Associations between Inflammation-Adjusted Vitamin A Status and Schistosoma japonicum Infection Intensity among Children and Adolescents in The Philippines: A Cross-Sectional Study

Vitamin A deficiency impairs immune function against parasitic pathogens, which may be linked to schistosomiasis morbidity in children. Adjusting measures of vitamin A status to account for inflammation is necessary to estimate vitamin A status during periods of infection. A secondary analysis of a treatment-reinfection study of children and adolescents with Schistosoma japonicum infection from the Philippines was performed in the present study. Measurements included S. japonicum infection intensity via Kato-Katz (eggs per gram of stool [EPG]), retinol-binding protein (RBP), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). The Thurnham Correction Factor (TCF) inflammation-adjustment method was applied to RBP using measures of CRP and AGP. A sample of n = 40 participants aged 8 to 18 years was randomly selected on the basis of S. japonicum EPG distribution. After applying the TCF method, 14 participants (35.9%) were vitamin A-deficient (RBP <0.7 µmol/L). Using multivariate regression models adjusting for sex, vitamin A deficiency was associated with higher S. japonicum EPG at baseline (P = 0.02). Baseline vitamin A status was not associated with S. japonicum infection intensity (EPG) at subsequent visits over 18 months. This association between vitamin A deficiency and increased schistosomiasis egg burden agrees with findings from animal studies and enhances understanding of nutritional modulation of infection, specific to schistosomiasis.