Volume 6 - Number 2 1997
Special Issue: STDs and Sexual/Reproductive Health

Published by SIECCAN
The Sex Information & Education Council of Canada

Gonorrhea: Epidemiology and Control Strategies

Michel Alary
Groupe de recherche en épidémiologie de l'Université Laval
Centre de recherche, Hôpital du St-Sacrement
Québec, Québec

Abstract:

Although gonorrhea is still the most common bacterial STD worldwide, there has been a sharp decline in the incidence of this disease in almost all Western countries since the 1970s and 1980s. In Canada, there has been a more than tenfold reduction in gonorrhea incidence between 1981 (226 per 100,000) and 1995 (19 per 100,000). The only feature of gonorrhea epidemiology that is shared by both developing and developed countries is the increasing importance of antibiotic resistant strains of Neisseria gonorrhoeae. In view of this dramatic decline, it is now possible to put forward goals for the elimination of locally transmitted cases of gonorrhea or a reduction to a very low incidence (<5 per 100,000). To attain this goal, it will be necessary to focus gonorrhea control activities to communities and groups with high incidence rates. These control strategies should incorporate specific surveillance, research, and policy/program needs. Control strategies should be adapted to the specific cultural features of communities and groups with high gonorrhea rates and should take advantage of recent non-invasive technologies for screening and treatment programs.

Key words:

• N. Gonorrhoeae, Gonorrhea control, Epidemiology, Canada

Acknowledgements:

The author thanks Dr. Robert C. Brunham for useful comments on the initial versions of the manuscript, the Division of STD Prevention and Control, Bureau of HIV/AIDS and STD, LCDC, for providing the data on gonorrhea in Canada, and Dr. Judith Wasserheit, from the CDC (Atlanta, Georgia, USA) for providing data on international comparisons of gonorrhea trends.

Correspondance concerning this paper should be addressed to Dr. Michel Alary, Centre de recherche, Hôpital du St-Sacrement, 1050 chemin Ste-Foy, Québec, Québec, G1S 4L8. Tel: (418) 682-7387; Fax: (418) 682-7949; email: michel.alary@gre.ulaval.ca

Background

Epidemiology of Gonorrhea Worldwide

Gonorrhea is the most common bacterial sexually transmitted disease (STD) in the world. For instance, in Africa, numerous surveys conducted in recent years have shown that Neisseria gonorrhoeae is the most important cause of male urethritis, accounting for 53-80% of the cases; whereas, the corresponding proportion for Chlamydia trachomatis ranges from 3-16% (Mabey, 1994). The magnitude of the health problems caused by N. gonorrhoeae in many developing countries can be seen at some urban STD clinics in large African cities where several hundred thousand men consult annually for urethritis (Hira & Sunkutu, 1993). In addition, the prevalence of gonococcal infection among women from these countries is high: it ranges from 20-40% among prostitutes and from 3-10% among pregnant women (Laga, Nzila, & Goeman, 1991; Vuylsteke et al., 1993; Germain et al., 1997). The high prevalence of N. gonorrhoeae in developing countries is largely related to poor accessibility to diagnostic tests and appropriate treatments (Laga et al., 1991; Alary, Laga, Vuylsteke, Nzila, & Piot, 1996). Furthermore, inappropriate use of antibiotics has led to the development of resistant strains of the disease. In numerous developing countries, the proportion of gonococcal strains that are resistant to antibiotics is very high. Penicillinase-producing N. gonorrhoeae (PPNG) accounts for 15-80% of isolated strains; whereas, tetracycline resistance varies from 20-65% (Osoba, Johnston, Ogunganjo, & Ochei, 1987; Van Dyck et al., 1992; Ison, Roope, Dangor, Radebe, & Ballard, 1993; Chenia, Pillay, Hoosen, & Pillay, 1997; Van Dyck et al., 1997). Chromosomal resistance is also frequent and emergence of resistance to other antibiotics, including ciprofloxacin, has been documented in the last few years (Grandsen, Warran, Phillips, Hodges, & Barlow, 1990; Bogaerts et al., 1993; Knapp et al., 1994).

The epidemiology of N. gonorrhoeae is different in developed countries. Indeed, since the beginning of the 20th century, peaks of reported cases of gonorrhea in developed countries occurred during World Wars 1 and 2, and following the "sexual liberation" of the late 1960s and early 1970s (Aral & Holmes, 1990). Thereafter, there has been a sharp decline in the incidence of this disease in almost all western countries (Figure 1). This decline occurred first in countries of Northern Europe. For instance, in Sweden, gonorrhea incidence (reported cases) decreased from 487 per 100,000 in 1970 to 31 per 100,000 in 1987, and was below 10 per 100,000 in 1994 (Ramstedt, 1995). In parallel with this decline, there has been a steady reduction in the male:female ratio of reported cases (Aral & Holmes, 1990). This early decline in incidence, as well as the reduction in the male:female ratio, can be attributed, at least in part, to improved screening programs for women and enhanced partner notification of STD cases (Aral & Holmes, 1990; Ramstedt, 1995).

In the United States, the peak incidence of reported cases of gonorrhea occurred later: it was 473 per 100,000 in 1975 (Figure 1). There was a plateau in the rate until 1982, followed by a decrease until 1984, then a slight increase until 1986, followed by a steady decrease continuing to the present. However, this latter decrease was not as significant as what occurred in Sweden. In 1995, the incidence rate of reported cases of gonorrhea in the United States was still around 150 per 100,000. This slower decrease, when compared to Sweden, may be explained by several factors. First, in the United States, the epidemiology of gonococcal infection varies according to ethnicity. The incidence in blacks is much higher and has declined less quickly (from 2,000 per 100,000 in 1981 to 1,450 per 100,000 in 1992) than in non-blacks (from 200 per 100,000 in 1981 to less than 50 per 100,000 in 1992) (CDC 1992). Also, differential access to care according to socio-economic status in the United States has led to difficulties in implementing large-scale screening and partner notification programs. It is currently thought that this decline in gonorrhea incidence has been related largely to behavioural changes resulting from the fear of AIDS (Aral & Holmes, 1990).

The situation in most of the other Western countries falls somewhere between the United States and the countries of Northern Europe (Figure 1). Because of the general decline in gonorrhea incidence in the developed world, it is no longer the most prevalent bacterial STD in these countries (Aral & Holmes, 1990).

Whereas these trends in gonorrhea morbidity in developed countries are generally encouraging, problems with gonococcal antibiotic resistance are discouraging. The first cases of PPNG were isolated in the United States in 1976 (Phillips, 1976). In relation to the decrease in local transmission of the infection and a proportional increase in the number of imported cases because of international travelling, the number of resistant strains has steadily increased. In 1987, 16,608 strains of PPNG had been isolated in the United States, and accounted for 1.8% of gonococcal isolates (Aral & Holmes, 1990). Since then, this proportion has continued to increase, and chromosic mediated resistance to penicillin (CMRNG) and tetracycline resistant (TRNG) strains have also become widespread. Resistance to other antibiotics, including quinolones, is also currently emerging (CDC, 1994).

Figure 1

Gonorrhea trends: International comparisons. Reproduced with permission from: Wasserheit, J. (1996, November). STD prevention in the United States: National objectives and strategies. Proceedings of the expert working group meeting to establish national goals for sexually transmitted diseases and sexual behaviours. LCDC, Toronto.

Epidemiology and Geography of Gonorrhea in Canada

Trends in the epidemiology of gonorrhea in Canada are similar to those in other developed countries. The number of reported cases of gonorrhea in Canada has decreased dramatically over the last 15 years (Table 1). The rate decreased from 223 per 100,000 in 1980 to 19 per 100,000 in 1995. This tenfold decrease within 15 years occurred in both men and women (Table 1). The male:female ratio has also decreased from 1:59 in 1980 to a low of 1:09 in 1988. It increased to 1:27 in 1990, and has remained relatively stable since (1:36 in 1995).

Among women, the highest incidence rate prior to 1985 was found in those aged 20-24 years; whereas, from 1985 to 1995, the rates were consistently higher among women aged 15-19 years. It should be noted, however, that by 1994, rates for women aged 15-19 and 20-24 had both declined to 89 per 100,000 and 73 per 100,000 respectively (Table 2). Among men, the highest rates for 1980-1995 have been in those aged 20-24 years, followed by the 25-29 years old age group. Among men aged 20-24 years, the rate decreased from approximately 1,000 per 100,000 in 1980-81 to 70 per 100,000 in 1995 (Table 2).

At the beginning of the 1980s, Northwest Territories (NWT) and Yukon had the highest gonorrhea rates in Canada (Table 3), and rates in British Columbia and the three prairie provinces (Manitoba, Saskatchewan and Alberta) were higher than the national rate. In 1995, the incidence rate was still nine times higher in NWT (164 per 100,000) compared to the national rate (19 per 100,000), but all the other northern or western provinces/territories, with the exception of Manitoba (55 per 100,000) and Yukon (53 per 100,000), had rates much closer to the national rate. All four Atlantic provinces had gonorrhea rates of 4 per 100,000 or less.

Generally speaking, it appears from provincial data that the highest rates of gonorrhea occur in regions of Canada with high concentrations of first nations people. This observation is supported by specific provincial data. For instance, in the province of Quebec, 106 of the 755 reported cases (14%) in 1993 came from the Nunavik area (Inuit people); whereas, this area accounts for only 0.1% of the Quebec population (Parent & Alary, 1995). The reported rate in this area has, however, dropped from 1,378 per 100,000 in 1993 to 741 in 1994 and 299 in 1995 (Parent & Alary, 1996). In comparison, the global rates for the province of Quebec were 9.4, 10.1 and 8.1 for 1993, 1994 and 1995 respectively. Similar observations of high gonorrhea rates in first nations people communities with large disparities from one community to the other have been made in Manitoba (Brunham, R.C., personal communication). It should be noted, however, that significant fluctuations in gonorrhea rates can be seen in areas mainly inhabited by first nations people. For instance, the highest gonorrhea rate reported in the Cree territories (Northern Quebec) since the beginning of the 1990s was 120 per 100,000 in 1994. This rate was 0 per 100,000 in 1993 and 96 per 100,000 in 1995 (8 cases).

Unfortunately in Canada, there are very little data available concerning gonorrhea rates among potential high risk groups from urban areas, and it is thus very difficult to clearly identify additional populations especially at risk for this infection.

Antibiotic resistance of N. gonorrhoeae has become an increasing problem in Canada. The number of PPNG strains identified at the National Laboratory for STDs (data below provided by the Bureau of Microbiology, Health Canada) was 1 in 1976, and progressively increased to 58 in 1981, 215 in 1985, 624 in 1988 and 1,138 in 1990. Thereafter PPNG strains have declined progressively to a low of 106 in 1994. In parallel, TRNG and PP/TRNG strains emerged, with large increases in the occurrence of both types. Indeed, TRNG was first identified in 1986 (2 cases) and increased to 65 in 1990, 618 in 1992, and to highs of 1,005 and 904 in 1994 and 1995 respectively. The number of PP/TRNG strains was 4 in 1986, 253 in 1990, 226 in 1992, and 223 in 1995. If we hypothesize that all resistant strains identified at the National Laboratory for STDs in 1994 came from reported cases, 21.3% of all cases had plasmid mediated resistance (1,313/6,162: 106 PPNG, 202 PP/TRNG and 1,004 TRNG). In addition, in 1995, 318 strains with chromosomic resistance, including 5 strains with MIC>2.0 mg/L for ciprofloxacin, were identified at the National Laboratory for STDs.

There are, however, some examples in Canada that suggest that it is possible to control the occurrence of antibiotic resistant strains of N. gonorrhoeae. For instance, in Quebec, where contact tracing of STD cases is generally the responsibility of treating physicians, a more intensive public health-based contact tracing program has been implemented for cases of PPNG. It should also be noted that all strains of N. gonorrhoeae isolated in Quebec are systematically submitted to the Laboratoire de santé publique du Québec for studies on resistance. As a result of this program, the proportion of PPNG among all gonococcal strains in Quebec has decreased from 10% in 1991 and 1992 to 5.6% and 4.7% in 1994 and 1995 respectively (Parent & Alary, 1996). This decrease has been particularly striking in some areas. For instance, these proportions have dropped from 11.8% to 4.9% in the Montreal area, and from 33% to 0% in the Nunavik area. These observations should, however, be interpreted with caution, because they could also be linked to a change in the profile of antibiotic resistance over time and may not have been directly caused by the intervention.

Setting Goals for Gonorrhea Control in Canada

There has been a more than tenfold decrease in gonorrhea incidence over the last 15 years in Canada. Given this observation and the fact that several countries in Northern Europe have already reduced gonorrhea incidence to levels lower than those reported in Canada, the goal of eliminating locally transmitted infection of N. gonorrhea by year 2010 appears attainable.

In addition to this main objective, a second goal is: To reduce secondary transmission of imported cases of gonorrhea to less than one per imported case (reproductive rate (R_o)<1). This will ensure that imported cases do not result in further local transmission.

Obviously, the achievement of these goals will require the establishment of intermediate objectives for years 2000 and 2005; however, these objectives will vary regionally depending of the local epidemiology of the disease. For instance, the intermediate goals will be much different for the Northwest Territories, which have the highest incidence rate in Canada, and Prince Edward Island, where no case has been reported since 1993.

Because considerable resources would be required to specifically eliminate all instances of gonorrhea transmission in Canada, a gonorrhea elimination program should be linked to a concurrent chlamydia control strategy. These two STDs share many epidemiologic and clinical features and thus, the elimination of gonorrhea can be seen as one outcome of a longer chlamydia/gonorrhea control program. If gonorrhea in Canada cannot be completely eliminated, an incidence rate of less that 5 per 100,000 would represent significant progress.

Proposed Priorities for Intervention

Table 4 shows proposed priorities for intervention that need to be implemented in order to achieve the goal of elimination (or reduction to very low incidence rates) of gonorrhea. These priorities concern surveillance, research, control strategies and public heath policy/programs. As mentioned above, most of the activities for gonorrhea elimination should be coupled with interventions for control of infections by Chlamydia trachomatis.

First, surveillance activities should be enhanced, especially for cases that necessitate particular interventions, such as for cases involving resistant strains (especially when resistant to currently recommended treatments, such as quinolones or third-generation cephalosporins) or those acquired abroad by travellers. For such cases, surveillance should be directly linked to a contact tracing program, which should be an important component of the control strategies.

Second, there is a need for research to better understand the differences in sexual behaviour leading to important variations in gonorrhea incidence between different first nations communities. Such data can be obtained from carefully designed ethnographic studies and will be essential to design and implement culturally adapted prevention programs.

Third, research on biological markers of core group contact among infected persons would allow to develop more focused contact tracing programs.

Fourth, the increased use of recently developed non-invasive testing technologies, such as polymerase chain reaction (PCR) or ligase chain reaction (LCR) on urine samples, within epidemiological studies could allow us to better identify high risk groups for gonococcal infection. The advantage of this approach is that it can lead to community-based screening and treatment programs that are not necessarily dependent on health care facilities. Such programs could be very useful to reach marginalized people or communities that are not naturally prone to attend standard health care services.

Finally, there are still disparities in Canada with regard to free access to STD treatments. These disparities should be corrected to ensure that all Canadians have access to free STD drugs in whatever province or territory they reside, independent of the type of health care facility (STD clinic, community clinics, private clinics) where they are treated.

Table 1 - Gonorrhea in Canada: Number of Reported Cases and Incidence Rates Per 100 000 by Sex, 1980-1995¹

Table 2 - Gonorrhea in Canada: Number of Cases and Incidence Rate Per 100 000 Per Age and Sex, 1995¹

Table 3 - Gonorrhea in Canada: Number of cases reported and incidence rate per 100,000 by province/territory, 1980-1995¹

Table 4 - Priorities for Intervention for Gonorrhea Control in Canada

References

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