This article {extract} was published in Communicable Diseases Intelligence Vol 31 No 1 March 2007 and may be downloaded as a full version PDF from the Table of contents page.

Results, continued

Sexually transmissible infections

In 2005, sexually transmissible infections (STIs) reported to NNDSS were chlamydial infections, donovanosis, gonococcal infections, and syphilis. Two categories of adult syphilis have been reported since 2004: syphilis of less than 2 years duration – infectious (primary, secondary and early latent); and syphilis of greater than 2 years or unknown duration. These 2 categories are combined under ‘syphilis – all.’ Congenital syphilis is also reported to NNDSS. These conditions were notified in all states and territories.

Other national surveillance systems that monitor STIs 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 national trends in the number and rates of STI notifications reported to NNDSS between 2000 and 2005 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^7,8 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.

Age adjusted notification rates were calculated for Indigenous and non-Indigenous populations for jurisdictions that had Indigenous status data completed in more than 50% of notifications. These data however, should be interpreted cautiously as STI screening occurs disproportionately among Indigenous populations. Similarly, rates of testing for STI also differ between sexes.

Chlamydial infection

Case definition – Chlamydial infection Only confirmed cases are reported. Confirmed case: Isolation of Chlamydia trachomatis or detection of Chlamydia trachomatis by nucleic acid testing or detection of Chlamydia trachomatis antigen.

Chlamydial infection continued to be the most commonly notified condition in 2005. A total of 41,311 notifications of chlamydial infection were received; a rate of 203 cases per 100,000 population. This represents an increase of 13% on the rate reported in 2004 (180 cases per 100,000 population). The rate of chlamydia notifications has increased each year since surveillance of the condition commenced in 1991. Between 2001 and 2005, chlamydial infection notification rates increased from 104 to 203 cases per 100,000 population, an increase of 95% (Table 4). This increase provided the impetus for the launch of Australia’s first National STI Strategy in July 2005.⁹ The prevalence of chlamydia varies by age group and other demographic and behavioural factors, and most major sections of the population are unaffected. ¹⁰

Chlamydial infection notification rates were higher than the national average in the Northern Territory (781 cases per 100,000 population), Western Australia (271 cases per 100,000 population), Queensland (245 cases per 100,000 population) and the Australian Capital Territory (215 cases per 100,000 population) (Table 3). At a regional level, the Northern Territory excluding Darwin had the highest chlamydial infection notification rate at 1,596 cases per 100,000 population ( Map 3).

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Map 3. Notification rate for chlamydial infections, Australia, 2005, by Statistical Division of residence

In 2005, notification rates of chlamydial infection in males and females were 166 and 240 cases per 100,000 population, respectively. In 2005, notification rates increased by 14% in males and by 13% in females compared to 2004. The male to female ratio in 2005 was 1:1.5, which is similar to previous years. Rates in females exceeded those in males in the 10–14, 15–19, and 20–24 year age groups with ratios of 1:7, 1:3 and 1:2, respectively (Figure 26). Sixty-six cases of chlamydia were identified as congenital chlamydia infections. These cases, while still included in the total number of chlamydial infections for 2005, were excluded from analyses.

Figure 26. Notification rate for chlamydial infections, Australia, 2005, by age group and sex

Age and sex notification rates between 2001 and 2005 show increases in all age groups between 10 and 39 years in both males and females (Figure 27). Since 2001, the highest average annual percentage increase occurred in the 20–24 year age group (21% in males and 20% in females).

Figure 27. Trends in notification rate for chlamydia infection in persons aged 10–39 years, Australia, 2001 to 2005, by age group and sex

In 2005, data on Indigenous status was complete in 39% of cases of chlamydia infection; this is a decrease on the 59% reported in 2004 and the 43% notified in 2003. The combined chlamydial infection notifications in 4 jurisdictions with greater than 50% completeness of Indigenous status (Northern Territory, South Australia, Victoria and Western Australia) show that in 2005, the age adjusted notification rate was 989.9 cases per 100,000 Indigenous population, and 191.5 cases per 100,000 non-Indigenous population. The age adjusted ratio of Indigenous to non-Indigenous was 5.2:1.

Although surveillance data continues to show a substantial increase in chlamydia notifications nationally, it is important to note that changes in notifications over time may not solely reflect changes in disease prevalence. As a large proportion of cases with genital chlamydial infection are asymptomatic, notification rates for this disease are particularly susceptible to the overall rate of testing as well as the targeted testing of certain population sub-groups. In past years Medicare Australia data were utilised to determine if the number of chlamydia tests were also increasing.¹⁰ With the changes to the Medicare item number, which occurred late in 2005 for chlamydia testing this is not currently possible.

Donovanosis

Case definition – Donovanosis Both confirmed cases and probable cases are reported. Confirmed case: Requires demonstration of intracellular Donovan bodies on smears or biopsy specimens taken from a lesion or detection of Calymmatobacterium granulomatis by nucleic acid testing of a specimen taken from a lesion AND clinically compatible illness involving genital ulceration. Probable case: Requires compatible sexual risk history in a person from an endemic area or a compatible sexual risk history involving sexual contact with someone from an endemic area.

Donovanosis is a sexually transmissible infection characterised by a chronic ulcerative genital disease. Although uncommon, it is a disease of public health importance because it predominantly occurs in Indigenous communities; it has been identified as a potential co-factor in HIV transmission; and it is preventable.¹¹

In 2005, 13 cases of donovanosis, 4 male and 9 female, were reported to NNDSS. Cases were reported from Northern Territory (4), Queensland (8) and Western Australia (1). Eleven cases of the total were among Indigenous people: 6 in Queensland, 4 in the Northern Territory and 1 in Western Australia. One non-Indigenous case and 1 case with unknown Indigenous status were reported in 2005 (Figure 28). Cases in 2005 ranged in age from 12 to 53 years and the majority were aged 30–44 years.

Figure 28. Number of notifications of donovanosis, Australia, 1999 to 2005, by sex and year of notification

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Gonococcal infections

Case definition – Gonococcal infection Only confirmed cases are reported. Confirmed case: Requires isolation of Neisseria gonorrhoeae, or detection of Neisseria gonorrhoeae by nucleic acid testing or detection of typical Gram-negative intracellular diplococci in a smear from a genital tract specimen.

In 2005, 8,015 notifications of gonococcal infection were received by NNDSS. This represents a rate of 39.4 cases per 100,000 population, an increase of 10% over the rate reported in 2004 (35.7 cases per 100,000 population). Nationally, there was an increase in the notification rates of females (by 13%), and males (by 9%) compared to 2004. The male to female ratio in 2005 was 2:1; unchanged in the previous 4 years and reflecting ongoing transmission among men who have sex with men.

The highest notification rate in 2005 was in the Northern Territory at 857 cases per 100,000 population (Table 3). Nationally, gonococcal notification rates for males and females were 54 and 25 cases per 100,000 population respectively. The exception to this pattern was the Northern Territory, where females had higher notification rates than males (820 versus 898 cases per 100,000 population). The geographical distribution of gonococcal notification rates shows that the highest rate occurred in the Northern Territory (excluding Darwin) at 2,020 cases per 100,000 population (Map 4).

Map 4. Notification rate for gonococcal infections, Australia, 2005, by Statistical Division of residence

Notification rates of gonococcal infection in males exceeded those in females in all age groups except in the 10–14 and 15–19 year age groups (Figure 29). Trends in sex specific notification rates show that rates in males in the 15–19, 20–24 and 25–29 age groups continued to increase. Notification rates for males in the 30–44 age groups also increased in 2005. In females, increases occurred in the 15–19 and 20–24 age groups (Figure 30).

Figure 29. Notification rate for gonococcal infections, Australia, 2005, by age group and sex

Figure 30. Trends in notification rate for gonococcal infections in persons aged 10–44 years, Australia, 2001 to 2005, by age group and sex

In 2005, the data completeness (68%) of Indigenous status of gonococcal infection notifications was similar to that in 2004. The combined gonococcal infection notifications of 5 jurisdictions with Indigenous status reported in more than 50% of notifications (the Northern Territory, Queensland, South Australia, Western Australia and Victoria) shows that the age adjusted notification rate in the Indigenous population was 1,590.9 cases per 100,000 population and 34.6 cases per 100,000 non-Indigenous population: a ratio of Indigenous to non-Indigenous of 46:1.

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Other surveillance of 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 determines the susceptibility of isolates to a core group of antibiotics using a standard methodology. The following is the summary of their 2005 annual report.¹²

In 2005, a total of 3,980 isolates of gonococci were tested for antibiotic susceptibility. Eighty-three per cent of isolates were from men, of which 75% were obtained from the urethra, 13% from the rectum and 9% from the larynx. In females, 93% of isolates were obtained from the cervix. Proportions for site of infection were similar to those reported in 2004.

Trends in the proportion of isolates resistant to penicillin, quinolones and tetracycline are shown in Figure 31. In 2005, the proportion of isolates resistant to penicillin by plasmid-mediated resistance remained similar to 2004 (10.5%) while the proportion of isolates resistance to penicillin by chromosomally-mediated mechanisms increased to 19%. Quinolone resistance also increased to 30.6% from 23.3% in 2004. Ninety-three per cent of the quinolone resistant isolates were also resistant at a higher minimal inhibitory concentration (MIC) of 1 mg/L or more.

Information on the country where resistant strains were acquired were available in 31% of infections for strains with plasmid-mediated resistance to penicillin, and 31% of infections for strains resistant to quinolone. This showed that 51% (66/128) of plasmid mediated resistance were locally required with the rest acquired from Western Pacific countries and South East Asia. Eight-four per cent of quinolone resistant strains were acquired locally and the remainder from overseas.

The distribution of infections with strains resistant to different antibiotic agents varies from jurisdiction to jurisdiction and urban to rural areas within each jurisdiction. The AGSP recommends that treatment regimes should be tailored to the local patterns of susceptibility. Nationally, the AGSP recommends the use of alternative treatments to quinolones for infections acquired.

Figure 31. Proportion of gonococcal isolates showing antibiotic resistance, Australia, 1998 to 2005

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Syphilis (both categories)

In 2004, all jurisdictions began reporting adult syphilis infections to NNDSS categorised as: infectious syphilis of less than 2 years duration; and syphilis of more than 2 years or unknown duration; this continued in 2005. Detailed analysis is reported for the 2 categories, as well as for syphilis of both categories for the purpose of comparing rates to previous years.

In 2005, a total of 2,203 cases of syphilis infection of both categories were reported, representing a notification rate of 10.8 cases per 100,000 population, a decrease of 7% on the 11.6 cases per 100,000 population reported in 2004 (Table 4). The Northern Territory continued to have the highest notification rate of syphilis (113 cases per 100,000 population), although in 2005 the rate was 20% lower than the previous year. In 2005, there were increases in notification rates in the Australian Capital Territory (16%), Queensland (29%), and Victoria (15%). Recent outbreaks among men who have sex with men in Melbourne and Sydney^13,14 may have peaked. At the regional level, the highest notification rate was in the Northern Territory (excluding Darwin) at 238 cases per 100,000 population (Map 5).

Tasmania reported an increase of 114% but this was most likely in syphilis of unknown duration and due to screening practices.

Map 5. Notification rate for syphilis infections, Australia, 2005, by Statistical Division of residence

Syphilis – less than 2 years duration

Case definition – Syphilis – infectious (primary, secondary and early latent), less than 2 years duration Only confirmed cases are reported. Confirmed case: Requires seroconversion in past two years (specific treponemal test (e.g. IgG enzyme immunoassay, Treponema pallidum haemagglutination assay, Treponema palladium particle agglutination, Treponema pallidum immobilisation assay), or fluorescent treponemal antibody absorption reactive when previous treponemal test non-reactive within past two years OR a fourfold or greater rise in non-specific treponemal antibody titre (e.g. Venereal Diseases Research Laboratory, Rapid Plasma Reagin) in the past two years, and a reactive specific treponemal test (e.g. IgG enzyme immunoassay, Treponema pallidum haemagglutination assay, Treponema pallidum particle agglutination, Treponema pallidum immobilisation assay, or fluorescent treponemal antibody absorption) OR demonstration of Treponema pallidum by darkfield microscopy (not oral lesions), direct fluorescent antibody tests, equivalent microscopic methods (e.g. silver stains), or nucleic acid testing or non-specific treponemal test (e.g. Venereal Diseases Research Laboratory, Rapid Plasma Reagin) reagin titre of greater than or equal to 1:8 AND presence of a primary chancre (or ulcer) or clinical signs of secondary syphilis.

In 2005, a total of 621 cases of syphilis of less than 2 years duration were reported. This represents a notification rate of 3.1 cases per 100,000 population. The Northern Territory had the highest notification rate at 46 cases per 100,000 population in 2005.

The notification rates of syphilis of less than 2 years duration for males and females were 4.9 and 1.2 cases per 100,000 population, respectively. Notification rates were higher in males than in females in most jurisdictions. Nationally, the male to female ratio was 4:1, which was similar to 2004. Notification rates in males peaked in the 35–39 year age group (13 cases per 100,000 population) and in females in the 15–19 year age group (5 cases per 100,000 population) (Figure 32).

Figure 32. Notification rate for syphilis of less than two years duration, Australia, 2005, by age group and sex

Data on Indigenous status was complete in 93% of cases of syphilis of less than 2 years duration. The age adjusted notification rate was 33.5 cases per 100,000 Indigenous population, and 2.3 cases per 100,000 non-Indigenous population: a ratio of Indigenous to non-Indigenous of 14:1. Age-specific notification rates showed that, compared to the non-Indigenous population, rates of syphilis of less than 2 years duration in the Indigenous population are an order of magnitude higher and peak in a younger age group (Figure 33).

Figure 33. Notification rate for syphilis of less than two years duration, Australia, 2005, by Indigenous status

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Syphilis of more than two years or unknown duration

Case definition – Syphilis of more than two years or unknown duration Only confirmed cases are reported. Confirmed case: Does not meet the criteria for a case of less than 2 years duration AND either a reactive specific treponemal test (e.g. IgG enzyme immunoassay, Treponema pallidum haemagglutination assay, Treponema pallidum particle agglutination, Treponema pallidum immobilisation assay, or fluorescent treponemal antibody absorption) which is confirmed either by a reactive non-specific treponemal test (e.g. Venereal Diseases Research Laboratory, Rapid Plasma Reagin) OR a different specific treponemal test if the non-specific treponemal test is nonreactive AND the absence of a history of documented previous adequate treatment of syphilis, or endemic treponemal disease (e.g. Yaws).

In 2005, a total of 1,582 cases of syphilis of more than 2 years or unknown duration were reported: a notification rate of 7.8 cases per 100,000 population. The Northern Territory had the highest notification rate at 67 cases per 100,000 population (Table 3).

In 2005, notification rates of syphilis of more than two years or unknown duration in males and females were 9.4 and 6.1 cases per 100,000 populations, respectively. Notification rates were higher in males in all jurisdictions. Nationally, the male to female ratio was 1.5:1. Notification rates in males and females were similar in the younger age groups up to 30–34 years. In females, the rate peaked in the 30–34 year age group (13 cases per 100,000 population) while in males it remained high from 35 years (Figure 34).

Figure 34. Notification rate of syphilis of more than two years or unknown duration, Australia, 2005, by age group and sex

Data on Indigenous status was complete in 67% of cases of syphilis of more than two years or unknown duration. The combined age adjusted rate for the jurisdictions with greater than 50% data completeness of Indigenous status (all jurisdictions except New South Wales and the Australian Capital Territory) was 121 cases per 100,000 Indigenous population, and 5 cases per 100,000 non-Indigenous population: a ratio of Indigenous to non-Indigenous of 24:1. Age specific notification rates showed a similar pattern with age and no single distinct peak for either Indigenous and non-Indigenous groups. Overall, rates in the Indigenous population were an order of magnitude higher than those in the non-Indigenous (Figure 35).

Figure 35. Notification rate for syphilis of more than two years or unknown duration, Australia, 2005, by Indigenous status

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Congenital syphilis

Case definition – Congenital syphilis Both confirmed cases and probable cases are reported. Confirmed case: Requires treponemal-specific antibody titres (e.g. Treponema pallidum haemagglutination assay, pallidum particle agglutination, fluorescent treponemal antibody absorption in infant serum greater than fourfold higher than in maternal serum OR treponemal specific antibody titres in infant serum comparable with those in maternal serum and specific treponemal IgM enzyme-linked immunosorbent assay or immunofluorescence assay positive OR T. pallidum DNA in normally sterile specimen from infant (CSF, tissue) by nucleic acid testing. OR Dark field microscopy of infant lesion exudate or node aspirate smears (not oral lesions) to demonstrate characteristic morphology and motility of T. pallidum OR demonstration of T. pallidum in infant tissues by special (e.g. silver) stains OR detection of T. pallidum DNA from an infant non-sterile site by nucleic acid testing OR reactive fluorescent treponemal absorbed-19S-IgM antibody test or IgM enzyme linked immunosorbent assay and treponemal-non specific antibody titre (e.g. RPR) in infant serum greater than fourfold higher than in maternal serum AND asymptomatic infection (in the infant of an infected mother) OR foetal death in utero OR stillbirth, which is a foetal death that occurs after a 20-week gestation or in which the foetus weighs greater than 500 g and the mother is untreated or inadequately treated for syphilis at delivery. Inadequate treatment is a non-penicillin regimen or penicillin treatment given less than 30 days prior to delivery OR clinical evidence of congenital syphilis on examination on: a. Age <2years: Hepatosplenomegaly, rash, condyloma lata, snuffles, jaundice (non-viral hepatitis), pseudoparalysis, anaemia, oedema b. Age >2 years: Interstitial keratitis, nerve deafness, anterior bowing of shins, frontal bossing, mulberry molar, Hutchinson teeth, saddle nose, rhagades or Clutton joints c. Evidence of congenital syphilis on long bone X-ray d. Evidence of congenital syphilis on cerebrospinal fluid (CSF) examination Probable case: An infant (regardless of clinical signs) whose mother has been inadequately treated for syphilis during pregnancy or an infant or child who has a reactive treponemal antibody test for syphilis and any one of the following: (1) any evidence of congenital syphilis on physical examination, (2) any evidence of congenital syphilis on radiographs of long bones, (3) a reactive cerebrospinal fluid Venereal Disease Research Laboratory Titre, (4) an elevated CSF cell count or protein (without other cause), (5) reactive fluorescent treponemal antibody absorbed assay –19S-IgM antibody test or IgM enzyme-linked immunosorbent assay.

There were 15 cases of congenital syphilis notified in 2005, 8 males, 6 female and 1 of unknown sex. Eight of the cases were reported in New South Wales, 5 in the Northern Territory and 2 in Queensland. Eight were Indigenous, 4 non-Indigenous and 3 were unknown. There has been a gradual decline in the number of congenital syphilis notified in the Indigenous population since 2001 (Figure 36).

Figure 36. Trends in notifications of congenital syphilis, Australia, 2000 to 2005, by Indigenous status* and year of notification

* Notifications with unknown Indigenous status are recorded as non-Indigenous.