Characteristics of the study population
Of the 15,400 samples obtained at both baseline mapping and sentinel site surveys, sociodemographic and parasitological results were obtained for 15,133 individuals across 130 communities in 15 districts. Of those, WaSH data from the household census was linked to 6,637 individuals (Figure 1).
Table 2 describes individual and household characteristics of the survey respondents by STH species. Overall, levels of infection were 9.5% for Ascaris, 1.8% for T. trichiura, 7.2% for hookworm, and 15.5% any STH. Infection was not significantly different for any species by participant’s sex. Pre-SAC were significantly more likely to be infected with Ascaris than older age groups (p<0.01). Similarly, hookworm was significantly higher in pre-SAC and older adults 36+ years (p<0.01) (see Table 2 and Figure 2).
Most households (78.7%) had access to improved drinking water sources where the majority accessed water from a public standpipe (54.7%). Access to improved drinking water was not statistically associated with any STH species. Of those households that did have access to improved drinking water, only half (50.7%) were able to collect water in less than 30 minutes round trip. Time taken to collect water did have a significant association with Ascaris and hookworm where infection was significantly higher in households that had to walk more than 30 minutes (14.7% vs. 12.6% and 12.2% vs. 8.5%, respectively). The JMP service ladder for drinking water (Table 1) considers both source and collection time. There was no association between JMP drinking water categories and STH.
Few households (15.9%) had an improved latrine at the household, which made it difficult to analyse any association between sanitation and STH infection. Most households (76.1%) had pit latrines without a slab, some reported no facility at all (7.7%). Households that shared a latrine, however, was significantly associated with greater Ascaris and hookworm infection (16.2% vs. 13.1% and 11.1% vs. 8.6%, respectively). Sanitation was categorized into the JMP service ladder (Table 1), which considers latrine type and whether it is shared with other households. There was a significant association between unimproved sanitation and increased hookworm infection (p=0.04). Most households with small children reported disposing of faeces in the latrine (68.5%). There was no statistical association between child stool disposal practices and any STH infection.
In the census respondents were asked about handwashing behaviour. Only hookworm was significantly greater among households with no handwashing facilities, with 12.3% infection in households without a place to wash hands vs. 7.8% in households with facilities. Access to soap at the handwashing facility was associated lower infection of any STH (i.e., non-species specific). Handwashing was categorized into the JMP service ladder (Table 1), which considers availability of water and soap to wash hands at the time of the survey. The lack of any handwashing facility was significantly associated with increased Ascaris, hookworm, and any STH infection. As expected, hookworm infection was significantly associated with shoe wearing, where individuals observed to be wearing shoes at the time of interview were less likely to be infected. Treatment with chlorine had a significant association with reduced Ascaris, Trichuris, and hookworm infection.
Table 3 describes individual and household characteristics by schistosomiasis prevalence. Overall, levels of infection were low for intestinal schistosomiasis (S.mansoni) by Kato Katz (0.85%), but greater using the more sensitive diagnostic POC-CCA when trace was considered positive (21.6%) and negative (13.1%). Haemastix were used to detect microhaematuria as a proxy for urinary schistosomiasis (S. haematobium) where 2.7% of samples were positive. Urine filtration was carried out on haemastix positive samples only, where eggs were detected in 0.5% of samples only. Given the low prevalence by urine filtration, only haemastix results are presented in the tables. As has been demonstrated previously in the literature, S. mansoni (by POC-CCA) and S. haematobium (by haemastix) were significantly higher in males and SAC (see Figure 2).
Households without access to improved drinking water sources were more likely to have individuals infected with S. mansoni considering POC-CCA trace positive (16.2% vs. 13.2%). As seen with STH, there was increased risk of S. mansoni infection when it took the household more than 30 minutes round trip to collect water. As expected, when clustering households into the JMP service ladder for drinking water there was increased risk of schistosomiasis infection (regardless of diagnostic or species) where limited (improved source >30min round trip) or surface water was used, compared to those with basic drinking water. Treatment with chlorine had a significant association with reduced S.mansoni (by POC-CCA Tr+) infection.
There was no association with access to an improved latrine, however, sharing a latrine did have a significant association with S.mansoni (by POC-CCA Tr+) and S.haematobium (by haemastix) (19.4% vs. 13% and 4.1% vs. 2.7%, respectively). If a household did not report disposing of child stool, there was a significant association with S.mansoni (by POC-CCA Tr+) and S.haematobium (by haemastix).
Schistosome parasite infections were significantly greater in households with limited handwashing facilities (no soap and/or water available at the time of the survey). There was only association between bathing and washing clothes in fresh water with S. mansoni diagnosed using Kato Katz.
Table 4 summarises the association between community sanitation and parasitological results. No communities had an average improved sanitation coverage of more than 50%. In general, individuals living in communities with lower sanitation usage had a higher prevalence and intensity of STH infection. Most communities had below 20% community sanitation coverage, where were consistently highest prevalence and intensity for all STH species. There was no statistically significant effect of community sanitation coverage on schistosomiasis prevalence or intensity.
Table 5 examines the association of community access to an improved drinking water, where lack of access had significantly higher prevalence and intensity of both STH and schistosomiasis infection again among communities in the 0-20% improved drinking water coverage category.
Table 6 shows odds ratios of infection in strata of community sanitation usage and household latrine coverage (by JMP category) with infection. The odds of Ascaris infection decreased as community sanitation coverage improved to 20-40% (OR:0.63) and further as coverage >40% (OR:0.35). Likewise, odds of Trichuris infection halved as community sanitation coverage reached greater than 40% (OR:0.51). Hookworm prevalence, however, was significantly modified by household sanitation where infection increased with limited sanitation (OR:1.49) and further still with unimproved latrine (OR:1.56). There was no significant association with community coverage and hookworm.