A Grower's Guide to Preventing Food-borne Illness from Berry Crops

Table of Contents

1. Introduction
2. Learning about the enemy
3. Contaminated irrigation/spray water
4. Contaminated soil/compost/manure
5. Personal hygiene
6. Contact with animal wastes
7. Post harvest handling and reducing the risk after harvest
8. Canadian Water Quality Guidelines for Irrigation Water:
9. Related Links
   

Introduction:

Ontario berries are nutritious and very safe to eat. Growers have a critical role to ensure that their crop production practices do not jeopardize Ontario's reputation for growing high quality berries.

This information provides growers with tools to develop on-farm food safety programs that will reduce the risk of microbial contamination of berries. Many of the recommendations here are logical and are already in place on your farms. Others may take a good practice one step further. Adapt the good agricultural practices that apply to your situation. Take time to formalize or document what you do. On-farm food safety plans can protect you from creating a potentially hazardous situation. It can also protect your reputation and your markets.

Today's strategies focus on prevention and risk reduction on the farm. However, science in the field of food safety is proceeding very rapidly. Our recommendations on how to reduce the risk of food-borne illness from eating fruit and vegetables will evolve as new and better information is developed.

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Learning about the enemy

Organisms causing food-borne illness:

Microbes are everywhere in our environment. Most are harmless; however, some have the potential to cause illness in people. Bacteria, parasites and viruses causing illness are referred to as "pathogens". They commonly occur in animal or human excrement and can be spread in water, soil or by handling. Foods that contain pathogenic microbes often look, smell and taste normal. Low levels of bacteria on the surface of soil or plants are usually killed by ultraviolet light from the sun. Once microbes are on berries it is very difficult with current technology to remove or kill them. Due to the absence of a kill step such as cooking, a preventative approach is required for berry food safety.

Bacteria are single-celled living organisms. They need moisture, food and warmth to multiply and grow. The temperature zone where bacteria multiply is called the "danger zone". This temperature range is between 4°C and 60°C (40°F and 140°F). Under ideal conditions, bacterial numbers can double about every 20 minutes. After berries are picked they should be kept at 4°C or less to keep them out of the danger zone.

Examples of bacteria that contaminate produce include:

E. coli 0157:H7: Escherichia coli is a very common bacteria found in livestock manure, especially cattle, deer, sheep manure and wildlife droppings. There are many different strains of this bacterium yet only a few strains cause human illness. Escherichia coli 0157:H7 causes no illness in livestock, but this particular strain can produce large quantities of potent toxins that may cause severe damage to the lining of the intestine, especially in children, immunocompromised individuals and the elderly. As few as 10 cells may cause illness. This type of E. coli has developed the ability to survive in acidic environments.

Salmonella: A bacteria that is carried in the intestinal tract of apparently healthy poultry, swine and reptiles. Sources of contamination include water, soil, insects and animal feces.

Shigella: This bacteria is found only in humans. It is transferred to food by unsanitary worker hygiene or by contaminated water.

Protozoa: Protozoa which include foodborne pathogens, have complicated life cycles and reproduce only inside a warm-blooded host. They produce cysts, which can be persistent and are not susceptible to chlorine treatment. Filtration from water supplies is possible but very expensive.
 
Cyclospora cayetanensis: This protozoa is an intestinal parasite which is found in human waste or contaminated water. Only recently was it identified as a pathogen. It is
not known to occur naturally in Ontario but has been implicated on imported produce.

Cryptosporidium parvum: This protozoa is found in feces of infected young calves and humans. Other species of Cryptosporidium infect birds and mice, but not likely humans. The cyst stage of the life cycle can survive in water for 12 months and is not controlled by chlorination. Cysts must be filtered out of polluted water supplies.

Giardia lambdia: A protozoa which is carried by domestic animals (dogs and cats) and wild animals (beavers and bears). It causes diarrhea in humans. Giardiasis is most frequently associated with the consumption of contaminated water.

Viruses are infectious agents that require a host in order to reproduce. Viruses that affect humans will not reproduce on or in a plant. Virus particles are very tiny and will pass through the pores of membranes used to filter bacteria.

Hepatitis A is a virus that causes jaundice, abdominal discomfort and other symptoms. It is excreted in waste of infected humans. It does not infect livestock. It is spread via contaminated water or foods. Contamination of foods commonly occurs in processing plants or restaurants if workers with poor hygiene handle food.

For more information see the "Bad Bug Book"

1. Potential causes of contamination of berry crops:
   
2. Contaminated irrigation and spray water
   
3. Contaminated soil/compost/manure
   
4. Poor worker hygiene
   
5. Contact with animal wastes
   
6. Improper post harvest handling

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1) Contaminated irrigation/spray water:

Our water supplies are very clean compared to some parts of the world where berries are grown. However, water used for irrigation or spraying is a potential vehicle for contamination of Ontario berries. The potential for contamination by water varies depending on the type of irrigation used (drip vs overhead), the source of water, the water quality, the number of days between irrigation and harvest, and the physical characteristics of the crop, drying conditions, etc. Growers can reduce the risk associated with contaminated water by taking these facts into consideration:

• Ground water is less likely to be contaminated than surface water.
  
• Water can be tested for E. coli or fecal coliform bacteria. This test does not detect the presence of protozoa such as Giardia, or Cryptosporidia, however, the presence of E. coli is a good indicator of other potential problems.
  
• Standard procedures for sampling water have not been developed. Levels of bacteria can fluctuate seasonally. Test surface water throughout the growing period. A test that does not indicate a problem does not mean contamination can't occur.
  
• Drip irrigation is less risky than overhead and sprinkler irrigation because there is less contact between water and fruit and less chance of splashing contaminated soil onto fruit.
  
• The longevity of some water-borne microbes on fruit is not known in all cases, however, the longer the interval between irrigation and harvest, the lower the risk of contamination.

Good Agricultural Practices For Water:

• When using surface water for irrigation or spraying restrict access of livestock to water. Consider fencing the pond to prevent or limit access by deer, wildlife and domestic animals.
• Be aware of potential for livestock contamination of water upstream. Significant urban run-off or storm sewer overflows upstream of the irrigation source may also cause problems.
  
  Protect wells and pump heads from contamination.
• Irrigated produce should be thoroughly dry before harvest. Berries with an irregular surface, (not smooth), especially raspberries, may take a long time to dry. The longer the interval between irrigation and harvest, the lower the risk of contamination.
  
  Water used for evaporative cooling should be of drinking water quality. This means, NO fecal coliforms or E. coli present.
• Consider testing irrigation water and water used for spraying for microbes. The indicator organism E. coli is preferred over fecal or total coliforms. Use the following
  water quality guidelines for irrigation water as one tool to indicate a problem. Testing may not detect specific pathogens, especially if they are present in low numbers. A single test may not indicate a problem with contaminated water. Maintain records of water tests.
• Canadian research indicates that microbes can multiply in pesticide spray solutions. For that reason, consider using potable water for spraying.

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2) Contaminated soil/compost/manure:

Because berries are grown near to the ground, they can become contaminated in the field if they contact soil containing harmful microbes. These harmful microbes can come from manure fertilizers, manure-based composts, polluted floodwater and contaminated dust. Strawberries are at greater risk than other berry crops for contacting soil-borne contaminants. However, rain-splashed soil may contact blueberry or raspberry fruit on lower branches, especially in new plantings where bushes are small.

Good Agricultural Practices For Soil:

• Do not use manure to fertilize berry crops before harvest, in the year of harvest.
  
• All manure or other organic amendments should be fully composted before application to fruit crops. Proper composting will reduce the level of most pathogens, but there has not been adequate research to ensure this is true for all pathogens. Composting is not the same as aging.
  
• Manure should be incorporated immediately after application when the soil is warm and not saturated.
  
• Be aware of land use around producing berry fields. Ensure that run-off or wind-blown debris from livestock operations or manure piles does not come in contact with berry fields.
  
• Do not let harvest containers or packaging come in direct contact with soil.

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3) Personal Hygiene:

Many human pathogens are harbored in the intestinal tract and spread in feces. These pathogens then come in contact with produce through contaminated hands. Virus diseases are also spread by hand contact, sneezing and coughing. It is essential that persons handling produce are healthy and have clean hands.

Good Sanitation Practices For Personal Hygiene:

• Insist that all persons handling berries wash their hands before working with produce and after using the toilet.
  
• Teach and emphasize hand washing procedures and good hygiene practices.
• Ensure that there are adequate, convenient, toilet facilities for all employees, and that these facilities are used.
• Provide toilet paper and hand washing stations at all toilets.
• Supply clean water, liquid soap, and disposable paper towels at all hand washing stations. Use an alchohol sanitizer or wipe if clean water is not available. These are not effective if hands are visibly dirty.
• Employees having open wounds, boils or open cuts on their hands should cover them with bandages or clean, waterproof gloves before being permitted to contact berries.
• Employees who are sick should be reassigned to jobs that do not come in contact with fresh produce.
• Pick-your-own operations and roadside markets should be equipped with clean toilet and hand washing facilities that are stocked with toilet paper, fresh water and paper towels.
• Encourage customers to wash all fruits and vegetables that will be eaten raw.
  
• Petting zoos should be equipped with hand-washing facilities. Do not allow customers to eat in this area.
  

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4) Contact with animal wastes:

This contact may come from wildlife, livestock, or pets. Birds are common carriers of Salmonella, E. coli and many other bacteria. Rodents and some insects may carry numerous human diseases. Berries may be contaminated by animal wastes in the field, in contaminated packaging, or in infested storages.

Good Agricultural Practice for Animal Wastes:

• Restrict field access by wildlife as much as possible, especially deer, dogs, cats, and geese.
• Enforce a no pets policy, especially in strawberry fields, before and during harvest.
• Do not use geese for weed control in strawberries in the year of harvest.
• Use clean containers for harvesting. Ensure that areas where containers are stored are free from birds, rodents, and other wildlife.
• Instruct pickers to discard berries contaminated with bird droppings.
• Disinfect and sanitize all surfaces ( i.e wagons and packing tables) which have been contaminated by animals.

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5) Post harvest handling and reducing the risk after harvest:

Record keeping: Keep records of what you do and when it is done, especially with respect to water testing, manure and compost applications, irrigation scheduling, harvest dates, worker training, and pesticide application. In a crisis, this information can be useful to show the steps you have taken on your farm to prevent food-borne illness.

Worker training: Develop a system where all workers receive a basic training at the beginning of the job and periodically during their employment. Training should include information on hand washing frequency, hand washing procedures and how to handle the berries.

Canadian Water Quality Guidelines for Irrigation Water:

Microbiological Parameters:

Fecal coliforms (E.coli): 100 bacteria per 100 ml water
Total coliforms: 1000 bacteria per 100 ml water

Source: Environment Canada, 2002 - Water Quality

Related Links

• Bad Bug Book
• Environment Canada, 2002 - Water Quality

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