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Results, cont'd

Gastrointestinal diseases

In 2010, gastrointestinal diseases notified to NNDSS were: botulism, campylobacteriosis, cryptosporidiosis, haemolytic uraemic syndrome (HUS), hepatitis A, hepatitis E, listeriosis, salmonellosis, shigellosis, Shiga toxin-producing Escherichia coli (STEC) infections and typhoid.

Overall notifications of gastrointestinal diseases decreased slightly from 31,695 in 2009 to 31,548 in 2010. Only notifications of salmonellosis were notably increased compared with the 5-year mean (exceeding the mean by more than 2 standard deviations).

Australia’s enhanced foodborne disease surveillance network, OzFoodNet, monitors the incidence of diseases caused by pathogens commonly transmitted by food, using population-based passive and enhanced surveillance for notifiable gastrointestinal diseases and for outbreaks of gastroenteritis and enteric disease. OzFoodNet aggregated and analysed data from NNDSS, supplemented by enhanced surveillance data, on the following 9 diseases or conditions, a proportion of which may be transmitted by food; botulism, campylobacteriosis, HUS, hepatitis A, listeriosis, non-typhoidal salmonellosis, STEC infection, shigellosis, and typhoid. The data and results from these analyses are summarised in the following sections and are reported in more detail in the OzFoodNet annual report 2010.

Botulism

Botulism is a rare but extremely serious intoxication resulting from toxins produced by Clostridium botulinum (commonly toxin types A, B and E). Three forms of botulism are recognised; infant, foodborne and wound.¹⁶ Infant botulism occurs when C. botulinum spores are ingested, germinate in the infant’s intestine and the organism produces botulinum toxin. It does not include cases where the preformed toxin is ingested, these are considered foodborne.

There were no cases of botulism reported to NNDSS in 2010. There was 1 notified case reported in 2009 and no cases reported in 2008.

Campylobacteriosis

The bacterium Campylobacter is a common cause of foodborne illness (campylobacteriosis) in humans. The severity of this illness varies and is characterised by diarrhoea (often bloody stools), abdominal pain, fever, nausea and or vomiting. Campylobacteriosis is notifiable in all Australian jurisdictions, except New South Wales.

In 2010, there were 16,966 notified cases of campylobacteriosis, a rate of 112 per 100,000, similar to the 16,081 notifications in 2009. Notification rates ranged from 71.8 per 100,000 in the Northern Territory to 153.8 per 100,000 in the Australian Capital Territory.

Notification rates were highest amongst males in nearly all age groups. The highest age-specific rate for both males and females was in the 0–4 age group (218.5 and 160.2 per 100,000, respectively) with additional peaks in the 20–24 and 80–84 year age groups (Figure 15).

Figure 15: Rate for campylobacteriosis, Australia, 2010, by age group and sex

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Cryptosporidiosis

Cryptosporidiosis is a parasitic infection of the lower intestine, characterised by abdominal cramping and usually large-volume watery diarrhoea. Ingesting contaminated water is a major risk factor for infection.

In 2010, there were 1,480 notified cases of cryptosporidiosis reported to NNDSS; a rate of 7 cases per 100,000. This represents a 68% decrease over the 4,625 notifications in 2009, which was the largest number reported since the disease became nationally notifiable in 2001.

Cryptosporidiosis notifications fluctuate from year to year, and notifications are most numerous in autumn and summer, with some regional variation.

Haemolytic uraemic syndrome

Haemolytic uraemic syndrome is a rare but serious clinically diagnosed disease, that is characterised by acute renal impairment, and results in chronic complications in 40% of cases.¹⁹ Not all diagnoses of HUS are related to enteric pathogens, but in Australia cases are commonly associated with STEC infection.

In 2010, there were 8 notified cases of HUS (rate 0.05 per 100,000 population) (Table 11), compared with 13 in 2009 and a mean of 19 notifications per year (0.1 per 100,000 population) between 2005 and 2009.

The median age of HUS cases between 2005 and 2010 was 6 years (range 0–89 years) and cases were most frequently reported amongst children in the 0–4 year age group (Table 11).

Table 11: Notified cases of haemolytic uraemic syndrome, Australia, 2005 to 2010, by age group

Age group	2005	2006	2007	2008	2009	2010
0–4	12	5	8	11	5	6
5–9	2	3	2	4	2	0
10–14	1	2	0	2	2	1
15–19	0	0	3	2	0	0
20–24	0	1	0	0	0	1
25–29	0	2	0	1	1	0
30–34	0	0	0	2	0	0
35–39	0	0	1	0	0	0
40–44	0	0	2	0	0	0
45–49	0	0	0	3	0	0
50–54	2	0	1	1	0	0
55–59	0	0	0	1	0	0
60–64	1	1	1	0	1	0
65–69	1	0	0	0	0	0
70–74	0	0	1	2	0	0
75–79	0	0	0	1	1	0
80–84	1	0	0	1	0	0
85+	0	0	0	0	1	0
Total	20	14	19	31	13	8

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Hepatitis A

Hepatitis A is a viral disease primarily of the liver that can develop into chronic liver disease including liver failure. Infection is usually spread via the faecal-oral route but can be foodborne or waterborne.

In 2010 there were 263 notified cases of hepatitis A in Australia, a rate of 1.2 notifications per 100,000 population. This was a 53% decrease compared with the 563 notifications in 2009 (Table 6). The increase in 2009 was largely attributable to an outbreak of locally-acquired infections between 1 March 2009 and 18 March 2010, associated with the consumption of semi-dried tomatoes.^20,21

Table 12: Hepatitis A notifications, Australia, 2005 to 2010, by place of acquisition

Year	Locally acquired		Overseas acquired		Unknown
	n	%	n	%	n	%
2005	140	42.8	151	46.2	36	11.0
2006	101	35.9	69	24.6	111	39.5
2007	74	44.8	35	21.2	56	33.9
2008	99	35.7	52	18.8	126	45.5
2009	416	73.9	68	12.1	79	14.0
2010	106	40.3	131	49.8	26	9.9

In 2010, 40% (106/263) of notified cases were locally-acquired with most of these being part of the 2009–2010 outbreak, and with a 5-year average (2005–2009) of 166 locally-acquired cases per year (Table 12).

Hepatitis A was most frequently notified amongst young adults and in 2010, the median age of notified cases was 27 years (range 0–97 years), and 51% (133/263) were male.

Indigenous status was known for 91% of notifications and of these no cases identified as being Indigenous.

Hepatitis E

Hepatitis E is a viral disease primarily of the liver that is transmitted by the faecal-oral route.

In 2010, there were 38 notified cases of hepatitis E; a rate of 0.2 per 100,000, compared with 33 notifications in 2009. Hepatitis E in Australia is associated with overseas travel, with 58% (n = 22) known to have been acquired overseas.

Listeriosis

Invasive listeriosis commonly affects the elderly or immunocompromised, and is most common amongst people with serious or terminal underlying illnesses. Listeriosis can also affect pregnant women and infect their unborn baby. Laboratory-confirmed infections in a mother and unborn child or a neonate are notified separately in the NNDSS. However, OzFoodNet counts such pairs as 1 case, with the mother reported as the primary case, which explains the differences in numbers from those reported in OzFoodNet annual reports.

In 2010, there were 71 notified cases of invasive Listeria monocytogenes infection; a rate of 0.3 per 100,000, compared with a 5-year historical mean of 65 notifications. This was a decrease from the 92 notified cases in 2009, when an outbreak associated with chicken wraps was reported.²²

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Salmonellosis (non-typhoidal)

Salmonellosis is a bacterial disease caused by Salmonella enterica. The disease is characterised by rapid development of symptoms including abdominal pain, fever, diarrhoea, muscle pain, nausea and/or vomiting. People can become infected via faecal-oral transmission, ingesting contaminated food, through animal contact and from environmental exposures.

There were 11,993 notified cases of salmonellosis in Australia in 2010; a rate of 53.7 per 100,000, compared with the 5-year mean of 8,825 notifications. In 2010, salmonellosis notifications continued to increase, with notifications exceeding the 5-year mean by more than 2 standard deviations.

Notification rates ranged from 40.4 per 100,000 in South Australia to 243.4 per 100,000 in the Northern Territory. In 2010, 51% (n = 6,111) of cases were in females, with the greatest proportion of cases in the 0–4 year age group (26%, n = 3,090).

Shigellosis

Shigellosis is bacterial disease characterised by acute abdominal pain and fever, small-volume loose stools, vomiting and tenesmus. Shigella is transmitted via the faecal-oral route, either directly (such as male-to-male sexual contact) or indirectly and can be foodborne.

In 2010, there were 552 notified cases of shigellosis; a rate of 2.5 per 100,000, with notifications being less than the 5-year mean of 665 notifications. As in previous years, the highest notification rate was in the Northern Territory (32.7 per 100,000).

Notifications for shigellosis were highest in the 0–4 year age group (21%, n = 115), and 53% (n = 293) of notified cases were female.

Information on Indigenous status was available for 82% (n = 451) of notifications, and this proportion varied by state or territory, with New South Wales, Queensland, South Australia and Tasmania being less than 85% complete. Amongst jurisdictions with greater than 85% completeness, the proportion of notified cases who identified as being of Aboriginal or Torres Strait Island origin was 35% (99/283).

Twenty-five per cent (n = 140) of notified cases were reported as being acquired overseas. The most frequently reported countries of acquisition for imported cases were Indonesia (34%, n = 48) and India (11%, n = 15).

Shiga toxin-producing Escherichia coli infections

Shiga toxin-producing E. coli are species of toxin-producing E. coli that cause diarrhoeal illness in humans. Severe cases can progress to HUS.²³

There were 81 notifications of STEC in Australia in 2010; a rate of 0.4 per 100,000 population.

Rates of STEC infection are strongly influenced by jurisdictional practices regarding the screening of stool specimens.²³ In particular, South Australia routinely tests all bloody stools by polymerase chain reaction (PCR) for genes coding for Shiga toxins and other virulence factors, making rates for this state the highest in the country at 2.0 per 100,000.

In 2010, 62% (n = 50) of notified cases were female. The median age of notified cases was 43 years (range 1–98 years).

Typhoid

Typhoid is a disease caused by S. enterica serotype Typhi. Transmission is the same as for salmonellosis, however typhoid differs in that humans are the reservoir for the bacterium.

There were 96 notified cases of typhoid during 2010 (rate 0.4 per 100,000), which was slightly higher than the 5-year mean of 88.

Similar to previous years, overseas travel was the primary risk factor for notified cases in 2010, with 76% (n = 73) of notified cases known to have been acquired overseas, compared with 89% (102/115) in 2009. India continues to be the most frequently reported country of acquisition, accounting for 43% (n = 41) of overseas-acquired cases in 2010, with a range of other countries in South and South East Asia reported as the place of acquisition, each by less than 1% of cases.