Trends in Secretory IgA Concentration, Breastfeeding, and Acute Respiratory Infection Among Infants in Laikipia, Kenya

Abstract

Acute respiratory infection (ARI) is a leading cause of morbidity and mortality among children under the age of five. Respiratory infections are of extreme importance in developing countries, where most childhood incidence occurs. Public health efforts to reduce the burden of ARI include promoting exclusive breastfeeding until six months of age. This means encouraging mothers to feed their infants with only breast milk and no other supplemental foods or liquids until their infants are six months old. This recommendation is based on observational studies that suggest that exclusive breastfeeding may offer a protective effect against ARI incidence, as breastfeeding is a mode by which mothers can pass antibodies to their immunologically naïve infants. We evaluated secretory immunoglobulin A (SIgA) because it is one of the most highly concentrated immune factors in breast milk and works in mucosal immune defense against respiratory infection. We explored the interplay between breastfeeding, ARI incidence, and SIgA concentration among infants in Laikipia County, Kenya. This study has two parts. The first is an analysis of records from Nanyuki District Hospital and Ilmotiok Health and Education Center, in which we compared risk between age groups and genders for hospital admission with or presenting with symptoms of ARI. We found that children under five years of age had the highest risk for reporting an ARI, including pneumonia and bronchiolitis; among this age group, boys had lower risk of being admitted with a lower respiratory tract infection. The next section is a case-control study in which we surveyed pastoralist mothers from Laikipia about ARI incidence in their infants and their breastfeeding practices. We also used anthropometric measurements to determine nutritional status and measured SIgA concentration in breast milk samples from mothers and saliva samples from infants. We found that SIgA concentration in breast milk varied with residence and was lower among mothers with older infants. SIgA in infants was negatively associated with SIgA in mothers. Exclusive breastfeeding did not demonstrate protection against ARI among the infants, and neither did increasing breastfeeding frequency. Girls had higher SIgA levels than boys only among the study participants who were using complementary feeding. We found that acute malnutrition in infants had a positive association, and chronic malnutrition had a negative association with the incidence of ARI. There was no association between SIgA concentration and ARI incidence.