This article was published in Communicable Diseases Intelligence Vol 35 Number 2, June 2011 and may be downloaded as a full version PDF file (1854 KB).
Zoonoses are ‘those diseases and infections which are naturally transmitted between vertebrate animals and man’.74 Approximately 60%–70% of emerging human infectious diseases are zoonoses75,76 and more than 70% of emerging zoonoses originate from wildlife.75 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’.77
The zoonoses notifiable to the NNDSS included in this chapter are anthrax, Australian bat lyssavirus or lyssavirus (unspecified) infection, brucellosis, leptospirosis, ornithosis, Q fever, and tularaemia. During 2009, 552 notifications of these zoonotic diseases were made to the NNDSS. Of these, Queensland accounted for 48% (263 notifications) and New South Wales 33% (183 notifications) of the zoonotic diseases. Notification numbers were generally higher in males (78%, 552 notifications). There were only 12 notifications (2%) of zoonotic disease cases aged less than 15 years and 19 notifications (3%) 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 is primarily a disease of herbivores; humans and carnivores are incidental hosts.21 Anthrax has a low incidence in animals, and occurs only sporadically in Australia.78 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 2009. Over the previous 10 years, only 2 human cases of anthrax were reported in Australia in 2006 and 2007,79,80 both of which were cutaneous anthrax. Australia has never recorded a human case of inhalational or gastrointestinal anthrax.
In 2009, 5 anthrax incidents were reported in livestock. Three occurred in New South Wales, where cases have been known to occur in the past, and two in north-eastern Victoria. In all instances, properties were subject to the recommended protocol of quarantine, disposal of carcasses, and vaccination and tracing of at-risk animals and their products. During 2009, an ‘animal side’ immunochromatographic test was used as a rapid anthrax screening test in Victoria to investigate sudden ruminant deaths. The results of this testing were consistent with confirmatory laboratory-based testing.78
Australian bat lyssavirus, rabies and lyssavirus (unspecified) infections
Classical rabies virus does not occur in Australia, although a related virus called Australian bat lyssavirus was identified in 1996 and is present in some Australian bats and flying foxes.81 No notifications of either Australian bat lyssavirus infection (ABL), rabies or lyssavirus (unspecified) infections were reported to the NNDSS during 2009.
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 were fatal.82,83 Surveillance indicates that ABL infection may have been present in Australian bats for at least 15 years prior to its first detection. Sick and injured bats and changes in bat ecology pose an increased public health risk.84 Bat testing conducted by the Australian Wildlife Health Network between January and December 2009 yielded 12 ABL detections compared with no detections in bats during 2008.85
Brucellosis is mainly an occupational disease for farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.21 However, the most common source of human infection in Queensland, which reported 69% of cases, is infected feral pigs and inadequate measures by feral pig hunters to prevent brucellosis infection.86
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 2009, 32 notifications of brucellosis were reported to the NNDSS; a national notification rate of 0.1 notifications per 100,000 population, compared with 0.2 notifications per 100,000 population in 2008. Queensland reported 22 notifications, with New South Wales reporting four, Victoria three, South Australia two, and Western Australia one. There has been little change in the number of notifications of brucellosis over the last 6 years (Figure 69). In 2009, the majority of notifications were male (27) and aged between 15 and 49 years (25) in 2009.
Figure 69: Notifications of brucellosis, selected jurisdictions, 2004 to 2009, by state or territory and month and year of diagnosis
Species data were available for 38% of notifications (12) of which eight were B. suis (all from Queensland). There were 4 imported cases of B. melitensis (Egypt, Saudi Arabia, Turkey and Kenya).
Bovine brucellosis (B. abortus) was eradicated from the Australian cattle herd in 1989 and is considered to be an exotic animal disease in Australia.78 Caprine and ovine brucellosis (caused by B. melitensis) has never been reported in Australian sheep or goats.78 Swine brucellosis (caused by B. suis) is confined to some areas of Queensland, where it occurs in feral pigs, with human cases predominantly seen in recreational feral pig hunters.86 Swine brucellosis was not detected in any of Queensland’s domestic piggeries during 2009.78
Leptospirosis is caused by spirochaetes of the genus, Leptospira, which is found in the genital tract and renal tubules of domestic and wild 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).21
Between 2004 and 2009 leptospirosis notifications ranged from 108 (2007) to 177 (2004) annually, with 146 notifications in 2009 (0.7 notifications per 100,000 population). Cases were reported in all jurisdictions except for South Australia and Tasmania (Figure 70). In 2009, the majority of notifications were from Queensland (110 notifications, 2.5 notifications per 100,000 population). Eighty-seven per cent of leptospirosis cases were male (127 notifications) and 82% of all cases were aged between 15 and 54 years (120 notifications).
Figure 70: Notifications of leptospirosis, Australia, 2004 to 2009 by state or territory and month and year of onset
The World Health Organization/Food and Agriculture Organization/World Organization of Animal Health Collaborating centre for reference and research on leptospirosis provided an annual surveillance report of leptospirosis cases in 2009. The most frequently identified leptospirosis serovars in 2009 were Arborea, Zanoni and Australis. Serovar Arborea was the most frequently reported during 2009, accounting for 29% (43) of all notifications and was a 79% increase on Arborea notifications reported in 2008 (24).87 The last reported death in Australia attributed to leptospirosis was reported in 2002.88
Ornithosis is caused by infection with the bacterium Chlamydophila 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 symptomatic. The mode of transmission to humans is by inhaling bacteria, usually from contaminated dried faeces, nasal or eye secretions and dust from infected birds.21 Person-to-person transmission is rare.
In 2009, 65 ornithosis infections were notified to NNDSS, giving a national rate of 0.3 notifications per 100,000 population. This was lower than the 2008 rate of 0.5 notifications per 100.000 population. Between 2004 and 2009, the annual number of ornithosis notifications has decreased from 239 to 65 respectively (Figure 71). The annual number of notifications in 2009 represents the lowest total number of ornithosis notifications since 2001.
Figure 71: Notifications of ornithosis, Australia (except Northern Territory), 2004 to 2009, by state or territory and month and year of diagnosis
Victoria had the highest number of notifications (38 notifications, 0.7 per 100,000 population). Notifications were also received from New South Wales (22), South Australia (3) and Western Australia (2). Sixty-five per cent of the notifications in 2009 were male (42 notifications) compared with 2008, where the minority of cases were male (47%). All notifications were aged 10 years or older and 75% of notifications were aged 40 years or over (Figure 72).
Figure 72: Notifications of ornithosis, Australia 2009, 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 experience a more severe illness.89
Q fever is caused by infection with the bacterium, Coxiella burnetii. Primary reservoirs of these bacteria are cattle, sheep and goats. These organisms are resistant to heat, drying and many common disinfectants, which enable 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. 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.21
In 2009, 309 notifications of Q fever were reported to the NNDSS, representing a national rate of 1.4 notifications per 100,000 population (Figure 73). Between 1991 and 2001, and prior to the introduction of the National Q Fever Management Program, Q fever notification rates ranged between 2.5–4.9 notifications per 100,000 population. The national notification rate for Q fever was lower in 2009 than in 2008 (1.4 and 1.8 notifications per 100,000 population, respectively). Between 2004 and 2009, the annual number of Q fever notifications ranged from 460 to 309 respectively.
Figure 73: Notification rate for Q fever, Australia, New South Wales and Queensland, 1991 to 2009
In 2009, the highest notification rates were from Queensland (131 notifications, 3.0 notifications per 100,000 population) and New South Wales (139 notifications, 2.0 notifications per 100,000 population). On a regional basis, the Central West Statistical Division of Queensland had the highest notification rate of 73 notifications per 100,000 population (Map 4). (Note: a small number of cases also occurred in South Australia, the Northern Territory, Victoria and Western Australia).
Map 4: Notification rates for Q fever in Queensland, New South Wales and Victoria, by Statistical Division of residence
Seventy-five per cent of notifications reported to the NNDSS were male (232). As in 2008, the highest age specific rates of Q fever for males was in the 55–59 years age group (32 notifications, 5.0 notifications per 100,000 population), and for females was in the 60–64 years age groups (2.1 notifications per 100,000 population). There were 4 notifications reported in people aged less than 15 years.
The Australian Government has facilitated the availability of the Q fever vaccine. 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 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.12
Tularaemia is caused by infection with the bacterium Francisella tularensis. 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.26
There were no notifications of tularaemia in 2009, and there has never been a case notified in Australia.]
This issue - Vol 35 No 2, June 2011
NNDSS Annual report 2009