Evaluation and application of potential schistosome-associated morbidity markers within large-scale mass chemotherapy programmes

Abstract

A primary objective of schistosomiasis control programmes is to achieve, and hence also demonstrate, a quantifiable reduction in schistosome-associated morbidity as a consequence of chemotherapeutic intervention. Inherent within such an objective, it is necessary to define and validate direct and indirect indicators of schistosome-related morbidity. However, to define and thereby document such morbidity, and its reduction following treatment, may not be straightforward, particularly for intestinal schistosomiasis-induced morbidity, which is often not apparent in all but the most severe or chronic cases. Within all 'Schistosomiasis Control Initiative' activities, across selected sub-Saharan African countries since 2002, a range of standard and novel potential morbidity markers have been monitored and evaluated. Parasitological intensity measures, combined with haemoglobin/anaemia counts and ultrasonography, proved valuable schistosomiasis-related morbidity indicators, being both logistically practical and informative. Additional measures tested, such as albumin excretion profiles, were promising, and are subject to ongoing research, whilst some measures, such as distended stomach/umbilical circumference, anthropometrics and health questionnaires proved less reliable. These results serve to both illustrate the success of current control activities in reducing schistosome-induced morbidity, and to highlight key tools and techniques for continued application within ongoing and future mass drug administration programmes.

Urinary schistosomiasis among preschool-age children in an endemic area of Kinondoni municipality, Dar es Salaam, Tanzania 2016

“…Early childhood infection undoubtedly contributes to pathology among preschool children in endemic areas, thus the finding of 12.0% prevalence of blood in urine indicates a probable cryptic morbidity of damage in the urinary tract due to S. haematobium infection despite the observed low prevalence (1.9%) of patent eggs count, all with a light intensity which is common in preschool age children [26]. The observed low prevalence of S. haematobium infection may be explained by the low sensitivity of the egg counts method used that are the corner stone of measurement of morbidity of schistosomiasis, which may not be optimal in the presence of light intensity of infection [27]. Nevertheless, the finding demonstrates that S. haematobium transmission is ongoing and with continued contact with water bodies infested with Bulinus spp.…”

Decline in infection-related morbidities following drug-mediated reductions in the intensity of Schistosoma infection: A systematic review and meta-analysis

“…In recent years, millions of people have been treated in different contexts and, in general, prevalence of morbidity has been reduced after treatment [7, 19–22]. Nevertheless, studies of morbidity reduction related to drug treatment have had some conflicting results [23–26], which may be a reflection of differences in follow-up after treatment, methods used to measure morbidities, the Schistosoma species, the presence of co-infections (especially malaria), the type of population and the region, the initial prevalence of infection, the incidence of reinfection, and other factors [7, 27].…”

Schistosomiasis in pre-school-age children and their mothers in Chikhwawa district, Malawi with notes on characterization of schistosomes and snails

“…In Cote d’Ivoire, Niger, Nigeria and Mali, urogenital schistosomiasis can be common in PSAC [15,30,31]. Putative morbidity can be assessed by ultrasonography and by POC assays for haematuria and albuminuria, used alongside detection of intestinal schistosomiasis with urine-CCA dipsticks [7,32-34]. …”