Re-emergence of meningococcal carriage on three-year follow-up of a kibbutz population after whole-community chemoprophylaxis

Abstract

A long-term study was conducted to determine the rate of re-emergence of throat carriage of meningococci in a semi-closed kibbutz community after the administration of chemoprophylaxis to all its members. Serotype B:4 was selected as marker organism since it was isolated from a fatal case and was the most frequently occurring strain (80 %) among serogroup B isolates, which themselves comprised 54 % of all meningococci. The carriage rate among Israeli residents (volunteer workers were analyzed separately) before treatment was 6.6 % (49/748) overall, with 4.3 % group B strains. Three weeks after treatment, in most cases with rifampicin (whereby three persistently positive persons were retreated with minocycline), no meningococci were recovered. Six months later, 1.9 % of a population sample aged ≤30 years were positive, while before treatment and one and three years later, 9.4 %, 8.6 % and 4.6 % respectively were positive in this age group. Serotype B:4 comprised 81.3 % of group B strains before prophylaxis, 5.3 % after one year, and 28.6 % after three years, thus possibly re-establishing itself as the single dominant serotype. The marked suppression of carriage after mass chemoprophylaxis appeared to last at least six months, with the meningococcal population being re-established within a year.