Schistosoma mansoni Infections in Young Children: When Are Schistosome Antigens in Urine, Eggs in Stool and Antibodies to Eggs First Detectable?

Abstract

BackgroundIn Uganda, control of intestinal schistosomiasis with preventive chemotherapy is typically focused towards treatment of school-aged children; the needs of younger children are presently being investigated as in lakeshore communities very young children can be infected. In the context of future epidemiological monitoring, we sought to compare the detection thresholds of available diagnostic tools for Schistosoma mansoni and estimate a likely age of first infection for these children.Methods and FindingsA total of 242 infants and preschool children (134 boys and 108 girls, mean age 2.9 years, minimum 5 months and maximum 5 years) were examined from Bugoigo, a well-known disease endemic village on Lake Albert. Schistosome antigens in urine, eggs in stool and host antibodies to eggs were inspected to reveal a general prevalence of 47.5% (CI95 41.1–54.0%), as ascertained by a positive criterion from at least one diagnostic method. Although children as young as 6 months old could be found infected, the average age of infected children was between 3¼–3¾ years, when diagnostic techniques became broadly congruent.ConclusionWhilst different assays have particular (dis)advantages, direct detection of eggs in stool was least sensitive having a temporal lag behind antigen and antibody methods. Setting precisely a general age of first infection is problematic but if present Ugandan policies continue, a large proportion of infected children could wait up to 3–4 years before receiving first medication. To better tailor treatment needs for this younger ageclass, we suggest that the circulating cathodic antigen urine dipstick method to be used as an epidemiological indicator.

Epidemiology of Schistosomiasis in Two High-Risk Communities of South Côte d'Ivoire with Particular Emphasis on Pre-School–Aged Children

“…25,28,33,34 The negative health impact of such early infections has been emphasized. 31,32,35,36 Our observation of CCA detected in the urine of a child as young as 3 months in the absence of S. mansoni eggs in fecal samples is in line with recent observations from a study in Uganda using different approaches for detecting Schistosoma infections in pre-school-aged children. 36 It might be explained by CCA from the mothers' colostrums 37 or CCA produced by the young developing stages of the worm before patency (hence, before egg production commences).…”

“…31,32,35,36 Our observation of CCA detected in the urine of a child as young as 3 months in the absence of S. mansoni eggs in fecal samples is in line with recent observations from a study in Uganda using different approaches for detecting Schistosoma infections in pre-school-aged children. 36 It might be explained by CCA from the mothers' colostrums 37 or CCA produced by the young developing stages of the worm before patency (hence, before egg production commences). 16,37 New research is needed to further elucidate this issue, which will be important to clarify operational research and control issues and help interpret diagnostic results.…”

“…Hence, the heavy infections observed in 12 pre-school-aged children above the age of 3 years are the likely result of very early infection followed by cumulative infections over time. 36 For both Schistosoma species, we observed specific ageprevalence curves and intensities in both study villages. Although it is commonly believed that the peak of Schistosoma infection prevalence occurs in children between 6 and 15 years of age (school age), age patterns in the intensity of infection are less clear cut, with variations generally attributed to the level of contact with contaminated freshwater bodies.…”

Changing Policy and Practice in the Control of Pediatric Schistosomiasis

“…48,49 Serologic methods that are more sensitive are applicable only before treatment because PZQ alters parasite-specific immune responses 50 ; molecular methods detecting parasite DNA 51 or microRNAs 52 have yet to be evaluated in this age group. It has recently been reported that egg count methods can result in misclassification of the endemicity of schistosomiasis in an area and consequently lead to fewer treatments than actually required.…”

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

“…Despite the high coverage of school-aged children with praziquantel preventive chemotherapy with significant reductions in morbidity among school age children, infants, preschool-age children and other community groups living in close proximity to potentially infected water bodies are likely to be infected and be the source of shedding S. haematobium eggs in the environment and continuity of transmission [5,6]. Hence, there is need to consider the groups left out in the praziquantel preventive chemotherapy campaigns [7][8][9][10]. The frequency of schistosome infections among infants and young children is increasingly being recognized, a situation previously overlooked partly because of emphasizing on school children, low output of parasite egg and the low sensitivity of the currently used diagnostic methods [8].…”