Megge Miller, Paul Roche, Keflemariam Yohannes, Jenean Spencer, Mark Bartlett, Julia Brotherton, Jenny Hutchinson, Martyn Kirk, Ann McDonald, Claire Vadjic

Results - Sexually transmissible infections

Sexually transmissible infections (STI) reported to the NNDSS in 2003 were chlamydial infection, donovanosis, gonococcal infections and syphilis including congenital syphilis. These conditions were notifiable in all states and territories.

Other national surveillance systems that monitor STI in Australia include the Australian Gonococcal Surveillance Programme, which is a network of specialist laboratories, and the National Centre in HIV Epidemiology and Clinical Research.

The number of notifications and notification rates of STI reported to the NNDSS between 1999 and 2003 are shown in Table 4. In interpreting these data it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence. Increases in screening rates, more targeted screening, the use of more sensitive diagnostic tests, as well as periodic public awareness campaigns may contribute to changes in the number of notifications over time.

As far as the data allowed, efforts were made to compare notifications rates among population subgroups. Again these data have to be interpreted cautiously, as STI screening occurs predominantly in specific high risk groups. For example, comparisons of STI notification rates between males and females and between Indigenous and non-Indigenous peoples must be interpreted in light of differences in rates of testing between these sub-groups.

Chlamydial infection

Chlamydial infection was the most commonly notified disease in 2003. In this year, a total of 30,161 notifications of chlamydial infection were received by the NNDSS, a rate of 152 cases per 100,000 population. This rate represents an increase of 23 per cent compared with that reported in 2002 (122 cases per 100,000 population). Between 1999 and 2003, Chlamydia notification rates increased from 74 to 152 cases per 100,000 population, an increase of 103 per cent (Table 4).

Chlamydial infection notification rates were higher than the national average in the Northern Territory (807 cases per 100,000 population), Queensland (202 cases per 100,000 population), Western Australia (193 cases per 100,000 population) and the Australian Capital Territory (162 cases per 100,000 population) (Table 3). The largest percentage increase in 2003 compared to 2002 was observed in New South Wales (32% increase). At the regional level, the Kimberly region of Western Australia had the highest chlamydial infection notification rate at 1,846 cases per 100,000 population.

Map 3. Notification rates of chlamydial infection, Australia, 2003, by Statistical Division of residence

In 2003, notification rates of chlamydial infection in females and males were 179 and 123 cases per 100,000 population respectively. Compared to 2002, notification rates increased by 22 per cent in males and by 23 per cent in females. The female to male ratio remained at 1.5:1, with rates in females exceeding those of males in the 10–14,15–19 and 20–24 age groups. In all other age groups the sex-specific rates were comparable (Figure 26).

Figure 26. Notification rates of chlamydial infections, Australia, 2003, by age group and sex

Trends in age and sex specific notification rates between 1999 and 2003 show increases in each of the 5-year age groups between 15 and 34 years in both males and females (Figure 27). Since 1999 the highest average annual percentage increase in notification rates occurred in males aged 20–24 years (23% increase per year) and females aged 15–19 and 20–24 years (20–21% increase per year).

Figure 27. Trends in notification rates of chlamydial infection in persons aged 10–39 years, Australia, 1999 to 2003, by age group and sex

In 2003, Indigenous status was reported in 43 per cent of chlamydial infection notifications. The notification of Chlamydia in the three jurisdictions with high completeness of reporting of Indigenous status (Northern Territory, South Australia and Western Australia) shows that in 2003, the crude notification rates of chlamydial infection increased in both Indigenous and non-Indigenous peoples. Western Australia reported the highest increase among Indigenous (28% increase) and non-indigenous (19% increase) peoples compared to 2002 (Table 8). Indigenous people have the highest burden of chlamydial infection notifications. The Indigenous to non-Indigenous age adjusted rate ratio was 5:1, 4:1 and 8:1 for the Northern Territory, South Australia and Western Australia, respectively.²

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Table 8. Trends in crude notification rates* (cases per 100,000 population) of chlamydial infection in the Northern Territory, South Australia and Western Australia, 1999 to 2003, by Indigenous status

Year	NT		SA		WA
	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous
1999	965.4	235.4	572.5	59.1	853.8	77.4
2000	1,198.6	240.8	700.0	56.1	1,101.9	105.8
2001	1,433.5	315.7	559.4	88.5	1,152.8	108.9
2002	1,518.3	386.3	666.1	109.3	1,035.5	128.5
2003	1,793.6	398.3	642.1	121.4	1,327.4	153.1

* The rates in non-Indigenous peoples include diagnoses in people whose Indigenous status was not reported.

Surveillance data continues to indicate substantial increases in chlamydial infection notifications over time by gender, age and jurisdiction. The impact on the number of notifications of factors such as new public health initiatives, changes in surveillance practices, changes in diagnostic tests and increases in testing for Chlamydia, is unknown.

Data from the Australian Health Insurance Commission (HIC) suggests that parallel to the increase in chlamydial infection notifications between 1999 and 2003 there has been an increase in the number of diagnostic tests for Chlamydia trachomatis (Figure 28). An ecological analysis, using the number of notifications as the numerator and the number of diagnostic tests (HIC data, http://www.hic.gov.au/statistics/dyn_mbs/forms/mbs_tab4.shtml) as the denominator, shows that from 1999 through 2003, the percentage positives (i.e., the proportion notified of the number tested for Chlamydia) within the 15–24 and 25–34 year age groups remained stable for both males and females (Figure 28). Subject to the limitations of an ecological analysis and the inherent limitations of each data set, this analysis suggests that an increase in the number of tests for Chlamydia may account for at least part of the increase in notifications. The surveillance of chlamydial infection via routine surveillance systems is problematic and the true extent of the disease burden in the Australian community is not known. It is therefore advisable to consider routine surveillance of chlamydial infection in conjunction with other sources of data such as population-based surveys and systematic sentinel site surveys.

Figure 28. Annual number of diagnostic tests for Chlamydia trachomatis and the proportion notified among persons aged 15–24 and 25–34 years, Australia, 1999 to 2003, by sex

Data source: National Notifiable Diseases Surveillance System and Australian Health Insurance Commission data.

Donovanosis

Donovanosis is a sexually transmitted infection characterised by a chronic ulcerative genital disease. Although relatively uncommon, it is a disease of public health importance in Australia because it predominantly occurs in Indigenous communities, it has been identified as a potential co-factor in HIV transmission, and it is preventable.^5,6 In 2001, donovanosis was targeted for elimination from Australia within three years through the donovanosis elimination project.

In 2003, 16 cases of donovanosis, six male and ten female, were reported to the NNDSS (Figure 29). An equivalent number were notified in 2002 (Figure 30). All cases were Indigenous, three male and six female cases were from Queensland, three male and three female cases were from the Northern Territory, and one female was from Western Australia. The case distribution by sex and age group is shown in Figure 29; cases ranged in age from 15–19 years to 50–54 years and the majority were aged 15–39 years.

The surveillance data indicate that the donovanosis elimination project has been successful to date but requires ongoing support to achieve its target of complete eradication of donovanosis in Australia.

Figure 29. Notifications of donovanosis, Australia, 2003, by age group and sex

Figure 30. Number of notifications of donovanosis, Australia 1999 to 2003, by sex

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Gonococcal infection

In 2003, 6,611 notifications of gonococcal infection were received by the NNDSS (Table 2). This represents a rate of 33 cases per 100,000 population, an increase of 4 per cent from the rate reported in 2002 (32 cases per 100,000 population). Nationally, this increase was attributed solely to an increase in the number of notifications in males (5%), as the rate in females was unchanged from that in 2002. The female to male ratio in 2003 was 0.4:1, compared to 0.5:1 in the previous two years.

The highest notification rate in 2003 was in the Northern Territory at 705 cases per 100,000 population (Table 3), while the highest increase in notification rate in 2003, compared to 2002, occurred in the Australian Capital Territory (99% increase overall; 107% in males and 66% in females). Victoria and South Australia each reported an increase of 41 per cent. In South Australia, there was a marked difference by gender, with rates increasing for males (70%) and decreasing for females (16%). New South Wales and Tasmania reported overall decreases in notification rates, 19 per cent and 6 per cent respectively.

In 2003, the national gonococcal infection notification rates for males and females were 46 and 21 cases per 100,000 population, respectively. The exception to this pattern was the Northern Territory, where females had higher notification rates than males (618 and 801 per 100,000 population respectively).

The regional distribution of gonococcal infection notifications shows that, as for chlamydial infection, the highest notification rate occurred in the Kimberly region at 1,479 cases per 100,000 population (Map 4).

Map 4. Notification rates of gonococcal infection, Australia, 2003, by Statistical Division of residence

Notification rates for gonococcal infection in males exceeded those in females in all age groups except for the 10–14 and 15–19 year age groups (Figure 31). Trends in age and sex specific notification rates show that compared to 2002, increases in notification rates occurred in the 15–19, 20–24, 25–29, 40–44 and 40–45 year age groups in males and only in the 15–19 and 20–24 year age groups in females ( Figure 32).

Figure 31. Notification rates of gonococcal infection, Australia, 2003, by age group and sex

Figure 32. Trends in notification rates of gonococcal infection in persons aged 15–39 years, Australia, 1999 to 2003, by age group and sex

Indigenous status was reported for 66 per cent of gonococcal infection notifications in 2003. The notifications for the three jurisdictions with high completeness of reporting of Indigenous status (the Northern Territory, South Australia and Western Australia) shows that compared to 2002, the crude notification rate increased in both the Northern Territory and Western Australia, while in South Australia, there was a marginal decrease in Indigenous and an increase in non-Indigenous people (Table 9). Nevertheless, gonococcal infection notification rates in Indigenous people are many times the magnitude of the notification rates in non-Indigenous people. The age adjusted rate ratio of Indigenous to non-Indigenous in 2003, was 13:1, 28:1 and 43:1 for the Northern Territory, South Australia and Western Australia, respectively.²

Table 9. Trends in crude notification rates* of gonococcal infection, Northern Territory, South Australia and Western Australia, 1999 to 2003, by Indigenous status

Year	NT		SA		WA
	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous
1999	1,674.4	161.7	628.1	5.6	1,185.5	16.3
2000	1,811.5	135.0	729.3	6.2	1,374.9	28.2
2001	2,059.8	198.4	481.2	6.8	1,697.4	16.3
2002	2,002.2	238.6	387.6	7.5	1,372.7	27.1
2003	2,013.9	162.9	376.6	13.4	1,391.8	29.8

* The rates in non-Indigenous peoples includes diagnoses in people whose Indigenous status was not reported.

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Other surveillance activities for gonococcal infections

The Australian Gonococcal Surveillance Programme (AGSP) is the national surveillance system of antibiotic susceptibility of gonococcal isolates. In each state and territory, a network of reference laboratories determine susceptibility of the organism to a core group of antibiotics using a standard methodology.

In 2003, a total of 3,772 isolates of gonococci were tested for antibiotic susceptibility. Eighty-five per cent of isolates were from men, of which 76 per cent were obtained from the urethra and 13 per cent from the rectum. In females, 90 per cent of isolates were obtained from the cervix.⁷

Trends in the proportion of isolates resistant to penicillin, quinolines and tetracycline are shown in Table 10.

Table 10. Proportion of gonococcal isolates showing antibiotic resistance, Australia, 1998 to 2003

Year	(% resistance)
	Penicillin Plasmid mediated	Chromosomally mediated	Quinolone	High level tetracycline
1998	5.3	21.8	5.2	NR
1999	7.4	14.3	17.2	7.9
2000	8.7	10.6	17.8	9.1
2001	7.5	15.3	17.5	9.4
2002	7.1	10.9	10.0	11.4
2003	9.0	9.0	14.4	11.2

Source: Australian Gonococcal Surveillance Programme, annual report 2003.

NR Not reported.

In 2003, the proportion of isolates resistant to penicillin by chromosomally-mediated resistance decreased by 17 per cent, but, the proportion of isolates resistant by plasmid-mediated resistance increased by 27 per cent. In 2003, quinolone resistance also increased by 44 per cent, compared to 2002. The level of quinolone resistance is of special concern in Australia. Until 1999 quinolone resistance was observed at a lower ‘minimal inhibitory concentration’ (MIC) range (0.06–0.5 mg/L) and was mainly in homosexually active males. In 2000 through to 2002 most of the quinolone resistance was at a high MIC (1 mg/L or more) and was widely spread among heterosexuals. This trend continued in 2003. Available data on countries were quinolone resistant strains were acquired shows that 63 per cent (69/110) were acquired from overseas. The AGSP advises that quinolones (including recently available groups) as unsuitable for treatment of overseas-acquired gonorrhoea.⁷

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Syphilis

The notification of syphilis includes both new infections and newly diagnosis cases that may not be newly acquired. During 2003, a total of 2,056 cases of syphilis infection were reported, giving a notification rate of 10.3 per 100,000 population, similar to that in 2002 (Table 2 and 3). In 2003, increases in notification rates occurred in New South Wales (29% increase) and Queensland (8% increase) but these were offset in the national data by decreases in notification rates in the other jurisdictions, ranging from 19 per cent in the Northern Territory to 35 per cent in South Australia.

The Northern Territory had the highest notification rate of syphilis in 2003 (159 cases per 100,000 population; Table 3). At the regional level, the highest notification rate was in the Kimberley Statistical Division of Western Australia and the Northern Territory at 204 cases per 100,000 population (Map 5).

Map 5. Notification rates of syphilis infection, Australia, 2003, by Statistical Division of residence

In 2003, syphilis infection notification rates in males and females were 13 and 7 cases per 100,000 population, respectively. Notification rates were higher in males than in females in all jurisdictions except in the Northern Territory, where females had a higher notification rate than males (164 and 156 cases per 100,000 population respectively). Nationally, compared to 2002, the notification rate of syphilis infection increased by 10 per cent in males but decreased by 12 per cent in females. In New South Wales, one of the two jurisdictions where notification rates increased in 2003, increases occurred in both males (36%) and females (15%).

Nationally, the female to male ratio in 2003 was 0.5:1, compared to 0.7:1 in the previous two years. The notification rates of syphilis infection in males peaked in the 35–39 year age group, while in females the rates in the 15–19, 20–24 and 25–29 year age groups were very similar (Figure 33). The peak age specific notification rate for males was 20–24 years in 2001 and 30–34 years in 2002.

Figure 33. Notification rates of syphilis, Australia, 2003, by age group and sex

Trends in age and sex specific notification rates for persons aged between 15 and 39 years show a steady increase in rates in males aged 30–34 and 35–39 years since 2001, and a general downward trend for all age categories in females (Figure 34).

Figure 34. Trends in notification rates of syphilis in persons aged 15–39 years, Australia, 1999 to 2003, by age group and sex

Indigenous status was reported for 77 per cent of syphilis infection notifications in 2003. The crude rate of syphilis for the three jurisdictions with high completeness of reporting of Indigenous status (the Northern Territory, South Australia and Western Australia) in 2003 is shown in Table 11. There was decrease in notification rates in 2003 compared to 2002 in both Indigenous and non-Indigenous populations. However, syphilis continues to have a high notification rate among Indigenous people. The Indigenous to non-Indigenous age adjusted rate ratio was 23:1, 45:1 and 63:1 in the Northern Territory, South Australia and Western Australia, respectively. 2

Table 11. Trends in crude notification rates of syphilis,* the Northern Territory, South Australia and Western Australia, 1999 to 2003, by Indigenous status

Year	NT		SA		WA
	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous	Indigenous	Non-Indigenous
1999	544.1	22.2	55.5	0.5	79.1	4.1
2000	414.6	27.7	54.5	0.1	120.8	3.3
2001	663.5	39.5	98.7	0.1	196.7	4.6
2002	576.6	42.6	109.0	0.3	210.9	3.6
2003	483.7	24.9	47.6	0.6	125.7	2.9

* Note that the rates in non-Indigenous peoples include diagnoses in people whose Indigenous status was not reported.

The surveillance data indicate unacceptably high levels of syphilis in Indigenous Australians. Men who have sex with men are another sub-population at high risk of syphilis and increases in rates in males in New South Wales and Queensland in 2003 may reflect increases in infection in men who have sex with men in these jurisdictions. Enhanced reporting of syphilis notifications would allow inferences about trends in relation to sexual behaviour.

Syphilis – congenital

There were 10 cases of congenital syphilis notified in 2003, one less than in 2002 (Figure 35). Six of the cases were male and four were female, and all reported cases were under one year of age. Eight of the cases were from the Northern Territory, one case was from New South Wales and one case was from Queensland.

Figure 35. Trends in notifications of congenital syphilis, Australia, 1999 to 2003

 

This article {extract} was published in Communicable Diseases Intelligence Vol 29 No 1 March 2005 and may be downloaded as a full version PDF from the Table of contents page.