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Pest control is an essential part of Good Manufacturing Practice in food processing from a hygiene, economic and regulatory viewpoint.
Pests can carry a wide range of diseases causing organisms, including bacteria, viruses, protozoa and helminths that can cause harm to consumers and staff of businesses processing and handling food. They can also cause physical contamination of ingredients and processed products from, for example, droppings, shed fur and feathers, body parts, nesting material and damaged packaging.
Legislation worldwide requires pests to be excluded from food processing plants and the prevention of food contamination by pests, by taking effective measures to maintain hygiene and keeping adequate documentation, following the recommendations of the Codex Alimentarius. This includes applying current good manufacturing practices and the use of systems such as HACCP (HARPC in the US) to:
Not taking adequate measures to prevent and control pests can lead to substantial financial costs to the business from stock and product loss, product recall, loss of reputation and legal action that could ultimately cause the closure of the business.
Pests can be brought into the food processing facility through the supply chain, in the ingredients or packaging, and the facility itself will attract pests through food odours and lighting. The buildings provide shelter, warmth, food, water and safety from predators, which are ideal conditions for proliferation unless appropriate action is taken.
Control of pests in food processing requires the implementation of an Integrated Pest Management program. This has three basic steps: inspection, identification and treatment but is a complex process that requires specialist expertise to implement to achieve accredited food standards and comply with legislation.
The range of pests found in food processing plants will vary according to climate, geography and food ingredients processed, but the most common ones are beetles, moths, rodents, cockroaches, and flies.
Stored product insects (SPIs) is a generic term that covers beetles, weevils, moths and mites (which are actually arachnids) infesting food in storage anywhere in the food chain from the farm to the kitchen.
A Rentokil commissioned survey of 1,000 companies in five countries found that they were the pest category that caused the most economic losses to food processing companies:
Stored product pests are most likely to be in a food ingredient on delivery to a processing factory or a processed food product when stored for a long time.
They can also enter packaging made of paper, cardboard, plastic, cellophane and foil. The entrance holes of some insect are smaller than can be seen by the human eye, so there may be no visible damage to packaging containing pests.
Insects and mites may only consume a small quantity of food but can contaminate large quantities through physical damage, faeces, cocoons, etc and the introduction of microorganisms that cause further degradation, making food unfit or unacceptable for human consumption.
The pest activity in raw product ingredients can also change their physical and chemical properties, causing them to cake during processing which can halt production lines and damage machinery.
The Rentokil research found high percentages of companies affected by direct costs and delays caused by SPIs:
Beetles & weevils
Stored product pest control
These pests are controlled by using standard quality control measures throughout the supply chain, for managing suppliers, logistics companies, incoming shipments, storage of raw materials, processing, packaging and storage of final product.
The ship rat, which used to be more common, is generally confined to some port areas.
Rats and mice are attracted by food supplies and do not venture far from their shelter or nesting sites, so in a large facility will nest close to accessible food stores.
Rats and mice are capable of a rapid increase in population given an abundant food supply, due to the number of litters they are capable of producing and the time to maturity, shelter from predators and benign environmental conditions inside a building.
The hazards to food processing facilities from rats and mice include:
Rats and mice have distinct but different signatures that show which pest is present:
Control of rodents involves the elimination of harbourage in and around buildings and preventing access to food, water and shelter. There may be many points of entry to a building, such as cracks, vents, pipes, cabling, drains, doorways, windows, screens, where measures can be taken to prevent access. Any rodents present must be controlled using traps or poison according to acceptable practices and legislation related to food processing.
Rodenticides used in food processing facilities must be approved products, placed in secure bait stations and restricted to areas where food is not processed.
If stored on site they must also be stored in suitable conditions that prevent contamination from the poison in food products and the environment.
Expertise is needed to determine the type of bait used, where it should be placed and the frequency, the monitoring regime and the documentation, which is best done using an outside contractor. If done in-house, staff will need to be certified to handle the chemicals and carry out the rodent control activities.
There are specific requirements for documentation in food standards and legislation, such as maintaining maps of all bait stations, records of sightings, records of training of staff, the monitoring regime, therefore it is important to have trained personnel responsible for this.
They cause particular problems for food processing because of their size (giving them the ability to hide in small places), their varied diet, rapid reproduction and the diseases they can carry.
There are over 3,000 species of cockroach, but just three species are commonly found in food processing plants:
German Cockroach (Blatella germanica): the adult is about 12-15mm long and light brown. It prefers wet, humid conditions and can infest production areas and equipment, food storage areas, vehicles, offices and administrative areas, kitchens and bathrooms.
American cockroach (Periplaneta americana): the largest cockroach that may infest facilities, adults are 35-40mm long and reddish brown. It requires warm, humid environments to survive. They are found in drains, sewers, basements, storage rooms and waste storage areas.
Oriental cockroach (Blatta orientalis): the adult is 20-25mm long, intermediate between the other two and has a dark brown or black body. It prefers cooler, dark and damp places to shelter, such as basements and drains, and can be found in storage rooms and waste storage areas.
Cockroaches are primarily nocturnal, sheltering in the daytime and coming out at night to find food and other sites for shelter.
The challenge with cockroaches is that they shelter in places, which are hard to reach using normal cleaning and sanitation methods.
They like dark places such as cracks, crevices, drains, sewers, inside equipment and machinery and hidden spaces that provide the right temperature and humidity.
Good sanitation practices in the food facility will help prevent infestations and pick up the presence of cockroaches:
Cockroaches can feed on small residues of food left from spills or in preparation areas, so good cleaning practices which eliminate the residues quickly will deny them a food supply;
Store food in cockroach-proof containers: they eat cardboard so this should not be used for storage;
Maintain drains in good condition to prevent accumulation of food debris and means of access and shelter;
Removal of waste from food production areas, garbage container design that denies access to all pests, positioning of garbage containers away from the food storage and processing areas, emptying and cleaning frequently, all reduce risk of infestation;
Good building design can reduce the risk of access eg through spaces around pipe and cable ways, vents, screens, windows, doorways, sewers; and harbourage in small spaces such as junction boxes.
A good inspection regime for equipment, buildings and shipments will pick up infestations and identify risks quickly.
A number of treatments are available for control of cockroaches, including sprays, aerosols, dusts and bait. In a food processing facility the insecticides used must be permitted for use by the relevant authority and will require competent, trained personnel to apply them.
Rentokil uses chemical-free control methods suitable for sensitive business environments and Insect Monitor Units to detect signs of activity.
The impact of a fly infestation on a business is not just a loss of income.
A number of fly species are attracted to the odours present around food processing plants, including fruit flies, drain flies and filth flies, including house flies.
Different fly species are attracted to different food products, including fermenting sugars, oils and fats, carbohydrates, and decaying proteins and vegetable matter.
Drain flies are attracted to rotting food, sewage and other organic waste material. They lay eggs in organic waste that can build up in drains or polluted shallow water.
They can breed in the gelatinous bacterial films — biofilms — that form on surfaces in drains, septic tanks, compost, etc, and are resistant to cleaning and pest-control chemicals.
Their ideal environment can be prevalent in food processing facilities where food particles are washed into the drains during regular cleaning activities.
Fruit flies are attracted to fermenting sugary liquids, in which they can feed and breed in very small amounts. The liquid can accumulate in:
In warm conditions with suitable ‘substrate’ to breed in flies have a short lifecycle and can multiply rapidly.
Food processing facilities can provide an attractive array of suitable substrates for flies, if hygienic practices are not adequate.
Filth flies, including house flies, drain flies and flesh flies are known to be able to carry over 100 pathogens that can cause disease in humans, including Salmonella, cholera, Shigella, Campylobacter, E. coli, Cryptosporidium, parasitic worms and fungi.
They feed on faecal matter, garbage, rotting materials as well as stored and processed foods in food processing plants.
They will regularly move between the contaminated food sources and clean areas, carrying contaminated filth on their bodies as well as microorganisms internally.
Many types of fly have hair like structures on their bodies, hairs and sticky pads on their feet and deeply channelled mouth parts that can pick up contaminated material as they feed.
Also flies such as house flies regurgitate digestive juices and defecate while feeding and resting, contaminating foods and surfaces with microorganisms that can cause disease or decay.
Fruit flies are not generally considered to be as great a health risk as other flies because they are not thought of as filth feeders. However, they do need a protein supply to produce eggs and this can be animal faeces.
Several studies have found that fruit flies can transmit faecal material to fruit, where they lay their eggs by puncturing the skin, and can transmit E. coli. (Sela, S et al. Mediterranean Fruit Fly as a Potential Vector of Bacterial Pathogens. Appl Environ Microbiol. 2005 Jul; 71(7): 4052–4056. doi: 10.1128/AEM.71.7.4052-4056.2005).
Therefore fruit flies need to be regarded both as potential vectors of spoilage microorganisms and disease.
The application of standard hygiene practices are particularly important for controlling flies to reduce the attractive odours, feeding material and breeding sites.
Exclusion is dependent on the design and maintenance of the facility, including:
As a last resort pesticide is applied using approved products applied by trained personnel following accepted practice.
The most common bird pests are pigeons, house sparrows, seagulls and starlings.
Birds can cause physical damage by dislodging roof tiles, particularly the larger birds, and blocking guttering with nests and feathers.
They produce substantial amounts of droppings which foul buildings, vehicles, paved areas and building entrances.
Inside buildings, bird droppings, nesting material and feathers can contaminate surfaces, machinery and food products.
Apart from being unsightly, birds can transmit many human pathogens including viruses, bacteria, fungi and protozoa. More common microorganisms include Salmonella, E coli and Campylobacter.
Bird nesting and roosting sites also encourage infestations, of arthropods such as bird mites, fleas and some beetle species.
Bird control consists of preventing access to food, water and shelter. Basic practices to prevent access to food and water are:
Denying shelter includes eliminating nesting and feeding sites on buildings and in the vicinity of the facility. This should start with the design of the facility and include measures to prevent access to flat roofs, balconies, ledges, chimney stacks, guttering and culverts, which are favourite areas for nesting.
Bird repellant systems include:
WHO. Public Health Significance of Urban Pests
Keener, K. Safe food guidelines for small meat and poultry processors. A Pest Control Program. Purdue Expension, Purdue University
Sela, S et al. Mediterranean Fruit Fly as a Potential Vector of Bacterial Pathogens. Appl Environ Microbiol. 2005 Jul; 71(7): 4052–4056. doi: 10.1128/AEM.71.7.4052-4056.2005
Lupo L. Control of small flies. Quality Assurance Magazine. 31 March 2015
Lupo L. Controlling Flies: Large and Small. Quality Assurance Magazine. 13 August, 2013
Lupo L. Cockroach FAQs. Quality Assurance Magazine. June 3, 2014
UNIDO. Good Manufacturing Practices: Pest Control. Paper 9