This article {extract} was published in Communicable Diseases Intelligence Vol 34 No 3 September 2010 and may be downloaded as a full version PDF from the Table of contents page.
Results, continued
Zoonoses
Zoonoses are 'those diseases and infections which are naturally transmitted between vertebrate animals and man'.60 Approximately 60%–70% of emerging human infectious diseases are zoonoses61,62 and more than 70% of emerging zoonoses originate from wildlife.61 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'.63
The zoonoses notifiable to the NNDSS included in this chapter are anthrax, Australian bat lyssavirus (ABL) or lyssavirus (NEC) infection, brucellosis, leptospirosis, ornithosis, Q fever, and tularaemia. During 2008, 633 notifications of these zoonotic diseases were made to the NNDSS, of which Queensland accounted for 47% (296 notifications) and New South Wales accounted for 35% (224 notifications. Notifications were generally higher in males (72%, 453 notifications). There were only 20 notifications (3%) in cases aged less than 15 years and 27 notifications (4%) in cases over the age of 70 years.
Several zoonoses notifiable to the NNDSS are included under other headings in this report. A zoonotic infection can be acquired directly from an animal or indirectly via an insect vector, the environment or contaminated food. For example, Salmonella and Campylobacter infections are typically acquired from contaminated food and are listed under the gastrointestinal diseases section.
Anthrax
Anthrax is primarily a disease of herbivores; humans and carnivores are incidental hosts.17 Anthrax has a low incidence in animals, and occurs only sporadically in Australia.64 It can be an occupational hazard for veterinarians, and agriculture, wildlife and industry livestock workers who handle infected animals or by-products.
No cases of anthrax were reported to NNDSS in 2008. Over the previous 10 years, only 3 human cases of anthrax have been reported in Australia, all which were the cutaneous form, in 1998, 2006 and 2007.65–67 Australia has never recorded a human case of inhalational or gastrointestinal anthrax.
In 2008, 12 outbreaks of anthrax were reported in livestock. Ten outbreaks occurred in New South Wales, where cases have been known to occur in the past, and two in northern Victoria. In all instances, 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 chains. During 2008, an 'animal side' immunochromatographic test was used as a rapid anthrax screening test to investigate sudden ruminant deaths. The results of this testing were consistent with confirmatory blood cultures and will continued to be used in Victoria.64
Australian bat lyssavirus and lyssavirus (NEC) infections
No cases of either ABL or lyssavirus (NEC) infections were notified during 2008. Only 2 known cases of ABL infection in humans have been reported in Australia, in 1996 and 1998. Both cases occurred after close contact with an infected bat and both cases were fatal.21
Surveillance indicates ABL is and may have been present in Australian bats for at least 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.68 However, bat testing conducted by the Australian Wildlife Health Network between January and December 2008 yielded no ABL detections compared with 8 detections in bats during 2007.69
Brucellosis
Brucellosis is mainly an occupational disease for farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.70 However, the most common source of human infection in Australia is from infected feral pigs and inadequate measures by feral pig hunters to prevent brucellosis infection.71
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 2008, 48 cases of brucellosis were reported to the NNDSS; a national notification rate of 0.2 per 100,000 population. Queensland reported 46 cases, with New South Wales reporting the remaining 2 cases. There has been little change in the number of notifications of brucellosis over the last 6 years (Figure 64). The national notification rate for brucellosis was the same in 2008 as in 2007. The majority of cases were male (38) and aged between 15 and 49 years (40).
Figure 64: Notifications of brucellosis, Australia, 2003 to 2008, by month and year of diagnosis
Species data were available for 14% of notifications (7) and all of these were B. suis (all from Queensland).
Bovine brucellosis (B. abortus) was eradicated from the Australian cattle herd in 1989 and is presently considered an exotic animal disease in Australia.64 Caprine and ovine brucellosis (caused by B. melitensis) have never been reported in Australian sheep or goats. 64 Swine brucellosis (caused by B. suis) is confined to small areas of Queensland, where it occurs in feral pigs, with human cases predominantly seen in recreational feral pig hunters.64,71 Swine brucellosis was not detected in any of Queensland's domestic piggeries during 2008.64
Leptospirosis
Leptospirosis is caused by spirochaetes of the genus, Leptospira, which are 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 (such as swimming or wading in contaminated water).17
Between 2003 and 2008 leptospirosis notifications ranged annually from 108 (2007) to 177 (2004), with 112 notifications in 2008 (0.5 per 100,000 population). Cases were reported in all jurisdictions except for the Australian Capital Territory, South Australia and Tasmania (Figure 65). In 2008, the majority of notifications were from Queensland (89 notifications, 2.1 per 100,000 population). Ninety-two per cent of leptospirosis cases were male (103 notifications) and 58% of all cases were aged between 20 and 39 years (65 notifications).
Figure 65: Notifications of leptospirosis, Australia, 2003 to 2008, by month and year of onset
The WHO/FAO/OIE Collaborating centre for reference and research on leptospirosis provides an annual surveillance report of leptospirosis cases in 2008. The most frequently identified leptospirosis serovars in 2008 were Arborea, Zanoni and Hardjo. Serovar Arborea was the most frequently reported during 2008, accounting for 24 (21%) of all notifications and was an increase from 8 (8%) notifications in 2007.72
Ornithosis
Ornithosis is caused by infection with the bacteria 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 Person-to-person transmission is rare.
In 2008, there were 103 ornithosis infections notified to NNDSS, corresponding to a national rate of 0.5 per 100,000 population. This was similar to the 2007 rate of 0.4 per 100.000 population. Between 2003 and 2008, the annual number of ornithosis notifications ranged from 239 (2004) to 93 (2007) (Figure 66).
Figure 66: Notifications of ornithosis, Australia, 2003 to 2008, by month and year of diagnosis
Victoria had the highest number of notifications (53 notifications, 1.0 per 100,000 population). Notifications were also received from New South Wales (41 cases), Western Australia (6 cases) and Queensland (3 cases). Forty-seven per cent of the notifications in 2008 were male (48 notifications) compared to 2007 where the majority of cases were male (64%). All cases were aged 10 years or over and 83% of cases were aged 40 years or over (Figure 67).
Figure 67: Notifications of ornithosis, Australia 2008, by age group and sex
People at risk of 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.73
Q fever
Q fever is caused by infection with the bacteria, Coxiella burnetii. Primary reservoirs of these bacteria are cattle, sheep and goats. These 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 most commonly by the airborne route through inhalation of contaminated 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 2008, 370 cases of Q fever were notified to the NNDSS, corresponding to a national rate of 1.7 per 100,000 population (Figure 68). Between 1991 and 2001, and prior to the introduction of the National Q Fever Management Program, Q fever notification rates ranged between 2.5 per 100,000 population and 4.9 per 100,000 population. The national notification rate for Q fever was lower in 2008 than in 2007 (1.7 and 2.1, respectively). Between 2003 and 2008, the annual number of Q fever notifications ranged from 560 (2003) to 351 (2005).
Figure 68: Notification rate for Q fever, Australia, New South Wales and Queensland, 1991 to 2008
The highest notification rates were from Queensland (158 notifications, 3.7 per 100,000 population) and New South Wales (164 notifications, 2.3 per 100,000 population). On a regional basis, the South West Statistical Division of Queensland had the highest notification rate of 84 per 100,000 population (Map 4).
The highest age specific rates of Q fever for males was in the 55–59 year age group (32 notifications, 5.0 per 100,000 population), and for females in the 60–64 year age group (2.1 per 100,000 population) (Figure 69). There were 11 notifications aged less than 15 years and 71% of notifications were male (264 cases).
Map 4: Notification rates for Q fever in Queensland, New South Wales and Victoria, by Statistical Division of residence
* Numbers shown in the Statistical Divisions represent the count of notifications.
Notification rates in geographic areas where estimated residential population and case numbers are small should be interpreted with caution.
Figure 69: Notification rate for Q fever, Australia, 2008, by age group and sex
Adults at risk of Q fever infection, including abattoir workers, farmers, veterinarians, stockyard workers, shearers and animal transporters should be considered for vaccination. The administration of the Q fever vaccine requires a pre-vaccination screening test to exclude those recipients with a previous (unrecognised) exposure to the organism. A Q fever vaccine may cause an adverse reaction in a person who has already been exposed to the bacterium. Vaccine is not recommended for children under 15 years of age.11
Tularaemia
Tularaemia is caused by infection with the bacteria Francisella tularaensis. The most common modes of transmission are through arthropod bites, handling infected animals, inhalation of infectious aerosols or exposure to contaminated food or water. Small mammals such as rodents, rabbits and hares are often the reservoir host.74
There were no notifications of tularaemia in 2008, and there has never been a case notified in Australia.
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This issue - Vol 34 No 3, September 2010
NNDSS Annual report 2008
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