Megge Miller, Paul Roche, Keflemariam Yohannes, Jenean Spencer, Mark Bartlett, Julia Brotherton, Jenny Hutchinson, Martyn Kirk, Ann McDonald, Claire Vadjic

Results - Zoonoses

Zoonoses are diseases transmitted between vertebrate animals and people.²⁷ The zoonotic diseases that were nationally notifiable in 2003 were anthrax, Australian bat lyssaviral or lyssaviral (unspecified) infection, brucellosis, leptospirosis, ornithosis and Q fever. A total of 903 notifications (0.9% of total notifications) were made during 2003. More detailed descriptions of these diseases were provided in the 2001 NNDSS annual report.⁹

Anthrax

Following the deliberate release of anthrax spores in the United States of America in 2001, anthrax became a notifiable disease in Australia. During 2003, no cases of anthrax were notified. The last human case of cutaneous anthrax in Australia, which occurred in a knackery worker, was reported in 1997.²⁶

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 incidents of anthrax in livestock were reported during 2003. Six incidents of anthrax were reported in New South Wales, where 74 sheep died in three separate incidents and 20 cattle deaths were recorded in the remaining three separate incidents. Victoria reported two cattle deaths on a dairy farm in northern Victoria. Action taken in response to the deaths included quarantine and vaccination of the remaining stock and stock on neighbouring farms.²⁷

Australian bat lyssaviral and lyssaviral (unspecified) infections

No cases of either Australian bat lyssaviral or lyssaviral (unspecified) infections were notified during 2003. 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.²⁸ 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.

Brucellosis

There were 17 cases of brucellosis notified during 2003, a rate of 0.1 cases per 100,000 population. This number of notifications lies within the lower end of the range observed (13–52 notifications) over the previous 11 years and was a decrease compared to the number in 2002, when 40 cases were notified. In 2003, most cases were notified from Queensland (13 notifications, 76%), with one case in New South Wales and three cases reported from Victoria.

Most cases were male (n=15, male:female ratio 7.5:1), and of these, nine were aged between 25 and 34 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 for whom species data were available, five were identified as Br. melitensis, and four as Br. suis.

Map 8. Notification rates of brucellosis infection, Australia, 2003, by Statistical Division of residence

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Leptospirosis

Leptospirosis is caused by the spirochaete, Leptospira. Nationally, 125 notifications of leptospirosis were received during 2003. This is relatively low compared to the previous years (Figure 55) and represents a continuation of the downward trend since a peak in 1999.

Figure 55. Trends in notifications of leptospirosis, Australia, 1991 to 2003

In 2003, the notification rate was highest in the Northern Territory (4 notifications, 2.0 cases per 100,000 population). The next highest rates occurred in Queensland (67 notifications, 1.8 cases per 100,000 population) and New South Wales (37 notifications, 0.6 cases per 100,000 population). More males were affected than females (male:female 5.6:1). The highest rates of notifications were in 30–39 year age group for males and the 35–59 year age group for females. The distribution of leptospirosis notifications by Statistical Division is shown in Map 9.

Map 9. Notifications rates of leptospirosis infection, Australia, 2003, by Statistical Division of residence

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Ornithosis

During 2003, 211 notifications of ornithosis were received (1.1 cases per 100,000 population), compared with 205 notifications in 2002. Victoria had the highest number of notifications (115 notifications, 2.3 cases per 100,000 population). The total number of notifications has continued to increase each year since 1997 (Figure 56). Most notifications were males in the 60–64 year age group (18 notifications, 4.1 cases per 100,000 population), and females in the 45–49 year age group (13 notifications, 1.8 cases per 100,000 population, Figure 57).

Figure 56. Trends in notifications of ornithosis, Australia, 1991 to 200 3

Figure 57. Notification rates of ornithosis, Australia, 2003, by age group and sex

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Q fever

There were 550 cases of Q fever notified during 2003, a decrease of 27 per cent on 2002. The number of cases notified had increased each year between 1999 and 2002. In 20 03, t he largest number of notifications were from New South Wales (278 notifications, 4.2 cases per 100,000 population) and Queensland (224 notifications, 5.9 cases per 100,000 population). The highest rate observed for males was 6.8 cases per 100,000 population, in the 45–49 year age group, and for females, 2.9 cases per 100,000 population, in the 50–54 year age group (Figure 58). The male to female ratio was 3.2:1, which is the same as the previous year.

There were six clusters of Q fever reported in 2003. Five occurred in Queensland, four of which were in families (2–3 cases in each cluster) and one was a cluster of five cases associated with a goat farm. South Australia recorded a cluster of three cases also associated with occupational exposure.

Figure 58. Notification rates of Q fever, Australia, 2003, by age group and sex

Q fever has long been associated with work in the Australian stock industry and abattoir workers are an occupational group at high risk of infection. Since October 2000, abattoir workers and shearers have been eligible for free vaccination against Q fever, under an Australian Government funded program. The second phase of the Q fever vaccination program began in October 2001 to include workers in the beef, sheep and dairy industries (Figure 59). The initial increase in notifications in 2002 is likely to be due to identification of cases through screening from the program. The decline in notifications in 2003 may be the result of a combination of control program activities and the natural variability in the prevalence of Q fever in Australia.

Figure 59. Notifications of Q fever, New South Wales and Queensland, January 2000 to December 2003, by month of onset

 

This article {extract} was published in Communicable Diseases Intelligence Vol 29 No 1 March 2005 and may be downloaded as a full version PDF from the Table of contents page.