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Volume: 26S6 - October 2000

1998/1999 Canadian Sexually Transmitted Diseases (STD) Surveillance Report

Gonorrhea (Neisseria gonorrhoeae)

After a steady decline in cases in Canada over the past two decades, the reported gonorrhea rates increased in 1998 to 16.4 per 100,000 from 14.9 per 100,000 in 1997 (Figure 7). Unlike chlamydia, gonococcal infection rates among males have traditionally been higher than among females. From 1997 to 1998, reported gonorrhea cases increased by 8% (346 cases): 10% among males and 5% among females.

Age group distribution

The overall age distribution of gonorrhea in 1998 has remained unchanged from other years, with the highest concentrations in 15-19-year-old females (80.2 per 100,000) and 20-24-year-old males (64.0 per 100,000) (Figures 8 and 9).

In 1998, females 15-19 years old accounted for 41% of all female cases; just over half (54%) of all male cases were in the 15-29 age range (15-19, 11%; 20-24, 23%; 25-29, 20%). Male cases of gonorrhea tend to be more evenly spread among the 5-year age groups between 20 and 39, while female cases tend to cluster in the 15-24 age range.

FIGURE 7 Reported Gonorrhea Rates¹ in Canada, 1980 to 1999²

¹ Rate per 100,000 population. Population estimates provided by Statistics Canada.
² 1999 numbers are preliminary.

Source: Health Canada, Bureau of HIV/AIDS, STD and TB, 2000

Among males, the age group that showed the greatest increase from 1997 to 1998 was the 40-59 group, with 20% more cases, followed by the 30-39 year group, with a 16% increase.

FIGURE 8 Reported Male Gonorrhea Rates¹ in Canada by Age Group, 1997 to 1999²

¹ Rate per 100,000 population. Population estimates provided by Statistics Canada.
² 1999 numbers are preliminary.

Source: Health Canada, Bureau of HIV/AIDS, STD and TB, 2000

FIGURE 9 Reported Female Gonorrhea Rates¹ in Canada by Age Group, 1997 to 19992

¹ Rate per 100,000 population. Population estimates provided by Statistics Canada.
² 1999 numbers are preliminary.

Source: Health Canada, Bureau of HIV/AIDS, STD and TB, 2000

Geographic distribution

Increases in the number of cases of gonorrhea from 1997 to 1998 occurred in the following provinces/territories: Alberta, Ontario, British Columbia, Yukon Territory, and Northwest Territory (former territorial boundary). The greatest increase in the number of cases was in Ontario, with 353 more cases in 1998 than in 1997 (from 16.8/100,000 in 1997 to 19.9/100,000 in 1998) (Figures 10 and 11).

Regionally, the largest decrease in reported gonorrhea cases was in Manitoba from 1997 to 1998 (518 cases in 1997, 424 cases in 1998, 45.2 and 37.2 per 100,000 respectively). The male:female ratio of reported gonorrhea cases differs geographically throughout Canada as well. Quebec had the largest male to female ratio (3.3:1) followed by British Columbia (2.5:1). The male to female ratio for Ontario in 1998 was 1.5:1.

FIGURE 10 Reported Male Gonorrhea Rates¹ in Canada by Province/Territory, 1997 to 1999²

¹ Rate per 100,000 population. Population estimates provided by Statistics Canada.
² 1999 numbers are preliminary. ^* Nunavut STD data in 1999 are from April 1, 1999.

Source: Health Canada, Bureau of HIV/AIDS, STD and TB, 2000

Discussion

Annual declines in the 20% range during the early 1990s have tapered to 12% in 1996 and 10% in 1997, and have changed to an increase of 8% in 1998. The end of the declining trend and the older ages of incident cases classify gonorrhea as in the decline phase of STD epidemics, according to Wasserheit and Aral's dynamic topology⁽⁴⁾. As gonococcal cases are becoming less common, any case is often an indicator that the person is within a core group network, or has engaged in a high-risk behaviour (sex or drugs), thus providing a "bridge" with a core group member. Blanchard et al found that in Winnipeg, core area members "more often had co-infection with chlamydia and gonorrhea and more often reported repeated infection within 12 months, supporting the notion that core areas contain a higher proportion of core group members"⁽⁵⁾. Wasserheit et al found that prevention efforts such as mass media campaigns begin to lose their effect when a disease shifts to the decline phase. In this phase, intervention strategies need to move from large-scale campaign dominance to targeted, community-level strategies aimed at the core group subpopulations. Recommended strategies include targeted health promotion, screening, and treatment services delivered in outreach formats (e.g. mobile vans or urine screening in storefronts and parking lots), peer risk-reduction counselling, health department-assisted partner notification, and sustainable community-level behavioural interventions to change sexual and health care seeking behaviours.

The phase of the disease often affects surveillance strategies as well. In the decline phase, surveillance needs to shift from general case counting to investigation of specific aspects. It becomes increasingly more valuable to survey specific variables such as behavioural risk factors and resistance to penicillins. Another indicator that gains importance in this phase is the site of infection: male rectal gonorrhea is an indicator that the infection was acquired through male-to-male sex. The national goal set for gonorrhea elimination by 2010 is still attainable with the application of new, targeted, community-level phase-specific strategies together with more specific surveillance activities. Whatever the scale, usefulness rather than novelty is the main test of public health policy; thus any successful intervention program needs to be sustained.

FIGURE 11 Reported Female Gonorrhea Rates¹ in Canada by Province/Territory, 1997 to 1999²

¹ Rate per 100,000 population. Population estimates provided by Statistics Canada.
² 1999 numbers are preliminary.

^* Nunavut STD data in 1999 are from April 1, 1999.

Source: Health Canada, Bureau of HIV/AIDS, STD and TB, 2000

Resistant Neisseria gonorrhoeae The National Laboratory for Sexually Transmitted Diseases receives all resistant strains of gonorrhea from the provinces. Table 2
shows the distribution of antibiotic resistance of the strains received and tested in 1998. Some strains have chromosomally mediated multiple resistance to the antibiotics tested, e.g. chromosomal resistance to penicillin/tetracycline/erythromycin represents 3.2% (128) of the 4,001 strains tested. Rising ciprofloxacin resistance is associated with importation from Asia. Emergence of cephalosporin resistance is likely just around the corner.

Table 2 Antimicrobial susceptibility of N. gonorrhoeae strains tested in Canada in 1998

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