Study site and design
In this community cross sectional survey, we recruited children from 19 out of the 22 different villages of Shamva district. Recruitment was conducted during their expanded immunisation programme (EPI) gatherings and at rural health centres. The study was carried out in Shamva district which is in Mashonaland Central province, Zimbabwe [12]. Shamva recorded the highest prevalence of schistosomiasis in Zimbabwe at 62.3%, during schistosomiasis and soil transmitted helminths (STH) national mapping exercise [13]. The district lies 945 m above sea level, has a warm climate and average temperature of 20.2 °C and an annual rainfall of 887 mm [14]. Shamva district has high farming activity due to presence of fertile soil. Residents get their water supply from Mazowe river which spans through the district [12].
Study inclusion criteria
Participants recruited into the study were lifelong residents of the Shamva district. The PSAC were aged between 1 to 5 years and had a previously reported inclusion criteria [14]. In addition participants had to have a Mantoux test reaction < 5 mm and a normal nutrition status (based on clinical examination, which included mid upper arm circumference measurement and weight-for-age as well as height-for-age measurements).
Sample size
Participant selection was by simple random sampling. Mothers were requested to bring their children to the clinic or EPI meeting points. The required sample size was calculated to be 363 participants using the Dobson formula [13], where the known schistosomiasis prevalence in Shamva district was 62% [13, 15].
Ethical statement
Ethical approval was obtained from Medical Research Council of Zimbabwe (MRCZ/A/2435). Approval was also obtained from the Provincial and District Medical Directors and Community Leaders. Written informed consent was obtained from the parents or guardians of the children. All participants with confirmed infections were offered appropriate treatment.
Data collection
A questionnaire designed for the study (supplementary file 1) was administered to the caregivers/parents and medical record of each child was accessed for those who had been hospitalised over the past year. The coinfections were selected from top causes of morbidity in Zimbabwean children under-5 years of age [15]. Information was extracted from the Zimbabwe demographic health survey, and Zimbabwe provincial and district census statistics [12, 14,15,16,17,18,19,20,21]. The data captured on under-5 mortality was then compared with the prevalence of the top mortality conditions in children which included HIV, malaria, diarrhoea and schistosomiasis [22,23,24,25].
Clinical examinations
The clinical examinations were conducted at a health facility or at EPI allocated facilities on PSAC (n = 415) by two medical practitioners independent of each other. The examinations were conducted based on a protocol as shown in Fig. 1.
S. haematobium infection diagnosis
Urine samples were collected using a wide open container that made it easier for the child to urinate in, children 1 year and below used paediatric urine collector attached by a clinician. The caregivers then brought the samples to the team that were examined as follows:
Haematuria check and parasitology
Haematuria check and parasitology was done as previously described [14]. The parasitology team recorded the results independently of the clinical team.
Blood processing and analysis
Serum and plasma obtained from each child was processed and tested for Toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus 1 and 2, HIV, typhoid and Hepatitis. The sera was processed using the Maglumi 4000 chemiluminescence immunoassay analyser (CLIA). Children diagnosed to have infection were managed appropriately by the doctors in the study and the community nurse.
Co-infections diagnosis
Upper respiratory tract infection (URTI)
URTI was diagnosed on clinical signs and symptoms after excluding allergy and influenza and as per IMCI guidelines [28,29,30,31]. Assessment of URTI progression into severe sequel (severe pneumonia was defined as per WHO guidelines [32, 33].
Fever of unknown origin (FUO)
FUO was defined as children who within the past 6 months had been admitted with a temperature of 38.5 °C and no other diagnosis found after blood, urine and stool cultures as represented from their medical records [34]. Assessment of FUO progression into severe sequel (seizures) were described as change in movement, attention or loss of consciousness in a child diagnosed with FUO, without a history of neurological symptoms [35].
Malaria
Parasitology examination
A few drops of anticoagulated participants blood specimen with EDTA were used for parasite identification and count. Briefly, about two drops of the blood sample were collected on glass slide for preparation of thin and thick blood smears in duplicate. The smears were stained with 10% Geimsa working solution for 10 mins, thin smears were fixed in 100% methanol before Geimsa staining. Malarial parasites were identified under a microscope and parasite load was calculated after counting asexual parasites per 200 white blood cells using the formula assuming that the mean WBC in children 1–5 years old is 11,000/μL [36].
Parasite count/ μL = number of observed asexual parasite × 11,000 WCC/ μL all divided by 200 WCC [37]. Assessment of malaria progression into severe sequel or complicated malaria was described as per WHO guideline for severe malaria: hyperparasitemia (parasite load > 100,000 parasites/μL), persistent vomiting, respiratory distress, convulsion (more than two in 24 h), posturing, comma, discoloration of urine, unable to walk, sit, and stand or unable to feed and drink in infants, hyperpyrexia and hypoglycaemia [33, 38].
Dermatophytosis
Skin scrapings were collected from children with signs of dermatophytosis, examined by microscopy on a warmed potassium hydroxide treated slide [39]. Assessment of dermatophytosis disease progression into severe sequel or severe dermatophytosis was described as ringworms covering greater than 20% surface area using the paediatric burns chart [40].
Statistical methods
Initial analysis was to determine a relationship between the top clinical conditions which children below 60 months old presented with at health facilities and the S. haematobium infection status. Data analysis was performed by STATA version 15, using regression and descriptive analysis. Results were reported as adjusted odds ratios (aORs) with 95% confidence interval (CI), along with the test for significance, as previously described [41]. A relationship was determined of being S. haematobium infected and the clinical conditions advancing to the severe sequels, this was done by multinomial regression analysis adjusted for sex, age and S. haematobium infection which gave adjusted odds ratio. Infection intensity for S. haematobium was defined as previously described that is arithmetic average egg count per ten millilitres of at least two urine samples.