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Gastrointestinal diseases

Gastrointestinal diseases are a major cause of illness in Australia. Recently, incidence of gastroenteritis in Australia has been estimated at approximately one episode per person per year.⁹ If 35 per cent of gastroenteritis is due to contaminated food, then there may be significantly more than the previously estimated four million annual cases of foodborne disease in Australia each year.¹⁰ Since the majority of gastroenteritis is mild and self-limiting, only a small proportion of cases present to medical practitioners, an even smaller number are investigated, and fewer yet are notified to health departments for transmission to the NNDSS.

In 2001, notifications of gastroenteritis increased to 26,086, which was 25 per cent of all notifications to NNDSS. This represents a 22 per cent increase from notifications in 2000. The overall increase in notifications was due to the changes in gastrointestinal diseases that were notifiable in Australia in 2001. Diseases notified are botulism, campylobacteriosis, cryptosporidiosis, haemolytic uraemic syndrome (HUS), hepatitis A and E, listeriosis, salmonellosis, shigellosis, shiga-like toxin producing E. Coli/verotoxigenic E. coli (SLTEC/VTEC) and typhoid.

Cryptosporidiosis was made a notifiable disease from 2001. Although the reporting of cryptosporidiosis was incomplete in 2001, the relatively large number of cases notified, accounts for some of the increase in total notifications of gastrointestinal disease in 2001. Other reasons for the increase in notifications include an 18 per cent increase in campylobacteriosis. In 2001, New South Wales reported shigellosis for the first time and Western Australia began reporting botulism, hepatitis E and SLTEC/VTEC.

Yersiniosis was removed from the list of gastrointestinal diseases notifiable in 2001. Notifications of this disease had declined from 370 cases in 1993 to 73 cases in 2000 (a decline from 3.2 to 0.6 cases per 100,000 population). This disease is rare in Australia and the USA, but common in Europe, where it is frequently associated with the consumption of undercooked pork.¹¹

In 2001, OzFoodNet a network of foodborne disease epidemiologists began work to enhance the surveillance of foodborne disease in Australia. The annual report of OzFoodNet activities in 2001⁶ contains additional information on gastrointestinal disease, which complements data in this report.

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Botulism

Botulism is a notifiable disease in all Australian states and territories. No cases of classic foodborne botulism have been reported since notification commenced. Infant (or intestinal) botulism cases arise from ingestion of Clostridium botulinum spores, which germinate in the intestine. Sources of spores are multiple, and include dust and foods such as honey.¹² There have been five cases of infant intestinal botulism reported since 1996, including two cases reported in 2001.

Of these two cases, one was from Victoria and the other from Queensland, and both occurred in infants aged less than one year. The first case was a five-month-old infant hospitalised after a three-day history of poor feeding, constipation, ptosis, difficulty in swallowing, weakness and loss of head control. Although there were various potential environmental exposures, including dust, no source for the child's infection could be determined.

The second case was a 10-week-old infant who presented with acute flaccid paralysis (prominent bulbar weakness). Subsequently, Clostridium botulinum type B was isolated from the faeces. The infant had a history of probable consumption of honey within the two weeks prior to onset of the disease. Parents are advised not to feed honey to infants or to dip pacifiers in honey, because of the risk of botulism.¹³

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Campylobacteriosis

There were 16,124 notifications of campylobacteriosis in Australia in 2001. This represents an increase of 18 per cent on the 13,595 cases reported in 2000 and continues a trend of increasing notifications of campylobacteriosis in Australia (Figure 15). The national rate of campylobacteriosis reported to NNDSS (125.2 cases per 100,000 population) makes this disease the most commonly reported disease in Australia and it exceeds that of Salmonella more than threefold. Data from the United Kingdom suggest that this disease may be under-reported by a factor of eight times.¹⁴ Campylobacter jejuni is now the most common bacterial cause of foodborne disease in industrialised countries.¹⁵

Figure 15. Trends in notifications of campylobacteriosis, Australia, 1991 to 2001, by month of onset



Reports were received from all states and territories except New South Wales, where cases are included in the categories 'foodborne disease' or 'gastroenteritis in an institution. ' The highest rates of campylobacteriosis were in South Australia (175.7 cases per 100,000 population) and the lowest in Queensland (109.2 cases per 100,000 population). Nationally, notifications were most common in October (1,688 reports). Despite the high rates of disease, only six outbreaks were identified during 2001. Three small outbreaks were associated with take-away kebabs and two were associated with the consumption of chicken.⁶

The highest age specific rate of campylobacteriosis was 296 cases per 100,000 population in children aged 0-4 years. Rates according to age group and sex are shown in Figure 16. In the 0-4 year age group the rates were higher in males (341 cases per 100,000 population) than in females (251 cases per 100,000 population). The male to female ratio in this age group was 1.4:1, while overall it was 1.2:1.

Figure 16. Notification rates of campylobacteriosis, Australia, 2001, by age group and sex



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Cryptosporidiosis

Cryptosporidiosis is spread by faecal contamination and includes person-to-person, animal-to-person, waterborne and foodborne transmission. The prevalence of infection is between 1 to 4.5 per cent of individuals in developed countries and between 3 to 20 per cent of individuals in developing countries.¹⁶ Children under two years of age, animal handlers, travellers and men who have sex with men are recognised to be at greater risk of infection.

Infections with Cryptosporidium are commonly asymptomatic and carriers can shed oocysts in their faeces and be a source of infection to others.¹⁶ The infective dose is very small (approximately a hundred oocysts) and previous exposure in immunocompetent adults is not entirely protective, although it may decrease the severity of the disease caused by subsequent infections. People with markedly impaired immune systems due to HIV infection are susceptible to severe persistent diarrhoea caused by cryptosporidiosis and the infection may spread to the biliary tract. Declines in the prevalence of cryptosporidiosis in HIV and AIDS patients treated with highly active anti-retroviral therapy have been reported.¹⁷

Notification of cryptosporidiosis to NNDSS was agreed by all Australian states and territories from January 2001. Since addition of new diseases to the notifiable list requires legislative change in each Australian jurisdiction, reports of cryptosporidiosis received by NNDSS in 2001 probably underestimate the national annual total.

In the autumn quarter of 2001 (April-June), sporadic cryptosporidiosis infections associated with use of swimming pools were reported from several states and territories in Australia. Compared to previous years, Victoria observed increased notifications of cryptosporidiosis, predominantly from the Melbourne metropolitan area. The majority of cases reported exposure to public swimming pools before becoming ill and small clusters were associated with several pools. Swimming pools are common sources for outbreaks of cryptosporidiosis. In summer 2001 in the United States of America, five protracted outbreaks of cryptosporidiosis associated with swimming pool use were reported.¹⁸ Such outbreaks can be prevented by rigorous control of water pool quality, provision of advice to people that they should not swim if they have gastroenteritis, and enforcement of a faecal accident policy. The Queensland government has published guidelines to prevent outbreaks of cryptosporidiosis in swimming pools (www.health.qld.au/phs/Documents/cdu/5436.pdf).

In Queensland, five linked cases of cryptosporidiosis were reported, which were associated with consumption of unpasteurised milk intended for animal consumption. Of the five cases, three were hospitalised.¹⁹ Cryptosporidiosis infection associated with consumption of unpasteurised products are possibly due to contamination with cow manure.¹⁶ A cluster of 45 Cryptosporidium infections occurred in northern Tasmania in November 2001 and an animal nursery at an agricultural show was suspected to be the source. The majority of cases were children who had attended the show, with secondary cases arising in families through person-to-person transmission. (Ashbolt, Commun Dis Intell submitted)

The notification rates for cryptosporidiosis by age group and sex are shown in Figure 17. More than half the cases were in children under the age of five years (869 cases, 53% of total). There was no difference in the notification rates between males and females.

Figure 17. Notification rates of cryptosporidiosis, Australia, 2001, by age group and sex



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Hepatitis A

There were 530 notifications of hepatitis A in Australia in 2001, the lowest since NNDSS began in 1991 and a 35 per cent decline from the 812 cases reported in 2000. The majority of cases occurred in the larger states: New South Wales (n=195), Queensland (n=120) and Victoria (n=102). The rates in these states were similar (2.1-3.3 cases per 100,000 population). The Northern Territory had the highest notification rate for hepatitis A (19.0 cases per 100,000 population, n=38). The highest age-specific rates were in males in the 25-29 year age group and females in the 20-24 year age group (8.1 and 2.8 cases per 100,000 population, respectively) and the overall male to female ratio was 2.6:1 (Figure 18).

Figure 18. Notification rates of hepatitis A, Australia, 2001, by age group and sex



Marked declines in the annual number of notifications of hepatitis A have been seen in north Queensland since hepatitis A vaccination was introduced for Indigenous children in the region in early 1999. There were 231 notifications of hepatitis A in Far North Queensland in 1999, 34 cases in 2000, and 11 cases in the first nine months of 2001. The last case in an Indigenous person was in June 2000. The majority of cases in Far North Queensland during 2000 and 2001 were acquired abroad, particularly in Papua New Guinea (PNG) (Jeffrey Hanna, Tropical Public Health Unit Network, personal communication, November 2001).

Apart from rare large outbreaks associated with food, such as the outbreak associated with oysters in 1997,²⁰ hepatitis A in Australia is most commonly acquired through household or close contact with a case, recreational drug use and overseas travel. Risk exposure information was available for 247 of the 530 cases (47%) in 2001 (Table 9).

Table 9. Risk exposures associated with infection with hepatitis A virus infection, Australia, 2001 by reporting state or territory

	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Injecting drug use	3	-	-	12	2	-	23	1
Household /close contact of case	1	-	9	17	3	-	6	2
Overseas travel	2	36	1	20	6	1	26	16
Childcare	-	-	-	32	0	-	0	-
Homosexual contact	-	-	-	6	1	-	6	-
Sex worker	-	-	-	0	-	-	0	-
Other	-	-	-	33*	-	2†	-	-
Total with risk factors identified	6	36	20	120	12	3	61	19
Unknown	8	159	28	0	8	1	41	18
Total	14	195	38	120	20	4	102	37

* Includes exposure to shellfish (n=17) and Indigenous person or contact with Indigenous community (n=13)
† The two cases notified from Tasmania became infected in Queensland.

A national cross-sectional hepatitis A seroprevalence survey of opportunistically obtained serum was performed in 1998 and reported in 2001.²¹ This study found 41 per cent of the samples were positive for antibodies to hepatitis A, and the proportion of positive samples increased with age. When combined with declining notifications of hepatitis A, these data support the idea of a declining incidence, with fewer young people being exposed to the virus.

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Hepatitis E

There were 10 cases of hepatitis E reported to NNDSS in 2001, the same number as in 2000. The cases occurred in New South Wales (n=6), Victoria (n=3) and Queensland (n=1). There were six female and four male cases and three of the women were of child-bearing age (15-49 years). All three of the cases reported in Victoria had travelled overseas.

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Listeriosis

Listeriosis is a serious bacterial disease caused by the consumption of food contaminated with Listeria monocytogenes. Changes in food processing and distribution and a growing population with predisposing risk factors for infection with Listeria monocytogenes has raised concerns about this pathogen.²²

In 2001, 62 cases of listeriosis were notified to NNDSS. This was lower than the 67 cases notified in 2000. The national rate was 0.3 cases per 100,000 population. Rates of 0.6 cases per 100,000 population were reported in Queensland (n=20) and Western Australia (n=11). There were no clusters or outbreaks reported. There was a predominance of male cases, with a male to female ratio of 2.2:1. Rates according to age group and sex are shown in Figure 19. OzFoodNet reported that 6 out of 61 cases were maternal foetal infections, which resulted in three foetal deaths.⁶ The majority of listeriosis notifications occurred in the elderly, with 40 cases (64% of total) occurring in people aged more than 60 years. OzFoodNet reported a mortality rate of 13 per cent among non-pregnancy-related cases.⁶

Figure 19. Notification rates of listeriosis, Australia, 2001, by age group and sex



A recent review of the epidemiology of listeriosis in Australia found a stable and low rate of listeriosis, which did not vary from jurisdiction to jurisdiction. ²³ There were inconsistencies identified in how a maternal-foetal pair was reported, either as a single case or mother and child reported separately.

Australia's Imported Food Program undertakes surveillance of imported food, and is a joint activity of Food Standards Australia New Zealand and the Australian Quarantine Inspection Service. All 'ready-to-eat' imported foods, such as soft cheese and smoked fish, must be free of Listeria. Data from the Imported Food Program from 1995 to 1998 show an increasing percentage of imported food items (up to 8%) was contaminated with Listeria.²⁴ Surveillance for Listeria contamination of imported food is therefore a vital measure for control of listeriosis in Australia.

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Salmonellosis (excluding typhoid)

Salmonellosis is the second most commonly notified gastrointestinal disease in Australia and is primarily associated with food.²⁵ In 2001, there were 7,045 cases reported, an increase of 14.5 per cent on the 6,151 cases reported in 2000. While there has been a variable trend over the last 10 years, improvements in the investigation of foodborne disease by states and territories may have contributed to recent increased notifications.

Cases of salmonellosis were reported from each Australian state and territory in 2001, and the national rate was 36.2 cases per 100,000 population. The highest rate was in the Northern Territory (186.5 cases per 100,000 population). Rates of salmonellosis varied by Statistical Division (Map 2), with the Kimberley district of northern Western Australia having the highest rate (602 cases per 100,000 population). In general, there were higher rates of salmonellosis in more northerly areas of the country. Reports of salmonellosis were highest in summer months (January-March, Figure 20). As in previous years, the highest age-specific rate was in children aged less than five years (196 cases per 100,000 population) and the male to female ratio was 1.1:1. Rates according to age group and sex are shown in Figure 21.

Map 2. Notification rates of salmonellosis, Australia, 2001, by Statistical Division of residence



Figure 20. Trends in notifications of salmonellosis, Australia, 1991 to 2001, by month of onset



Figure 21. Notification rates of salmonellosis, Australia, 2001, by age group and sex



The National Enteric Pathogens Surveillance Scheme reported 6,932 cases of Salmonella infection in 2001.²⁶ The 10 most frequently isolated serovars and phage types of Salmonella which account for 45.2 per cent of all isolates, are shown in Table 10.

Top of pageTable 10. Top 10 isolates of Salmonella, Australia, 2001

Organism	State or territory								Aust	Total %
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
S. Typhimurium PT135	5	257	9	140	25	4	91	104	635	9.2
S. Virchow	5	65	1	289	21	0	95	2	478	6.9
S. Typhimurium PT9	10	139	0	52	48	11	122	17	399	5.8
S. Typhimurium PT126	4	94	9	73	111	2	18	2	313	4.5
S. Enteritidis	6	79	3	62	20	8	50	66	294	4.2
S. Saintpaul	1	33	20	175	5	2	8	43	287	4.1
S. Birkenhead	2	109	0	132	2	0	6	2	253	3.6
S. Bovismorbificans	5	54	2	54	13	2	30	7	167	2.4
S. Chester	1	30	15	64	13	0	11	31	165	2.4
S. Typhimurium PT64	1	61	3	5	31	1	11	35	148	2.1
Others	44	768	309	1,076	324	131	631	510	3,793	54.8
Total	84	1,689	371	2,122	613	161	1,073	819	6,932

Source: National Enteric Pathogens Surveillance Scheme, annual report, 2001.

Outbreaks of Salmonella

Salmonella Typhimurium Definitive Type 104

During 2001 the Victorian Department of Human Services investigated an outbreak of Salmonella Typhimurium Definitive Type 104 (STM DT104), which was found to be associated with helva, a sweet made from sesame seeds, sugar and flavourings, imported from Turkey. The investigation in Victoria was in conjunction with Sweden, Norway and other European countries, where salmonellosis cases associated with helva were also identified.²⁷ Twenty of the 23 (87%) of Australian cases occurred in Victoria, and two cases occurred in New South Wales and one in Queensland.

S. Typhimurium DT104 emerged worldwide during the 1990s and now constitutes 8 to 9 per cent of isolates in the USA. DT104 constituted only 0.4 per cent of isolates in Australia in 2001, almost all of which were cases from the outbreak reported above. The DT 104 strain carries resistance to multiple antibiotics (ampicillin, chloramphenicol, trimethoprim-sulphamethazol, streptomycin and tetracycline). Isolates of DT104 with decreased susceptibility to fluoroquinolones have been isolated in the United Kingdom and the emergence of this additional resistance is linked to veterinary use of these antibiotics.²⁸

Salmonella Stanley

An outbreak of 24 cases of Salmonella Stanley infection, associated with the consumption of contaminated dried peanuts imported from China, affected several Australian states and territories in 2001. Two people with Salmonella Newport infections also reported eating the same brand of peanuts. Three Salmonella serovars: Stanley, Newport and Lexington were isolated from the peanuts. These findings triggered an international product recall and assisted health agencies in Canada and the United Kingdom who were investigating similar outbreaks.²⁹

Salmonella Typhimurium phage type 126

A community-wide outbreak of Salmonella Typhimurium phage type 126 (STM 126) involving 88 cases occurred in South Australia. The outbreak lasted for several months, with cases emerging in other states and territories later in the epidemic. A case-control study demonstrated that illness was associated with consumption of chicken. Descriptive epidemiology and microbiological evidence of pathogens from samples of raw chicken provided corroborating evidence for this link. The South Australian Department of Human Services observed a decrease in human cases of STM 126 following interventions at breeder farms, hatcheries and processing plants.

Salmonella Bovismorbificans

In June 2001, Queensland investigated a state-wide increase in Salmonella Bovismorbificans phage type 32. The outbreak was suspected to be linked to a food product purchased from a fast food restaurant. A case control study implicated a product containing iceberg lettuce, and environmental investigations identified a mechanical slicer at the processing facility that was positive for Salmonella Bovismorbificans phage type 32. Thirty-six cases occurred, six of whom were hospitalised.³⁰

Salmonella Mgulani

The Northern Territory reported 15 cases of S. Mgulani in October and November 2001. Previously, this serovar had rarely been identified in the Territory. Cases were widely dispersed and occurred mostly in non-Indigenous people. Although interviews were conducted, no food source was identified.³¹ A cluster of S. Mgulani in New South Wales in December 1999 and January 2000 involved 542 cases.²

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Shigellosis

It is estimated that the majority of shigellosis is due to person-to-person transmission and that only 20 per cent may be foodborne.²⁵ In Australia, the majority of Shigella infections are seen in men who have sex with men, Indigenous communities and travellers returning from overseas. Foodborne outbreaks are rare in Australia, largely as a result of improved standards of sanitation and food-handling.³³ The last outbreak of foodborne shigellosis was in 1998,³⁴ although outbreaks via person-to-person contact have been reported.^35,36 OzFoodNet reported no outbreaks or confirmed links with food among shigellosis cases notified in 2001.⁶

Shigellosis became a notifiable condition in New South Wales for the first time in 2001. This accounts for the increase in the number of cases (562 cases compared with 487 cases in 2000). Despite this, the national notification rate (2.9 cases per 100,000 population) continued to decline (Figure 22). The highest notification rate was in the Northern Territory, with 51.5 cases per 100,000 population. By age, the highest rates were in children aged less than five years (11 cases per 100,000 population). Overall there was a slight predominance of males (male:female ratio 1.3:1). Rates according to age group and sex are shown in Figure 23.

Figure 22. Trends in notifications of shigellosis, Australia, 1991 to 2001, by month of onset



Figure 23. Notification rates for shigellosis, Australia, 2001, by age group and sex



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Shiga-like toxin producing Escherichia coli/verotoxigenic E. coli

There were 49 cases of SLTEC/VTEC notified to NNDSS in 2001. This was an increase of 48 per cent on the 33 cases reported in 2000. Reports of SLTEC/VTEC infections were received from Queensland and Western Australia for the first time in 2001. The notification rate rose slightly to 0.3 cases per 100,000 population.

As in previous years, more than 50 per cent (27/49) of cases were notified in South Australia, reflecting a policy of screening all bloody stools for toxin genes by polymerase chain reaction. OzFoodNet reported that E. coli O157 was identified in 3 of 26 cases in South Australia, 2 of 4 cases in Victoria and 4 of 10 cases in Queensland, although typing methods are difficult to compare between jurisdictions.⁶

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Haemolytic uraemic syndrome

Infections with SLTEC/VTEC have the potential to cause severe and life-threatening illness, including haemolytic uraemic syndrome. Young children are more at risk and HUS in children is typically post-diarrhoeal. E. coli O157:H7 infection in children aged less than five years progress to HUS in 10 to 14 per cent of cases.³⁷

There were only three cases of HUS notified to the NNDSS in 2001, which was markedly lower than the 15 cases reported in 2000. There is evidence that notified cases of HUS represent only a small proportion of all cases. In California only 44 per cent of cases were reported to public health authorities.³⁷ The Australia Paediatric Surveillance Unit recorded 325 reports of HUS from paediatricians between July 1994 and December 2000, in children aged less than 15 years. Of these 137 were confirmed and 97 were associated with diarrhoea.³⁸ In the same period, only 83 cases were notified to the NNDSS. A survey of Australian hospitalisation data conducted by OzFoodNet has shown 90 separations for HUS in the 1998-99 financial year and 47 in the 1999-00 financial year. By contrast, for the same periods there were 21 and 16 notifications of HUS to NNDSS, respectively.⁶ Ongoing studies are needed to address the differences seen between the datasets and notification mechanisms in the states and territories.

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Typhoid

Typhoid infections in Australia are usually associated with overseas travel. In 2001, there were 84 notifications of typhoid to the NNDSS. This represents a 43 per cent increase on the 60 cases reported in 2000. Of the 84 cases, the highest notification rates were in the 20-24 year age group (1.2 cases per 100,000 population) and there was a male to female ratio of 1:1. Rates according to age group and sex are shown in Figure 24.

Figure 24. Notification rates of typhoid, Australia, 2001, by age group and sex



The National Enteric Pathogen Surveillance Scheme identified 69 isolates of S. Typhi in 2001. Fifty-two isolates were from Australian residents, nine from refugees in detention centres and eight from overseas visitors. The percentage known to be acquired overseas was 84 per cent (58/69). There was a single case of typhoid acquired within Australia, which was a laboratory-acquired infection.²⁶


This article was published in Communicable Diseases Intelligence Volume 27, No 1, March 2003.