Carriage of N-lactamica in a population at high risk of meningococcal disease

Carriage of Neisseria lactamica among household contacts of meningococcal d isease (MCD) cases was investigated during an epidemic in Auckland, New Zea land. The overall carriage rate for N. lactamica was 10.5 % (95 % CI 7.4-13 .5 %) with a peak carriage rate in 2-year-olds of 61.5 % (95 % CI 26.6-88.1 %). Factors associated with a significant (P < 0.05) increase in the likeli hood of carriage included runny nose, the number of people per bedroom and youth. Genetic analysis of isolates revealed a striking correlation of stra ins within the same household but a high level of diversity between househo lds, suggesting that household contact is an important factor in acquisitio n. For household contacts aged less than 5 years, there was a higher rate o f carriage amongst those in contact with MCD cases under 8 years old than f or contacts of cases aged 8 years and over. It is likely that development o f MCD is a reflection of the nature and intensity of the exposure to a viru lent strain of N. meningitidis, coupled with an absence of host resistance among those individuals not carrying N. lactamica.