Environmental interventions and the pattern of geohelminth infections in Salvador, Brazil

Cattaneo 2009 selected controls using propensity score matching and adjusted for confounders, while Aiga 2002 and Moraes 2004 controlled for potential confounders.

“Cattaneo 2009 selected controls using propensity score matching and adjusted for confounders whilst two studies controlled for potential confounders (Aiga 2002; Moraes 2004).”

Both Cattaneo 2009 and Moraes 2004 collected stool samples to measure the prevalence of intestinal parasites.

“Both collected stool samples to measure the prevalence of intestinal parasites.”

Just two studies described methods to minimise detection bias: Gonzalez-Navarro 2010 ensured participants were not informed of study objectives during household interviews, and Moraes 2004 blinded microscopists examining stool samples to intervention status.

“Just two studies described methods to minimise detection bias. One RCT ensured participants were not informed of the study objectives during household interviews with field workers as a way to minimise bias (Gonzalez‐Navarro 2010). One supporting study blinded microscopists examining stool samples to the intervention status of the community from whom the samples had been collected (Moraes 2004).”

Three supporting studies (Moitra 1987; Moraes 2004; Parikh in press) did not consider the degree to which the intervention or its components were delivered as intended.

“Three supporting studies did not consider the degree to which the intervention or its components were delivered as intended (the fidelity of the intervention) (Moitra 1987; Moraes 2004; Parikh in press).”

Moraes 2004 aimed to examine the impact of drains or drains and sewerage, but paved paths and tenure were also provided as part of the intervention.

“Similarly, Moraes 2004 aimed to examine the impact of drains or drains and sewerage but it was apparent that paved paths and tenure were also provided as part of the intervention.”

Moraes 2004 described rigorous methods to assess self-reported diarrhoea, by measuring episodes every two weeks over the period of a year, using diarrhoea calendars and quality checking data obtained.

“In addition, Moraes 2004, described rigorous methods to assess self‐reported diarrhoea, by measuring episodes every two weeks over the period of a year, using diarrhoea calendars and quality checking data obtained.”

Among the studies reviewed, the most reliable outcome measures were utilised in the supporting studies Cattaneo 2009 and Moraes 2004.

“Among the studies reviewed, the most reliable outcome measures were utilised in the supporting studies Cattaneo 2009 and Moraes 2004.”

Two supporting studies (Aiga 2002; Moraes 2004) emphasised one aspect of a slum upgrading strategy without detailed consideration of co-interventions.

“Two supporting studies emphasised one aspect of a slum upgrading strategy being implemented without detailed consideration of co‐interventions.”

In Moraes 2004, there was no difference between study groups regarding intensity of Ascaris infection (eggs per gram stool).

“There was no difference between the study groups regarding the intensity of infection (eggs per gram stool) in those with Ascaris.”

In Moraes 2004, both drains and drains plus sewerage interventions were associated with lower incidence of Ascaris, Trichuris and Hookworm infections in children aged 5 to 14 compared to control, with the lowest risk in the drains and sewers group.

“Both interventions were associated with lower incidence of the three species when compared to the control group, with the lowest risk observed in the drain and sewers group.”

In Moraes 2004, Hookworm intensity was highest in the drains and sewerage intervention group.

“Trichuris had a significantly higher intensity in the control than in the intervention groups, and contrary to expectation Hookworm intensity was highest in the drains and sewerage intervention group (Moraes 2004).”

In Moraes 2004, the drains and sewerage group was associated with lower frequent diarrhoea in children under 5 compared to control (RR 0.14).

“Children under 5 years old having frequent diarrhoea (more than twice the expected number of episodes) in intervention groups compared to control Drains group: RR = 0.42 * Drains and sewerage: RR = 0.14 *”

In Moraes 2004, Trichuris had a significantly higher intensity in the control than in the intervention groups.

“Trichuris had a significantly higher intensity in the control than in the intervention groups, and contrary to expectation Hookworm intensity was highest in the drains and sewerage intervention group (Moraes 2004).”

In Moraes 2004, the drains group was associated with lower frequent diarrhoea in children under 5 compared to control (RR 0.42).

“Children under 5 years old having frequent diarrhoea (more than twice the expected number of episodes) in intervention groups compared to control Drains group: RR = 0.42 * Drains and sewerage: RR = 0.14 *”

In Moraes 2004, monthly household per capita income given as the mean proportion of the Brazilian Minimum Wage in August 1983 had MD 0.3 for drainage and sewers compared to control.

“Monthly household per capita income given as the mean proportion of the (Brazilian Minimum Wage in August 1983) in intervention compared to control $$ MD = 0.3* Drainage and sewers MD = 0.2* Drainage only”

In Moraes 2004, schooling of household head in years comparing intervention households to controls had MD 1.60 years for drains.

“Schooling of household head (years), comparing intervention households to controls^. Drains: MD = 1.60 years* Drains and sewerage: MD = 1.40 years*”

In Moraes 2004, schooling of household head in years comparing intervention households to controls had MD 1.40 years for drains and sewerage.

“Schooling of household head (years), comparing intervention households to controls^. Drains: MD = 1.60 years* Drains and sewerage: MD = 1.40 years*”

Moraes 2004 results did not account for clustering.

“Results did not account for clustering.”

In Moraes 2004, monthly household per capita income given as the mean proportion of the Brazilian Minimum Wage in August 1983 had MD 0.2 for drainage only compared to control.

“Monthly household per capita income given as the mean proportion of the (Brazilian Minimum Wage in August 1983) in intervention compared to control $$ MD = 0.3* Drainage and sewers MD = 0.2* Drainage only”

One CPI study found mean schooling of household head was greater in both the sewerage and drainage group (MD 1.4) and drainage only group (MD 1.6) compared to the control group (Moraes 2004).

“Mean schooling of household head was greater in both the sewerage and drainage group (MD of 1.4) and drainage only group (MD of 1.6) compared to the control group (Moraes 2004).”

An increase in the intensity of hookworm infections was observed in the fullest community sanitation neighbourhoods (drainage and sewers) than in drainage only or control groups (Moraes 2004).

“An increase in the intensity of hookworm infections was observed in the fullest community sanitation neighbourhoods (drainage and sewers) than in drainage only or control groups (Moraes 2004).”

There were no increases in intensity of Ascaris or Trichuris, and the prevalence of all three infections were lower in slums receiving the interventions (Moraes 2004).

“however the results should be viewed cautiously as there were no increases in intensity of Ascaris or Trichuris, and the prevalence of all three infections were lower in slums receiving the interventions.”

Two supporting studies with mixed or high risk of bias found a lower incidence of parasitic infections in single cement floor intervention groups (Cattaneo 2009) or multicomponent slum upgrading (Moraes 2004).

“When compared to controls, a lower incidence of parasitic infections was observed in single cement floor intervention groups (Cattaneo 2009) or multicomponent slum upgrading (Moraes 2004).”

Two supporting studies indicated adverse results for two health outcomes; intensity of hookworm eggs per gram stool (Moraes 2004) and increased proportion of 'ill-health' (Abelson 1996).

“However the harvest plots (Figure 5) highlight two supporting studies indicated adverse results for two health outcomes; intensity of hookworm eggs per gram stool (Moraes 2004) and increased proportion of 'ill‐health' (Abelson 1996).”

Of the remaining studies, water and sanitation provision was poor in all studies, except for Moraes 2004 which reported that many houses had some form of water supply.

“Of the remaining studies, water and sanitation provision was poor in all studies, except for Moraes 2004 which reported that many houses had some form of water supply.”

Energy infrastructure was generally not described, though two studies reported good access to electricity.

“Energy infrastructure was generally not described, though two studies reported good access to electricity (Cattaneo 2009; Moraes 2004).”

Propensity score matching was utilised by Cattaneo 2009 and effect estimates were controlled for potential confounders in three studies to try to minimise such bias.

“Propensity score matching was utilised by Cattaneo 2009 and effect estimates were controlled for potential confounders in three studies (Aiga 2002; Cattaneo 2009; Moraes 2004) to try to minimise such bias.”

Two further supporting studies were conducted in Latin America, including Mexico and Brazil.

“Two further supporting studies were conducted in Latin America, including Mexico (Cattaneo 2009) and Brazil (Moraes 2004).”

Supporting studies were judged to have either high to moderate external validity.

“Supporting studies were judged to have either high (Moraes 2004; Joshi 2002) to moderate (Abelson 1996; Aiga 2002; Cattaneo 2009; De Leon 1986; Milone 1993; Moitra 1987; Parikh in press) external validity.”