FACTSHEET –THE IMPACT OFANIMALS ON THE RISKOF FOODBORNE ILLNESSIN FRESH PRODUCE
- May 8
- 7 min read
Updated: 6 days ago
FACTSHEET –THE IMPACT OF ANIMALS ON THE RISKOF FOODBORNE ILLNESSIN FRESH PRODUCE
This fact sheet addresses the issue of the impact of intensive animal production and
animal intrusion on the risk of foodborne illness in fresh produce
Why are we seeing increased foodborne illness associated with fresh produce?
Demand for fresh and healthy convenience foods has led to greater consumption of fresh horticultural produce over the last two decades1. Fruits and vegetables can be major vehicle of foodborne outbreaks as they are often consumed
raw, with no kill step to eliminate pathogens
2 FACT SHEET
that can be acquired from the field or processing environment or human contact2.
In the US, foodborne illnesses from fresh produce increased from 12% in the 1990s to 24% in the 20103,4. In Australia, there have been 32 fresh produce-related outbreaks between 2010 and 2015 with 1260 reported cases of illness5. Improved technologies detecting human pathogens – such as whole genome sequencing – has resulted in greater awareness and traceability of fresh produce being linked to foodborne illnesses.
Identification of environmental sources and understanding the transmission processes of
foodborne pathogens in the food supply chain are necessary to manage food safety risks.
Animals are a source of foodborne illness pathogens in fresh produce
Wild and domestic animals are the main reservoir for a broad range of pathogenic zoonotic agents and includes bacteria (Campylobacter spp., Escherichia coli, Salmonella spp., Listeria monocytogenes, and Yersinia spp.) and parasites (Cryptosporidium spp.
and Angiostrongylus cantonensis). Animals carrying these human pathogens in
their intestinal tract often appear healthy, even though the pathogens can cause severe disease in humans. Among the faecal-borne zoonotic pathogens, Salmonella enterica (14.1%), and Shiga toxin–producing E. coli (STEC; 5.7%), were the most commonly reported causative agents of global fresh produce related outbreaks3-5. Animal production and wildlife intrusion in proximity or upstream along an irrigation water source from fresh produce producers can pose a significant risk of pathogen transfer to produce via aerosols, faecal deposition or contaminated irrigation water as shown in Fig 1. Sources of enteric foodborne pathogens that can impact horticultural produce include runoff or bioaerosols from nearby domestic animal operations, human sewage/septic facilities, infected farmworkers, contaminated agriculture water, untreated manure-based soil amendments,
“Contamination may occur through; direct contact of the crop with faeces;
use of irrigation water from polluted dams or rivers; or untreated manure-
based soil amendments.
lies or other invertebrates and wild animal intrusion/defecation in the production area6.
What are the major zoonotic pathogens associated with intensive animal production
and wildlife? Salmonella spp. Salmonella enterica is one of the most important human foodborne bacteria in industrialised countries and is potentially spread through farmed animals such as chickens, cattle, sheep and pigs, as well as wild animals such as
rodents, amphibians and reptiles, mammals and birds. Contamination may occur through: direct contact of the crop with faeces; use of irrigation water from polluted dams or rivers; or untreated manure-based soil amendments. Shiga toxin producing E. coli (STEC) This pathogen can cause illness with severe symptoms and further complications. Cattle is the major reservoir of this pathogen but it has also been isolated from other livestock and domesticated animals including sheep, goats, pigs, horses, cats and dogs10. Wild animals, such as rodents, rabbits, ruminants like deer, wild boar and feral swine, and birds, as well
as invertebrates, such as flies, can be reservoirs or transient carriers for STEC. Birds, especially, can move E. coli across long distances to, from, and among agricultural facilities.
What risks exist in having intensive animal production close to produce production areas?
Run-off water into nearby aquatic environments and bioaerosols from intensive animal production operations are important risk factors associated with fresh produce contamination7, 11, 12. However, cattle on rangeland, as well as livestock on small-scale diversified farms, can also be sources of foodborne pathogens, and potential
interspecies transmission with wildlife has been documented (e.g. transmission between pastured cattle and feral pigs)13. Intensive animal operations often produce large numbers of livestock in concentrated confinements.
These are environments that harbour high loads of zoonotic pathogens and enable pathogens to proliferate. Water acts as a transmission pathway for pathogens and poses a risk to nearby or downstream produce production areas. Strawn et al.14 found significantly higher prevalence of Salmonella in produce farms with livestock operations located nearby, particularly in water samples. Intensive animal operations such as feedlots or poultry barns are also significant sources of bioaerosols. Zoonotic pathogens can become airborne and deposited on land, facilities and water sources by wind carriage. Handling and application of slurry and solid biowastes are sources of bioaerosol generation as well as turning
of compost15.
Research in the USA has shown that the current
leafy green field distance guidelines of 120 m
may not be adequate to limit the transmission of
airborne E. coli O157:H7 to produce crops planted
near concentrated animal feeding operations,
although additional research is needed in
other geographical regions in the US and other
countries15
What is the risk from wildlife incursions in
production sites?
Faecal contamination of produce or surrounding
watersheds as well as intrusion by wild animals
into production sites is considered one of the
significant risk factors for pre-harvest produce
contamination.
Foodborne outbreaks have been associated with
wildlife intrusion including birds, deer, rodents,
feral pigs, turtles, dogs, rabbits, hares, kangaroos
and wallabies. In Australia, STEC and Salmonella
have been isolated from faecal samples of native
marsupials16, and wild western grey kangaroos17,
respectively.
The public health importance of kangaroo to
human transmission of pathogenic E. coli and
Salmonella could not be determined as no fresh
produce outbreaks or cases of salmonellosis or
pathogenic E. coli infection have been linked to
kangaroo intrusion.
Farming operations can encroach on, change or
destroy wildlife habitats, especially when land is
cleared to expand. This causes increased wildlife
contact and pathogen transmission into farmland
and farm water sources12. Management of food
safety risks from potential wild animal sources
is particularly challenging in open crop fields
and orchards. Weller et al.18 reported that the
percent of E. coli transferred from faeces to
fresh produce decreased with time after faecal
placement, and with distance between the
produce and the faeces. They suggest that a
Key take-home messages:
History of the land use and adjacent lands:
Spatial knowledge of land use of the fields and surrounding areas, and their history, is essential to developing an effective co-management risk reduction strategy
at the grower level. Harvesting time and wildlife activity: Know whether harvesting times correspond to periods of increased wildlife activity. Manage your risks: There is no uniform
approach for assessing wildlife intrusion risk. Each farm (and even field) will be different
and may change across seasons and years. Therefore consult wildlife and food safety
specialists to assess which wildlife species are potential problems.
Good practices for managing co-existence of animal and crop production:
• Control livestock movement by keeping farm animals confined and/or far away from
water sources, growing fields and storage area • Establish buffering zones between livestock
operations and crops/water sources e.g. riparian zones and wetlands, non-crop or
low-risk crop plantations
• Use dedicated tools for farm animal
activities and crop activities
• Compost biowaste to reduce microbial load
before application to fields
• Do not spread manures prior to heavy
rainfall
• Prevent intrusion and minimise habitat of
wild animals in the crop production area
e.g. using fences, buffer zones and bird
repellents
• Do not use pesticides or chemical
repellents in the growing field
• Support co-management of food safety
goals and maintaining biodiversity near
farmlands
• Take corrective actions when clear
evidence of animal intrusion in the field is
found
“Faecal contamination of produce
or surrounding watersheds as well
as intrusion by wild animals into
production sites is considered one
of the significant risk factors for
pre-harvest produce contamination.”
FOOD SAFETY CULTURE 5
no-harvest buffer of 0.5 m around in-field wildlife
faeces would reduce the proportion of E. coli
transferred to fresh horticultural produce by
approximately 1.5 logs.
A similar study by Jeamsripong et al.19 showed a
0.72 log reduction in E. coli transferred to fresh
produce with a 1.524 m no-harvest zone and
suggested extending the holding time between
irrigation and harvest. These findings provide key
data that may be used in hazard characterisations
and risk assessments at the grower level to
eliminate food safety risks associated with wildlife
intrusion and intense animal production.
Recommended practices for animal
intrusion, resource conservation and food
safety co-management
The wildlife component of global guidelines
generally involves conducting pre-season and
pre-harvest environmental risk assessments;
monitoring for animal intrusion and faecal
contamination of the production environment
during growth and harvest; establishment
of no-harvest zones where product may be
contaminated by animal activity/faeces; and
training of farm workers to recognise, report and
mitigate these risks20. While seeking practices
to reduce wildlife attraction is essential for food
safety, some food safety practices have resulted in
conflicts with conservation of natural resources and
agricultural areas due to the limited understanding
of best management practices for potential wild
animal risks.
Hence, the concept of co-management emerged
and was defined as an approach to conserve and
protect soil, water, air, wildlife and other natural
resources while simultaneously minimising
microbiological hazards associated with food
production21.
Recommended primary production practices to
minimise food-safety risk from animal intrusion
include:
i. planting low-risk crops as a buffer between
high-risk crops and pathogen sources (e.g.
pastures),
ii. planting non-crop vegetation around farm
fields to filter pathogens from runoff,
iii. fencing upstream waterways from livestock
and wildlife,
iv. distancing livestock from upstream waterways
with water troughs, food supplements, and
feed,
v. vaccinating livestock against foodborne
pathogens,
vi. constructing wetlands near feedlots and
intensive animal operations,
vii. reducing the use of agricultural chemicals
to bolster bacteria that will keep zoonotic
foodborne pathogens under control,
viii. composting effectively with high temperatures
and regular turnings before amending into soil
to enhance fertility, and
ix. maintaining diverse wildlife communities
to prevent the transmission of zoonotic
diseases20.
In the USA, several industry guidelines such as
California Leafy Green Marketing Agreements,
Western Growers, and Arizona Leafy Green
Marketing Agreements, have incorporated
the co-management concept into their best
practices21-25.
Pre-harvest microbial contamination from wild and
domestic animal activity in primary production
environments pose a public health risk because of
the low infectious dose of many of these zoonotic
foodborne pathogens, and the potential for their
downstream survival and amplification during
harvest, processing, transportation and storage.
There is an urgent need to better understand the
predisposing factors that contribute to microbial
contamination of horticultural crops from domestic
and wild animals to develop targeted mitigation
strategies and to promote co-management of food
safety and conversation of nature.
Knowing the history of adjacent lands, times of
increased wildlife activity and consulting with
experts on species that pose a potential problem are
important activities to undertake in managing risk
he FPSC is providing these fact sheets to translate
relevant published research for the Australia and
New Zealand fresh produce industries.
Fresh Produce Safety Centre Australia & New Zealand
Room 517, Level 5, Life Earth & Environmental
Sciences Building, F22
The University of Sydney, NSW 2006 Australia
Twitter: @safeproduceANZ
The information on this document is intended to
provide users with information of a general nature only.
Please read our disclaimer here.
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