It's a bug's life

As the old joke goes, the only thing worse than finding a beetle in your sandwich is finding half a beetle - where did the other half go?

Naturally, pest control is no laughing matter for food and drink processors. They would rather there were no beetles at all - or any other creepy crawly, for that matter.

Unfortunately, the pests are more prevalent than consumers would like to believe. In a recent presentation at Leatherhead Food International's Sensing Profit for The Food Industry conference, Dr Angus Knight, research specialist in molecular biology, said: "The US Food and Drug Administration detection limits for accidental mixing in corn meal are 25 insect fragments, two rodent hairs or one rodent excreta fragment in every 50g of cornmeal. For tomato juice the limit of detection is five fly eggs and two maggots in every 100g of tomato juice."

That such limits exist illustrates how hard it is to eradicate pests from factories or storage areas. But the threat posed by their activity is too great to be ignored.

The variety of animals that could infiltrate a premises bear an equally exotic variety of pathogens. E.coli, no stranger to the food industry in the past year, can be spread by flies, cockroaches, rodents and birds. Salmonella, Listeria and Toxiplasma can all be passed on by rodents and birds. Flies can also pass on Campylobacter and Streptococci and cockroaches can carry Staphylococcus aureus. Then there's the ever present threat of bird flu. "Most technical managers are aware of the risk of birds and the general level of education around this issue is getting better," says Rentokil md Jed Kenrick. "The Department for Environment, Food and Rural Affairs is very, very concerned about bird flu."

Of course, it could be argued that the risk of pests transmitting diseases to humans via processed food is minimal. Independent consultant Slim Dinsdale has worked with many food processors over the years and has never come across a direct link between pest infestation and consumer infection. "If you read the text books, pests can carry all kinds of bacteria, but I've never seen any evidence. If a mouse has Salmonella, it's going to make it ill and its chances of survival are reduced, so the transmission risk is quite low."

This may be true, but infection can happen. "Insects can carry a variety of organisms in their bodies and rats and mice can carry diseases in their guts," says Gill Palmer, consultant for Reading Scientific Services. "Pests are also fairly mobile and can transfer infection from canals and waste sites, for example."

And if human infection is traced back to a pest problem, the ramifications are huge, especially where deaths are involved. "In consequence terms, microbiological risks are bigger; in food safety terms, they're smaller," says Kenrick.

The biggest risk is financial, either in terms of equipment problems and subsequent production delays or in terms of damaged reputation, say experts. "Webbing from moth cocoons can clog machines," says Sam Osili, md of pest controller Pest Free Environmental Services. "Pests damage equipment. They chew cables and can bring plants to a standstill."

Oliver Madge, chief executive of the British Pest Control Association, says: "If pests contaminate your production line, you will have to stop, clean it and start again. Hundreds of thousands of pounds will be lost for every hour you're not producing."

But there may be even larger financial consequences, says Kenrick. "If you have an own-label contract with a retailer, it may represent 70-75% of your trade, but if a mouse paw is found in your food, it won't hesitate to pull the contract."

Firms found to have infestations face potentially unlimited fines. Those deemed responsible could be jailed for up to two years and banned from managing food businesses.

Fighting pests is therefore a war worth waging and major manufacturers take the issue seriously enough to spend hundreds of thousands of pounds on continuous pest control programmes, says Kenrick. But as any army is aware, knowing your enemy is half the battle. So what are the beastly forces arrayed against the different food and drink sectors?

According to Osili, rodents are common to all foodstuffs, aside from possibly soft drinks and coffee. Mice often hitch a ride on pallets returned from supermarkets. Flour beetles and pigeons are the bane of bakers' lives, while fruit flies afflict dairy and jams and preserves processors, and brewers "because of the pools of stagnant water you find in breweries". Grain weevils can be a nightmare for brewers and bakers alike. Wasps and ants can be found scuttling around jams and confectionery, while saw-toothed beetles can frequent chocolate makers. Ready meal and canned goods manufacturers can be plagued by cockroaches "because of their wet, hot and humid environments", says Osili. Meanwhile, Dinsdale says moths can be a problem if you're dealing with dried soups. "They lay eggs, the larvae hatch and people get very distressed if they find them."

Every war has its high tech weaponry and fortunately the food industry has an arsenal at its disposal when it comes to deterring, detecting and eliminating the opposition.

With deterrence, it's good to go back to basics, says Palmer. "A lot of pest control is about prevention rather than cure. You have to ensure there's no ingress for pests, so for example make sure warehouse doors are shut when not in use." A ring of external traps certainly help, but there's no substitute for plugging holes and keeping doors closed. "Doors often get left open, for example in goods out areas," says Osili. "In areas such as bakeries it can be hot, so people ventilate them by keeping doors and windows ajar."

Look for gaps anywhere, says Palmer. One hot spot is where cables feed into buildings. Gaps should be sealed with hard, gnaw resistant materials, such as cement, mortar, hard filler, brush strips or fine gauge mesh wire, says Leicester City Council. Hoses should be capped on container vehicles when not in use, so they don't provide access to pests.

Drains and toilets can be weak points. In addition, puddles of water or scraps of food can attract animals, which is why high standards of hygiene and cleaning are so important.

Blocking potential access points is fundamental, but some pretty unusual tricks can also be used. If you thought falconry was only really useful in the Middle Ages, for example, think again. Kenrick says the use of birds of prey remains one of the best ways to ward off birds. "If you regularly sweep your premises with a falcon, especially at peak times of year, such as spring nesting time, it has a deterrent effect on birds. You can contract them from a falconry or from ourselves."

Whatever your defences are, though, they can easily be breached. One of the latest devices to detect incursion is Rentokil's bait box, which automatically sends a mobile phone text message alert when it has been triggered by movement. It also carries a bar code so pest controllers can quickly scan check it using radio frequency technology while performing inspections. But even gadgets have limitations. "Once activated, some smart bait boxes become inoperative until reset," says Osili. "We have designed one that is permanently active with the University of Brunel."

Detection boxes are also vulnerable to damage in the dusty, wet and hot environment of many factories and some people even steal them. There's no substitute for painstaking manual inspections, which can uncover tell-tale signs such as droppings and stock damage, says Osili.

If an infestation is detected, there are a host of means to eliminate the foe. Rentokil, for example, has just launched Radar, billed as the world's smartest mousetrap, which provides two entrances for mice, one at each end of the unit. If the mouse trips two consecutive infrared beams, the trap is sealed and carbon dioxide is released to gas the critter to death.

Traps that use ultraviolet rays to attract flies, then either capture them with glue boards or electrocute them, are still commonly used in the industry.

Pheromones are used to lure moths, but at the moment they mainly attract the male of the species and their effectiveness can be diluted by air conditioning or fans, says Osili. He says the pest control industry is moving away from powder-based pesticides to deal with rodents towards gels. "Powders get blown about and can come into contact with workers."

Other changes to pesticide use may be in the wind. Impending amendments to the European Biocidal Directive may present problems for the industry. The resultant financial impact, especially if only the more expensive pesticides are permitted, could be an issue, he says. "If you're a smaller pest control outfit, it could make it harder to compete."

Clearly, pests present a considerable risk for the food industry, both disease-related and financial. But if you don't want to be at the end of a lawsuit launched by the customer who found half a beetle in their sandwich, it's as well to be forewarned and forearmed.