Pests: A source of contamination in food establishments

By Marilyn Collins

Marilyn Collins is a former Director of the Government Analyst Food and Drugs Department. She is currently a lecturer at the University of Guyana

Between 2007 and 2009 the Peanut Corporation of America (PCA) was forced to initiate recalls of Peter Pan Peanut Butter which affected more than 600 persons and resulted in nine deaths during a massive Salmonella outbreak. This product recall triggered liability and litigation implications in excess of US$11.2 million. Unsanitary conditions which lead to pest violation were pointed to in this Salmonella outbreak which had disastrous public health consequences.

Sanitation is a key pillar of pest management. It eliminates the factors that attract pests to food facilities. Those pest security factors are food, water and shelter. The proliferation of pests within food establishments can present a major nightmare for the regulator but moreso for the proprietor and consumers. The sight of pests can result in significant customer loss. Pests can also directly result in morbidity and mortality arising out of consumption of contaminated foods.

20150911marilyn collinsPest management is an important component of good manufacturing practice. It demands documented procedures on methods of eradication and control. Pest and vermin frequent dirty places and thrive on dead and decaying plant and animal matter. Thus, they readily carry disease-causing organisms on their bodies and legs which can contaminate food and food contact surfaces. Additionally, they deposit larvae, insect casings and body parts on foods.

Flies, cockroaches, rats and mice are common pests. Flies are capable of carrying over 100 pathogens including those that cause typhoid, cholera, salmonello-sis, Staphylococcus aureus, bacillary dysentery, anthrax and parasitic worms. Flies eat only liquid or semi liquid food. Solid food is liquefied by the fly’s saliva or vomit. Since their food intake is so high, they also defecate constantly. Virtually any time a fly lands on a surface, it is either regurgitating or defecating, which is why they are treated as a serious sanitation issue.

Rodents (rats and mice) in addition to eating our food also constantly urinate and defecate. Mouse dander (minute scales from hair and skin) also trigger asthma attacks in sensitive individuals. In addition, both rats and mice directly transmit such diseases as hantavirus, tularemia, plague, leptospirosis and salmonellosis, as well as indirectly spreading rickettsialpox and typhus.

Cockroaches are some of the most difficult insects to control and reportedly spread at least 33 kinds of bacteria, 6 kinds of parasitic worms and 7 other human pathogens.

There are pests that arrive in stored products, like weevil or beetles. Other pests include birds, ants, pets and silver fish.

Pesticides control pests but pesticides alone are not the solution. Improper use of toxic pesticides can lead to food contamination with disastrous consequences. A better solution is to have a holistic pest management programme as part of your food safety programme. This approach to pest management is intended to minimize reliance on chemical pesticides. This holistic or integrated technique focuses on pest exclusion, sanitation, baiting, environmental sanitation and harborage prevention. It also utilizes management tools such as reports on pest location, pest type, needed repairs and processes. It warrants knowing pests that can be located in your food establishment so that you can use their own habits and behaviours against them.


Control of pests

Cockroaches like to hide in narrow areas that touch their bodies both above and below; special attention is paid to cracks and crevices walls and gaps between shelving. The two species of cockroaches that normally infest food service establishments can be classified as colonizers or invaders. Colonizers, as the name suggest, are difficult to eradicate. Invaders live on the outside and enter the premises when conditions on the outside become unfavourable.

One of the major problems with spraying has to do with the contamination of uncovered foods and food ingredients. Additionally, this type of treatment kills only cockroaches near the surface. Flushing agents within the spray can cause the cockroaches to spread to previously uninfected areas. Additionally, spraying does not penetrate egg cases to kill eggs. When those eggs hatch, the baby cockroaches eat anything they can, grow, reproduce and the cycle begins all over again.

Thus, spraying could serve like farming cockroaches, since it empties the environment, which leaves plenty of room and food for unaffected cockroaches to thrive, causing the cycle to begin again.

Bait works very well for cockroach infestations but is different since it does not disperse like sprays. In addition, the cockroaches eat the bait and it is carried where the other cockroaches have gathered. When they defecate, the poisonous faeces are consumed by the baby cockroaches resulting in death. Sprays can contaminate baits and interfere with the baits’ attractiveness to the cockroach. However sprays known as insect growth regulators are highly recommended, since the insect’s development can be arrested at all stages prior to reproduce.



All rodents share the common characteristic of a pair of upper and lower incisors, which grow throughout their lives and must gnaw against each other to keep from growing to unmanageable lengths. Since rodents are forced to gnaw, they can be very destructive to property and can cause electrical fires by gnawing on wiring. The average rodent can fit into an opening the size of a dime by collapsing its rib cage to squeeze through any opening that is bigger than its skull. Usually droppings are one of the first signs of an infestation. Some other common signs are gnawed food and a musky smell,

Knowing the characteristics and behaviour of rodents can aid in the development of pest control strategies. It is estimated that rats and mice consume or contaminate up to one-third of all the food produced in the world annually. Some rodents are curious, but that curiosity wears off after a day or two, so the baits and/or traps become ineffective. They also have limited memories, so after they forget about the bait and/or traps that have been placed, they will return for another visit. Other rodents have been described as neophobic, or afraid of new things. Advantage is taken of this neophobia in pre-baiting, firstly using nonpoisonous grains, then gradually introducing lethal, slow-acting poisons. Rats demonstrate a high level of intelligence in that in large colonies the smallest and weakest rats are used as tasters. They are the ones that eat the new food and the rest of the colony watches to see what happens. Accordingly, poisons must be both painless and slow acting, because rats will observe their companions to see whether they have adverse reactions. Rats do require a source of water, so eliminating any free-standing water in a facility will do a great deal to resolve a rat problem.

Another successful strategy for baiting or trapping is to search out the best hiding place for rats and bait exclusively at that location. When the top rat in the hierarchy is eliminated; the others that replace him will die in turn until all the rats are gone.

Keeping rodent infested areas clear of clutter will prevent and restrict their ability to hide, since they despise open spaces.


House flies

Most foods establishment become concerned about flies when they see them flying around as adults. However, it is much easier to control them as larvae. Flies hatch from eggs as maggots, feed on wet organic matter and then leave that matter to pupate, emerging from the pupae as adult flies. Wet, organic matter occurs in many places in a food establishment. It takes only a day or so for the fly to hatch from the egg, and about a week or more to pupate. Twice-weekly thorough cleaning of wet organic matter from the areas mentioned can completely disrupt the fly’s life cycle. Interior light electrocutors can be used to trap and kill adult flies, but sanitation will reduce fly populations to much more manageable levels.


Knowledge of pests

Information on the characteristics, habits and behaviour of pests is critical in developing pest control strategies. Cockroaches carry bait back to where they gather and poison their young. Some rodents are curious and check out baits/traps, then check them out again when they are replaced after a delay. Some rodents will take baits after they become used to them. Flies are best controlled when they move around the least, that is, when they’re larvae. It is knowing the pest that allows us to eliminate, or at least control, the creature and prevent food contamination.

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