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

Results - Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis (TB) were notifiable in all states and territories in 2003 and classified as ‘other bacterial infections’ in NNDSS. A total of 1,826 notifications were included in this group in 2003, which accounted for 1.7 per cent of all the notifications to NNDSS, a similar total and proportion as in 2002 (1,980 notifications and 1.9% of total).

Legionellosis

Legionellosis includes notifications of infections caused by all Legionella species. There were 328 notifications of legionellosis reported in 2003 giving a national rate of 1.6 cases per 100,000 population.

The annual trend since 1991 (Figure 60) shows a marked increase in notifications in 2000, which included the Melbourne aquarium outbreak.²⁹ Between 1991 and 2000, there was a significant increase in the national legionellosis notification rate, even after excluding cases related to outbreaks.³⁰

In 2003, the highest rates of legionellosis were reported in South Australia (4.3 cases per 100,000 population) and Western Australia (3.3 cases per 100,000 population). Legionellosis notifications showed a peak in reports in autumn and spring.

Figure 60. Trends in notifications of legionellosis, Australia, 1991 to 2003, by month of onset

Men accounted for 214/328 (65%) of all cases of legionellosis resulting in a male to female ratio of 1.9:1. Cases occurred in all age groups above 14 years, with the highest rates in the 70–74 year age group for men (12 cases per 100,000 population) and the 75–79 year age group for women (5.7 cases per 100,000 population; Figure 61).

Figure 61. Notification rates of legionellosis, Australia, 2003, by age group and sex

Data on the causative species were available for 320 (98%) of the legionellosis cases. Of these, 131 (41%) cases were identified as L. pneumophilia, 185 (58%) were L. longbeachae and 4 (1%) were other species (L. micdadei and L. bozemannii, Table 18).

Table 18. Notifications of legionellosis, Australia, 2003, by species and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Total
Legionella longbeachae	1	37	2	12	54	0	25	54	185
Legionella pneumophila	0	23	1	25	10	2	63	7	131
Other species*	0	0	0	0	1	0	3	0	4
Unknown species	0	0	0	2	0	0	2	4	8
Total	1	60	3	39	65	2	93	65	328

* Other includes species of Legionella micdadei and Legionella bozemannii.

Data on the death or survival of legionellosis cases were available for 224 (68%) notifications. In all there were 13 deaths identified as due to legionellosis in Australia in 2003, giving a case fatality rate of 4 per cent. The break down of deaths by jurisdiction and infecting Legionella species is shown in Table 19. The case fatality rate for infections with L. pneumophila (9/131, 6.9%) was higher than for L. longbeachae infections (4/185, 2.2%) but this difference did not reach statistical significance.

Table 19. Deaths due to legionellosis by species, Australia, 2003, by species and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Total
Legionella longbeachae	0	0	0	0	2	0	0	2	4
Legionella pneumophila	0	2	0	1	1	1	3	1	9
Other species*	0	0	0	0	0	0	0	0	0
Unknown species	0	0	0	0	0	0	0	0	0
Total	0	2	0	1	3	1	3	3	13

* Other includes species of Legionella micdadei and Legionella bozemannii.

There was an outbreak of legionellosis in South Australia in December 2003. Five cases and two deaths were reported in cases infected with L. longbeachae and four of the cases had exposure to potting mix.³¹ Potting mixes in Australia have been identified as a source of infection with L. longbeachae for some years.³²

The largest outbreak of legionellosis in Australia was in Melbourne in April 2000. A report into the investigation was recently published.³³ Risk factors for acquiring legionellosis in this outbreak identified current smoking as a dose-dependent risk, while underlying chronic illness and duration of exposure were not significant risks. The number of cases identified in this outbreak was possibly inflated by the large proportion of mild cases detected by the urinary antigen test.

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Leprosy

Leprosy is a chronic infection of the skin and peripheral nerves with the bacterium Mycobacterium leprae. Leprosy is a rare disease in Australia, with the majority of cases occurring among Indigenous communities and migrants to Australia from leprosy-endemic countries.

In 2003, four leprosy cases were notified compared with three in 2002. The cases in 2003 occurred in New South Wales, Victoria and Western Australia. Two were male and two female and the age range was 21 to 42 years. Two cases were multibacillary (lepromatous, more than 5 skin lesions), two were paucibacillary (tuberculoid, less than 5 skin lesions) leprosy and one had evidence of neuritis at presentation.

The WHO has established the goal of eliminating leprosy from every country by 2005, which is defined as a reduction in the prevalence of leprosy to less than one case per 10,000 population. The Western Pacific Region, comprising 37 countries including Australia, reached this target in all but two countries in 2003.³⁴

Leprosy transmission continues to occur in parts of Australia (such as the Kimberley region of Western Australia), despite the fact that Australia has a prevalence of leprosy well below the WHO elimination goal. Leprosy in Australia is most prevalent amongst Indigenous people³⁵ and among migrants to Australia from leprosy-endemic countries.

Invasive meningococcal disease

Meningococcal serogroups A, B, C, Y and W–135 are major human pathogens. In Australia, serogroups B and C are the major cause of invasive meningococcal disease.

In 2003, there were 550 notifications of invasive meningococcal disease in Australia: a decrease of 20 per cent on the 684 cases reported in 2002. The national notification rate was 2.8 cases per 100,000 population. The highest rates were reported from the Northern Territory (5.5 cases per 100,000 population). The largest number of cases occurred in winter and spring (Figure 62).

Figure 62. Trends in notification rates of meningococcal infection, Australia, 1991 to 2003, by month of onset

The highest age specific rate was in children aged 0–4 years (12.7 cases per 100,000 population) and in the 15–19 year age group (7.3 cases per 100,000 population). There was a small excess of cases among males (male to female ratio 1.1:1, Figure 63).

Figure 63. Notification rates of meningococcal infection, Australia, 2003, by age and sex

Of the 550 meningococcal notifications, 465 (84.5%) were serogrouped. Of these 289 (62%) were serogroup B, 158 (34%) were serogroup C, 18 (4%) were serogroup W135 or serogroup Y and there was a single case of serogroup A (Table 20).

Table 20. Notifications of meningococcal infection, Australia, 2003, by serogroup, and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Total
Serogroup B	3	100	10	54	26	9	54	33	289
Serogroup C	9	46	0	39	3	10	45	6	158
Other serogroups*	1	7	1	2	2	0	4	1	18
Unknown serogroup	0	45	0	10	1	1	22	6	85
Total	13	198	11	105	32	20	125	46	550

* Other includes serogroups A, Y and W135.

In 2003 there were 35 deaths due to meningococcal disease giving a crude case fatality rate of 6.4 per cent. The breakdown of deaths by jurisdiction and serogroup are shown in Table 21. The case fatality rate for infections with meningococcal group C (21/158, 13.3%) was more than three times higher than for meningococcal group B infections (11/289, 3.8%, Chi = 12.4, p<0.001).

Table 21. Deaths due to meningococcal infection by serogroups, Australia, 2003, by serogroup, and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Total
Serogroup B	0	6	1	0	4	0	0	0	11
Serogroup C	0	6	0	9	0	0	6	0	21
Other serogroups*	0	0	0	0	0	0	0	0	0
Unknown serogroup	0	2	0	1	0	0	0	0	3
Total	0	14	1	10	4	0	6	0	35

* Other includes serogroups A, Y and W135.

In response to community concerns about increases in meningococcal disease in Australia, the Commonwealth Government approved the National Meningococcal C vaccination program, which commenced in January 2003.³⁶

In 2003, examination of Neisseria meningitidis carriage in nasop haryngeal and tonsil swabs and saliva found a low prevalence of the meningococci in saliva and concluded that salivary contact is unlikely to transmit meningococcal disease.³⁷ The Communicable Diseases Network Australia is revising the Guidelines for th e early clinical and public health management of meningococcal disease in Australia to take into account these new findings.

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Laboratory-based meningococcal surveillance

The Australian Meningococcal Surveillance Programme was established in 1994 for the purpose of monitoring and analysing isolates of Neisseria meningitidis from cases of invasive meningococcal disease in Australia. The program is undertaken by a network of reference laboratories in each state and territory, using agreed standard methodology to determine the phenotype (serogroup, serotype and serosubtype) and the susceptibility of N. meningitidis to a core group of antibiotics. The results of the surveillance in 2003 have recently been published.³⁸

In 2003, a total of 303 isolates of N. meningitidis were analysed by the program, a decrease from the 393 isolates analysed in the previous year. Consistent with routine surveillance data, Serogroup B continues to be the predominant strain for the disease (183 isolates, 60.4%) nationally, followed by serogroup C (102 isolates, 33.6%). However, there was mix in the phenotypes circulating in the different states and territories. Serogroup B strains predominated in all jurisdictions except the Australian Capital Territory where all isolates were serogroup C, and Tasmania and Victoria where equal numbers of serogroup B and C were isolated.

The pattern of age distribution for meningococcal infection varied by the phenotype. Serogroup B was more frequently reported in the 0–4 age group (42.5%), while the largest proportion of serogroup C occurred in the 15–19 age group (20.6%).

In 2003, about two-thirds of all the isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06 to 0.5 mg/L). All isolates tested were susceptible to third generation cephalosporins and ciprofloxacin. Two isolates were resistant to the prophylactic antibiotic, rifampicin.

Tuberculosis

While Australia has one of the lowest rates of tuberculosis in the world, the disease remains a public health problem in the overseas-born and Indigenous communities. In 2003, 944 tuberculosis (TB) notifications were received by NNDSS, a rate of 4.7 cases per 100,000 population; a similar number and rate to 2002. The notification rates of TB were lower than the national average in Queensland, South Australia, Tasmania and Western Australia, as in previous years. The highest rate was reported in the Northern Territory (14.6 cases per 100,000 population).

In 2003, the male to female ratio was 1.1:1. TB cases occurred in all age groups, with the highest age-specific rates reported in the 80–84 year age group (12.0 cases per 100,000 population). The highest incidence was reported in people born overseas (19.9 cases per 100,000 population) and Indigenous Australians (8.5 cases per 100,000 population). By contrast the rate in the non-Indigenous Australian-born population was 0.9 cases per 100,000 population (Figure 64).

Figure 64. Trends in tuberculosis notification rates, Australia, 1991 to 2003, by Indigenous status and country of birth

Detailed analyses of tuberculosis in Australia have recently been published.³⁹

 

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.