This extract of the NNDSS annual report 2010 was published in Communicable Diseases Intelligence Vol 36 No 1 March 2012. A print friendly full version may be downloaded as a PDF 1862 KB.
Zoonoses are ‘those diseases and infections which are naturally transmitted between vertebrate animals and man’.68 Approximately 60%–70% of emerging human infectious diseases are zoonoses69,70 and more than 70% of emerging zoonoses originate from wildlife.69 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’.71
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 2010, 532 notified cases of these zoonotic diseases were reported to the NNDSS. Queensland accounted for 47% (n = 251) and New South Wales 33% (n = 173) of notified cases. Notifications were generally more frequent amongst males (77%, n = 412). There were only 5 notified cases (< 1%) of zoonotic disease in persons aged less than 15 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.16 Anthrax has a low incidence in animals, and occurs only sporadically in Australia.72 It can be an occupational hazard for veterinarians, and agriculture, wildlife and industry livestock workers who handle infected animals or animal by-products.
One case of anthrax was reported to NNDSS in 2010. The case occurred in New South Wales in February 2010. Over the previous 10 years, only 2 human cases of anthrax were reported in Australia. Both cases were cutaneous anthrax and were reported in 2006 and 2007.73,74 Australia has never recorded a human case of inhalational or gastrointestinal anthrax.
In 2010, 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.
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.75 No notified cases of either Australian bat lyssavirus infection (ABL), rabies or lyssavirus (unspecified) infections were reported to the NNDSS during 2010. 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.76,77 Surveillance indicates that ABL 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.78 Testing of bats conducted by the Australian Wildlife Health Network between January and June 2010 yielded 4 ABL detections compared with 12 detections in bats during 2009.79
Several Brucella species can infect both animals and humans including Brucella melitensis from sheep and goats, Brucella suis from pigs and Brucella abortus from cattle. B. abortus was eradicated from Australian cattle herds in 198972 and B. melitensis has never been reported in Australian sheep or goats.72 All human cases of B. melitensis or B. abortus in Australia are related to overseas travel. B. suis is confined to some areas of Queensland, where it occurs in feral pigs.
Internationally, brucellosis is mainly an occupational disease of farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.16 In Australia, 83% of cases since 1991 have been reported from Queensland, where feral pig hunting is the most common risk factor for infection.80
In 2010, there were 21 notified cases of brucellosis reported to the NNDSS; a 49% decline in notifications compared with the 5-year average of 41 cases (Figure 61). Seventy-six per cent of notifications were from Queensland (n = 16). Most cases were in males (81%, n = 17) aged between 15 and 49 years (85%, n = 18).
Figure 61: Notified cases of brucellosis, Australia, 2005 to 2010, by month and year and state or territory*
* There have been no cases reported from the Australian Capital Territory.
The species of the infecting organism was available for 38% of notifications (n = 8), of which seven were B. suis (all from Queensland, and all in males aged between 27 and 43 years). There was 1 imported case of B. melitensis, which was acquired in Iraq.
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 certain agricultural sectors and swimming or wading in contaminated water).16
Figure 62: Notified cases of leptospirosis, Australia, 2005 to 2010, by month and year and state or territory
Figure 63: Notified cases of leptospirosis, Australia, 2010, by age group and sex
In 2010, there were 131 notified cases of leptospirosis reported; giving a rate of 0.6 per 100,000 population compared with the 5-year mean of 128.0 notifications. Cases were reported in all jurisdictions, but Queensland accounted for 64% (n = 84) of notifications (Figure 62). Eighty-seven per cent (n = 127) of leptospirosis cases were male and 82% (n = 120) of all cases were aged between 15 and 54 years (Figure 63).
The WHO/FAO/OIE Collaborating Centre for Reference and Research on Leptospirosis provides an annual surveillance report of leptospirosis cases that are sent for typing. In 2010, the reference centre typed 94 cases of leptospirosis. The most frequently identified serovars were Arborea (21% n = 20, Australis (16%, n = 15), Zanoni (15%, n = 14), and Hardjo (15%, n = 14).81 In 2009, Serovar Arborea was the most frequently reported serovar, accounting for 29% of all notifications.82 The last reported death in Australia attributed to leptospriosis was in 2002.
Ornithosis (or psittacosis) 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 species of parrot. 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.16 Person-to-person transmission is rare.
In 2010, there were 56 notified cases of ornithosis reported; giving a rate of 0.3 per 100,000 population. The number of ornithosis notifications has declined steadily in recent years (Figure 64), and case numbers in 2010 are the lowest since 2001.
Figure 64: Notified cases of ornithosis, Australia, 2005 to 2010, by month and year and state or territory
Notifications were from all states and territories except the Northern Territory, but the majority of notifications were from Victoria (64%, n = 36). This represents a change from the previous 5 years, where the majority of cases were from New South Wales (53%, 312/589). Sixty-six per cent of cases in 2010 were male (39 cases). All cases were aged 20 years or older and 83% were aged 40 years or older. Cases of ornithosis over the previous 5 years have been mainly in adults, with a median age of 54 years (Figure 65).
Figure 65: Notified cases of ornithosis, Australia, 2005 to 2010, by age group and sex
Individuals 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.83
Q fever is caused by infection with the bacterium, Coxiella burnetii. The primary reservoirs of these bacteria are cattle, sheep and goats. C. burnetii is resistant to environmental conditions and many common disinfectants.16 Q fever is most commonly transmitted via the airborne route, where the organism is carried in dust contaminated with tissue, birth fluids or excreta from infected animals.84 It can also occur through 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. Prior to vaccination programs in Australia, approximately half of all cases in New South Wales, Queensland and Victoria were amongst abattoir workers.16,85,86 The Australian Government previously funded the National Q Fever Management Program between 2001 and 2006 for states and territories to provide free vaccine to at risk groups (such as abattoir workers). The Australian Government has secured the supply of vaccine through to 2016.
In 2010, there were 323 notified cases of Q fever reported to the NNDSS; a rate of 1.4 per 100,000 population. Between 1991 and 2001, and prior to the introduction of the National Q Fever Management Program, Q fever notification rates ranged between 2.5 and 4.9 per 100,000 population (Figure 66).
Figure 66: Notified cases of Q fever, Australia, by year
In 2010, the highest notification rates were from Queensland (151; 3.3 per 100,000 population) and New South Wales (136; 1.9 per 100,000 population). Cases also occurred in Victoria (n = 16), South Australia (10 cases) and Western Australia (n = 8). There was 1 case each in the Australian Capital Territory and the Northern Territory.
Between 1991 and 2010, Q fever cases have been most frequently reported amongst males aged between 20 and 59 years, and it is in these groups that are likely to be at highest risk of infection where the declines in notifications are most pronounced (Figure 67). Whilst the ending of drought conditions may have contributed to the decrease, it is likely that vaccination programs have been highly effective at preventing Q fever amongst those most at risk.
Figure 67: Notified cases of Q fever, Australia, by year, 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 pre-vaccination screening test to exclude those recipients with a previous (unrecognised) exposure to the organism. 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 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 notified cases of tularaemia in 2010, and no cases in any previous years.
This issue - Vol 36 No 1, March 2012
NNDSS Annual report 2010