Human psittacosis in Japan: notification trends and differences in infection source and age distribution by gender, 2007 to 2016.

Purpose: Psittacosis is a bacterial zoonosis caused by Chlamydia (Chlamydophila) psittaci that infects birds. Although potentially fatal, infections can be reduced by controlling the source of infection. We therefore described the epidemiology of psittacosis, focusing on the infection source.

Methods: We descriptively analyzed psittacosis cases reported through national surveillance in Japan from 2007 to 2016. We also analyzed Chlamydia psittaci prevalence among captive psittaciformes during the same period.

Results: One hundred eleven cases were reported, and the annual number and notification rate of psittacosis declined. While 58% were male and the median age was 61 years, the median age differed by gender (males: 63 years, females: 53 years), with more female cases in those aged <50 years. In addition, the most common infection source differed by gender (men: columbiformes; women: psittaciformes). The decline in notifications was associated with a decline in psittaciformes-associated cases, with a concomitant decline in female cases. The prevalence of C. psittaci among captive psittaciformes also decreased over the period.

Conclusions: We found important differences in the epidemiology of psittacosis by gender, and the recent decrease in notifications correlated with decreasing C. psittaci prevalence in birds. Risk communications for psittacosis should consider the current epidemiology regarding gender, age, and infection source.