Chlamydia and LGV guide: Etiology and epidemiology

Etiology and epidemiology of Chlamydia trachomatis infections (including lymphogranuloma venereum (LGV)).

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Etiology

Chlamydia is a bacterial infection caused by C. trachomatis genotypes D to K.

LGV is a bacterial infection caused by C. trachomatis genotypes L1, L2 or L3.

Epidemiology

Chlamydia

Chlamydia is the most common reportable sexually transmitted infection (STI) in Canada. Rates have been increasing steadily since 1997Footnote 1. Adolescents and young adults are disproportionately represented in national case reports for chlamydia, with the highest rates among 20- to 24-year olds for both males and females.Footnote 2 Between 2012 and 2019, national rates of chlamydia increased by 10% for females and 45% for males. In 2020 and 2021, reported rates of chlamydia were below pre-pandemic levels with the COVID-19 pandemic reducing the demand for and access to services related to sexually transmitted and blood-borne infections (STBBI), including testing Footnote 3.

Chlamydia may be under-detected because the majority of people with an infection are asymptomaticFootnote 4Footnote 5 and empiric treatment may be given without laboratory testing.

Males may be under screened due to infrequent health visitsFootnote 5 Footnote 6 Footnote 7 and people at higher risk for chlamydia infections may also be under screened.

LGV

LGV is relatively rare. Prior to 2004, most Canadian cases were identified in travellers returning from endemic regions of Africa, Southeast Asia, the Caribbean and Latin AmericaFootnote 8. Since 2004, there have been LGV outbreaks in Canada, mainly among gay, bisexual and other men who have sex with men (gbMSM).

National enhanced surveillance of LGV was carried out from 2004-2012. During this time, 104 confirmed and 66 probable cases were reported to the Public Health Agency of Canada (PHAC) by provinces and territories. Confirmed cases were reported from Quebec, Ontario, British Columbia and Alberta; probable cases were reported from these provinces as well as from Nova Scotia.

More information

Local epidemiological information: Consult with your public health unit.

National epidemiological information:

Global epidemiological information:

References

Footnote 1

Choudhri Y, Miller J, Sandhu J, Leon A, Aho J. Chlamydia in Canada, 2010-2015. Can Commun Dis Rep 2018 Feb 1;44(2):49-54.

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Footnote 2

Public Health Agency of Canada. Chlamydia, gonorrhea and infectious syphilis in Canada: 2021 surveillance data update. 2023. Pub.: 230461. Available from: https://www.canada.ca/en/public-health/services/publications/diseases-conditions/chlamydia-gonorrhea-infectious-syphilis-2021-surveillance-data.html

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Footnote 3

Public Health Agency of Canada. Survey on the impact of COVID-19 on the delivery of STBBI prevention, testing and treatment, including harm reduction services, in Canada. Ottawa, ON: Public Health Agency of Canada; 2022. Pub.: 210294. Available from: https://www.canada.ca/en/public-health/services/publications/diseases-conditions/survey-impact-covid-19-delivery-stbbi-prevention-testing-treatment.html

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Footnote 4

Farley TA, Cohen DA, Elkins W. Asymptomatic sexually transmitted diseases: the case for screening. Prev Med 2003 Apr;36(4):502-509.

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Footnote 5

Marrazzo JM, Whittington WL, Celum CL, Handsfield HH, Clark A, Cles L, et al. Urine-based screening for Chlamydia trachomatis in men attending sexually transmitted disease clinics. Sex Transm Dis 2001 Apr;28(4):219-225.

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Footnote 6

Chen MY, Donovan B. Screening for genital Chlamydia trachomatis infection: are men the forgotten reservoir? Med J Aust 2003 Aug 4;179(3):124-125.

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Footnote 7

Andersen B, Olesen F, Moller JK, Ostergaard L. Population-based strategies for outreach screening of urogenital Chlamydia trachomatis infections: a randomized, controlled trial. J Infect Dis 2002 Jan 15;185(2):252-258.

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Footnote 8

Mabey D PR. Lymphogranuloma venereum. Sex Transm Infect 2002;78:90-92.

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