Results - Part 7

Zoonoses

Overview

Zoonoses are those infectious diseases that are naturally transmitted between vertebrate animals and humans.¹³² Approximately 60% to 70% of emerging human infectious diseases are zoonoses^133–135 and more than 70% of emerging zoonoses originate from wildlife.¹³⁴ 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”.¹³⁶

The zoonoses notifiable to the NNDSS included in this chapter are: anthrax, Australian bat lyssavirus (ABLV) or lyssavirus (unspecified) infection, brucellosis, leptospirosis, ornithosis, Q fever, and tularaemia.

Several zoonoses notifiable to the NNDSS are included under other headings in this report. For example, salmonellosis and campylobacteriosis are typically acquired from contaminated food and are listed under the gastrointestinal diseases section. Rabies is listed under Quarantinable diseases.

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Anthrax

Anthrax is caused by the bacterium Bacillus anthracis and most frequently causes cutaneous infection. However, it can also cause gastrointestinal and respiratory infections. Anthrax is primarily a disease of herbivores; humans and carnivores are incidental hosts. It can be an occupational hazard for veterinarians, and agriculture, wildlife and livestock workers who handle infected animals or by-products.

In Australia, the areas of anthrax risk are well defined and include the northern and north-eastern districts of Victoria and central New South Wales.¹³⁷ Anthrax occurs only sporadically in livestock in the at-risk areas. Rare or isolated incidents or cases in animals have historically occurred in Queensland, South Australia, Tasmania and Western Australia.¹³⁷

Epidemiological situation in 2014

In 2014, there were no notified cases of anthrax in Australia. Over the previous 10 years, only 3 human cases of anthrax were reported in Australia in 2006, 2007 and 2010.^138–140 All had domestic farm or animal related exposures and all were cutaneous anthrax. Australia has never recorded a human case of inhalational or gastrointestinal anthrax.

There was 1 anthrax incident reported in livestock in Australia in 2014. It occurred on a property located within the known New South Wales anthrax endemic area.¹³⁷

Australian bat lyssavirus and lyssavirus (unspecified)

ABLV belongs to the genus lyssavirus, which also includes the rabies virus. Both invariably result in progressive, fatal encephalomyelitis in humans.¹⁴¹ ABLV was first identified in Australia in 1996^142,143 and is present in several Australian species of bats (including flying foxes and microbats). Australia is free of terrestrial rabies.

The best way to prevent ABLV infection is to avoid contact with bats. For people whose occupation (including volunteer work) or recreational activities place them at increased risk of being exposed to ABLV, rabies virus vaccine is effective in preventing infection. Pre-exposure vaccination with rabies virus vaccine is recommended for bat handlers, veterinarians and laboratory personnel working with live lyssaviruses.¹⁴⁴ Post-exposure prophylaxis for ABLV consists of wound care and administration of a combination of rabies virus vaccine and human rabies virus immunoglobulin, depending on exposure category and prior vaccination or antibody status.^32,144

Epidemiological situation in 2014

In 2014 there were no notified cases of ABLV or lyssavirus (unspecified) infection in Australia.

There have been 3 cases of ABLV infection recognised in humans in Australia, with single cases notified in each of 1996, 1998 and 2013. All 3 cases occurred following close contact with an infected bat in Queensland and all were fatal.^145–147 In 2013, the Queensland Department of Agriculture, Fisheries and Forestry confirmed the first known equine cases of ABLV infection in 2 horses on a Queensland property.^148,149

The bat health focus group of Wildlife Health Australia (formerly the Australian Wildlife Health Network) gathers and collates information from a range of organisations on opportunistic testing of bats for ABLV. In 2014 there were 32 ABLV detections in bats compared with 14 detections during 2013.¹⁵⁰

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Brucellosis

Brucellosis is characterised by a fever of variable duration with a range of other symptoms including headache, weakness, profuse sweating, chills, arthralgia, depression, weight loss and generalised aching.²² Brucella species that can cause illness in humans include Brucella melitensis acquired from sheep and goats, Brucella suis from pigs and Brucella abortus from cattle. B. abortus was eradicated from Australian cattle herds in 1989 and B. melitensis has never been reported in Australian sheep or goats.¹³⁷ Therefore, all 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 is known to occur in feral pigs. Eales et al (2010)¹⁵¹ found that feral pig hunting was the most common risk factor for brucellosis in Townsville during 1996 to 2009.

Internationally, brucellosis is mainly an occupational disease of farm workers, veterinarians, and abattoir workers who work with infected animals or their tissues.²²

Epidemiological situation in 2014

In 2014, there were 17 notified cases of brucellosis in Australia (0.1 per 100,000), representing a 37% decrease compared with the 5-year (2009 to 2013) mean (n=27).

Geographical distribution

Just under half of notified cases (47%, 8) were Queensland residents (Figure 94), with a state-specific notification rate of 0.2 per 100,000 and since 1991, 82% of notifications have been Queensland residents.

Figure 94: Notifications of brucellosis, Australia, 2009 to 2014, by month and year of diagnosis and state or territory

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The species of the infecting organism was available for 71% (12/17) of notified cases in 2014. There were 3 cases of B. suis, all from Queensland, and all males aged between 30 and 46 years. There were 9 cases of B. melitensis, with the countries of acquisition listed as India (n=4), Iraq (n=2), Lebanon (n=1), Pakistan (n=1) and Sudan (n=1). The 5 remaining cases where the infecting organism was not specified, were all acquired in Australia.

Age and sex distribution

The majority of notified cases (76%, 13/17) were aged between 25 and 49 years (Figure 95). In 2014, the median age of notified brucellosis cases was 34 years (range 3 to 66 years) and 82% (14) were male.

Figure 95: Notifications of brucellosis, Australia, 2014, by age group and sex

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Leptospirosis

Leptospirosis can cause a variety of illnesses varying in severity from a mild influenza-like illness to Weil’s syndrome, meningitis or pulmonary haemorrhage with respiratory failure possibly leading to death.²² 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 in certain agricultural sectors and swimming or wading in contaminated water).^152,153 The last reported death in Australia attributed to leptospirosis was in 2002.¹⁵⁴

Epidemiological situation in 2014

In 2014, there were 88 notified cases of leptospirosis in Australia (0.4 per 100,000), which was a 36% decrease compared with the 5-year mean (2009 to 2013) (n=138).

Geographical distribution

Over two-thirds (67%, 59) of notified cases were Queensland residents (Figure 96), with a state-specific notification rate of 1.2 per 100,000.

Figure 96: Notifications of leptospirosis, Australia, 2009 to 2014, by month and year of diagnosis and state or territory

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Age and sex distribution

The highest counts were observed in males in the 25–29 years age group (n=17) (Figure 97). In 2014, the median age of notified leptospirosis cases was 40 years (range 13 to 78 years) and 82% (72) were male.

Figure 97: Notifications of leptospirosis, Australia, 2014, by age group and sex

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Microbiological trends

The WHO/Food and Agriculture Organization/World Organisation for Animal Health Collaborating Centre for Reference and Research on Leptospirosis (Leptospirosis Reference Laboratory, Queensland) routinely conducts PCR-based serotyping for leptospirosis cases from Queensland (from whence the majority of cases are reported), and collates national data that may be submitted to the laboratory from other states or territories. At the time of compiling this report, data for 2014 were not publicly available.

In Australia, serotyping is only conducted on pathogenic Leptospira species of which typing information was available for 72% (56/78) of these cases. The most frequently reported serovars were L. interrogans serovar Zanoni (23%, n=18), L. borgpetersenii serovar Arborea (15%, n=12) and L. interrogans serovar Australis (15%, n=12). In 2013, L. interrogans serovar Arborea was the most frequently reported serovar (13/78).

Ornithosis

Ornithosis (or psittacosis) is a pneumonia-like illness caused by infection with the bacterium Chlamydophila psittaci.²² It is transmitted to humans primarily from infected psittacines, but transmission to humans has also been known to occur from poultry and a range of other birds.¹⁵⁵ Transmission to humans occurs via the inhalation of contaminated dried faeces, nasal or eye secretions and dust from the feathers. Individuals at risk of contracting ornithosis include bird owners and those with occupational exposure to birds.¹⁵⁶

Epidemiological situation in 2014

In 2014 there were 41 notified cases of ornithosis in Australia (0.2 per 100,000), which was a 34% decrease compared with the 5-year mean (2009 to 2013) (n=62).

Geographical distribution

Similar to previous years, more than half of the 2014 notifications were Victorian residents (51%, 21) (Figure 98).

Figure 98: Notifications of ornithosis, Australia, 2009 to 2014, by month and year of diagnosis and state or territory

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Age and sex distribution

In 2014, the median age of ornithosis notifications was 53 years (range 11 to 80 years) and 56% (23) were female (Figure 99).

Figure 99: Notifications of ornithosis, Australia, 2014, by age group and sex

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Q fever

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.¹⁵⁷ 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.¹⁵⁸ Prior to the commencement of vaccination programs in Australia, approximately half of all cases in New South Wales, Queensland and Victoria were among abattoir workers.^159,160

The Australian Government funded the National Q Fever Management Program (NQFMP) between 2001 and 2006 for states and territories to provide free vaccine to at-risk occupational groups (such as abattoir workers).¹⁶¹

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 (possibly unrecognised) exposure to the organism, including previous vaccination. A Q fever vaccine may cause an adverse reaction in a person who has already been exposed to the bacterium. Vaccination is not recommended for children under 15 years of age or pregnant females.³²

Epidemiological situation in 2014

In 2014, there were 469 notified cases of Q fever in Australia (2.0 per 100,000), which was a 26% increase compared with the 5-year mean (2009 to 2013) (n=373).

Geographical distribution

Between 1991 and 2001, and prior to the introduction of the NQFMP, Q fever notification rates ranged between 2.5 and 4.9 cases per 100,000.¹⁶¹ In 2014, the highest notification rate was in Queensland (5.1 per 100,000, n=240). Cases were reported in all jurisdictions except Tasmania (Figure 100).

Figure 100: Notifications of Q fever, Australia, 2009 to 2014, by month and year of diagnosis and state or territory

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‘Hot spots’ for Q fever occur in central Queensland and in the areas that border Queensland and New South Wales, with rates in those areas reaching as high as 142.2 per 100,000 (Figure 101).

Figure 101: Notification rate for Q fever, Australia, 2014, by Statistical Area Level 3

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Age and sex distribution

The median age of Q fever cases was 46 years (range 5 to 87 years) and 75% (352) were male. Almost a third (30%, 143) of notified cases were males aged between 40 to 59 years (Figure 102). This was consistent with a report that found higher rates of Q fever in men aged 50 to 59 years, and that agriculture-related occupations (including farming) are the most commonly reported occupation.¹⁵⁸

Figure 102: Notifications of Q fever, Australia, 2014, by age group and sex

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Tularaemia

Tularaemia is a non-specific disease with diverse manifestations, often with an influenza-like onset, caused by infection with the bacterium Francisella tularensis.²² 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.¹⁶²

Epidemiological situation in 2014

In 2014, there were no notified cases of tularaemia in Australia. Tularaemia was last notified in 2011, with 2 cases in Tasmanian residents. This was the first time that F. tularensis type B had been detected in the Southern Hemisphere.^163–165

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