Association of S. haematobium Infection Morbidity and Severity on Co-infections status in Pre-school Age Children Living in a Rural Endemic Area in Zimbabwe

Background: Individuals living in S. haematobium endemic areas are often at risk of having other communicable diseases, simultaneously. This usually creates diagnostic difficulties leading to misdiagnosis and overlooking schistosomiasis infection. In this study we investigated the prevalence and effects of coinfections in pre-school age children. Methodology : About 465 Preschool age children were clinically examined for the following top morbidity conditions: respiratory tract infections, dermatophytosis, malaria and fever of unknown origin. S. haematobium infection was diagnosed by urine filtration and the children were screened for other communicable infections common in rural areas. Results : Prevalence of S. haematobium was 35% (145). A positive relationship between S. haematobium prevalence and under-5 mortality rate in Zimbabwean provinces was demonstrated. The odds of co-infections observed for S. haematobium were: upper respiratory tract infection AOR = 1.98 (95% CI 1.657 to 2.48), dermatophytosis AOR = 5.10 ( 95% CI 2.99 to 8.72), fever of unknown origin AOR = 9.07 ( 95% CI 5.70 to 14.44) and malaria AOR = 0.91 ( 95% CI 0.54 to1.54). The risk ratio of having S. haematobium and co-infections in children who had fever of unknown origin 138%, dermatophytosis 38%, Upper respiratory tract infection 1% increase risk and malaria had a 2% reduced risk. Odds of having severe sequelae following the above conditions were: severe pneumonia AOR = 8.41(95%CI 3.09-22.93), complicated malaria AOR = 7.09 (95% CI 1.51-33.39), severe and persistent dermatophytosis AOR=20.3 (95% CI 4.78-83.2) and seizures AOR=1.62 (95%CI 1.56-4.73). Conclusion : This study is novel as it identifies a possible causal relationship between S. haematobium infection and top morbidity conditions in children under five years. There is need to alert policy makers so to initiate early treatment of schistosomiasis in pre-school age


Introduction
Human schistosomiasis is a parasitic disease caused by blood flukes called trematode worms of the genus Schistosoma, predominantly affecting people in low-and middle-income countries (1). An estimated 206.4 million people in 78 countries required treatment for schistosomiasis in 2016(2,3). In sub-Saharan Africa alone, about 52 endemic countries reported moderate to high prevalence (4).
Individuals living in schistosomiasis-endemic areas are often at risk to several pathogens simultaneously (5). These coinfections could arise due to chance because of host susceptibility or cocirculation of various disease agents (6). Alternatively, schistosomiasis may increase or decrease the risk for another infection (7). Studies on co-infection in adults have shown that schistosomiasis coinfection hinders diagnosis and treatment of other communicable diseases [8,10]. To date, however, little focus has been given to pre-school age children (PSAC), who were regarded as a low risk group.
However, recent studies suggest that they may have similar risk to adults (11). The prevalence and relationship of schistosomiasis to co-infections in PSAC has not yet been described.
The World Health Organization (WHO) Sustainable Developmental Goal (SDG) 3 aims to reduce under-5 mortality to at least as low as 25 per 1,000 live births in every country by 2030 (4). In Zimbabwe, the top causes of morbidity and mortality in PSAC include acute respiratory tract infections (ARI), malaria, diarrhoea, fever and skin diseases(12)(13). In this study we investigated the prevalence and extent of morbidity associated with S. haematobium coinfections in children under the age of five years in an endemic district of Zimbabwe.

Study site and design
The study was conducted in Shamva District in Mashonaland Central Province of Zimbabwe, with the highest prevalence of schistosomiasis in Zimbabwe at 62.3%. Children were recruited from 19 different villages in Shamva district and Shamva district hospital. All children were assessed for schistosomiasis, upper respiratory tract infections, dermatophytosis and malaria. Clinical screening was done by experienced clinician and laboratory work was done by experienced laboratory scientist.

Study inclusion criteria
Participants recruited into the study were residents of the Shamva district in Zimbabwe. The PSAC were aged between 1 to 5 years and met the following inclusion criteria: 1. Be lifelong residents of the study area 2. Had no previous anti-helminthic treatment exposure 3. Parental/guardian consent to participate 4. Be negative for Schistosoma mansoni and geohelminths 5. Be negative for the ToRCHeS (toxoplasmosis, rubella, cytomegalovirus, hepatitis and syphilis) screen 6. Be HIV negative 8. Have a widal TO ratio <1:160 9. Mantoux test reaction <5mm 10. Had a normal nutrition status

Ethical statement
Ethical approval was obtained from Medical Research Council of Zimbabwe (MRCZ/A/2435).

Gatekeeper approval was 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 treatment.

Data collection
A questionnaire was administered and medical records assessed for those who were admitted.
Information was extracted from the demographic and health survey-Zimbabwe statistics (13). The coinfections were selected from top morbidity causes in children under-five years old in Zimbabwe (12).

Clinical examinations
The clinical examinations were conducted on PSAC (n = 415) by two medical practitioners independent of each other according to a protocol ( Figure 1)

S. haematobium infection diagnosis
Urine samples collected were examined for macrohematuria using the Uristix reagent strips (Uripath, Plasmatec, UK) dipped into fresh, well-mixed urine for 40 sec and the test area was compared with a standard colour chart as per manufacturer's instructions. The parasitology team conducted parasitology examination and results were recorded separately, not accessed by the clinical team.
Approximately 50 ml of urine sample was collected from each participant on three consecutive days.
The samples were collected between 10am and 2pm and processed within 2 hours of collection by urine filtration method and were examined using microscopy for S. haematobium eggs detection. The number of eggs were reported per 10ml of urine.

Upper Respiratory Tract Infection
URTI was diagnosed on clinical signs and symptoms after excluding allergy and influenza (14)(15)(16).
Severe pneumonia was defined as per WHO guidelines (17,18).

Fever of unknown origin (FUO)
FUO was defined as children who within the past six months had been admitted with a temperature of 38.5 o C and no other diagnosis found after blood, urine and stool cultures as represented from their medical records (19). Seizures were described as change in movement, attention or loss of consciousness in a child diagnosed with FUO, with no family history of febrile seizures (20).

Malaria
Thick and thin blood film slides were stained using the geimsa stain and examined for malaria parasites using microscopy, as previously described (21). Complicated malaria was described as per WHO guideline for severe malaria (18,22).

Dermatophytosis
Skin scraps were collected from individuals with signs of dermatophytosis, examined on a warmed potassium hydroxide treated slide for microscopy(23). Severe dermatophytosis was described as ringworms covering greater than 20% surface area using the paediatric burns chart (24).

Statistical method
Data analysis was performed using STATA version 15. The statistical methods applied were descriptive statistics providing relative risk and regression analysis for odds ratio. Results were reported as adjusted ORs (AORs) and risk ratios (RR) with 95% confidence interval (CI), along with the test for significance, as previously described (25). Infection intensity for S. haematobium was defined as the arithmetic mean egg count/10ml of at least two urine samples collected on three consecutive days.

Results
Screening involved 465 PSAC aged one to five years from the Shamva district, 415 of whom met the eligibility criteria and consented to be part of the study. The sex ratio was equal, and the mean age was 3.39 years. Those with malaria had P. falciparum as the parasite.

Severity of morbidity associated with co-infections
PSAC with schistosomiasis and URTI had an eight-fold higher odds of pneumonia than children with URTI alone AOR=7.90 ( 95% CI 2.76 to 27.5), p=0.008 (Table 3) Considering URTI, dermatophytosis and FUO; a strong positive association between schistosomiasis and URTI; dermatophytosis and FUO were observed. The trends revealed an association between schistosomiasis and under-5 mortality rate from the national data provided by the Ministry of Health in Zimbabwe. There was a negative association between schistosomiasis and malaria, though participants with the two as co-infections had a greater likelihood of presenting with complicated malaria. Similarly, participants with URTI, FOU and dermatophytosis as coinfections had a higher likelihood of having severe sequelae of the diseases.
A positive association on comparing schistosomiasis prevalence with under-5 and child mortality rate in different provinces of Zimbabwe was demonstrated. The provinces that had a high schistosomiasis rate also had high mortality rate (12,13). This made us wonder if schistosomiasis co-infections were possibly worsening the disease courses as we also found that in co-infections there was a greater chance of the disease course turning out to be severe (12). It is necessary to explore the effects of schistosomiasis and other diseases co-infections in all the top morbidity and mortality causes in PSAC.
Early schistosomiasis treatment in PSAC has the potential to lower the under-five mortality rate, by reducing the incidence of severe sequelae of the top morbidity conditions in this age group which are also top causes for mortality in this age group. This should be shared with policy makers in low and middle income countries.
Children infected with S. haematobium had a 20-fold higher odds of severe dermatophytosis, after adjusting for other clinical conditions. S. haematobium infection had a 38% increased risk of getting dermatophytosis. There is no previous documentation between S. haematobium and dermatophytosis. In literature extensive dermatophytosis was noted in a case report involving S. mansoni (26). It is postulated that S.mansoni exacerbated dermatophytosis by lowering immunity due to the liver involvement or by suppression of the T-helper 1 system which is involved in suppressing fungal infections (27,28). Dermatophytosis cause great morbidity in PSAC in Zimbabwe (13). Since it is a skin condition, it is associated with psychological trauma via discrimination in its severe form. It is necessary to notify clinicians in schistosomiasis endemic areas of this finding in-order to decrease the morbidity rate associated with dermatophytosis. Further studies on this association and immunological profiling is recommended.
Children with schistosomiasis had risk reduction associated with malarial plasmodium coinfection. It is documented that malaria infection is exacerbated/ameliorated by schistosomiasis co-infection [19 -21]. The enhanced T-helper 1 system and an increase in anti-interferon-gamma antibody causes a protective effect against the malarial parasite (32). Of note is; though schistosomiasis was demonstrated to have a protective effect with malaria in the event of co-infection malaria infection had 7-fold chance of exacerbating to complicated malaria requiring hospital admission. This makes it crucial for PSAC to be included in national schistosomiasis control programs, as there is capacity of improving the morbidity and mortality rate in children under the age of five. However, the dilemma in PSAC infections and diseases require agent attention as this is the age of growth and development during which the immune system is developing. Further studies are required to understand coinfection in PSAC inclusive of malaria infection outcome.
There was a 10-fold chance of finding FUO and schistosomiasis as a coinfection, children with schistosomiasis had 138% risk of FUO. Despite advances in medicine, the proportion of patients discharged with undiagnosed FUO after systematic examination has not improved (33). The cause of febrile illness is not identified in approximately 9 -51% of patients, this is even higher in resource limited areas endemic for childhood illnesses (34). Of the children who had FOU and schistosomiasis there was a 2-folded chance of them having serious sequelae such as seizures. Most clinician tend to think of other conditions in contrast to neglected tropical diseases when a patient presents with a fever (18). It might be necessary to make it a priority to screen for schistosomiasis when a child from an endemic area presents with a fever. However further immunological investigations are necessary in-order to find if the fever is due to schistosomiasis infection itself or exacerbation of a co-infection, during the early immunological responses to diseases manifestation.
In our study the odds of having URTI was 2% higher in schistosomiasis infected children with a 1% increases risk of S. haematobium infected children acquiring a URTI. Furthermore, in the coinfected cohort odds of ending up with severe pneumonia was 7-fold compared to schistosomiasis negative population. This is a very significant finding as ARIs are the leading cause of morbidity and mortality in children under the age of five in Zimbabwe (13). Thus tackling schistosomiasis crisis in this age group will have enormous contribution in reducing the mortality and morbidity rate.
The strength of this study included that although the calculated sample was 368, we managed to enrol 415 participants. We focused on the major morbidity and mortality causes in this age group from our study area which also fit into most of the low income countries were schistosomiasis is endemic. The main limitation of this study is there is a possibility that the children may have had more than two infections as co-infections which might make our data biased, however we did thorough clinical examinations and laboratory tests in all the participants to rule this out. We also considered socioeconomic status as a confounding factor by focusing on children with a similar background and in the same villages with similar lifestyles.

Conclusion
This study is novel as it demonstrates an association between schistosomiasis and top morbidity conditions in a schistosomiasis endemic area namely: URTI, dermatophytosis, malaria and FUO.
Furthermore, we demonstrated a detrimental effect were coinfection led to severe sequelae of these clinical conditions. The clinical conditions described in this paper have a high impact on morbidity and mortality in children under the age of five. This brings out the importance of including PSAC in national schistosomiasis control programs. It is of paramount importance that clinician and policy makers in endemic areas are alerted of these associations in order to reach the WHO sustainable developmental goal (SDG) 3 by 2030.

Declarations
We would like to acknowledge the Ministry of Health and Child Care, the Medical Research Council of Zimbabwe, village health workers, nursing staff, parents and children from Shamva. A special thanks to members of the Biochemistry Department at the University of Zimbabwe for technical support during field parasitology and sampling. Our most profound gratitude to the participants and their parents or guardians for taking part in this study.    Trends showing schistosomiasis prevalence and under 5 child mortality per 1000 live births from Zimbabwe provinces.