Prevalence and mean intensity of S. mansoni infection was lower in the snack schools , @ % ( @ % CI @ % -@ % ) and @ eggs per gram of stool ( epg ) ( @ % CI @-@ @ ) , compared to that in the non-snack schools , @ % ( @ % CI @ % -@ % ) ( p = @ ) and @ epg ( @ % CI @-@ @ ) ( p = @ ) , respectively .