Results, continued

Zoonoses

Zoonoses are diseases transmitted to humans from animals that are the primary host. The zoonotic diseases that were nationally notifiable in 2002 were anthrax, Australian bat lyssavirus or lyssavirus (unspecified) infection, brucellosis, leptospirosis, ornithosis and Q fever. A total of 1,155 notifications (1.1% of total notifications) were made during 2002. More detailed descriptions of these diseases were provided in the 2001 NNDSS annual report.¹⁴

Anthrax

Following the deliberate release of anthrax spores in the United States of America in 2001, anthrax became a notifiable disease in Australia. During 2002, no cases of anthrax were notified. The last human case of cutaneous anthrax in Australia, which occurred in a knackery worker, was reported in 1997.³⁶

Certain rural areas in New South Wales and Victoria are associated with recurring cases of anthrax in cattle and sheep. In these areas stock can be protected with vaccination. Despite this, a number of outbreaks of anthrax in livestock were reported during 2002. Three outbreaks involving sheep and cattle occurred in New South Wales, and two involved cattle in Queensland. Anthrax in stock in Queensland is considered rare, and these two outbreaks were the first recorded since 1993. Three sporadic cases in cattle occurred in northern Victoria.³⁷

Australian bat lyssavirus and lyssavirus (unspecified)

No cases of either Australian bat lyssavirus (ABL) or lyssavirus (unspecified) disease were notified during 2002. Two cases of infection with Australian bat lyssavirus, in 1996 and 1998, occurred following close contact between bat-handlers and infected bats. Both resulted in the death of the infected person.

Molecular biological research into the genetic sequences of lyssaviruses isolated from different groups of bats suggests that the virus has been associated with bats in Australia for more than 1,500 years.³⁸ That is, the virus was well established before European colonisation, and its recent 'emergence' is more to do with changes in human behaviour and encroachment on bat habitats.

The ABL virus was isolated from one bat in Queensland showing clinical signs. Other animal surveillance data released in 2002 indicated that the ABL virus is taxonomically and geographically more widespread in Australian microchiroptera than previously recognised.

A human case of the related European bat lyssavirus 2 (EBL-2) infection occurred in Scotland in late 2002. Because of the case's occupational exposure as a bat-handler, the link to a lyssavirus infection was able to be made. The man was admitted to hospital with an acutely progressing neurological illness, and died. This was the first human rabies-like infection to occur in the United Kingdom since 1902. There have been 630 human cases of European bat lyssavirus infections in Europe between 1977 and 2000 (ProMed 20021213.6054).

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Erratum - Commun Dis Intell 2006;30:221

An error has been noted in the section of the 2002 annual report of the National Notifiable Diseases Surveillance System for 2002 in the section on Australian bat lyssaviruses. The statement in the last sentence of this section is incorrect and should read: ‘There have been 630 bats detected with European bat lyssavirus in Europe between 1977 and 2000.’

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Brucellosis

There were 40 cases of brucellosis notified to NNDSS during 2002, a rate of 0.2 cases per 100,000 population. This number of notifications lies within the range observed (13-52 notifications) over the previous 11 years, but was an increase compared to the number reported in 2001, when 19 cases were notified. In 2002 most cases were notified from Queensland (35 notifications, 87 per cent), and two each from New South Wales and Victoria.

Most cases were male (n=34, male:female ratio 5.7:1), and of these, 23 were aged between 20 and 39 years. Bovine brucellosis (Brucella abortus) was eradicated from Australia in 1989, and most human cases occurring now are due to other Brucella species. Among notified cases, five were identified as Br. melitensis, and four as Br. suis.

Leptospirosis

Leptospirosis is caused by the spirochaete Leptospira. Nationally, 155 notifications of leptospirosis were received during 2002. This is relatively low compared to the count of previous years (Figure 55) and represents a downward trend since a peak in 1999.

Figure 55. Trends in notifications of leptospirosis, Australia, 1991 to 2002

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In 2002, the notification rate was highest in Queensland (n=91 notifications, 2.5 cases per 100,000 population). The next highest rates occurred in the Northern Territory (3 notifications, 1.5 cases per 100,000 population) and New South Wales (36 notifications, 0.5 cases per 100,000 population). More males were affected than females (male:female ratio, 8.1:1). The largest rates of notifications, for both sexes, were in the 20-34 year age range. The distribution of leptospirosis notifications by Statistical Division is shown in Map 9.

Map 9. Notifications rates of leptospirosis infection, Australia, 2002, by Statistical Division of residence

The annual report by the National Leptospirosis Reference Laboratory (www.health.qld.gov.au/qhpss/qhss/lepto_home.htm) provides details of Leptospira serovars causing infections in 2002. Of the 128 isolates serotyped, 74 per cent were identified as one of three serovars: Leptospira interogans var. hardjo (33%); var. zanoni (22%); and var. australis (19%).

The report identifies a strong association between leptospirosis infection and working in the Queensland banana industry. More specifically, work on banana farms in the Innisfail region is particularly associated with the Leptospira zanoni serovar. Butchery in the meat industry was another risk factor identified.

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Ornithosis

During 2002, 205 notifications of ornithosis were reported to NNDSS (1.0 cases per 100,000 population), compared with 131 notifications in 2001. New South Wales had the highest number of notifications with 148 cases (2.2 cases per 100,000 population). In 2002, the total number of ornithosis notifications was the highest yet observed (Figure 56). Most notifications were males aged 50-54 years (n=25 cases, rate 3.85 cases per 100,000 population), and females aged 60-64 year (n=11 cases, rate 2.62 cases per 100,000 population) (Figure 57).

Figure 56. Trends in notifications of ornithosis, Australia, 1991 to 2002

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Figure 57. Notification rates of ornithosis, Australia, 2002, by age group and sex

An outbreak of 60 confirmed cases of ornithosis-the largest yet recorded in Australia-occurred in the Blue Mountains, west of Sydney, during 2002. The cases occurred between March and June and involved mostly males aged between 50 and 65 years. The outbreak was identified following the unusual presentations of men to the Blue Mountains Hospital, with atypical pneumonia. A case-control study identified the main risk factors as contact with wild birds or lawn-mowing.³⁹ The ornithosis outbreak is thought to be linked to the large areas of the Blue Mountains being burnt out in the bushfires of previous summers. This is likely to have led to food shortages for native bird populations and a consequent utilisation of residential gardens.

Q fever

There were 761 cases of Q fever notified to NNDSS during 2002, an increase of 10 per cent from 2001. Notifications have increased each year since 1999, when 515 cases were notified. The largest numbers were from Queensland (n=339, 9.1 per 100,000 population) and New South Wales (n=292, 4.4 per 100,000 population). The highest rate observed for males was 10.4 cases per 100,000 population, in those aged 55-59 years, and for females, 3.7 cases per 100,000 population, in the 40-44 year age group (Figure 58). The male:female ratio was 3.2:1.

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Figure 58. Notification rates of Q fever, Australia, 2002, by age group and sex

Two clusters of Q fever were identified in 2002. In South Australia, seven cases were notified between August and September from a rural community. While two were related to occupational exposure, no other exposures could be identified for the remaining five, apart from the presence in the community of meat and livestock industry.

In the second cluster, cases associated with a Victorian abattoir led to screening of the workforce and detection of more cases. In total 28 cases were identified. The abattoir's workforce had been screened two years previously, but following this a large number of new employees had been recruited.

In October 2000, the Australian Government announced funding for the National Q Fever Management Program. The Program aims to reduce the burden of disease associated with Q fever, through a targeted screening and vaccination program.

At a cost of $10.6 million over three years, Phase 1 of the Program commenced in 2001 and is industry-focussed, targeting abattoir workers, those contracted to abattoirs, and sheep shearers. Commencing in 2002 and costing $8 million over three years, Phase 2 of the Program is targeting sheep, dairy and beef cattle farmers, their employees and unpaid family members working on farms.

Reasons for the increase in Q fever notifications in 2002 may include increased suspicion of Q fever as a diagnosis by general practitioners delivering the vaccination campaign, and individual screening for previous exposure to Q fever prior to vaccination. The longer-term results of the campaign will be of much interest, as Australia is the only country in the world to vaccinate against Q fever, despite the worldwide distribution of the disease.^40,41