The Topic of This Month Vol.25 No.8(No.294)

Genital chlamydial infection in Japan, 1999-2003

(IASR 2004; 25 : 198-199)

Chlamydia trachomatis has recently been known as the etiological agent of the most prevalent sexually transmitted disease (STD) in the world, and its prevalence together with the increase in HIV infection has raised a social problem in Japan.

Among females, it causes cervicitis, adnexitis, and uterine tube infection that results in adhesion or tubal patency disturbance, a cause of tubal pregnancy and infertility. In advanced stage, it causes perihepatitis. Inclusion conjunctivitis and pneumonia occur at high frequency in neonates infected during delivery from the mother suffering from cervicitis. In males, it causes urethritis and epididymitis (see Pharyngeal infection may occur frequently from oral sex; adult cases of pharyngeal infection have been reported (see p. 200 of this issue).

Based on the new classification of genus Chlamydia proposed in 1999, C. trachomatis has been classified into biovar Trachoma and biovar Lymphogranuloma venereum (LGV) (see p. 200 of this issue). LGV is found only rarely as an imported infectious disease; genital chlamydia in Japan is mostly due to biovar Trachoma.

National Epidemiological Surveillance of Infectious Diseases (NESID): Reports of genital chlamydial infection (GCI) from about 600 STD sentinel clinics were started in 1987 (see IASR, Vol. 17, No. 10, Vol. 19, No. 9). After enactment of the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections (the Infectious Diseases Control Law) in April 1999, it was included in the Category IV infectious diseases to be reported by STD sentinels, which counted at about 900. After the amendment of the Infectious Diseases Control Law in November 2003, it was placed under the Category V infectious diseases. Positive cases determined by isolation, antigen detection or DNA detection should be reported; positive cases by antibody test alone are excluded (see In this article, the trend of GCI after April 1999 is described.

The trend after 1999: Reports of GCI cases were on a gradual increase, but since 2002, they have remained on the same level (see Table 1 and Fig. 1). We must await the future course to find if GCI cases will increase again.

Monthly cases per sentinel tend to increase after May and decrease after October (Fig. 2). It is speculated on the increase in chances of infection in summer.

The proportion of age groups among GCI cases does not change largely from year to year (Fig. 3). The peaks of cases were seen at 20-24 years of age for both males and females, followed by 25-29 years of age. In females, as was the case in HIV infection (see IASR, Vol. 25, No. 7), it was characteristic that the rate of such younger generation as 15-19 years of age was markedly high (20%), and the rate of 20-24 years of age was higher (>30%) than that of males. On the other hand, the rate of 40 years of age and older in males was higher than that in females.

Points to be discussed: At prefectural and municipal public health institutes where chlamydia antibody tests are undertaken on individuals visiting health centers for HIV testing and counseling, high antibody-positive rates are reported (see p. 202-204 of this issue). Since it cannot be ruled out that the positive results are due to past infection or to the possible cross reaction with Chlamydophila pneumoniae antibody, it seems necessary to consider adopting or using PCR tests together for more accurate understanding of infectious status (see p. 202 of this issue).

Concerning the GCI test method, by recent advance of methods for DNA detection, pathogen detection has become possible to a certain degree in specimens which are easy to collect such as urine. However, it is pointed that the detection rate in urine specimens in screening tests is high in males, while slightly low in females as compared with genital swabs (see p. 202 of this issue).

It is reported, although in relatively rare occasions, that there are plasmid-defective strains giving negative results with conventional PCR test kits for C. trachomatis DNA detection, and that there are double infections with C. trachomatis and C. pneumoniae or Chlamydophila caviae , whose natural host is the guinea pig, among gynecology patients. C. pneumoniae and C. caviae may give negative results with C. trachomatis DNA-detection kits as do plasmid-defective strains. This has been pointed out as a problem involved in the diagnosis. The importance of isolation of chlamydia and characterization of chlamydia isolates has been shown (see p. 204 of this issue).

In the present NESID, there is a limitation in monitoring the trend of chlamydial infection by other transmission routes. A part of neonatal pneumonia cases caused by mother-to-child infection is reported from sentinel hospitals as chlamydial pneumonia, but C. trachomatis pneumonia is not distinguished from C. pneumoniae pneumonia in reporting, therefore, the actual state is not well understood. Spread of C. trachomatis pharyngitis is anticipated, but it is not included in the NESID. The actual state of these diseases may be the matter of future investigation.

Yearly reports of GCI by prefecture are shown in Fig. 4. Reports per sentinel exceed 20 in some prefectures, while less than five in other prefectures, and there is a discrepancy between the distribution of prefectures where more male cases were reported and that of those where more female cases were reported. To find how the actual state of GCI is reflected, an improvement in the NESID system seems necessary so that it can analyze data for each sentinel and even for each clinical unit of the sentinel clinic.

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