal Democratic Republic of Ethiopia Refugees and Returnees Service (RRS) and subsequently from the RRS regional office and camp coordination offices. Written informed consent or assent was secured from all adult participants, as well as from parents or guardians for minors and illiterate participants, with trained personnel assisting in participants’ native languages (including Nuer, Arabic and Dinka) to ensure comprehension. Privacy and confidentiality were strictly maintained, with all identifying data anonymized and securely stored, accessible only to the research team. The study followed all relevant guidelines for research on human subjects, implementing additional safeguards to protect participants’ rights, dignity, and welfare.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Jacobson RL. Leishmaniasis in an era of conflict in the middle East. Vector-Borne Zoonotic Dis. 2011;11(3). [DOI] [PubMed]
- 2.Desjeux P. Leishmaniasis: current situation and new perspectives. Comp Immunol Microbiol Infect Dis. 2004;27(5):305–18. [DOI] [PubMed] [Google Scholar]
- 3.WHO. Leishmaniasis [Internet]. 2023 [cited 2024 Sep 7]. Available from: https://www.who.int/news-room/fact-sheets/detail/leishmaniasis
- 4.Glans H, Dotevall L, Söbirk SK, Färnert A, Bradley M. Cutaneous, mucocutaneous and visceral leishmaniasis in Sweden from 1996–2016: a retrospective study of clinical characteristics, treatments and outcomes. BMC Infect Dis. 2018;18(632):1–10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.DNDi. Leishmaniasis [Internet]. 2022. pp. 1–4. Available from: https://www.dndi.org/wp-content/uploads/2018/12/Factsheet2018_Leishmaniasis.pdf
- 6.Alvar J, Vélez ID, Bern C, Herrero M, Desjeux P, Cano J, et al. Leishmaniasis worldwide and global estimates of its incidence. PLoS One. 2012;7(5). [DOI] [PMC free article] [PubMed]
- 7.Boussery G, Boelaert M, Van Peteghem J, Ejikon P, Henckaerts K. Visceral leishmaniasis (kala-azar) outbreak in Somali refugees and Kenyan shepherds, Kenya. Emerg Infect Dis. 2001;7(3):603–4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Herrero M, Orfanos G, Argaw D, Mulugeta A, Aparicio P, Parreño F, et al. Natural history of a visceral leishmaniasis outbreak in Highland Ethiopia. Am J Trop Med Hyg. 2009;81(3):373–7. [PubMed] [Google Scholar]
- 9.Abubakar A, Ruiz-postigo A, Pita J, Lado M, Ben-ismail R, Argaw D, et al. Visceral leishmaniasis outbreak in South Sudan 2009–2012: epidemiological assessment and impact of a multisectoral response. PLoS Negl Trop Dis. 2014;8(3):2012–5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Alvar J, den Boer M, Dagne DA. Towards the elimination of visceral leishmaniasis as a public health problem in east Africa: reflections on an enhanced control strategy and a call for action. Lancet Glob Heal [Internet]. 2021;9(12):e1763–9. Available from: 10.1016/S2214-109X(21)00392-2 [DOI] [PMC free article] [PubMed]
- 11.UNHCR. Executive Summary Global Report 2023 [Internet]. 2023. Available from: https://reporting.unhcr.org/global-report-2023-executive-summary
- 12.Hailu A, Berhe N, Yeneneh H. Visceral leishmanaisis in Gambella, Western Ethiopia. Ethiop Med J. 1996;34. [PubMed]
- 13.Al-Salem W, Herricks J, Hotez P. A review of visceral leishmaniasis during the conflict in South Sudan and the consequences for East African countries. Parasites Vectors. 2016;9(1):1–11. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Rocha R, Pereira A, Maia C. Non-Endemic leishmaniases reported globally in humans between 2000 and 2021 — A comprehensive review. Pathogens. 2022;11(121):1–42. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Argaw D, Mulugeta A, Herrero M, Nombela N, Teklu T, Tefera T, et al. Risk factors for visceral leishmaniasis among residents and migrants in Kafta-Humera, Ethiopia. PLoS Negl Trop Dis. 2013;7(11):e2543. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Nackers F, Mueller YK, Salih N, Elhag MS, Elbadawi ME, Hammam O, et al. Determinants of visceral leishmaniasis: A Case-Control study in Gedaref State, Sudan. PLoS Negl Trop Dis. 2015;9(11):1–16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Leta S, Dao THT, Mesele F, Alemayehu G. Visceral leishmaniasis in ethiopia: an evolving disease. PLoS Negl Trop Dis. 2014;8(9):1–7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Yared S, Deribe K, Gebreselassie A, Lemma W, Akililu E, Kirstein OD, et al. Risk factors of visceral leishmaniasis: a case control study in north-western Ethiopia. Parasites Vectors. 2014;7(1). [DOI] [PMC free article] [PubMed]
- 19.UNHCR-CO Ethiopia. UNHCR Ethiopia | Overview of Refugee camps and sites September 2023 [Internet]. Available from: https://data.unhcr.org/en/documents/details/104087
- 20.Tsegaw T, Gadisa E, Seid A, Abera A, Teshome A, Mulugeta A, et al. Identification of environmental parameters and risk mapping of visceral leishmaniasis in Ethiopia by using geographical information systems and a statistical approach. Geospat Health. 2013;7(2):299–308. [DOI] [PubMed] [Google Scholar]
- 21.Gadisa E, Tsegaw T, Abera A, Elnaiem DE, Den Boer M, Aseffa A, et al. Eco-epidemiology of visceral leishmaniasis in Ethiopia. Parasites Vectors. 2015;8(1). [DOI] [PMC free article] [PubMed]
- 22.Belay H, Eyelachew E, Abose E, Aklilu E, Gebrewold G, Tadesse H, et al. Serological and molecular analysis of leishmania infection in a recent outbreak of visceral leishmaniasis in South Omo Zone, Ethiopia. Trans R Soc Trop Med Hyg. 2025;119(1):65–76. [DOI] [PubMed] [Google Scholar]
- 23.Bekele F, Belay T, Zeynudin A, Hailu A. Visceral leishmaniasis in selected communities of Hamar and Banna-Tsamai districts in lower Omo Valley, South West ethiopia: Sero-epidemological and Leishmanin skin test surveys. PLoS ONE. 2018;13(5):1–13. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Diro E, Techane Y, Tefera T, Assefa Y, Kebede T, Genetu A, et al. Field evaluation of FD-DAT, rK39 dipstick and KATEX (urine latex agglutination) for diagnosis of visceral leishmaniasis in Northwest Ethiopia. Trans R Soc Trop Med Hyg. 2007;101(9):908–14. [DOI] [PubMed] [Google Scholar]
- 25.Van Griensven J, van Henten S, Mengesha B, Kassa M, Adem E, Seid ME, et al. Longitudinal evaluation of asymptomatic leishmania infection in HIV-infected individuals in North-West ethiopia: A pilot study. PLoS Negl Trop Dis. 2019;13(10). [DOI] [PMC free article] [PubMed]
- 26.Khatun M, Alam SMS, Khan AH, Hossain MA, Haq JA, Alam Jilani MS, et al. Novel PCR primers to diagnose visceral leishmaniasis using peripheral blood, spleen or bone marrow aspirates. Asian Pac J Trop Med [Internet]. 2017;10(8):753–9. Available from: 10.1016/j.apjtm.2017.08.002 [DOI] [PubMed]
- 27.Ayehu A, Aschale Y, Lemma W, Alebel A, Worku L, Jejaw A, et al. Seroprevalence of asymptomatic leishmania donovani among laborers and associated risk factors in agricultural camps of west armachiho district, Northwest Ethiopia: a cross-sectional study. J Parasitol Res. 2018;2018. [DOI] [PMC free article] [PubMed]
- 28.Tadese D, Hailu A, Bekele F, Belay S. An epidemiological study of visceral leishmaniasis in North East Ethiopia using serological and Leishmanin skin tests. PLoS One. 2019;14(12). [DOI] [PMC free article] [PubMed]
- 29.Bashaye S, Nombela N, Argaw D, Mulugeta A, Herrero M, Nieto J, et al. Risk factors for visceral leishmaniasis in a new epidemic site in Amhara region, Ethiopia. Am J Trop Med Hyg. 2009;81(1):34–9. [PubMed] [Google Scholar]
- 30.Wijerathna T, Gunathilaka N. Diurnal adult resting sites and breeding habitats of phlebotomine sand flies in cutaneous leishmaniasis endemic areas of Kurunegala District, Sri Lanka. Parasites and Vectors [Internet]. 2020;13(1):1–10. Available from: 10.1186/s13071-020-04154-7 [DOI] [PMC free article] [PubMed]
- 31.van Dijk NJ, Carter J, Kiptanui D, Mens PF, Schallig HDFH. A case–control study on risk factors for visceral leishmaniasis in West Pokot County, Kenya. Trop Med Int Heal. 2024;29(10):904–12. [DOI] [PubMed] [Google Scholar]
- 32.Alebie G, Worku A, Yohannes S, Urga B, Hailu A, Tadesse D. Epidemiology of visceral leishmaniasis in Shebelle Zone of Somali Region, eastern Ethiopia. Parasites and Vectors [Internet]. 2019;12(1):1–10. Available from: 10.1186/s13071-019-3452-5 [DOI] [PMC free article] [PubMed]
- 33.Sales KGDS, De Oliveira Miranda DE, Costa PL, Da Silva FJ, Figueredo LA, Brandão-Filho SP, et al. Home sweet home: Sand flies find a refuge in remote indigenous villages in north-eastern Brazil, where leishmaniasis is endemic. Parasites and Vectors [Internet]. 2019;12(1):1–12. Available from: 10.1186/s13071-019-3383-1 [DOI] [PMC free article] [PubMed]
- 34.Aklilu E, Gebresilassie A, Yared S, Kindu M, Tekie H, Balkew M, et al. Comparative study on the nocturnal activity of phlebotomine sand flies in a Highland and lowland foci of visceral leishmaniasis in north-western Ethiopia with special reference to phlebotomus orientalis. Parasites Vectors. 2017;10(1):1–10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Hammam O, Hicks J. Visceral leishmaniasis control strategies in Sudan: a review with recommendations. 2021;9:1–16.
- 36.Fuller GK, Lemma A, Haile T, Atwood CL. Kala-azar in Ethiopia I: Leishmanin skin test in Setit humera, a kala-azar endemic area in Northwestern Ethiopia. Ann Trop Med Parasitol. 1976;70(2):147–63. [DOI] [PubMed] [Google Scholar]
- 37.Marlet MVL, Sang DK, Ritmeijer K, Muga RO, Onsongo J, Davidson RN. Emergence or re-emergence of visceral leishmaniasis in areas of Somalia, Northeastern Kenya, and south-eastern Ethiopia in 2000-01. Trans R Soc Trop Med Hyg. 2003;97(5):515–8. [DOI] [PubMed] [Google Scholar]
- 38.Belay H, Abera A, Aklilu E, Bishaw T, Alemu A, Tasew G, et al. Prevalence of asymptomatic leishmania donovani infection and associated factors in ethiopia: a systematic review and meta-analysis. BMC Infect Dis. 2025;25(1):78. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
Data is provided within the manuscript or supplementary information files.