Tungiasis infection among primary school children in Northeastern Tanzania: prevalence, intensity, clinical aspects and associated factors

Highlights

• •Tungiasis is among the neglected ectoparasitoses affecting children in Tanzania.
• •Moderate prevalence of tungiasis infection was observed among children.
• •Not keeping a dog/cat at home was a protective factor.
• •Tungiasis infection was contributed by host, agent and environmental factors.

Abstract

Objective

To investigate the prevalence, intensity, clinical aspects and factors associated with tungiasis infection among primary school children in Northeastern Tanzania.

Methods

A quantitative school-based cross-sectional study was conducted among 401 primary school children. Participants were assessed through clinical examination to look for embedded Tunga penetrans in their hands, feet, arms and legs. A structured questionnaire was used to enquire about factors associated with tungiasis infection. The data were analysed using descriptive statistics, Chi-squared test and logistic regression, with p<0.05 taken to indicate significance.

Results

The overall prevalence of tungiasis infection was 21.2%. Of the 85 tungiasis-infested children, 54 [63.5%, 95% confidence interval (CI) 53.1–74.1] had mild infection, 25 (29.4%, 95% CI 19.0–39.6) had moderate infection, and six (7.1%, 95% CI 1.2–12.9) had heavy infection. A moderate level of knowledge was significantly associated with high odds of tungiasis infection [adjusted odds ratio (AOR) 3.16, 95% CI 1.50–6.67], while not keeping a dog/cat at home was a protective factor (AOR 0.47, 95% CI 0.25–0.89).

Conclusions

Moderate prevalence of tungiasis infection was observed among primary school children favoured by factors related to the host, parasitic agent and environment. There is a need for a health education programme in schools encouraging use of appropriate footwear (closed shoes), use of locally accessible repellents (coconut oil), fumigation of households, and washing dogs/cats with insecticides.

Introduction

Tungiasis is a parasitic skin disease caused by female sand fleas known as Tunga penetrans and T. trimamillata which are endemic in Africa, Asia (India and Pakistan) and Latin America [1]. Tungiasis is a zoonotic disease affecting humans and animals. Hosts are infected by skin penetration, after which the posterior portion of the parasite protrudes from the epidermal surface for breathing, defaecation, copulation and egg expulsion [2]. The average life span of the embedded T. penetrans is 4–6 weeks [2]. In the environment, the off-host stage of T. penetrans inhabits premises with crevices, cracks and dust [1]. Tungiasis is widely distributed in tropical and subtropical regions, with a high burden in areas with poor living conditions, proximity to animals (dogs, cats and pigs), inadequate sanitation and unhygienic practices [1,3]. People of all ages can get tungiasis; however, elderly people, children (5–14 years) and individuals with disabilities are the most vulnerable populations [1]. According to the World Health Organization (WHO), the prevalence of tungiasis infection in endemic areas may be as high as 60% in the general population and 80% in children [1]. A study conducted in 2020 reported that the pooled prevalence of tungiasis infection in sub-Saharan Africa was 33.4%, with the highest prevalence reported in Ethiopia (46.5%), Cameroon (44.9%) and Tanzania (42.0%) [4].

In tungiasis-endemic areas, most skin penetration and consequent lesions occur on the toes, sole or heel of the foot due to the poor ability of the fleas to jump [5]. In the acute phase of tungiasis infection, the most common signs and symptoms are itching, swelling, redness and skin peeling at the site of penetration. Inflammation, ulceration, and secondary bacterial and fungal infections can result in nail loss, auto amputation of the digits and lymphangitis. Gangrene may occur when the female flea grows larger and begins to lay eggs [1,6]. In the adult population, severe complications secondary to infection have been described in patients with comorbidities impairing tissue repair, such as diabetes and death [7]. The most common treatment practised in endemic areas, as reported by WHO, is surgical extraction of embedded sand fleas using sterile instruments – undertaken at a health facility by an experienced health worker – followed by topical treatment [1]. However, in endemic areas, self-extraction using non-sterile instruments in a non-sterile environment has been reported, leading to inflammation and bacterial superinfection [1,3,8]. Tungiasis infection affects the quality of life of the affected individuals. The condition is associated with stigmatization and social rejection in school-aged children, causing absenteeism and poor performance in studies [1,3,8].

Tungiasis is a public health problem in some regions of Tanzania, as documented in a few studies and case reports [9], [10], [11]. Despite the endemicity, there are limited epidemiological data on the burden and factors associated with tungiasis infection among vulnerable populations such as school-aged children. This gap needs to be addressed to achieve appropriate control and management of the condition in endemic areas by planning effective strategies and interventions for interruption of the transmission cycle. Therefore, this study investigated the prevalence, intensity, clinical aspects and factors associated with tungiasis infection among primary school children in Northeastern Tanzania.

Materials and methods

Study area and demographics

This study was conducted in Lushoto district, one of the eight districts of the Tanga region. Lushoto district lies at latitude 4° 57′ 54.3168′' S and longitude 38° 30′ 5.7132′' E, and is bordered to the east by Muheza district, northeast by Kenya, northwest by the Kilimanjaro region, and south by Korogwe district [12]. Lushoto district has an area of approximately 4091.62 km² and an approximate population of 492,441 people (53.2% men, and 46.8% women) [13].

According to the administrative division, Lushoto district has 18 wards and 125 villages (the lowest government administrative structure at community level). Tungiasis is endemic in all villages. The district experiences warm and cold seasons, with average temperature >24.4°C during the warm season and rainfall throughout the year [12]. The warm season provides a conducive temperature and a suitable environment for breeding of T. penetrans. The main economic activities in Lushoto district are agriculture, tourism, forestry and livestock keeping [12]. Lushoto district was selected as the study area due to tungiasis endemicity.

Study design and population

A school-based cross-sectional study utilizing a quantitative data collection method was carried out to investigate the prevalence, intensity, clinical aspects and factors associated with tungiasis infection among primary school children. The investigation was undertaken from May to June 2022. The study population was school children attending primary schools in Lushoto district. The inclusion criteria were age 6–15 years, being a student in classes 1–7, and being a permanent resident of the study area (i.e. a child who lives in Lushoto district permanently or on a long-term basis). School children unable to communicate due to medical conditions were excluded from this study.

Sample size determination and sampling

The formula for cross-sectional studies (n=z² p (100-p)/ε²) [14] was used to estimate the sample size of school children, considering a standard normal deviation of 1.96 at the 95% confidence interval (CI), prevalence of 50% due to lack of data in the area, and a margin of error of 5%. The sample size was then adjusted to account for a 10% non-response rate and a design effect of 1.5. As a result, the total sample size was 634 primary school students. Participants were selected using a multi-stage sampling technique. In the first stage, one ward (Magamba) was chosen at random from a list of 18 tungiasis-endemic wards in Lushoto district. In the second stage, one village (Irente) was chosen at random from a list of four tungiasis-endemic villages in Magamba ward. In the third stage, the village executive officer provided a list of all three schools in Irente, from which Mhelo Primary School was chosen at random. At school level, the total number of students in each class was obtained from the head teacher to estimate the sample size per class. A large number of students contributed to a large number of participants and vice versa. However, of the estimated sample size of 634 students, only 401 students were recruited due to parental/guardian verbal rejection for their child's participation.

Physical examination of school children for estimation of prevalence and intensity

The children were clinically examined to detect the presence of embedded T. penetrans in their feet, arms, hands and legs. The Fortaleza classification was used for diagnosis [5,15]. The diagnostic features were: presence of a brownish-black dot with diameter of 1–2 mm; dark itchy spots on the skin, crater-shaped sores on the skin and suppurated lesions; a central black dot with a necrotic brownish-black crust; and a circular yellow-white watch glass-like patch with a diameter of 3–10 mm. Lesions were counted, and embedded sites were recorded in order to estimate prevalence and intensity. Intensity was classified based on the number of lesions in infested children as: mild (≤5 lesions), moderate (6–30 lesions) and heavy (>30 lesions) infection. In addition, the sequelae of tungiasis infection were examined and registered for each participant infected with tungiasis.

Questionnaire survey

A pretested structured questionnaire divided into four sections was used to collect data. Section A focused on sociodemographic characteristics of the children, Section B focused on risk factors associated with transmission or acquisition of tungiasis, and Sections C and D focused on knowledge and preventive practices among the children. The questionnaires were administered to children by trained school teachers.

Outcome and independent variables

The study outcome was the prevalence of tungiasis, recorded as positive if T. penetrans was present on clinical examination, or negative if T. penetrans was not present on clinical examination. The independent variables were sex (male or female), age categorized into three groups (5–9 years, 10–14 years and 15–18 years), class (recorded as class 1–7), family size categorized into three groups (less than five members, six to nine members, 10–13 members), and risk factors including environmental conditions at home and school, knowledge of tungiasis and preventive practices.

Quality control

The research tools (structured questionnaire and checklist) were pre-tested in 64 children (10% of the estimated sample size) at Kwembago Primary School. Pre-testing gave room for modification in terms of restructuring or rephrasing the questions that were unclear to the schoolchildren. The primary school that participated in pre-testing was not sampled for actual data collection.

Data analysis

Collected data were analysed using Statistical Package for the Social Sciences Version 23 (IBM Corp., Armonk, NY, USA). Descriptive statistics were used to summarize the variables (independent and dependent) to frequencies, proportions and 95% CI in tables. The prevalence and intensity of tungiasis were summarized based on sociodemographic characteristics. Pearson's Chi-squared test was used to determine the significance of relative frequency differences. Univariate analysis was used to determine the predictors of tungiasis in children. Predictors with p<0.25 were included in multi-variate logistic regression to adjust for the confounders and p<0.05 was considered to indicate significance.

The knowledge section had a total of nine questions with 15 correct responses. Knowledge was analysed based on the scoring scale. For each question, the correct response was scored 1 and incorrect responses scored zero. The total score for each individual was tabulated to categorize their knowledge level. Scores were classified as follows: ≤5 (low level of knowledge), 6–10 (moderate level of knowledge) and ≥11 (high level of knowledge).

Practices were assessed with a Likert scale with nine statements, with a Cronbach's alpha value of 0.857. For each participant, the sum score was computed, and a scale ranging from 9 to 27 points was created. The mean practice score of 22 was used to classify inappropriate (9–21 points) and appropriate (22–27 points) preventive practices.

Ethical consideration

Muhimbili University of Health and Allied Sciences provided ethical approval via a review board (Ref. No.DA.282/298/28K/). Permission to conduct the study in Lushoto district was obtained from the Lushoto administrative authorities. A written informed consent agreement was signed by the school head teacher on behalf of the school children who participated in the study after verbal acceptance by informed parents/guardians. To maintain confidentiality, numbers were used instead of names. The records of the children were kept strictly confidential. The infected participants were transferred to a nearby health centre for surgical assessment and extraction of the embedded fleas, followed by a prescription of topical benzyl benzoate, according to clinical indication.

Results

Sociodemographic characteristics, prevalence and intensity of tungiasis infection among the study participants

In total, 401 primary school students from classes 1 to 7 were recruited (response rate 63.2%). Approximately half of the participants were females (n=205, 51.1%), more than two-thirds were aged 11–15 years (n=271, 67.6%), and nearly two-thirds came from a family composed of two to five members (n=256, 63.8%) (Table 1).

Table 1.

Sociodemographic characteristics, prevalence and intensity of tungiasis infection among study participants

Variable	Total n (%)	Prevalence of tungiasis n/n (%)	p-value	Mild infestation (%)	Moderate infestation (%)	Heavy infestation (%)	p-value
Sex
Male	196 (48.9)	49 (25.0)	0.044a	33 (67.3)	11 (22.4)	5 (10.2)	0.150
Female	205 (51.1)	36 (17.6)		21 (58.3)	14 (38.9)	1 (2.8)
Age (years)	11.06 ± 2.26
6–10	130 (32.4)	43 (33.1)	0.000a	27 (62.8)	14 (32.6)	2 (4.7)	0.602
11–15	271 (67.6)	42 (15.5)		27 (64.3)	11 (26.2)	4 (9.5)
Class
1	61 (15.2)	18 (29.5)	0.000a	12 (66.7)	6 (33.3)	0 (0.0)	0.139
2	53 (13.2)	23 (43.4)		14 (60.9)	7 (30.4)	2 (8.7)
3	57 (14.2)	14 (24.6)		11 (78.6)	3 (21.4)	0 (0.0)
4	52 (13.0)	10 (19.2)		4 (40.0)	6 (60.0)	0 (0.0)
5	57 (14.2)	5 (8.8)		3 (60.0)	1 (20.0)	1 (20.0)
6	66 (16.5)	9 (13.6)		7 (77.8)	1 (11.1)	1 (11.1)
7	55 (13.7)	6 (10.9)		3 (50.0)	1 (16.7)	2 (33.3)
Family size (n people)
2–5	256 (63.8)	53 (20.7)	0.225	33 (62.3)	15 (28.3)	5 (9.4)	0.455
6–9	136 (33.9)	28 (20.6)		17 (60.7)	10 (35.7)	1 (3.6)
10–13	9 (2.2)	4 (44.4)		4 (100.0)	0 (0.0)	0 (0.0)

^aSignificant (p<0.05).

The overall prevalence of tungiasis infection among primary school children was 21.2% (85/401). A higher prevalence of tungiasis infection was observed among males [25% (49/196) vs 17.6% (36/205) among females], participants aged 6–10 years [33.1% (43/130) vs 15.5% (42/271) for older participants], students in class 2 [43.4% (23/53)], and children from families with 10–13 members [44.4% (4/9)]. There was a significant difference in the prevalence of tungiasis by sex (p=0.044), age group (p<0.000) and class (p<0.000) (Table 1).

The number of T. penetrans infestations ranged from one to 71, and the mean infection intensity in school-aged children was 8.06 (standard deviation 12.41). Based on the Fortaleza criteria for the categorization of T. penetrans intensity [5,15], of the 85 school children who were infested with T. penetrans, 54 (63.5%, 95% CI 53.1–74.1) had mild infection, 25 (29.4%, 95% CI 19.0–39.6) had moderate infection, and six (7.1%, 95% CI 1.2–12.9) had heavy infection. Heavy infection was more common among males [10.2% (5/49) vs 2.8% (1/36) in females], children aged 11–15 years [9.5% (4/42) vs 4.7% (2/43) for younger participants], and students in class 7 [33.3% (2/6)]. However, the observed differences were not significant (Table 1).

Clinical signs and symptoms of tungiasis among infested study participants

The most common signs and symptoms of tungiasis among the infested school children were difficulties in walking, skin desquamation, constant pain, itching, black dots and fissures, and these were present in more than one-quarter of the infested children [29.4% (25/85)] (Figure 1 and Table S1, see online supplementary material).

Figure 1.

Physiopathology of tungiasis. (A) Pictorial view of Tunga penetrans invading epidermis, with hypertrophic changes in abdominal segments. The oviposition and excretion of faeces continues until the parasite's death. Around the parasite, the epidermal layer shows hypertrophic and hyperkeratotic changes. Hyperaemia and inflammatory changes occur in the dermal layer, where T. penetrans acquires nutrients. (B) The five stages of Fortaleza classification: 1: invasion by the parasite; 2: complete penetration of epidermis and faecal excretion; 3: hyperkeratotic changes of epidermis and hypertrophic changes of abdominal segments; 4: lesion involution after parasite's death; 5: residual skin abrasion. Complications with infection and necrosis are summarized in the last square. (C) Photographs of lesions at different stages of infection, indicated by a number.

Knowledge on tungiasis among primary school children

The majority of participants [87.3% (350/401)] had heard of tungiasis, with the leading source of information being home [57.4% (201/350)]. The majority [73.1% (256/350)] correctly knew that the female flea was the cause of tungiasis, but less than half [42.0% (108/257)] reported walking barefooted as the mode of tungiasis transmission. All of the 73.7% (258/350) of participants who knew that tungiasis is preventable mentioned wearing closed shoes regularly as a means of preventing tungiasis (Table 2).

Table 2.

Knowledge on tungiasis among study participants (n=401)

Variable	n (%)	95% CI
Heard of tungiasis
Yes	350 (87.3)	83.3–90.5
No	51 (12.7)	9.5–16.7
Source of information
Home	201 (57.4)	51.6–63,3
Street	24 (6.9)	4.5–9.4
School	22 (6.3)	3.7–9.1
Home and school	85 (24.3)	19.7–29.0
Home and friend	16 (4.6)	2.8–6.9
School and street	2 (0.6)	0.0–1.4
Cause of tungiasis
Female flea	256 (73.1)	68.8–78.2
Do not know	94 (26.9)	21.8–31.2
Knew the mode of tungiasis transmission
Yes	257 (73.4)	68.8–77.8
No	93 (26.6)	22.2–31.2
Mode of tungiasis transmission
Walking barefooted	108 (42.0)	35.8–48.1
Playing with dirty soil	12 (4.7)	2.3–7.2
Touching each other	9 (3.5)	1.2–6.0
Walking barefooted and playing with dirty soil	122 (47.5)	41.0–53.6
Walking barefooted and touching each other	6 (2.3)	0.8–4.3
Knew the symptoms of tungiasis
Yes	267 (76.3)	71.6–81.0
No	83 (23.7)	19.0–28.4
Symptoms of tungiasis
Itching at the site of infection	153 (57.3)	51.0–62.8
Lesion at the site of infection	37 (13.9)	10.0–17.8
Severe pain	23 (8.6)	5.1–12.2
Oedema	21 (7.9)	4.9–11.5
Desquamation	33 (12.4)	8.6–16.3
Is tungiasis curable?
Yes	309 (88.3)	85.0–91.4
No	41 (11.7)	8.6–15.0
Ways to treat tungiasis
Surgical extraction at hospital	176 (57.0)	51.2–63.3
Swallowing tablets	65 (21.0)	16.7–26.3
Traditional medicine	03 (1.0)	0.0–2.0
Self-extraction at home	65 (21.0)	16.7–25.5
Is tungiasis preventable?
Yes	258 (73.7)	69.3–78.4
No	92 (26.3)	21.6–30.7
Ways to prevent tungiasis
Regular wearing of closed shoes	258 (100)	100.0–100.0
Regular application of repellents	00 (0.0)	0.0–0.0

Preventive practices on tungiasis among study participants

More than two-thirds of the participants [67.3% (270/401)] knew that avoiding playing with dogs and cats can prevent tungiasis. The majority [73.8% (296/401)] knew that transmission can be prevented by treating dogs and cats with chemicals that kill the fleas. Also, more than two-thirds [68.8 (276/401) and 66.6% (267/401), respectively] knew that wearing closed shoes regularly and taking a bath after playing in soil can prevent tungiasis infection (Figure 2).

Figure 2.

t Preventive practices on tungiasis among study participants.

Classification of the levels of knowledge and preventive practices among the study participants

Based on the criteria for categorization of knowledge levels, none of the participants had a high level of knowledge. However, the majority [77.1% (270/350)] had a moderate level of knowledge. A low level of knowledge was more common among females [25.1% (47/187) vs 20.2% (33/163) among males], children aged 6–10 years [37.8% (42/111) vs 15.9% (38/239) among older participants], and students in class 1 [46.8% (22/47)]. There were significant differences between the levels of knowledge and sex (p<0.000) and classes (p<0.000) (Table S2, see online supplementary material).

More than half of the participants [54.9% (220/350)] were aware of appropriate practices for tungiasis prevention. Reference to inappropriate preventive practices was high among females (46.8%, 96/205), children aged 6–10 years [60% (78/130)] and students in class 2 [69.8% (37/53)]. There were significant differences between the levels of preventive practices and age groups (p<0.000) and classes (p<0.000) (Table S2, see online supplementary material).

Factors associated with tungiasis infection among study participants

On univariate analysis, the factors associated with tungiasis infection were sex, age group, class, family size, knowledge and practice levels, keeping a dog/cat at home, walking barefooted, and playing in the soil. On multi-variate analysis, factors that were significantly associated with tungiasis infection were class [class 2 (p=0.014) and class 3 (p=0.001)], knowledge level (p=0.003), and keeping a dog/cat at home (p=0.018) (Table 3).

Table 3.

Factors associated with tungiasis infection among the study participants (n=401)

Variable	Tungiasis infection		Univariate analysis		Multi-variate analysis
	Yes n (%)	No n (%)	COR (95% CI)	p-value	AOR (95% CI)	p-value
Sex
Male	49 (25.0)	147 (75.0)	1		1
Female	36 (17.6)	169 (82.4)	1.31 (1.08–1.57)	0.002	0.66 (0.37–1.19)	0.164
Age (years)
6–10	43 (33.1)	87 (66.9)	1		1
11–15	42 (15.5)	229 (84.5)	0.37 (0.23–0.61)	0.000	1.17 (0.36–3.84)	0.792
Class
1	18 (29.5)	43 (70.5)	1		1
2	23 (43.4)	30 (56.6)	0.29 (0.11–0.80)	0.010	0.13 (0.03–0.66)	0.014a
3	14 (24.6)	43 (75.4)	0.16 (0.06–0.48)	0.002	0.08 (0.02–0.37)	0.001a
4	10 (19.2)	42 (80.8)	0.38 (0.13–1.06)	0.042	0.31 (0.10–1.00)	0.050
5	05 (8.8)	52 (91.2)	0.51 (0.17–1.53)	0.179	0.50 (0.16–1.65)	0.261
6	09 (13.6)	57 (86.4)	1.27 (0.37–4.42)	0.706	1.26 (0.35–4.60)	0.726
7	06 (10.9)	49 (89.1)	0.78 (0.26–2.33)	0.654	0.69 (0.22–2.16)	0.524
Family size (n people)
2–5	53 (20.7)	203 (79.3)	1
6–9	28 (20.6)	108 (79.4)	3.06 (0.80–11.81)	0.040	4.04 (0.86–18.91)	0.077
10–13	04 (44.4)	05 (55.6)	3.09 (0.78–12.25)	0.067	4.24 (0.88–20.38)	0.071
Level of knowledge
Low	16 (12.4)	113 (87.6)	1		1
Moderate	69 (25.4)	203 (74.6)	2.40 (1.23–4.67)	0.010	3.16 (1.50–6.67)	0.003a
Classification of practices
Appropriate	53 (24.1)	167 (75.9)	1		1
Inappropriate	32 (17.7)	149 (82.3)	1.48 (0.90–2.42)	0.119	1.64 (0.86–3.13)	0.131
Keep dog/cat at home
Yes	27 (34.6)	51 (65.4)	1		1
No	58 (18.0)	265 (82.0)	0.41 (0.24–0.71)	0.002	0.47 (0.25–0.89)	0.018a
Walk barefooted
Never	37 (25.0)	111(75.0)	1		1
Sometimes	33 (18.2)	148 (81.8)	1.27 (0.64–2.50)	0.495	1.33 (0.61–8.83)	0.475
Always	15 (20.8)	57 (79.2)	1.50 (0.88–2.54)	0.137	1.40 (0.75–2.60)	0.293
Playing in soil
Never	29 (18.7)	126 (81.3)	1		1
Sometimes	28 (18.9)	120 (81.1)	1.00 (0.55–1.80)	0.963	0.90 (0.45–1.80)	0.773
Always	28 (28.6)	70 (71.4)	0.58 (0.32–1.04)	0.069	0.45 (0.25–1.00)	0.499
Type of house
Mud	24(20.7)	92 (79.3)	1
Block	61 (21.4)	224 (78.6)	1.00 (0.56–1.63)	0.874
Material used for roof
Iron sheets	72 (21.2)	268 (78.8)	1
Grasses	13 (21.3)	48 (78.7)	1.01 (0.52–1.96)	0.981
Type of floor in house
Tiles	01 (12.5)	07 (87.5)	1
Cement	52 (20.1)	207 (79.9)	0.57 (0.07–4.73)	0.601
Soil	32 (23.9)	102 (76.1)	0.46 (0.05–3.84)	0.470
Bathing with soap
Never	01 (12.5)	07 (87.5)	1
Sometimes	13 (18.3)	58 (81.7)	0.64 (0.07–5.64)	0.685
Always	71 (22.0)	251 (78.0)	0.50 (0.06–4.17)	0.526

COR, crude odds ratio; AOR, adjusted odds ratio; CI, confidence interval.

^aSignificant (p<0.05).

Discussion

This study is one of few studies in Tanzania that has established the burden and factors associated with tungiasis infection. The overall prevalence of tungiasis infection among primary school children was 21.2%, indicating that tungiasis is among the public health problems in Northeastern Tanzania, with potential to cause severe disease and deformities in vulnerable populations. The prevalence observed in this study was lower than that reported in other studies from Tanzania (39–97%) [10,11], Ethiopia (23.9–52.3%) [3] and Nigeria (45%) [16]. The low prevalence of tungiasis infection in the area could be due to the time the study was conducted. The study was conducted immediately after the rainy season, so the dust level was lower; this is not conducive to T. penetrans survival [8]. The prevalence of tungiasis has been reported to vary significantly throughout the year in endemic areas, peaking in the dry season [17]. The highest prevalence of tungiasis was observed among males aged 6–10 years in class 2, probably because this represents the younger, most active group in terms of playing in a risk environment with poor hygiene practices. The findings are in line with a systematic review which reported that males were infected significantly more often than females (35.5% vs 27.4%; p<0.000) in sub Saharan Africa [4]. In addition, the present findings agree with a study from Kilifi which showed high prevalence of tungiasis among children aged <10 years compared with other age groups [18].

Heavy tungiasis infection was observed in males aged 11–15 years in class 7, indicating that intensity increased with age and class. It is evident that tungiasis infections in endemic areas start early in life, with intensity increasing as children grow [16,19]. Studies have shown high prevalence and intensity of tungiasis infection among children aged 5–14 years, with higher intensity among children aged 10–14 years compared with the adult population [16,19]. Tungiasis infection in children entails chronic sequelae leading to chronic discomfort, foot deformity, foot mutilation and reduced mobility. Also, as for other ectoparasites such as scabies, this affects school attendance, causing poor performance and contributing to dropout rates [16,19,17]. Signs and symptoms of tungiasis among infested children were skin desquamation, digits and nail deformation, itching, black dots, fissure, constant pain and difficulty walking. This is in line with the signs and symptoms observed in other studies in tungiasis-endemic countries [8,10,16,[19], [20], [21]].

The majority of participants had heard of tungiasis infection, and knew that female fleas are the causative agent, possibly because of the endemicity of the disease in the area, with children predominantly affected. These findings contrast with a recent study from Kenya which reported that only 1% knew that fleas could cause tungiasis [22]. Misconceptions about the transmission mode were observed, such as through touching each other, indicating the need for health education focusing specifically on transmission modes of the infection. Itching at the site of infection was the main symptom reported because this is the most common sign of infection in the acute phase. Itching can cause scratching of the lesion, and bacterial and fungal superinfection can then occur leading to abscesses and life-threatening complications [1]. Similar misconceptions on transmission modality, attributed to contact with infected individuals or water, and the finding of itching as the most mentioned symptom have been reported in Kenya and Nigeria [19,23]. Regarding treatment, self-extraction at home was considered to be the correct treatment for tungiasis by participants, thus reflecting the common use of inappropriate treatment practices. Self-extraction at home has been reported to involve the use of non-sterile sharp instruments (e.g. safety pin, needle, scissors, knife, thorn), hence causing transmission of blood-borne infections and complications such as tetanus, gangrene and post-streptococcal glomerulonephritis [1]. The unsafe practice of self-extraction has been associated with rupture of the embedded female T. penetrans, causing an inflammatory response [24]. Wearing appropriate footwear has proven to be effective in the prevention of tungiasis infection in endemic areas [5]. All participants knew that wearing closed shoes regularly could prevent tungiasis infection. However, this may not be applicable in actual practice. None of the participants had high knowledge of tungiasis, with the lowest level observed among children aged 6–10 years and children in class 1, indicating the urgent need for health education in this group.

The low level of knowledge on tungiasis and poor hygienic practices likely contributed to the high prevalence of tungiasis observed in children aged 6–10 years. However, a similar study in Kenya reported that adequate knowledge of tungiasis does not translate into prevention practices [23]. The poorest practices were related to the extraction of T. penetrans, where the majority (78.2%) considered self-management in non-sterile conditions as an effective way to manage tungiasis. The observed practice is consistent with practices reported in Brazil, Ethiopia and Nigeria [5,15,16].

The risk factors that were predictive of tungiasis infection among primary school children were sex, age group, class, family size, knowledge and practice scores, keeping a dog/cat at home, walking barefooted, and playing in soil. These findings are in agreement with other studies reported in Tanzania and in other endemic countries [3,5,11,16]. Of the predictive factors mentioned, only class, knowledge level and keeping a dog/cat at home were significantly associated with tungiasis infection. Low odds of tungiasis infection were observed among participants who did not keep a dog/cat at home. Similar to the observation reported in Tanzania, Ethiopia, Kenya and Nigeria observed high odds of tungiasis infection in communities that kept a dog/cat at home [[3], [4], [5],9,22]. Dogs and cats have been found to harbour T. penetrans, hence increasing the odds of transmission to humans via contact [22]. The odds of tungiasis infection were three times higher for children with moderate knowledge compared with those with low knowledge. This observation confirms that being aware and knowledgeable about tungiasis does not ensure that appropriate preventive practices are followed. However, findings from Kenya have shown that good/adequate knowledge of tungiasis can influence the uptake of preventive measures to control tungiasis infection [22].

Study limitations

This study had the following limitations; data were collected immediately after the rainy season, when the transmission of T. penetrans is low, leading to the possibility of underestimation of tungiasis infection. The factors assessed relied on participants’ responses at school rather than checklist observations at their home; hence, the findings could be subject to recall bias. Also, water and sanitation components were not assessed despite their direct link with tungiasis infection. The cross-sectional design of the study made it impossible to determine a temporal relationship between exposures (factors) and outcome (prevalence of tungiasis) because of their concurrent assessment. However, notwithstanding these limits, the study adds crucial epidemiological data on the burden and factors associated with tungiasis among vulnerable populations in Northeastern Tanzania.

Conclusions and recommendations

The study findings revealed unacceptable ongoing tungiasis infection among primary school children in Northeastern Tanzania. The factors found to be associated with tungiasis infection were class, knowledge level and keeping a dog/cat at home. Therefore, it is essential to develop a health education programme that addresses all aspects of tungiasis infection and prevention, and to integrate this into the primary school curriculum. The programme should promote the use of proper footwear (closed shoes), coconut oil repellents, and improved personal hygiene. Health education will help to increase understanding of tungiasis and ultimately contribute to behavioural change. The Ministry of Health, through the Neglected Tropical Diseases Control Programme, should design and carry out regular screening and treatment programmes for primary school children. Fumigation should be performed regularly for households with a dog/cat, with animals washed using insecticides.

Conflict of interest statement

None declared.