Guest Editor

Prof. Joseph Allotey
University of Botswana
Gaborone, Botswana

Food safety is a scientific discipline describing handling, preparation and storage of food in ways that prevent food-borne illness.  This includes a number of routines that should be followed to avoid potentially severe hazards. Food can transmit disease from person to person and food poisoning from microorganisms (bacteria and fungus) can cause many disorders in the body or general ill health. Food is a vital necessity for life and any food commodity is liable to contamination by various agents of bio-deterioration namely, microorganisms, insects, mites and so on. In many parts of Africa, the trend towards global urbanization causes a number of problems, which do not only include overcrowding, reduced sanitation, increased air and water pollution, but also an increase in both communicable and insect-borne diseases.  For example, cockroaches are commonly found in households of varying socio-economic brackets.  Insects are commonly found in the African tropics and some of them are vectors, transmitting micro-organisms, which are sometimes pathogenic to man through their interaction with his/her food and many unpleasant materials like excrement and filth from different sources.  Places such as bus stops, train stations, public gatherings such as sport occasions or exhibitory venues, which are popular to food vendors, are equally popular to some insects.  The street food vendors will take their food business to where people are available regardless of the conditions of the surrounding area or environment.  The surrounding areas might be a breeding place for insects, which transmit disease causing microorganisms to the food by their feet, body and mouth parts, through regurgitation of their vomit and through ingestion and deposition of fecal matter [1, 2].

A number of fungi have mutual symbiotic relationships with insects and insects serve as external and internal carriers of fungal spores, and contaminate food with various fungi upon physical contact.  Cockroaches (Blattella germanica, Periplaneta americana), Flies (House fly: Musca domestica, Blowfly: Calliphora spp. and Lucilia spp.) and Ants (Hymenoptera: Formicidae) and stored product insects (beetles and moths) are important insects in the human environment from the phytosanitary point of view.

Cockroaches and food safety

Cockroaches are omnivorous, their mouthparts are of the generalized biting-chewing type and they feed on a great variety of foods, with preferences for starchy and sugary materials. They will sip milk, nibble at cheese, meat pastry, grain products, sugar and in fact no edible material available for human consumption is exempt from contamination.  They also feed on excrement, sputum, fresh and dried blood, finger and toe nails.  Since they feed principally at night, many people live in ignorance of their dangerous and disgusting feeding habits.  They habitually disgorge portions of their partly digested food at intervals and drop feces wherever they go.  Cockroaches impart a persistent and typical “cockroach odor to food and dishes with which they come into contact; due to discharge of nauseous secretions from the mouth and from glands opening on the body. Because of their unsanitary habits, cockroaches have been suspected as aiding in the transmission of various illnesses.  For example, they are known to carry pathogenic viruses such as poliomyelitis, protozoa such as Entamoeba histolytica, Trichomonas hominis, Giardia intestinalis and Balantidium coli, and bacteria such as Escherichia coli, Staphylococcus aureus, Shigella dysenteriae, and Salmonella species including S. typhi and S. typhimurium [1, 3, 4]. Cockroaches act as vectors of pathogenic bacteria, yeasts and moulds in the hospital environment and have, therefore, been associated with nosocomial infections including dermatological diseases caused by Monilia moniliformis [5]. This infestation of hospitals and nursing homes poses a danger to the ill and the elderly whose immune systems may already be compromised.

The existence of antibiotic resistance patterns of various bacterial isolates from cockroaches to antimicrobial (antimicrobial) agents has been revealed [4].  This raises concern as some of these agents are antibiotics of choice in the treatment of some common ailments.  Conidia of the fungus Aspergillus niger were isolated from the faeces of American cockroaches, P. americana [6]. This indicates a potential for dispersal of these plant pathogens during storage and onto food.  Penicillium spp, A. niger, A. terreus, and Fusarium spp. have been isolated from various parts of cockcroaches [4].

Flies and food safety

Flies belong to the large and important order Diptera.  They feed on a variety of substances such as sugar, milk, and almost all food of man, rotten vegetables and carcasses, excreta and vomit, and almost any organic material.  During feeding, the mouthparts are extended downwards onto the food. The method of feeding differs according to the state of the food.  The proboscis is provided with a profusion of hairs that readily collect germs and filth.  The legs of the fly are fitted with hairy structure and pads that secrete a sticky material, thus adding to its collecting ability.  The fly usually acquires microorganisms by walking over materials containing them; both its feet and wings can be contaminated. For example, Salmonella are pathogenic enterobacteria and include various serotypes which cause salmonellosis in poultry. Salmonella pulorum causes disease in poultry and can be passed from the larva of a fly to the adult stage.  The opportunity for flies to become infected, therefore, is so great in all communities, even in the most sanitary, that no fly should be trusted to alight on food prepared for human consumption.

The insect families in the Diptera, most often represent and belong to the Muscidae (true flies such as the housefly) and Calliphoridae (blow flies).  Flies are known to become contaminated with many species of pathogenic organisms, including the causative organisms of amebic and bacillary dysentery, typhoid fever, cholera, salmonellosis, anthrax, leprosy, yaws, trachoma, poliomyelitis, infectious hepatitis and many more others. The housefly, Musca domestica, can transmit a large number of diseases to man owing to their habit of visiting almost indiscriminately faeces and other unhygienic matter and then the food of man.  In addition, they vomit during feeding and frequently defaecate on food.  They are also vectors of amebic dysentery caused by Entamoeba histolytica, Giardia lamblia, and eggs of a variety of tapeworms, for example.  Taenia spp., including T. solium, Hymenolepsis nana, H. diminuta, Diphyllobothrium latum, and Dipylidium caninum..  They also carry parasitic nematodes such as Necator americanus, Ancylostoma duodenale, Enterobius vermicularis and Ascaris lumbricoides. Blow flies (Calliphora and Lucilia) are commonly heavily contaminated with microorganisms.  They have access to carrion and offal in slaughter houses and have been shown to be contaminated with the bacteria Salmonella and Clostridium [7, 8]. There is also evidence that Lucilia spp. may carry poliomyelitis. Meat or fish intended for human consumption must be protected from oviposition by blow flies; otherwise, it will be fly blown.

Transmission of diseases by flies is in most cases mechanical, and the pathogens do not undergo cyclical development in them.  When foods infected with fly maggots are eaten, the maggots may be passed more or less intact in the excreta, often causing considerable alarm with regard to the origin of the maggots, for example, whether they are from the food consumed.

Ants and food safety

Ants are among the most common pests of the home. Their nests are found almost everywhere in lawns, under houses, in the walls of the house, in open ground, under stones or wood, in wood of decaying trees or in locations that afford protection.  Ants are social insects of the order Hymenoptera and live in colonies.  They enter buildings when seeking sweet or fatty substances in the kitchen, pantry, storeroom, or warehouse.  In crawling back and forth over exposed food, ants may mechanically introduce pathogenic microorganisms into the food.  Small size ants such as Crematogaster spp. can enter containers not easily accessible to larger ants.  All ants infest pantries, shelves, cabinets and cupboards even though they have been kept closed and scrupulously clean.  Thief ants, Solenopsis molesta will eat practically anything, but appear to prefer foods with high protein content; they will eat sweets also [9].  The ant, Iridomyrmex humilis is attracted to sweet substances while S. molesta is attracted to meat or fatty foods. The Pharaoh’s ant, Monomorium pharaonis is attracted to both meat and fatty foods but small pieces of raw liver are especially attractive [3].  Some ants often visit moist or liquid substances for water and can be seen in drains, urinals, on faeces, sputum and so on.  An investigation of the bacteria carried out by M. pharaonis revealed a number of unpleasant pathogens, including Salmonella spp., Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus spp. and Clostridium spp. [10].  A general objection to all kinds of invading ants is the unpleasant sight of workers clustering on food.  Their actual depredations are slight, but may be sufficient to damage the appearance of food, for example by biting holes in iced cakes.

Stored product insects and food safety

A considerable amount of stored food commodity is damaged, destroyed and contaminated by various agents of bio-deterioration such as insects and microorganisms every year, and insects occupy a key position among them.  Insects that normally infest stored grain rarely occurred in the absence of fungi, and several species are able to feed and survive on fungal diets.  Storage insects are disseminators of fungi in stored foods such as cereals and, pulses and promoters of mycotoxins in foods and animal feeds.  The presence of insects and their damage can lead to increased incidence of fungi especially Aspergillus, Penicillium, Rhizopus, Mucor and Fusarium.  Interaction between insects and fungi in stored food commodity could indirectly lead to increase in the production of fungal toxins (mycotoxins) since the insects may spread the spores of dangerous moulds (toxigenic fungi). The mycotoxins are health hazards to mankind.  For example the mycotoxins known as aflatoxins, which is associated with maize has been found to affect children leading to deformity and mental retardation.  Of great importance is the possible distribution of such harmful bacteria as Salmonella, Streptococcus and Escherichia coli by grain infesting insects. Sitophilus oryzae has been reported to contain Salmonella montevideo internally and externally after being in contaminated wheat for seven days.

Normally, freshly harvested grains, even before being milled into flour, are already contaminated with a range of potentially determinative agents, particularly insects and fungi from field and storage facilities.  Mycolflora such as Aspergillus, Penicillium and Cladosporium have been reported hidden in maize grains that can serve as nutrient sources for insect development. The storage fungi normally accompany or follow insect infestation.

Contamination of food commodities is further aggravated by poor practices of post-harvest handling.  The generation of metabolic heat and water by insects in stored food also increases the water activity (aw) and temperature of the maize flour to levels suitable for fungal growth and multiplication.  The presence and activities of these spoilage agents lead to deterioration of the food commodity, which is manifested by off-odours, discoloration, heating, caking rancidity and toxicity through production of mycotoxins [11].

The risk of mould and mycotoxins contamination of a food commodity depends on a complex interaction of several factors, which include moisture content, temperature, types of fungi, and their interaction with insects and previous storage history.

Environment and the consumer

Access to a secure supply of safe food is a human right. Everyone involved from food production, harvesting, processing, marketing and service, has a role in ensuring that food that reaches consumers will not be a hazard to human health.  National food control systems should be designed to ensure a safe food supply and to promote good health.  Food legislation requires food business such as food vendors, restaurants and hoteliers to conduct hazard analysis; and measures should be introduced to ensure production of safe food.  There are guidelines for food safety management systems (FSMS) defined by WHO and FAO Codex Alimentarius Commission based on general requirements for hygiene and the principles of HACCP, systems.  For example, the control of cockroaches wherever they occur is the key to preventing contamination of food by micro-organisms associated with cockroaches or their shed body parts and faecal pellets.  The use of integrated pest management system that incorporates cultural methods, good sanitation, use of environmentally sensitive insecticides and baits should be advocated and promoted.  At home level, this should include general cleanliness, proper discarding of left-over food, timely washing up of dishes and pots, rinsing of cans or bottles before disposal and use of cockroach-proof garbage bins.  Once inside a building, cockroaches spread rapidly and require access to air, food, water and a protected harbourage for survival and reproduction.  Therefore, removal of food remnants, water and hiding places needed by the cockroaches are some of the most important steps in cockroach management.  Access to water can also be reduced by proper construction practices even though cockroach populations cannot be removed entirely.  The following are recommended for households [12]:

1.         Storage of food items in insect-proof containers.
2.         Proper disposal of garbage and food remains from kitchens and stores.
3.         Keeping shelves clean and regularly vacuuming and cleaning household items.
4.         Prompt attendance to plumbing repairs, cracks and cockroach harbourages.
5.         Use of sticky straps for detection and monitoring of cockroach infestation.
6.         Minimal use of insecticides.

Outside the home, control should include proper management of landfills, use of proper disposal facilities in public vending and eating sites, proper sanitation and use of environmentally friendly chemicals to control the cockroaches. Special attention needs to be given to cockroach infestations in food processing and handling environments [13]. For example, bakeries, the institutions that turn various grain products into consumer edible items are prone to infestation of pests mainly insects such as cockroaches, flies, flour beetles and ants.  Hence the use of integrated pest management against these pests cannot be over emphasized.


For effective disease and pest management in the food environment, municipalities and planners and vendors have to come up with strategies.  These should include: 1) improvement in vending infrastructure; including primary infrastructure such as roads, water, sewage and light; and vending booths; 2) Improvement on provision and disposal of packaging material; 3) Effective legislation and monitoring; education of vendors, consumers, legislators and law enforcement officers to include HACCP (Hazard Analysis Critical Control Point) principles; 4) Aggressive campaign against agents of food-borne diseases (microorganisms, insects and rodents); 5) National, regional and international networking to confront the problem of microbial and insect-borne diseases associated with contamination of food. The application of HACCP is an important step for the majority of the food industry and one which, if approached sensibly and with the conviction to make it work, should make food safer with a consequential reduction in the number of people becoming ill and dying from food poisoning.  Pest control has an important part to play, provided that in their working partnership, the food and pest control industries are aware of each other’s priorities and systems.  This should prove a benefit to both and, more importantly, it will prove to be a positive benefit for the consumer by the production of safer food.

Many thanks to the Editor-in- Chief and Founder of AJFAND, Hon. Prof. Ruth Oniang’o, for pursuing academic excellence and application of knowledge acquired. Joseph Allotey


  1. Service MW A guide to Medical Entomology.  Macmillan Press Ltd., London. 1980.

  2. Service MW Medical Entomology for students.  2ndedition, Cambridge University Press, USA 2000; 212 pp.

  3. Busvine JR Insects and Hygiene: the biology and control of insect pests of medical and domestic importance.  Chapman and Hall Ltd., London.1980.

  4. Mpuchane S, Gashe BA, Allotey J, Simpanya MF, Matsheka MI, Jordaan A and SH Coetzee Cockroaches in the home, cockroaches everywhere.  A technical bulletin on common domestic cockroaches. Printing and Publishing Company, Gaborone. 2004; 74pp.

  5. Marty AM Cockroaches can vector human diseases.  International Journal of Dermatology 1998; 37:639-640.

  6. Onuegbu BA Dispersal of viable conidia of onion black mould (Aspergillus niger) by the cockroach (Periplaneta americana) Onion Newsletter for the Tropics 1994; 6: 63-64.

  7. Greenberg B Blowflies as vectors. Ann. Entom. Soc. Amer. 1960; 53:125.

  8. Greenberg B Blowflies as vectors.  Am. J. Hyg.1963; 77:177.

  9. Ebeling W Urban Entomology, University of California Press, Berkeley, 1978; 695pp.

  10. Beatson SH Pharaoh’s ant as vectors.  Lancet. 1972; 19:425.

  11. Sinha RN, Tuma D, Abramson D and WE Muir  Fungal volatiles associated with mouldy grain in ventilated and non-ventilated bin-stored wheat.  Mycopathologia 1998; 101:53-60.

  12. Allotey J, Mpuchane S, Gashe BA, Simpanya M and I Matsheka   Trapping of Blattella germanica (L) populations in human dwellings in Gaborone, Botswana.  Journal of Applied Zoological Researches 2009; 20(2): 175-188.

  13. Mpuchane S, Allotey J, Matsheka I, Simpaya M, Coetzee S, Jordaan A, Mrema N and BA Gashe  Carriage of micro-organisms by domestic cockroaches and implications on food safety.  International Journal of Tropical Insect Science 2006; 26 (3): 166-175.

 Back to top