Syphilis(Treponema pallidum)

Syphilis, an infection caused by the bacterium Treponema pallidum, has been nationally notifiable since 1924. If left untreated, it progresses through different stages, with primary, secondary and early latent (less than one year after the point of infection) stages being infectious. Only these infectious stages are included in national reports. Untreated syphilis will enter into a non-infectious late latent stage of the infection that may lead to serious complications associated with tertiary syphilis. This includes damage to the central nervous system, cardiovascular system, eyes, skin and other internal organs. Untreated syphilis can be fatal^1c. Individuals infected with syphilis are at an increased risk of contracting and transmitting HIV^2c.

Congenital syphilis is caused by the vertical transmission of Treponema pallidum from an infected mother to her fetus. Congenital syphilis may not be diagnosed until later in life, as the disease can often be asymptomatic for life or may present with symptoms that are not identified in the first few weeks. Only early congenital syphilis cases (diagnosed in those under 2 years of age) are reported nationally.

Reported rates of infectious syphilis in Canada remained stable between 1999 and 2001, then spiked upwards in the following three years, particularly among males. Since 2004, the rates are climbing at a slower rate in both sexes.

• From 1993 to 2000, reported rates of infectious syphilis were relatively stable and similar between genders (Figure 10). Reported rates started to climb sharply in 2001, more so in men than in women.
• In 2008, 1,394 cases of infectious syphilis were reported to PHAC, corresponding to a rate of 4.2 per 100,000. The overall rate increased by 568.2% since 1999 (0.6 per 100,000) (Figure 10).

Figure 10: Reported Rates of Infectious Syphilis by Sex and Overall, 1993 to 2008, Canada

• Historically, a greater number of cases have been reported in men than in women. In 2008, men accounted for 86.1% of reported cases.
• Between 1999 and 2008, reported rates of infectious syphilis increased in both sexes, but primarily in males. During this period, the rate in men increased by 870.7% (from 0.7 to 7.3 per 100,000) and in women increased by 123.4% (from 0.5 to 1.1 per 100,000) (Figure 10).
• The male-to-female rate ratio increased from 1.5:1.0 in 1999 to 6.4:1.0 in 2008, reflecting that more males than females were reported with infectious syphilis, and this disparity increased over time (Table 4).
• The male-to-female ratio is much higher in some jurisdictions: Québec, Ontario and British Columbia outbreaks are predominantly among men.

Table 4: Male-to-Female Ratio of Reported Rates of Infectious Syphilis by Province/Territory, 2008, Canada

Jurisdiction	Male-to-Female Rate Ratio
Canada	6.4 : 1.0
BC	13.9 : 1.0
AB	1.4 : 1.0
SK	2.0 : 1.0
MB	3.4 : 1.0
ON	13.6 : 1.0
QC	45.7 : 1.0
NB	1.8 : 1.0
NS	N/A
PE	N/A
NL	N/A
YT	N/A
NT	1.3 : 1.0
NU	N/A

 

The age-specific distribution of infectious syphilis cases differed from chlamydia and gonorrhea in that reported rates were highest in the older population, particularly in males aged 30 to 39.

• In 2008, people aged 30 and older accounted for 73.6% of reported cases.
• In men, the highest reported rate of infectious syphilis was shared between 25 to 29 year olds and 30 to 39 year olds (13.3 per 100,000) (Figure 11). Together, these age groups accounted for almost 40% of reported cases in men in 2008.
• In women, the highest reported rate was in 20 to 24 year olds (3.6 per 100,000) (Figure 11).

Figure 11: Reported Rates of Infectious Syphilis by Sex and Age Group, 2008, Canada

While highest rates of infectious syphilis are reported in males over 30, more recently, the greatest increases were in men 20 to 29 years old.

• In males, the greatest absolute increase in reported rates of infectious syphilis was in 25 to 29 year olds. The rate increased from 1.0 per 100,000 in 1999 to 13.3 per 100,000 in 2008 (Figure 12).
• Although reported rates in young men remained low compared to men aged 30 to 59, substantial increases were seen since 1999. The reported rate in 20 to 24 year old males increased by 1192.4% from 1.2 per 100,000 in 1999 to 8.9 per 100,000 in 2008 (Figure 12).

Figure 12: Reported Rates of Infectious Syphilis in Males by Age Group, 1999 to 2008, Canada

 

• In women, the greatest absolute increase in reported rates of infectious syphilis was in 20 to 24 year olds (Figure 13). The rate increased from 1.2 per 100,000 in 1999 to 3.6 per 100,000 in 2008.

Figure 13: Reported Rates of Infectious Syphilis in Females by Age Group, 1999 to 2008, Canada

The majority of reported cases were concentrated in Canada’s most populous provinces. However, the highest reported rate was in NWT due to a recent outbreak.

• In 2008, the highest reported rate of infectious syphilis was in the Northwest Territories, followed by Alberta (Table 5).
• Between 1999 and 2008, the largest increase in reported rates of infectious syphilis was in Alberta, with an increase of 6700% (Table 5).
• During the same period, outbreaks of infectious syphilis were reported across Canada, including Vancouver, Edmonton, Calgary, Winnipeg, Toronto, Ottawa, Montreal, and Yukon^7-14. Most recently, an outbreak of infectious syphilis amongst injection drug users and heterosexuals was reported in the Northwest Territories¹⁵.

Table 5: Reported Cases and Rates¹ of Infectious Syphilis by Province/Territory, 1999 and 2008, Canada

Jurisdiction	Number of Cases		Rate per 100,0003		Rate Change (%)
	1999	2008	1999	2008	1999–2008
Canada	191	1,394	0.6	4.2	600.0
BC	129	235	3.2	5.4	68.8
AB	2	244	0.1	6.8	6,700.0
SK	1	12	0.1	1.2	1,100.0
MB	0	13	0.0	1.1	*
ON	54	444	0.5	3.4	580.0
QC	4	369	0.1	4.8	4,700.0
NB	0	11	0.0	1.5	*
NS	1	4	0.1	0.4	300.0
PE	0	1	0.0	0.7	*
NL	0	8	0.0	1.6	*
YT	0	0	0.0	0.0	*
NT	0	53	0.0	122.4	*
NU2	N/A	0	N/A	0.0	N/A

Congenital Syphilis

• Congenital syphilis rates in Canada are very low. However, data from recent years suggest an increase in reported cases and corresponding rates and can be linked to jurisdictions that have reported outbreaks of syphilis¹⁶ (Table 6).

Table 6: Reported Cases and Rates of Confirmed Early Congenital Syphilis¹, 1999 to 2008, Canada

Year	Total reported cases	Rate (per 100,000 live births)2	Number of reported cases1
			BC	AB	SK	MB	ON	QC	NB	NS	PE	NL	YT	NT	NU
1999	1	0.297	0	0	0	0	1	0	0	0	0	0	0	0	0
2000	2	0.610	1	0	0	0	0	1	0	0	0	0	0	0	0
2001	1	0.300	1	0	0	0	0	0	0	0	0	0	0	0	0
2002	3	0.912	0	1	1	0	1	0	0	0	0	0	0	0	0
2003	0	0.000	0	0	0	0	0	0	0	0	0	0	0	0	0
2004	0	0.000	0	0	0	0	0	0	0	0	0	0	0	0	0
2005	8	2.338	3	5	0	0	0	0	0	0	0	0	0	0	0
2006	7	1.974	2	4	0	0	1	0	0	0	0	0	0	0	0
2007	8	2.175	2	5	0	0	1	0	0	0	0	0	0	0	0
2008	8	2.136	4	2	0	0	1	0	0	0	0	0	0	1	0

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