Results, continued

Zoonoses

Zoonoses are 'those diseases and infection which are naturally transmitted between vertebrate animals and man'.⁵⁸ Approximately 60%–70% of emerging human infectious diseases are zoonoses^59,60 and more than 70% of emerging zoonoses originate from wildlife.⁵⁹ An emerging zoonosis is defined by WHO as 'a zoonosis that is newly recognised or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range'.⁶¹

In 2007, zoonotic diseases notifiable to NNDSS were anthrax, Australian bat lyssaviral or lyssaviral (unspecified) infection, brucellosis, leptospirosis, ornithosis, Q fever, and tularaemia. During 2007, 687 notifications of zoonotic disease (0.5% of total notifications) were made to NNDSS. Queensland accounted for 40% (278 cases) of the zoonotic diseases. Notification numbers were generally higher in males (72%, 497 cases). Notifications of cases aged less than 15 years accounted for 4%, (27 cases) of all notifications. There were no cases of tularaemia reported to NNDSS during 2007.

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Anthrax

Anthrax is primarily a disease of herbivores; humans and carnivores are incidental hosts.¹⁷ Anthrax has a low prevalence in animals, and occurs only sporadically in Australia.⁶² It can be an occupational hazard for veterinarians, and agriculture and wildlife workers who handle infected animals.

One case of cutaneous anthrax was reported to NNDSS in 2007. The case was a male knackery worker from northern Victoria, and who had contact with 2 cattle that were subsequently confirmed to have died of anthrax.⁶³ Over the previous 10 years, only 2 other human cases of anthrax had been reported in Australia, both the cutaneous form, in 1998 and 2006 respectively.^{19, 64} Australia has never recorded a human case of inhalational or gastrointestinal anthrax.

In 2007, 13 outbreaks of anthrax were reported in livestock. Twelve outbreaks occurred in New South Wales, where cases have been known to occur in the past, and one in Central Victoria. In all cases, properties were subject to the recommended protocol of quarantine, carcass incineration, site disinfection and vaccination of in-contact animals. All movements from affected properties were traced to ensure that relevant product did not enter the export and domestic food production chains.⁶²

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Australian bat lyssaviral and lyssaviral (unspecified) infections

No cases of either Australian bat lyssaviral or lyssaviral (unspecified) infections were notified during 2007. Previously, 2 known cases of human infection with Australian bat lyssavirus were fatal and occurred in 1996 and 1998 following close contact with an infected bat.¹⁹

Surveillance indicates Australian bat lyssavirus infection is and may have been present in Australian bats 15 years prior to its first detection. Sick and injured bats (opportunistic specimens) and change in seasonality and bat ecology pose an increased public health risk.⁶⁵

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Brucellosis

Brucellosis is mainly an occupational disease for farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.¹⁷

Several Brucella species can infect both animals and humans. Infections that can cause illness in humans include Brucella melitensis from sheep and goats, Brucella suis from pigs and Brucella abortus from cattle.

In 2007, 38 cases of brucellosis were reported to NNDSS; a national notification rate of 0.2 cases per 100,000 population. Cases were from Queensland (30 cases), New South Wales (4 cases) and 1 case each from South Australia, Victoria, Tasmania and Western Australia. There was little change in the number of notifications of brucellosis over the last 6 years (Figure 57). In Australia, the notification rate for brucellosis in 2007 was lower than in 2006 (0.28 and 0.24, respectively). The highest notification rate of 53 cases per 100,000 population was reported from the Central West Statistical Division of Queensland. The majority of cases were male (n=28) and aged between 20 and 54 years (n=34).

Figure 57: Notifications of brucellosis, Australia, 2002 to 2007, by month and year of onset

Species data were available for 39% of notifications (n=15). Of these, nine were B. suis (all from Queensland), and 4 cases were B. melitensis (a single case in Queensland, Tasmania, Victoria, Western Australia). Each of the notified cases of B. melitensis were reported to have had recent history of overseas travel. A single case of B. abortus (South Australia) was notified to NNDSS. This case had a recent history of overseas travel to Iraq and reported eating numerous unpasteurised milk products.

Bovine brucellosis (B. abortus) was eradicated from the Australian cattle herd in 1989 and is presently considered an exotic animal disease in Australia.⁶² Caprine and ovine brucellosis (caused by B. melitensis) has never been reported in Australian sheep or goats.⁶² Swine brucellosis (caused by B. suis) is confined to small areas of northern Australia, where it occurs in feral pigs, with human cases predominantly seen in recreational feral pig hunters.^62,66

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Leptospirosis

Leptospirosis is caused by spirochaetes of the genus, Leptospira, which is found in the renal tubules of wild and domestic animals. In affected areas, where there is exposure to infected urine of domestic and wild animals, this disease can be an occupational and recreational hazard.¹⁷

Between 2002 and 2006 (Figure 58), annual leptospirosis notifications ranged from 126 (2003) to 177 (2004), with 106 notifications in 2007 (0.5 cases per 100,000 population). Cases were reported in all jurisdictions except the Australian Capital Territory.

Figure 58: Notifications of leptospirosis, Australia, 2002 to 2007, by month and year of onset

In 2007, the majority of notifications were from Queensland (75 notifications, 1.8 cases per 100,000 population). Ninety per cent of leptospirosis cases were male (n=95) and the majority of cases were aged between 15 and 54 years (n=84). The highest notification rate of 21 cases per 100,000 population was reported from the Far North Statistical Division of Queensland.

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Ornithosis

Ornithosis is caused by Chlamydia psittaci and is transmitted to humans by exposure to waterfowl, seabirds, shore birds, pigeons and doves and many psittacine birds. Birds can become carriers of the disease without becoming infected. The mode of transmission to humans is by inhaling bacteria usually from contaminated dried faeces, nasal or eye secretions and dust from infected birds.¹⁷ Human to human transmission is rare.

In 2007, there were 92 ornithosis infections notified to NNDSS, giving a national rate of 0.4 cases per 100,000 population. In Australia, the notification rate for ornithosis in 2007 was lower than in 2006 (0.4 and 0.8, respectively). Between 2002 and 2006, the annual number of ornithosis notifications ranged from 239 (2004) to 164 (2005) (Figure 59).

Figure 59: Notifications of ornithosis, Australia, 2002 to 2007, by month and year of diagnosis

Victoria had the highest number of notifications (50 notifications, 1.4 cases per 100,000 population). Notifications were also received from New South Wales (34 cases), Western Australia (3 cases), South Australia (2 cases), Queensland (2 cases), and Tasmania (1 case). The majority of cases were male (n=59, 64%). All cases were aged 15 years or older and 78% of cases were 40 years or over (Figure 60).

Figure 60: Notification rate for ornithosis, Australia, 2007, by age group and sex

At risk groups of people contracting ornithosis include bird owners, pet shop employees, veterinarians, poultry-processing workers, zoo workers and taxidermists. Older adults and pregnant women may have a more severe illness.⁶⁷ An outbreak in the Blue Mountains in June 2002 was novel in that infections were predominantly associated with wild birds, rather than with pet birds and aviaries as generally reported in the scientific literature.⁶⁸ The risk factors for the cases of ornithosis notified in 2007 is unknown.

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Q fever

Q fever is caused by Coxiella burnetii. Primary reservoirs of these bacteria are cattle, sheep and goats. The organisms are resistant to heat, drying and many common disinfectants, which enables the bacteria to survive for long periods in the environment. The mode of transmission to humans is commonly through the airborne route in dust, but it can also occur though direct contact with infected animals and other contaminated material. Humans are often very susceptible to the disease, and very few organisms may be required to cause infection. Person-to-person transmission is rare.¹⁷

In 2007, 450 cases of Q fever were notified to NNDSS, representing a national rate of 2.1 cases per 100,000 population (Figure 61). Between 1991 and 2001, and prior to the introduction of the National Q Fever Management Program, Q fever notification rates ranged between 2.5 cases per 100,000 population and 4.9 cases per 100,000 population. In Australia, the notification rate for Q fever in 2007 was similar to 2006 (2.1 and 2.10, respectively). Between 2002 and 2006, the annual number of Q fever notifications ranged from 795 (2002) to 353 (2005).

Figure 61: Notification rate for Q fever, Australia, New South Wales and Queensland, 1991 to 2007

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The highest rates of notifications were from Queensland (171 notifications, 4.1 cases per 100,000 population) and New South Wales (215 notifications, 3.2 cases per 100,000 population). The highest notification rate of 88 cases per 100,000 population was reported from the South West Statistical Division of Queensland (Map 11).

Map 11: Notification rates for Q fever, Australia, 2007, by Statistical Division of residence and Statistical Subdivision for the Northern Territory

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The highest age specific rates (Figure 62) of Q fever were in the 45–49 years age group for males (44 cases, 5.8 cases per 100,000 population), and in the 50–54 years age groups for females (1.8 cases per 100,000 population). There were 19 cases reported in people aged less than 15 years. Seventy per cent of cases were male (314 cases).

Figure 62: Notification rate for Q fever, Australia, 2007, by age group and sex

The National Q Fever Management Program commenced in July 2001. The program provided funding for free vaccine for people at risk of Q fever from their work environment.⁶⁹ Production of the Q fever vaccine in Australia ceased at the end of 2005.⁷⁰ At the end of 2006, the Australian Ministers for Health and Agriculture announced funding for CSL Limited to recommence production of the Q fever vaccine.⁷⁰ Vaccine from the new facility will commence in 2009. Adults at risk, including abattoir workers, farmers, veterinarians, stockyard workers, shearers, animal transporters and many others exposed to cattle, sheep or goats or their products should be considered for vaccination. The vaccine is not recommended for children under 15 years of age.¹³