Disease trends and estimated cost of foodborne illness in Australia

Words by Dr Craig Shadbolt

In reviewing trends, climate change stands out as having an observable effect on foodborne illness and increased risk of outbreaks, which the food industry and regulators are increasingly forced to grapple with.

What was less predictable (and unforeseen) in 2020 was the impact of COVID-19 on health systems, supply chains, workforces and trends in foodborne disease notifications (in Australia and internationally).

These issues pose real challenges for epidemiologists when interpreting and attributing potential cause and effect of food safety interventions and the impact of other events on disease statistics.

Revised cost of foodborne illness in Australia

Food Standards Australia New Zealand1 have recently published updated estimates for the number of foodborne illness cases and their cost, based on 2019 data (as shown in Table 1). Key figures to note are the total estimates for the number of foodborne illness cases per annum (4.68 million) and costs associated with this ($2.44b per annum). The previous estimated cost of illness was $1.25b, based on 2006 data.

Campylobacter is one of the leading causes of bacterial foodborne diseases, and is estimated to be the single most expensive pathogen in Australia, with an associated cost burden of $375m. By comparison, Salmonella (the most common pathogen associated with foodborne outbreaks) has an annual cost burden of $140m. While there are few notified cases, listeriosis is by far the most expensive foodborne disease with an estimated cost per case of $785,000, due to the severity of associated illness and fatality rate (compared with a cost of $1,390 per case for Campylobacter).

Foodborne disease trends in Australia

Australian notifications for nontyphoidal Salmonella, Campylobacter and Listeria in the period 2015-2021 are shown in Table 2. These figures represent laboratory confirmed detections of illness across Australian jurisdictions, but do not account for underreporting of cases which are estimated in the above FSANZ report.

Campylobacter became notifiable in NSW (Australia’s most populous state) from April 2017, which accounts for a significant rise in notifications around this time. Irrespective of this, total notifications of this pathogen remain stubbornly high and are of major concern for regulators and food industry commodities that are major sources of Campylobacter.

Listeriosis notifications declined steadily over 2015-2021. Improvements in understanding and education of the risks to pregnant women and the immunocompromised, along with improved practices in sectors such as the melon industry, may have contributed to this decrease.

Another potential success story is the decline in salmonellosis notifications from 2015-2021. Several state and territory food safety regulators developed specific interventions targeting causes of Salmonella outbreaks. Improvements across various industry sectors also contributed to the salmonellosis decrease. For example, the majority

of layer hens in the egg industry are now vaccinated against Salmonella Typhimurium (the most common serovar implicated in foodborne disease).

Improvements in throughchain biosecurity as a result of a Salmonella Enteritidis outbreak in NSW and Victoria in 2018-19 are also reducing opportunities for spread within and between farms. More recent outbreaks linked to fresh produce in 2020 and 2021 are being addressed through draft food safety standards across leafy greens, berry and melon production. However, the overall decline in salmonellosis, while promising, is complicated by the impact of COVID-19.

COVID-19 and impacts on foodborne pathogen notifications

A common statistic in many countries was the reported decrease in foodborne illness coinciding with the SARS-CoV-2 pandemic and associated control measures. In the UK, there was a 34% decrease of laboratory confirmed gastrointestinal illness during the first six months of the COVID-19 response in 2020, compared to the previous five-year average.2 Similarly, disease statistics published by the US CDC showed a 26% decrease in foodborne illness in 2020, compared to the 2017-2019 average.3 This was the single largest decrease on record in the history of FoodNet reporting in the US.

Australia also observed a 27% decrease in salmonellosis during 2020.4 States with stricter, longer periods of movement restrictions generally saw the largest declines in notified salmonellosis cases. While these restrictions would have had a significant impact on disease statistics, other factors may have included changes to health seeking behaviour (sick people using telehealth instead of physical visits to a health facility where a stool sample might otherwise have been collected); laboratory resources prioritised for COVID-19 over other diseases (including Salmonella diagnostics); reduction of travel-associated cases linked to closure of international borders; and improvements in hand hygiene.

Table 1 – Estimated number of foodborne illnesses and cost in Australia in 2019 (FSANZ, 2022).

Table 2 – Australian trends in campylobacteriosis, listeriosis, and salmonellosis notifications, 2015-2021 (extracted from NNDSS, 22 March 2022 and provided by OzFoodNet).

Conclusion

The updated burden of foodborne disease and associated cost estimates demonstrate that Australia still has significant room for improvement in managing illness. Future management efforts will be challenged by the effects of climate change and extreme weather events increasing the likelihood of foodborne outbreaks. Other confounding factors, including current disruption to health systems arising from the COVID-19 pandemic, are adding to the complexity of interpreting disease causality and effects of future food safety interventions.

References

1. FSANZ (2022) “The Annual Cost of Foodborne

Illness in Australia” (to be published soon) 2. Love NK, Elliot AJ, Chalmers RM, et al. Impact of the COVID-19 pandemic on gastrointestinal infection trends in England, February– July 2020.

BMJ Open 2022;12:e050469. https://bmjopen. bmj.com/content/bmjopen/12/3/e050469.full. pdf 3. FoodNet 2020 Preliminary Data | FoodNet | CDC 4. Salmonellosis in Australia in 2020: possible impacts of COVID-19 related public health measures. Barbara P F Davis, Janaki Amin, Neil

Franklin, Paul J Beggs. https://pubmed.ncbi.nlm. nih.gov/35092999

Dr Craig Shadbolt is Principal Food Safety Scientist with the NSW Food Authority, regulating food safety from paddock to plate. f