RETRACTED ARTICLE: The epidemiology and chemotherapeutic approaches to the control of urinary schistosomiasis in school-age children (SAC): a systematic review

We carried out a computer-aided search of PubMed, Web of Science, Science Direct, African Journals OnLine (AJOL) and the database of World Health Organization (WHO). However, the information obtained from these sources was supplemented with additional literatures from Mendeley, Research Gate, and Google. The searches were performed independently by the authors using the key words: “urinary/urinary schistosomiasis” in combination with “prevalence”, “intensity”, “morbidity”, “control/praziquantel”, “school” and “children”.

Literatures that address prevalence, intensity, morbidity, indicators or risk factors as well as the control of US, without restriction to year of publication, were included in this review article. Besides, such papers addressed school children specifically. The implication of this is that articles exclusively addressing intestinal schistosomiasis or other Neglected Tropical Diseases were not considered eligible for inclusion.

The secondary data presented in this manuscript were manually extracted from the articles included in this review paper. Data imported into Microsoft Excel Spreadsheet were used to generate Bar Charts.

The search yielded 183 literatures. After proper scrutiny of the retrieved literatures, 93 full text research, review and online articles were deemed fit for inclusion. Consequently, this review is a product of the findings from these articles. The flow chart in Fig. 1 shows the result of our search.

Of the 93 literatures included in this review, majority, 46 (49.46%), were products of researches/reviews carried out in African WHO Region, with Nigeria recording the second largest number of articles, 19 (20.43%). Switzerland in European Region, however, accounted for the largest, 22 (23.66%), which were all technical reports/review articles (see Table 1).

The sampling years reported by the 61 research articles included in this review ranged from 1984 to 2017, with the studies executed between 2004 and 2017 being 11 times more in number than those carried out in each of 1984–1993 and 1994–2003. Sixty-Five point Fifty-Eight percent (40), 63.93% (39), and 60.66% (37) of the studies were cross-sectional in nature, carried out in school settings and rural areas respectively (see Table 1).

However, it is worthy of note that sample size determination, sampling method, and intensity of US were not reported by 49.18% (30), 54.09% (33) and 46.34% (19) of the studies included in this review (see Table 1).

Meanwhile, schistosomiasis, an infectious disease of poverty, is easily contracted through poor hygiene and play habits of school children. In majority of areas endemic for US, a peak of morbidity is usually observed in school children within age range 7–14 years [16]. On the long run, it prolongs squalor and as a result, blocks cognitive academic performance and normal growth of children. This culminates in suffering and sometimes, death [17]. The extent of morbidity due to US is strongly linked with the intensity and the length of infection period. Because US is more prevalent in SAC, control programme is directed at them so that the duration of heavy infection intensity could be reduced markedly [18, 19].

Unfortunately, as our findings revealed, majority of SAC are from Africa which had previously been reported to have accounted for an estimate of over 85% of all cases of schistosomiasis globally [20]. Therefore, promoting the health of SAC has been an integral part of the programme of WHO, United Nations Educational, Scientific and Cultural Organization (UNESCO), United Nations Children’s Fund (UNICEF), and other international agencies since the 1950s [21]. SAC are a target group for Mass Drug Administration (MDA) since WHO expert committee on schistosomiasis met for the first time 64 years ago [18, 22].

This is ascertained by the projected budget of about USD 116 million for 2009 to 2013 global procurement and delivery of drug to endemic countries by WHO and the UN systems without custom fees and clearance charges due to existing agreements [23, 24]. In Central Nigeria, study on the epidemiology of US in SAC using the WHO paradigm of ≥50% prevalence has been used as a benchmark for the treatment of the disease in adults [25].

Various strategies have been applied in the control of US. These include indiscriminate mass treatment, active case finding and treatment of particular risk groups such as school-aged children [26]. However, before the advent of PZQ, other drugs effective against different species and stages of development were used (see Table 5). Drugs of intervention for schistosomiasis progressed from antimonial compounds to PZQ which is the drug of choice today [27]. Metrifonate and Hycathone mesylate are effective for the treatment of US. Lucanthone hydrochloride was used from 1948 to mid-sixties. When given a short treatment from 3 to 6 days, it had moderate activity againstS. haematobium. Niridazole is used against S. mansoni, S. japonicum andS. haematobium [28]. Corticosteroids and anticonvulsants are used to treat katayama fever in order to suppress the hypersensitivity reaction and with PZQ to eliminate the already mature adult. PZQ should be administered with great caution in the case or concurrent neurocysticercosis [29]. The use of Artemisinin derivatives as prophylaxis for acute schistosomiasis, possibly in combination with PZQ, has been investigated. However, Artemisinin use in malaria-endemic areas is not encouraged because of anticipated drug resistance [30].

However, the most rapid and cost-effective way to control morbidity due to schistosomiasis is through a chemotherapeutic intervention with PZQ [31]. PZQ and Albendazole can, however, be administered together safely where there is co-endemicity of schistosomiasis and Soil-Transmitted Helminthiasis (STH) [32]. It is already well known that after chemotherapy, cessation of symptoms is evidenced in the reduction of egg excretion, proteinuria, haematuria, urinary iron loss, leucocyturia, and few remaining schistosomes which cannot multiply [17, 18, 33‐36]. Consequently, they pose little or no threat to their hosts. Therefore, control programmes should focus on the achievement of a sharp decline in the intensity of infection [17]. Based on this premise, in 2001, the World Health Assembly adopted resolution 54.19 which set a target for all endemic countries to regularly treat over 75% of all SAC at risk of morbidity due to schistosomiasis and STH by 2010 [37, 38]. It is pertinent to state that the result of this review clearly showed that this aim was not achieved (see Table 6).

Nevertheless, the greatest challenge of MDA is to extend regular drug coverage to reach all the children at risk of morbidity due to infection by helminths [23]. There are two perspectives to this. One, each School-age Child (SAC) treated may not have access to enough PZQ that would clear all the parasites. Two, the distribution coverage may not cater for the whole population of infected SAC. Consequently, symptoms of chronic infection may show up after 5–15 years in children who were partially treated as a result of poor coverage of PZQ [20]. However, the report of a School-Based Treatment carried out in Zanzibar Island, Tanzania, where 8000 pupils were treated showed amazing coverage of 85.2 and 86.9% in Pemba and Unguja Districts respectively [39].

PZQ is not without its adverse reactions like abdominal pain, dizziness, headache, vomiting, diarrhea, round, swollen and itching skin rashes, and fever [40]. These are usually mild and last for 24 h. These are reactions from dying worms.

In addition, studies have shown that false negative results cause infected SAC to escape treatment, leading to chronic condition and if such case occurs after MDA, cure rate may be overestimated and this may be a prelude to drug resistance and further transmission of US [41].

It is hoped that in the nearest future, global schistosomiasis control programmes will receive a boost when the current “evolutionary” process of vaccine-linked chemotherapy culminates in approval by WHO. A good number of these vaccines undergoing preclinical and clinical trials on the field are particularly made for children [42].

This review took articles reported in English into consideration instead of including those reported in other languages. Besides, we noticed that mean intensity of infection with US was either underreported or not reported by some authors of articles included in this review article. Consequently, the report of the mean intensity reported here may not be an accurate reflection of what is obtainable among SAC globally.