1. Epidemiology of Chlamydia trachomatis
Marjan Javanbakht, MPH, PhD
Los Angeles County Department of Health Services
Sexually Transmitted Disease Program

2. Taxonomy
History
Epidemiology
Implication
Conclusion
Taxonomy
Chlamydia trachomatis is an important pathogen of humans and 1 of 4 species within the genus
C. trachomatis (natural host: humans)
C. pneumoniae (natural host: humans)
C. psittaci (natural host: birds, lower mammals)
C. pecorum (natural host: sheep, cattle, and swine)
4 biovars of C. trachomatis
Murine biovar
Swine biovar
Lymphogranuloma venereum (LGV) biovar
Trachoma biovar
CT is an important pathogen of humans and is 1 of 4 species within the genus though only two of these species have humans as their natural host. C. trachomatis has 4 biovars and you don’t really need to know the details of this, but I just wanted to note that there is an LGV biovar that causes the disease it’s name after and a trachoma biovar which causes the more common genital tract diseases and trachoma.

3. Taxonomy
History
Epidemiology
Implication
Conclusion
History
Human disease caused by C. trachomatis have been recognized since antiquity
Trachoma was described in Egyptian papyri
LGV was described in the 8th century
However, the genital tract infections were not recognized until identification of the organism in the 20th century
First isolated from patients with LGV in 1930s
First isolate from genital tract (other than LGV) was made in 1959
Major breakthrough in 1960s was the development of tissue culture isolation procedures

4. Taxonomy
History
Epidemiology
Implication
Conclusion
History:
1975 – 1985 thought of as cell culture era which made it possible to:
link C. trachomatis to specific clinical syndromes
Majority of NGU in men was attributed to chlamydia
Cervicitis and pelvic inflammatory disease also associated with chlamdyia
In terms of prevention, culture era focused on teaching clinicians to recognize chlamydia associated symptoms
Provide empiric treatment for patients based on chlamydia associated syndromes without actual diagnostic testing
Likewise provide treatment of partners of these empirically treated patients

5. History: 1975 -1985 Limitations of cell culture
Taxonomy
History
Epidemiology
Implication
Conclusion
History:
Limitations of cell culture
Due to expense and technical difficulty, chlamydia testing by cell culture never became widely available
Consequently, screening programs were not feasible
Focus of prevention efforts was largely directed at patients attending STD clinics and family planning clinics

6. Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1985 – 1995
nonculture tests (i.e., antibody tests) became available for chlamydia which allowed for:
Widespread access to clinic based testing
Increased opportunities to screen for adolescent women and other high risk groups
Screening of pregnant women and selective screening in low prevalence populations became feasible for the first time
Although more people screened, most treatment remained syndromic and empiric

7. Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1990’s - present
Mid 1990’s – present, nucleic acid amplification tests (NAATS) became available for routine clinical use
These tests have had a major impact on our understanding of the epidemiology and approaches to prevention because of 3 unique characteristics:
Improved sensitivity (by as much as 20%)
Urine based testing (no pelvic exams, urethral swabs, presence of physician not required  access to new patient populations  increase in number screened)
Ability to test for multiple pathogens (CT/GC)

8. Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1990’s - present
Revisions of Chlamydia epidemiology in the NAATS era (last 10 years):
Because of increased sensitivity, NAATS tests have demonstrated an increased prevalence in all populations
Increased recognition of and emphasis on asymptomatic infections
Prevalence of ~10% in female recruits joining the army (even higher among adolescents)
Prevalence of 2-7% in a random sample of households participating in NHANES III
Door-to-door household survey of women showed a 3.2% overall prevalence (even higher among adolescents)

9. History: 1990’s - present Impact of NAATS on prevention
Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1990’s - present
Impact of NAATS on prevention
Expanded efforts to screen asymptomatic young women
New venues to identify asymptomatic adolescents – a group least likely to be encountered in routine clinical care
Street-based testing (eg., mobile van outreach)
High-school based testing
Testing of military recruits

10. History: 1990’s - present Impact of NAATS on prevention (cont’d)
Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1990’s - present
Impact of NAATS on prevention (cont’d)
Increased appreciation of the high incidence of recurrent/persistent urogenital infections especially among adolescents
15% recurrence in 3-years among women in Washington State Chlamydia registry; 17% recurrence within 2 years among women under 20
17% recurrence in 4-years among young women (10-24 years) in Los Angeles County; with highest incidence rate among those aged years
CDC multicenter cohort study to evaluate recurrences of chlamydial infection found 13% recurrence 4 months after identification and initial therapy

11. History: 1990’s - present Impact of NAATS on prevention (cont’d)
Taxonomy
History
Epidemiology
Implication
Conclusion
History: 1990’s - present
Impact of NAATS on prevention (cont’d)
Until NAATS era recommendation for all chlamydia screening was focused on women, but because of new test rationale emerged to screen young men
Most importantly, noninvasive test makes it more acceptable to men
Substantial prevalence of asymptomatic infection in men
Identification and treatment in men would constitute primary prevention for women
Identification and treatment of asymptomatic male reservoir might help to prevent reinfection in women

12. Epidemiology Most frequently reported bacterial STI in the U.S.
Taxonomy
History
Epidemiology
Implication
Conclusion
Epidemiology
Most frequently reported bacterial STI in the U.S.
Estimated annual incidence of 3 million cases
Estimated annual costs exceeding 2 billion
Under-reporting is substantial since most cases are asymptomatic
“Silent” disease because 75% of women and 50% of men are not aware of their infection
If symptoms do occur, usually 1 – 3 weeks after exposure
Symptoms include discharge (vaginal, penile, rectal), burning sensation when urinating, bleeding between menstrual cycle, pain and swelling in testicles
CT infections are not only the most commonly reported notifiable disease but also the most prevalent of all reported STIs. Read bullets.

13. Taxonomy
History
Epidemiology
Implication
Conclusion
Epidemiology
Like the disease, the damage that chlamydia causes is “silent”
~40% of women with untreated chlamydia develop PID  chronic pelvic pain, infertility, and ectopic pregnancy
Chlamydia infections can facilitate transmission of HIV
Infected women are 2-5 times more likely to become infected with HIV if exposed
Complications among men rare, but can cause pain, fever, and rarely sterility

14. Reported Sexually Transmitted Diseases, United States, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Reported Sexually Transmitted Diseases, United States, 2004
In 2002, over 834 thousand cases of chlamydia were reported to CDC from 50 states and DC and really represents the largest proportion of all STDs reported to the CDC. As you can see, the reported number of chlamydia infections was more than twice the number of reported cases of gonorrhea.
Source: CDC Sexually Transmitted Disease Report, 2004

15. Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Number of states that require reporting of Chlamydia trachomatis infections: United States, 1987–2003
Although regulations for reporting started in , the year 2000 was the first time all 50 states and the district of columbia had regulations requiring the reporting of chlamydia cases to CDC.
All States and DC
CA reporting
LA reporting

16. Chlamydia — Rates: United States, 1984–2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Rates: United States, 1984–2004
Potential reasons for continuing increase:
Use of more sensitive diagnostic tests
Expansion of screening services
More complete national reporting
Improvement in information systems for reporting
320 51
Note: As of January 2000, all 50 states and the District of Columbia had regulations requiring the reporting of chlamydia cases.
Source: CDC Sexually Transmitted Disease Report, 2004

17. Chlamydia — Rates by sex: United States, 1984–2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Rates by sex: United States, 1984–2004
Potential reasons for gender differential:
1. Greater number of women screened
2. Sex partners of women not diagnosed or reported
485
134
In 2002, the overall rate of reported chlamydial infection among women in the US was over 3 times higher than the rate among men. Again, why would that be??? Well, it likely reflects a greater number of women screened for the infection. The lower rates among the men suggest that many of the sex partners of women with chlamydia are not diagnosed or reported. However with the advent of highly sensitive nucleic amplification tests that can be performed on men (as compared to urethral swabs which are far more invasive), symptomatic and asymptomatic men are increasingly being diagnosed with chlamydial infections. For example, from 1998 – 2002 there was a 55% increase in the infection rate in men, while the increase in women was about 20% for the same period.
Nonetheless, it’s absolutely critical that sexual partners of the infected women are treated as well – because just treating the women isn’t really going to work because her sexual partner is likely to reinfect her. And this is where partner delivered therapy will play a key role in breaking the cycle of transmission – where the infected women will not only get treatment for herself but for her partner as well.
Urine screening*
*From 2000 – 2004: 47% increase (males): cases per 100,000; 22% increase (females): 397 to 485 cases per 100,000
Source: CDC Sexually Transmitted Disease Report, 2004

18. Chlamydia — Age- and sex-specific rates: United States, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Age- and sex-specific rates: United States, 2004
For women, the highest age specific rates of reported chlamydia in 2002 were among 15 – 19 year olds and 20 – 24 year olds. Although the age specific rates were substantially lower in men, they are highest in the same age groups. Chlamydia really is a disease of youth – physiologically young women are more susceptible to the bacteria.
Source: CDC Sexually Transmitted Disease Report, 2004

19. Chlamydia Reported Rates by Race and Gender: United States, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia Reported Rates by Race and Gender: United States, 2004
In addition to gender disparities, there are also racial and ethnic disparities. In 2004, the rate of chlamydia among African-American females in the United States was more than seven and a half times higher than the rate among white females (1,722.3 and per 100,000, respectively) (Table 11B). The chlamydia rate among African-American males was 11 times higher than that among white males (645.2 and 57.3 per 100,000 respectively).
Source: CDC Sexually Transmitted Disease Report, 2004

20. Chlamydia — Rates by state: United States and outlying areas, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Rates by state: United States and outlying areas, 2004
In terms of the geographic distribution, in 2002 reported rates of chlamydia in the southern states were higher than the rates in most other regions of the US. And we see that california is also one of the states with more than 300 per 100,000
Note: The total rate of chlamydia for the United States and outlying areas (Guam, Puerto Rico and Virgin Islands) was per 100,000 population.
Source: CDC Sexually Transmitted Disease Report, 2004

21. Chlamydia — Rates by county: United States, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Chlamydia — Rates by county: United States, 2004
Specifically, in terms of a breakdown of rates by county, we can see that LA is one of the county’s with rates greater than 300 per 100,000 in 2002
Source: CDC Sexually Transmitted Disease Report, 2004

22. Reported Sexually Transmitted Diseases, Los Angeles County, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Reported Sexually Transmitted Diseases, Los Angeles County, 2004
So now we will look more specifically at Los Angeles County data. In 2002, over35 thousand cases of chlamydia were reported to the county STD program and similar to national trends it represents the largest proportion of all STDs reported to the county and in fact LA county contributed to 4% of the cases nationally. As you can see, the reported number of chlamydia infections was about 4 times the number of reported cases of gonorrhea.
(4% of national cases)
Source: LAC DHS STD Program 2004

23. Los Angeles County Chlamydia Rates, 1991-2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Los Angeles County Chlamydia Rates,
Potential reasons for continuing increase:
Use of more sensitive diagnostic tests
Expansion of screening services
More complete reporting
Improvement in information systems for reporting
There has been a net increase in the rate of chlamydia infections since reporting began in LA county in Again, the reasons from this increase are similar to those we discussed in terms of the national data. You can see that the urine test were introduced in 1996 which is not only a more sensitive test, but it’s also less invasive.
Source: LAC DHS STD Programs 2004

24. Los Angeles County Chlamydia Rates by Gender, 1991- 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Los Angeles County Chlamydia Rates by Gender,
Potential reasons for gender differential:
1. Greater number of women screened
2. Sex partners of women not diagnosed or reported
In 2002, the overall rate of reported chlamydial infection among women in the county was over 2 times higher than the rate among men. Again, why would that be??? Well, it likely reflects a greater number of women screened for the infection. The lower rates among the men suggest that many of the sex partners of women with chlamydia are not diagnosed or reported. However with the advent of highly sensitive nucleic amplification tests that can be performed on men (as compared to urethral swabs which are far more invasive), symptomatic and asymptomatic men are increasingly being diagnosed with chlamydial infections. For example, from 1998 – 2002 there was a 88% increase in the infection rate in men, while the increase in women was about 32% for the same period.
Nonetheless, it’s absolutely critical that sexual partners of the infected women are treated as well – because just treating the women isn’t really going to work because her sexual partner is likely to reinfect her. And this is where partner delivered therapy will play a key role in breaking the cycle of transmission – where the infected women will not only get treatment for herself but for her partner as well.
*From 2000 – 2004: 80% increase (males): 132 to 238 cases per 100,000; 21% increase (females): 469 to 569 cases per 100,000
Source: LAC DHS STD Programs 2004

25. Los Angeles County Chlamydia Rates by Age and Gender, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Los Angeles County Chlamydia Rates by Age and Gender, 2004
For women, the highest age specific rates of reported chlamydia in 2002 were among 15 – 19 year olds and 20 – 24 year olds. Although the age specific rates were substantially lower in men, they are highest in the same age groups.
Source: LAC DHS STD Programs 2004

26. Los Angeles County Chlamydia Rates by Gender and Ethnicity, 2004
Taxonomy
History
Epidemiology
Implication
Conclusion
Los Angeles County Chlamydia Rates by Gender and Ethnicity, 2004
In addition to gender disparities, there are also racial and ethnic disparities. In 2002, the reported rate of chlamydia among AA females in the LA county was 10 times higher than the rate among white females and the rate among AA males was also 10 times higher as compared to white males.
Source: LAC DHS STD Programs 2004

27. Chlamydia Rates by Service Planning Area, Los Angeles County, 2003
In terms of geographic distribution, we see the age adjusted rate of reported chlamydia by service planning area. The highest reported rates are in the south SPA which is essentially includes cities such as ………….

28. Taxonomy
History
Epidemiology
Implication
Conclusion
Implications
Age is the most important risk marker for chlamydia infection
U.S. Preventive Task Force recommends that clinicians routinely screen all sexually active women aged 25 and younger
Evidence supports repeat screening every 3 to 4 months for those who initially test positive as well as continued 6 month screenings in this group
However, practice falls short of recommendations
Only 2 – 42% of physicians offered screening to their sexually active patients under the age of 25
Only 18% of female CT positive STD clinic clients in Los Angeles County retested within 4 months
Thus, educational efforts are needed to foster chlamydia practices among physicians and resources to enhance case management and follow-up
Points to take away from this presentation…..

29. Partner Treatment/Management
Taxonomy
History
Epidemiology
Implication
Conclusion
Partner Treatment/Management
The importance of the role of patient-delivered partner therapy (PDPT)
In 2001 CA authorized PDPT for sex partners of patients with chlamydial infection – aka expedited partner therapy
Clinic guidelines for PDPT
Once patient is diagnosed, clinician discusses the importance of partner treatment
Clinician assesses the patients ability to notify relevant sex partners (within past 60 days)
Likelihood that partners will return for evaluation and patients comfort level in delivering the medication is evaluated
Patients receive a therapy packet as well as an information sheet to deliver to their partners
Partners are strongly advised to visit a doctor for evaluation and follow-up
Points to take away from this presentation…..

30. Partner Treatment/Management
Taxonomy
History
Epidemiology
Implication
Conclusion
Partner Treatment/Management
Given the burden of disease, traditional strategies of self-referral or health-department assisted follow-up and management maybe ineffective or not feasible
Review of 3 randomized trials on PDPT showed reduction in re-infection rates
In Los Angeles County
PDPT used to improve treatment rates in incarcerated women and their partners
Evaluation of acceptability from patient and partner perspective demonstrated that:
It is widely favored regardless of demographic and behavioral characteristics
Most useful for steady partners (vs. Casual or Once-Only partners)
Points to take away from this presentation…..

31. Conclusion Most common bacterial STD
Taxonomy
History
Epidemiology
Implication
Conclusion
Conclusion
Most common bacterial STD
Chlamydia rates have been increasing since the late 80s
Increase rates are due (in part) to:
increased screening and use of more sensitive screening tests
Gender disparities probably reflect increased screening among women
However, the availability of urine based tests have resulted in more men being tested for chlamydia
Can be easily treated and cured with antibiotics
All sexual partners should be evaluated, tested, and treated to avoid reinfection
Points to take away from this presentation…..

32. References
Gaydos CA, Howell MR, Pare B, et al. Chlamydia Trachomatis Infection in female military recruits. N Engl J Med 1998; 339:
Mertz KJ, McQuillian GM, Levine WC, et al. A pilot study of the prevalence of chlamydial infection in a national household survey. Sex Transm Dis 1998; 25:
Klausner JD, McFarland W, Bolan G, et al. Knock-knock: a population based survey of risk behavior, health care access, and Chlamydia trachomatis infection among low-income women in the San Francisco bay area. J Infect Dis 2001; 183:
Xu F, Schillinger JA, Markowitz LE, et al. Repeat Chlamydia trachomatis infection in women: analysis through a surveillance registry in Washington State, 1993 – Am J Epidemiol 2000; 152:1164 – 1170
Whittington WLH, Kent C, Kissinger P, et al. Determinants of persistent and recurrent Chlamydia trachomatis infection in young women: results of a multicententer cohort study. Sex Transm Dis 2001; 28:117 – 123
Burstein GR, Gaydos CA, Diener-West M, Howell MR, Zenilman JM, Quinn TC. Incident Chlamydia trachomatis infections among inner-city adolescent females. JAMA 1998; 280:
Mangione-Smith R, McGlynn EA, Hiatt L. Screening for chlamydia in adolescents and young women. Arch Pediatr Adolesc Med. 2000; 154:
Points to take away from this presentation…..