Schistosoma mansoni reinfection: Analysis of risk factors by classification and regression tree (CART) modeling

Abstract

Praziquantel (PZQ) is an effective chemotherapy for schistosomiasis mansoni and a mainstay for its control and potential elimination. However, it does not prevent against reinfection, which can occur rapidly in areas with active transmission. A guide to ranking the risk factors for Schistosoma mansoni reinfection would greatly contribute to prioritizing resources and focusing prevention and control measures to prevent rapid reinfection. The objective of the current study was to explore the relationship among the socioeconomic, demographic, and epidemiological factors that can influence reinfection by S. mansoni one year after successful treatment with PZQ in school-aged children in Northeastern Minas Gerais state Brazil. Parasitological, socioeconomic, demographic, and water contact information were surveyed in 506 S. mansoni-infected individuals, aged 6 to 15 years, resident in these endemic areas. Eligible individuals were treated with PZQ until they were determined to be negative by the absence of S. mansoni eggs in the feces on two consecutive days of Kato-Katz fecal thick smear. These individuals were surveyed again 12 months from the date of successful treatment with PZQ. A classification and regression tree modeling (CART) was then used to explore the relationship between socioeconomic, demographic, and epidemiological variables and their reinfection status. The most important risk factor identified for S. mansoni reinfection was their “heavy” infection at baseline. Additional analyses, excluding heavy infection status, showed that lower socioeconomic status and a lower level of education of the household head were also most important risk factors for S. mansoni reinfection. Our results provide an important contribution toward the control and possible elimination of schistosomiasis by identifying three major risk factors that can be used for targeted treatment and monitoring of reinfection. We suggest that control measures that target heavily infected children in the most economically disadvantaged households would be most beneficial to maintain the success of mass chemotherapy campaigns.

Impacts of host gender on Schistosoma mansoni risk in rural Uganda—A mixed-methods approach

“…The similarity of water contact behaviours between genders is reflected in our epidemiological data presented here, with no significant differences by gender between reinfection risk for SAC. These findings support other epidemiological studies [11,13]. After a period of clearance, egg production is observed less than six weeks later in 37% (n = 20) of the longitudinal cohort.…”

“…reinfection found that males (children and adults) were more often reinfected between 6 and 12 months after treatment with praziquantel than females (pooled OR: 1.45, p = 0.04 [12]). However, two recent studies looking at reinfection with S. mansoni in school-aged children specifically (ages 6-14 years), in endemic settings in Tanzania and Brazil, found no difference in reinfection between boys and girls at 5, 8 [13], and 12 months [11] after treatment.…”

“…Praziquantel treatment clears between 80-95% of Schistosoma mansoni (main cause of intestinal schistosomiasis) adult worms in an individual [10] but treatment does not prevent reinfection. Reinfection is a particular challenge in areas with high rates of transmission, where parasite reservoirs in snail vectors and untreated humans can quickly reinfect treated individuals [11]. A metaanalysis of 32 studies on Schistosoma spp.…”

Core components, concepts and strategies for parasitic and vector-borne disease elimination with a focus on schistosomiasis: A landscape analysis

“…However, epidemiological considerations and modelling results suggest that a focus on MDA for schoolchildren risks ignoring a potentially substantial reservoir (and morbidity burden) [ 14 , 36 , 75 , 92 , 93 , 103 , 104 ]. Risk factors related to occupation, behavior, and proximity to, as well as dependency on, open water sources have long been identified as challenges to elimination efforts, further underscoring the need to treat also other at-risk populations [ 105 , 106 ] at high coverage [ 92 , 93 , 103 ].…”

CCR5 and CCR5Δ32 in bacterial and parasitic infections: Thinking chemokine receptors outside the HIV box

“…After frequent exposure to parasite antigens, in some individuals, the host immune response can develop resistance to reinfection (McManus et al, 2018). However, reinfection is very frequent in schistosomiasis patients, especially among those living in endemic areas (Dejon‐Agobé et al, 2019; Gazzinelli et al, 2017; Woldegerima, Bayih, Tegegne, Aemero, & Jejaw Zeleke, 2019). The development of resistance or susceptibility to reinfection is influenced by age, pretreatment infection intensity, host immune characteristics, the occurrence of “heavy” infection at baseline, among other factors (Gazzinelli et al, 2017; Mbanefo et al, 2014).…”