Murine typhus on the northern Dalmatian islands, Yugoslavia.

The present epidemiological study had the objective to establish whether and to what extent resident islander populations might be affected by the natural foci of murine typhus. To this end, 294 serum specimens were collected during summer and autumn of 1985 from the northern Dalmatian islanders, all of which were tested for anti-Rickettsia typhi (R. typhi) complement fixing (CF) antibodies. These were detected and confirmed at both stages of the screening, namely during the first stage, conducted on the northern Dalmatian islands, where 63.3% of the representative population had a titre of 1:4 or higher and during the second stage, carried out on the island of Vir, with 68.1% of the residents found R. typhi positive unlike in the former. The majority of positive sera were found in the 21-60-year group, peaking in the 21-30- and 31-40-year groups with fewer positive sera among the subjects over 60 and the fewest among the residents below 20 years of life. Thus, current differences in antibody rates in various age groups were shown to be statistically significant. Murine typhus immunity in resident islander populations could be detected from the age of 10 years on, and was shown to become almost equal to the adult population's positive sera levels in the 16-20-year age group. No differences were revealed with regard to the infective agent exposure between the male and female populations representative of the total population or in any of the age groups.