Epidemiology of Chlamydia trachomatis Infection in Finland During
1983–2009
ERIKA WIKSTRÖM
Department of Dermatology and Venereology, Oulu University Hospital, FI-90220 Oulu, Finland. E-mail: erika.wikstrom@oulu.?
Erika Wikström defended her PhD thesis on June 7, 2013 at the University of Oulu. Her main supervisors
were Professor Matti Lehtinen, University of Tampere, Professor Jorma Paavonen, Helsinki University Central
Hospital, Associate Professor Heljä-Marja Surcel, National Institute of Health and Welfare, and Professor Kaisa
Tasanen-Määttä, Oulu University Hospital and University of Oulu, Finland. The opponent was Associate Professor Dan Apter, the Family Federation of Finland, Helsinki, Finland. The thesis is available at http://urn.?/
urn:isbn:978-952-62-0153-5.
Chlamydia trachomatis epidemic continues at a slowly, albeit
steadily increasing rate in the Western world despite health
education, easy/user-friendly diagnostic measures, and effective treatment. In Finland, 8,031 and 13,227 C. trachomatis
infections were reported in 1995 and 2012, respectively. Over
half of the chlamydia cases were diagnosed among young
women, who suffer from the chlamydia-related complications such as infertility many years after initial infection. The
rates of all but ?rst of the following major chlamydia-related
complications: cervical intraepithelial neoplasia, ectopic pregnancy, hospitalised pelvic in?ammatory disease, tubal factor
infertility have, however, decreased since the 1990s.
The aim of this study was to clarify the discordance between
the apparently increasing incidence of C. trachomatis and
decreasing C. trachomatis IgG antibody rates (seroprevalence).
The study material consisted of a random subsample of ?rst
trimester serum samples of 7,999 women from the populationbased Finnish Maternity Cohort (FMC) registry from 1983 to
2005, and 147,148 women and men with a total of 177,138 C.
trachomatis genital infections reported to the Finnish National
Infectious Diseases Registry (NIDR) during 1995–2009. Both
registries are maintained by the National Institute for Health
and Welfare (THL).
Serum IgG antibodies were measured by a C. trachomatis
major outer membrane protein-speci?c peptide enzyme
immunoassay and the standard micro-immuno?uorescence
method. We found that while C. trachomatis seroprevalences
decreased > 50% among fertile-aged women the seroconversion rates (seroincidences) were comparable to the NIDR
reported rates.
The numbers of annual repeated C. trachomatis infection in
the NIDR increased until 2009 by 49% in women and 39%
in men. In 2009, about 25% of the females and 20% of the
Forum for Nord Derm Ven 2013, Vol. 18, No. 4
Erika Wikström defended her PhD thesis on Chlamydia trachomatis epidemiology in Oulu, Finland on 7th June, 2013. Left to right: Opponent,
Associate Professor Dan Apter, PhD Erika Wikström, Associate Professor
Heljä-Marja Surcel.
males had had an earlier C.trachomatis infection, 34% of the
repeat diagnoses occurring within 12 months. Most of the ?rst
infections were observed among females and males under 25
years of age, but the numbers of repeated chlamydial infections increased up to the age of 30 years.
The C. trachomatis serotype distribution changed between the
1980s and 1990s, but the leading 1980 serotypes bounced
back by 2005. The numbers of women with multiple serotype
infections peaked in the 1990s, and serotypes G and J were
temporarily replaced by serotypes E and D.
In conclusion, the serological observations ?t the polymerase
chain reaction (PCR) -based data on C. trachomatis epidemiology. The observed increases in the repeated chlamydial infections among young women and men comply with increasing
sexual risk-taking behaviour in Finland. Our observations
help to understand the discrepancy between C. trachomatis
occurrence and sequelae rates as the overall C. trachomatis
infection burden in the population may be decreasing despite
the increasing incidence trend.
DISSERTATIONS
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