Flies and Food Safety – The Issues

The association between flies and food safety is basic stuff for all food managers. As you are no-doubt aware, houseflies and blowflies pose a particular problem for all caterers. Due to their nature, breeding patterns and habits they are able to transmit pathogenic bacteria directly via food or indirectly via contact with surfaces and equipment. You are also likely to know about their tendancy to regurgitate onto food and to deposit faecal matter. Traditionally the fruit fly has been seen as a mere nuisance. Common to bar areas, fruit flies can affect customer areas and spoil dining experiences. However, it is now recognised that they too are vectors for food poisoning organisms.

The life cycle of the fly involves the laying of multiple eggs (up to 150 at a time) which subsequently develop into larvae (maggots) before pupating in about a week or so. The pupal stage can aslt for a week or two before the adult fly emerges. The larva may hatch anything from 8 to 48 hours after laying; it is therefore important that food is not exposed to contamination by flies during preparation or storage. Food being cooled after cooking, for example, will typically be used within a maximum of a few days after preparation; this provides ample time for larvae to develop. In some cases larva can be layed directly in food as they may be held in the body of some females after hatching. However, regardless of the life cycle, the food will have become contaminated, potentially with harmful pathogens, at the point of first contact.

Flies and Food Safety – Control Measures

Physical control methods should be prioritised. Flies should be prevented from entering a building in the first instance. Double entry doors, self-closing mechanisms, closed windows and fly-screening may also help prevent ingress into catering facilties and kitchens. When staff use entrances or when deliveries are made it is important that doors be kept open for as little time as possible. Positive air pressure inside the building can also help prevent entry by pushing air out.

The outside of the building should be kept clean. Positioning of bin areas away from building entrances will help minimise access. Refuse storage areas should be kept clean and bins fitted with tightly fitting lids. Regular cleaning of hard-standing in refuse storage areas should take place.

Inside the building, all areas of the food business must be kept clean and spillages cleaned up. Non-absorbent surfaces are a must as is a well fitted structure. Drains and gullies should be cleaned out and any open waste piping removed or capped. Ultra-violet insect traps can also be used (positioned away from potential food contact) to help capture strays.

One last thing… don’t leave food out in the open – keep it covered.

When I inspect a food establishment the sight of a single fly will not lead to an infringement or penalty for the business. What I expect though is that the operator has taken sufficient preventative measures. A lack of control will lead to some form of action.

(This A to Z of pests is a nice little reference if you are interested in other pests.)