Prevalence and associated risk factors of gastrointestinal helminth infection among primary schoolchildren in Dembi district, southwest Ethiopia

Background: Gastrointestinal helminths (GIH) are widespread in developing countries including Ethiopia. The prevalence and distribution of GIH infection in Ethiopia varies from place to place due to different exposing risk factors. This study aimed to identify the prevalence and associated factors of GIH infection among primary school children in Dembi district, southwest Ethiopia, where data for helminths infections are previously unpublished. Methods: A cross-sectional study involving 291 school children in Dembi district were included. Fresh stool samples were collected from each student and examined by direct wet mount using both normal saline and Lugol's iodine preparation and concentration techniques using salt and formol-ether solutions. Questioners and observation were also used to identify socio-demographic and associated risk factors. Data were analyzed using SPSS 20.0 statistical software. p -value <0.05 were considered significant. Results: Six parasite species of gastrointestinal helminth with an overall prevalence of 30.9% were identified. The predominant parasites were found soil transmitted helminth (STH) type including Ascaris lumbricoides (43.3%), hookworm (26.7%), Ttrichuris trichiura (8.9%) and Strongliodes stercoralis (3.3%). Teania species (6.7%) and Hymanolepis nana (3.3%) were also the gastrointestinal parasites detected from the stool samples. The highest prevalence of GIH infection has been observed in the age of 5 8 years children (36.7%) followed by 9 12 (33.3%) and ≥13 (30.0%) years. Sex, age, source of water supply and latrine usage has a significant association with GIH infection. Male (37.9%) students were two times more likely to have parasite infection (COR= 2.0, 95% CI= 1.17 3.22,

p=0.011) than female (24%) students. Comparing age groups, 5 8 years were more likely to have higher parasite infection (COR=1.23, 95% CI=0.233 0.797, p=0.007) than older age groups ( 13 years). Those students used stream as a source of water supply and latrine sometimes were also 1.4 (p=001) and 2.7 (p=0.001) times more likely to have helminthic infection than students used pipe water and latrine, respectively. The STHs are widely distributed throughout the tropics and subtropics due to favorable climatic conditions as an important factor for their existence and infection [2]. For instance, adequate moisture and warm temperature are an essential environmental for larval development in the soil [3]. Poverty, inadequate water supply, sanitation and poor personal hygiene (especially shoe wearing and hand washing) were also previously reported important epidemiological factor for STHs [1,4].

Conclusions
Soil-transmitted helminth infections have profound effect on the health of growing children including stunted growth, intellectual retardation, anemia and poor school attendance [5]. These problems are significant in Sub-Saharan Africa (SSA) [4].
Ethiopia is estimated to have the second (26 out of 173 million), third (11 out of 198 million) and fourth highest (21 out of 162 million) burden of ascariasis, hookworm and trichuriasis diseases among SSA countries, respectively [4,6]. In terms of national STH prevalence rate in Ethiopia, A. lumbricoides, T. trichiura and hookworm accounted 37, 30 and 16%, respectively [7].

Methods
Study area and period 5 The study was carried out among three primary school children in Dembi district from December 2014 to May 2015. The district is located 430 km from Addis Ababa and situated between 8°4'0"-8°5'30"N latitude and 36°27'30"-36°28'30"E longitude in Ilu Abba Bora zone, Oromia regional state southwest Ethiopia. The district elevation is also between 1701 and 1827 meters above sea level.
The area annual rain fall ranges from 500-1000 mm, while the minimum and maximum temperature ranged from 15-19 o C and 23-25 o C, respectively. The main water supply in the district is streams and rivers and in some areas pipe borne supply. In Dembi district, there is only one health center, one private clinic and three primary schools namely Kambo, Tululami and Dembi.

Study population and subject selection
A cross-sectional study was carried out among primary school children of Dembi distrct. The year 2015 updated list of Kambo, Tululami and Dembi primary schools were the target population of this study. Among 545 male and 655 female students in the three Dembi district schools, a minimum sample size was selected using an appropriate sampling fraction method (Eq. 1).
Where S is the required sample size, x (1.96) is the standard deviation at 95% confidence interval, N is the total population size, P is the estimated prevalence (50%) and d is the allowed relative error (0.05) [15]. The minimum sample size after calculation was 291 from the three primary schools including 133, 91 and 67 students from Kambo, Tululami and Dembi schools, respectively.

Data collection and parasitological examination
In this study, the effect of shoe wearing habits, finger nail statuses, hand washing habits, age and sex as independent variable on the prevalence of GIH infection as dependent variable were considered.
Questionnaire was used to gather information on socio-demographic and sanitary facilities of students. The study participants were also examined physically for the presence or absence of dirt materials in their fingernails. At the time of the study, the investigator explained about the purpose of the study (students, school administrators and teachers) and asked school children to complete questionnaires that were prepared based on common risk factors of GIH infection with the help of their teachers.
After the investigator also demonstrated the school children how to collect the sample and handle the samples, they were given a sterile wide mouth plastic containers with screw caps having the appropriate information and identification number. A wooden applicator was also provided to each student. Stool samples for parasitological examination were collected early in the morning before bathing or defecation. In case, if a student couldn't able to collect the morning stool sample by themselves, they were informed to get help from their mothers/guardians. Stool specimens were transported to the laboratory using ice boxes. These specimens were examined by direct wet mount, Lugol's iodine, and formol-ether sedimentation techniques for the presence of intestinal parasites. The samples were first scanned with low power objective (10x) microscopic lens and then switched to 40x objective lens for detail parasitic morphology examination. All specimens were scanned by single investigator to avoid inter-observer error.

Data analysis
Data entered into excel and analyzed by using statistical package for social scientists (SPSS) window version 20.0 software. Association of risk factors with GIH parasites was analyzed by using binary logistic regression. Logistic regression model was generated by inclusion of significant independent predictors (sociodemographics, hygienic habits, and others) at the univariate level against the dependent variable (intestinal parasitic infections). Descriptive statistics was also used. The p-value < 0.05 was considered to be statistically significant.

Results
Among 1200 total students in the three primary schools in Dembi district, 145 (49.8%) male and 146 (50.20) female students were included in the study (Table 1).
The age composition of the study participants were ranged from 5 17 years. The majority (41.2%) of the participants were at the age of 13 years, however, the percentage of parasitic infection was found relatively low (22.5%). Age group 5 8 years were found to be significantly (p=0.007) at higher risk (1.2 times) with parasitic infection than higher age group (≥13 years).
Except Strongliodes stercoralis and Teania species, females were infected by three parasitic worms. However, the six parasitic worms were identified in male participants with higher infection rate than females, particularly Ascaris lumbricoides, Trichuris trichiura and Hymenolepis nana. Hookworm was identified in equal proportion from males and females. Moreover, the co-infection also observed in males and females ( Table 2). Younger age groups (5 8 years) were found to be more prevalent for Ascaris lumbricoides. However, Hymenolepis nana and Teania species were not detected at lower age groups. Participants at the age group of 9 12 years were found to be more affected by Trichuris trichiura (83.3%) and Teania species (62.5%) than other parasitic species. Relatively, older age groups (>12 years) were also affected by higher proportion of Hymenolepis nana, hookworm and Ascaris lumbricoides ( Table 2). Table 3, the majority (58.4%) of the students were used stream water for cooking and drinking purpose. This result has been found statistically significant and at higher risk for parasitic infection (COR=1.4, 95% CI=0.47 4.15, p=0.001).

As shown in
However, students that used pipe borne water for drinking and cooking activities were found statistically insignificant (p=0.55). Those students who used latrine sometimes were also more likely (2.7 times) at higher risk to get infected with GIH parasites (Table 3). Other independent variables such as hand washing, raw meat eating, shoe wearing habit and finger nail status of the respondents were also assessed; however, none of these parameters were found statistically significant (Table 3).

Discussion
Although it is neglected disease in the developed world, GIH/STH infections are still remaining the major public health problem in developing countries, particularly in the tropics where appropriate parasitic growth factors exist. As a result, epidemiological study on the prevalence of GIH/STH infection in different region of the developing world is a primary objective to identify high-risk communities and formulate appropriate intervention [5,[8][9][10][16][17][18][19]. In line with this view, the present study attempted to assess the prevalence of different GIH infections in primary school children in Dembi district (southwest Ethiopia).
In the current study, 30.9% overall prevalence of GIH which have public health importance were identified. Except 7.8% school children specimen samples showed  (Table 4). However, the current study result has been found much higher (4.5 22.8%) than a report from Gondar [5] and Ambo [12] towns in Ethiopia and elsewhere in the world including Taiwan [23], Kenya [17], China [24] and Marshall Islands [25] (Table 4). Still, the present study prevalence was identified lower than study result from Tilili town (44.2%), Wolaita zone (72.2%), Azezo town (72.9%) and Chencha town (81.0%) in Ethiopia (Table 4). Comparatively, higher helminthic prevalence were also reported in Saud Arabia (45.4%) El Salvador (53.0%), Tanzania (57.1%), India (75.6%), China (86.0%), Nigeria (86.2%) and Malaysia (88.2%) ( Table 4). The possible explanations for the discrepancy between the present and previous study findings might be the result of variation in the geographic location, socio-economy of the subjects, selection of study participants, sample size, method of parasitological examination, time of the study, access to health care facilities and awareness. Indeed, the comparative result shown in Table 4 is from different geographic locations (Africa, Asia, Middle East, Latin America and Europe) and participants from different population group (pre-/school children, rural community, patients from medical centers and hospitals). The number of participants (sample size) were also varies higher (n=6976) from northern Samar in Philippines [19] and lower (n=69) from Yunnan in southwest China [26].
In this study, a total of six intestinal parasitic worm was detected which could be comparable with study in Nepal [11] that was identified six parasitic worms. As shown in Table 4, our finding was also comparable to studies in Ethiopia (five parasites in Ambo town and seven parasites in Wolaita zone and Chencha) and elsewhere in the world (five parasites in Kisumu city, western Kenya and seven parasites in El Salvador). Relatively, small number (three) of parasitic worm infection (Table 4) was reported in Guizhou (southwest China), Peninsular Malaysia and Uttar Pradesh (India). In school children, four intestinal parasitic worms (Table   4) were also reported in Nairobi city (Kenya), Western city (Turkey), Tilili town (Ethiopia) and Yunnan (southwest China). Studies conducted in Saud Arabia [20] and Taiwan [23] were also reported 20 and 13 intestinal parasitic worm species using hospital patient, respectively which was higher than maximum number of parasitic species reported in school children (nine) in Gondar town (north Ethiopia) [5] and Majuro city (Marshall Islands) [25].
The majority of infections in the current and previous studies were single infection types (  (Table 4). This difference might be due to study population, environmental factors, investigation time and diagnosis method. It is obvious that the target population for the community and hospitals participants were at any age group and educational level, which was not true for school age children that have narrow age range and educational level.
In this study, STHs such as A. lumbricoides and hookworm infections were found the major public health problem. The prevalence of A. lumbricoides among school children in the current study area was found to be 43.3%. This prevalence of A. lumbricoides was higher than the national prevalence estimate (37%) in Ethiopia [7] and reports from other parts of the country such as 7.5% in northwest [5] and 28.9% south Gondar [33], 23.6% in Jimma [34], and 37.2% in Bushulo village [35].
Lower prevalence value of A. lumbricoides also reported in Kenya [21] and Malaysia [32] with a prevalence of 4.9% and 23.8%, respectively. However, the current study A. lumbricoides prevalence result was much lower than a report from Wondogent (83.3%) [36] and Chencha town (60.5%) [9] in Ethiopia, Nigeria (57.2%) [30] and Nepal (57.9%) [18]. There are several studies that mentioned STHs vary among localities due to variations in geographic location, socio-economic conditions and hygienic condition of the population under consideration. Of course, the higher prevalence of A. lumbricoides in the current study than the national estimates and elsewhere could be due to lack of drinking water source and latrine usage, which has been found significantly (Table 3) associated with STH infection in the current study area. Compared with sources of drinking water, students using stream water for drinking and food preparation have found a statistical significant difference for STHs than students using pipe water for similar purpose. This supports that the transmission of A. lumbricoides infection which is contracted through ingesting embryonic egg through water and food [1]. In terms of gender, male students were identified more prevalent for A. lumbricoides than female students, which could be due to boys playing on soil and prefer to eat their food without proper hand washing (Table 2). Moreover, lower age (5 8 years) groups were found more prevalent to for A. lumbricoides than higher age groups (Table 2), which agrees with other studies that said lower age groups are more affected than higher age groups [16,32]. As reported in other studies [1,16], latrine usage has been found a significant risk factor for STH including A. lumbricoides ( Table 3).
The prevalence of hookworm infection among primary school children of Dembi district was identified 26.7%, which is higher than the national hookworm infection prevalence (16.0%) in Ethiopia [7]. The prevalence of this helminthic infection was also higher than a report from different areas of Ethiopia and other countries including 4.9% in Gamo area, south Ethiopia [37] and 12.9% in south Gonder [33], 6.1% in Kenya [21] and 17.8% in Nigeria [30]. Infection by hookworm was much lower when compared to a report from southeastern Ethiopia [14] and Philippines [19] which revealed 60.5% and 28.4%, respectively. In fact, hookworm disease caused by two worm species (Ancylostoma duodenale and Necator americanus) has been reported one of the most common infections in SSA which affects around 198 million people in the region [4,6]. It causes iron deficient anemia and protein malnutrition [1]. Compared to age groups, hookworm infection has been found highest for older age groups (>12 years) than lower age groups (Table 2), which agrees with other studies [6,26,31]. For instance, Hotez and Kamath [6] mentioned that hookworm infection has steadily raised in the intensity during late childhood with either a peak or a plateau in adulthood.
The overall prevalence of T. trichiura, Teania species (6.7%), S.stercoralis (3.3%) and H.nana (3.3%) were found to be relatively very low. Interestingly, T. trichiura which is estimated 24% among STHs infection prevalence in Ethiopia from SSA prevalence proportion [4,6], is found to be much lower (8.9%) among school children in Dembi district. This prevalence has also been lower than the previous school (23.1%) and community (57%) based study in Jimma/Ethiopia [34] and Peninsular Malaysia [32], respectively suggesting that relatively better toilet facilities, good hand washing habit and better awareness about health in the current study area.

Conclusions
Findings from this study revealed that GIH particularly STH infections were higher among the primary school children of Dembi district. The most prevalent parasite was A. lumbricoides and hookworm. Although the proportion was very low, T. trichuira, S. stercoralis, Teania species and H. nana were also detected in the stool sample. Males were highly affected sex by GIH than females. Infection rate of GIH was generally higher among age group 5 8 years than older groups. However, among STH the prevalence of hookworm infection was increased with an increased age group. Absence of safe water supply in the school as well as in the community led to higher prevalence of GIH infection among school children. Moreover, latrine usage habit was also a significant risk factor for GIH infection.