Pharyngeal carriage and acquisition of anticapsular antibody to Haemophilus influenzae type b in a high-risk population in southwestern Alaska.

Abstract

Haemophilus influenzae type b disease in Alaskan Eskimos is characterized by greatly increased disease incidence at younger ages. This suggests that Eskimo infants have increased exposure to the disease. Exposure was studied in 1982-1983 in children less than age three years who lived in four Eskimo villages, as well as in a random sample of their family members (354 people from 132 households). During a 12-month period, up to four pharyngeal cultures and two serum specimens were obtained from each participant. Colonization with H. influenzae type b was relatively uncommon (overall 2.5% of cultures, 6.8% of individuals) and was not associated with age, sex, season, or prior incidence of disease in the village. Biotyping and outer-membrane-protein typing of H. influenzae type b isolates revealed homogeneity within villages, with differences between villages. Matched sera revealed a significant decline in H. influenzae type b capsular antibody in the course of the study year. However, pharyngeal carriage of H. influenzae type b was associated with increases in antibody for carriers and members of their households. Antibody levels were positively associated with age. Only one case of H. influenzae type b disease developed during the study. Low carriage of H. influenzae type b was coincident with low incidence of disease and declining levels of capsular antibody in these villages. Mechanisms for increased exposure which would not be reflected in high carriage rates may exist for these young children.