Heppro Ltd North East Pest Control, Property And Grounds Maintenance
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Bed Bugs
Bedbugs – what’s the score?
Wall lice, bug flats, crimson ramblers, chinches, Norfolk Howards, mahogany flats, etc., etc.. The humble bed bug (Cimex
lectularius) has gained a place in world-wide folk lore and is universally reviled. Many years of onslaught in the UK had
reduced their populations significantly, but recently this troublesome pest has had a resurgence, both in terms of numbers
and in several instances of pesticide tolerance. Why? Let’s begin with a review of the pest and its habits.
As man moved from a hunter-gatherer to living in urban settlements, many insects took advantage of this localised
situation. Initially, flies and beetles were attracted to food storage and preparation areas. Bed bugs moved in as the human
dwellings improved and became more permanent. They are closely related to the bat bug (Cimex pilosellus) and probably
first became associated with man when they were living in caves in Africa.
Humans (very much as they are now) were sought for a blood meal whilst they slumbered on the floor of the cave. The
bugs would locate their host by detecting their body heat and the carbon dioxide given off in their breath and through
their skin. Interestingly, there is still a species of bed bug (Leptocimex boueti) that still feeds off the blood of both humans
and bats in West Africa.
As civilisation evolved, the bed bug became our bed fellow, moving into our homes in ever increasing numbers. Sanitation
and personal cleanliness were offered as a defence against lice and other bodily pests. In 1602, Ulysses Aldrovandi, a
renowned social observer, reported that bed bugs were much more common in houses of the poor than in those of the
rich, because the rich had the means to keep their houses cleaner than those of the poor. In the late 1800s, bed bugs
were regarded as probably the most serious urban pest. Commercial pest control companies began to form in the larger
cities across Europe at this time. Their preparations ranged from chemicals that we would run a mile from today, to several
that we still recognise and use today – mercuric chloride in alcohol was regarded as an excellent treatment for bed bugs,
and pyrethrum and rotenone were beginning to arrive from the Orient.
In more recent times, the success of pesticides, such as organophosphorous compounds and pyrethroids, has meant
wide-scale eradication of bed bug populations. We realise now that dirty housing is not a pre-requisite for bed bug activity,
but it is thought that the unfortunate decline in social standards in some areas of the populous, coupled with an increase
in close-packed communities HMOs (houses of multiple occupancy, student accommodation, bed-sits and not forgetting
down-and-outs) have led to bed bug populations increasing significantly.
So what exactly is a bed bug? These insects are members of the order Hemiptera, the true bugs, which includes bugs
that attack house plants and pond skaters that live on the water’s surface.
The bed bug has a simple or incomplete metamorphosis. Mating is a rough affair, with the male actually puncturing the
female’s abdomen to inject sperm directly (a process known as “traumatic” insemination for obvious reasons!). A female
can lay up to 200 eggs over about two months. There are five nymphal stages which take 35 to 150 days to pass through,
depending on conditions. Adults are able to survive long periods in unoccupied houses or in furniture in store. In
desperation, they can survive on other species, such as poultry, sparrows, rats, mice and guinea pigs (which may explain
some long-term continued infestations). Adults that are well fed can then resist long periods of starvation – timescales of
nearly one and a half years have been recorded.
Nymphal instars take about three minutes to have a blood meal, but adults need over ten minutes to become engorged.
The mouthparts are adapted to form two pairs of stylets that puncture the skin. The outer pair is provided with barbs to
saw into the skin, and the inner pair form two tubes, one for sucking up the blood, and one for injecting saliva containing
an anticoagulant. A fully engorged adult can be 6-8mm long.
For many, the bite is painless, but some can detect it straight away. A typical red “wheal” is left by the biting insect,
caused by an allergic reaction to the saliva. The location of the bite(s) is very useful to a pest controller in diagnosing the
biting species. Flea bites are most commonly on the lower leg or ankle, whereas bed bug bites are often on the face, neck
arms or hands, and occasionally around the waist.
Where do they live? Within the urban ecosystem, there are three primary components, the human and non-human and
the physical structures. The habitat that is made up of human settlements is known as “Anthropobiocoenosis”. Probably
the biggest word ever used in Pest Control News, this lengthy term means the part of the environment that has been
completely changed by man. It can even be sub-divided into “peridomestic” habitats, which are those outside dwellings,
and “domestic” habitats, which are located inside dwellings. The bed bug has invaded most areas of the latter category,
but principally those areas where we sleep. This is because time is needed to take a blood meal, and unless you are a
couch potato, humans do not sit still long enough for this to occur in the sitting room!
Control of bed bugs has always been relatively straightforward, although often a great deal of searching and a thorough
treatment or series of treatments was needed. However, in recent months, reports have been appearing in the national
press of “super infestations” of “resistant mutant bed bugs”. This situation needs explaining.
It is known that the incidence of bed bugs is increasing, especially in London and in some of the university towns and
cities such as Cambridge. It is also known by a number of pest controllers that several populations are becoming very
difficult to treat successfully. Expressions like “pesticide-resistant” are thus bandied about. Such a term is not warranted.
True resistance is a biological term, meaning a population which, over time, has become “immune” to the effects of a
pesticide. This can only be conferred by surviving adults to their offspring and so takes time and several generations. The
instances reported in the press are more likely to be ones of “tolerance”, whereby the bed bugs are able to tolerate a
pesticide and survive. (The offspring of these survivors would therefore be “resistant”).
Like all treatments where a given product appears not to work, the selection of a pesticide from another group of active
ingredients if often the answer. Currently, the infestations that are causing some difficulty seem to be able to tolerate the
use of pyrethroids, and some are also carbamate-tolerant.
Nigel Binns, Biologist for Killgerm Chemicals Ltd., commented: “We are receiving a number of phone calls where
technicians are experiencing difficulty in controlling bed bug infestations. If they have used pyrethroids and/or
carbamates, a return to the use of organophosphorous pesticides usually does the trick. The down-side to this is that they
are often a little ’smelly’, and so the customer should be advised. Organophosphorous pesticides that are approved for
use as public health products are perfectly safe in such situations, providing the technician follows the label
recommendations.”
Finally, the bed bug does have predators. T. Pergande, a Union soldier in the American Civil War, reported that Pharaoh’s
ants (Monomorium pharaonis) attacked and dismembered bedbugs in an infested quarters in Mississippi – perhaps this
is a novel form of biological control that we could choose to employ. Two infestations for the price of one!
Cockroach and dust mite
Many allergies are well-recognised and understood, but insect and mite allergies are still being examined. A study in 1997,
supported by the US National Institute of Allergy and Infectious Diseases (NIAID) conclusively demonstrated that the
combination of cockroach allergy and exposure to the insects is an important cause of asthma-related illness and
hospitalizations among children in U.S. inner-city areas.
“Some of the most vulnerable of our citizens, children in the poorest neighbourhoods of our large cities, suffer
disproportionately from asthma,” says Anthony S. Fauci, M.D., NIAID director, in the report. “Allergy and exposure to
cockroach allergen clearly play an important role in the alarming rates of asthma-related sickness among these children.”
“Reducing exposure to cockroach allergen, as part of a multi-faceted approach to asthma management, may be a cost-
effective way of reducing the burden of this serious disease,” says Daniel Rotrosen, M.D., acting director of NIAID’s
Division of Allergy, Immunology and Transplantation. “Simple and relatively low-cost interventions that have been explored
in the NCICAS, such as patient education, roach traps and child-safe insecticides, are potentially important.”
The first five-year phase studied 476 of these children. The researchers measured levels of cockroach, dust mite and cat
allergens in the children’s homes, and determined with allergy skin tests that 37 percent of the children were allergic to
cockroaches, 35 percent to dust mites, and 23- percent to cats. The investigators then assessed the severity of the
children’s asthma over 12 months.
They found that children who were both allergic to cockroaches and exposed to high cockroach allergen levels were
hospitalised for their asthma 3.3 times more often than children who were allergic but not exposed to high levels of
cockroach allergen, or children who were exposed to high levels of cockroach allergen but who were not allergic. Children
who were both allergic and heavily exposed to cockroach allergen also missed school more often, needed nearly twice
as many unscheduled asthma-related medical visits, and suffered through more nights with lost sleep.
In addition, the activities of the adults who cared for these children were frequently disrupted. Researchers also collected
dust samples from each child’s bedroom with a hand-held vacuum cleaner to measure the level of each allergen. While
most bedrooms had detectable levels of all allergens, 50.2% contained high disease-inducing levels of cockroach allergen
compared with 12.6% of rooms with high levels of cat allergen and 9.7% with high dust-mite allergen levels.
Even when families do all the right things at home, though, “…the biggest cockroach problem, in some cases, is at the
schools themselves,” says Dr Jean Hanley-Lopez, Los Angeles Breathmobile Director. “In inner-city L.A. schools, students
have a high level of cockroach exposure,” she says, “but I’m sure the school district is not even aware how big a problem
this is for students with asthma.”
Dr. Thomas Platts-Mills, one of the NIAID researchers, mentions several difficulties. “People don’t always understand that
they have cockroach allergies. Cockroach dust also disperses ‘all over the house,’ making it difficult to eliminate. Sprays
make a lot of asthma patients worse,” Platts-Mills adds, “and you can use all the bait traps you want, but they won’t work
if the cockroaches have a supply of food.”
“It’s all very well to have ambitions to decrease cockroaches,” he concludes, “but we need more understanding of how
to do it.” Dr. Richard Evans, an asthma specialist at Children’s Memorial Hospital in Chicago agrees: “The one thing I
would do is help people get rid of cockroaches.”
Dust mite allergy is an allergy to a microscopic organism that lives in the dust that is found in all domestic dwellings and
places of work. People are slowly recognising that dust mites and their droppings are perhaps the most common cause
of asthma and allergic rhinitis.
House dust is not a single substance but a cocktail of potentially allergenic materials. It may contain fibres from different
types of fabrics, feathers and other stuffing materials, dander from cats, dogs and other animals, bacteria, mold spores,
bits of plants and insects and other particles peculiar to an individual building. House dust also contains thousands of
microscopic mites which live in bedding, upholstered furniture, carpets etc. They thrive in summer and tend to die in
winter. However, in warm, humid environments such as a centrally-heated house, hospital or office, they continue to
thrive.
Each mite produces about twenty waste pellets a day, each containing a small amount of one of the most dangerous
chemicals known to science. Not only is the allergen of the house dust mite the usual cause of babies and small children
becoming asthmatic, it is also the commonest on a long list of irritants which cause existing asthmatics to have respiratory
symptoms.The constant presence of house dust mite droppings in the air inside homes keeps the lungs of asthmatics sensitive to
all the other factors which trigger asthmatic symptoms. If sufferers can avoid the dust mite allergen for a few months, then
usually the other factors lose much of their power.
Because mites are so tiny, their body water regulation is critical. As a result, the droppings they produce are very dry. The
average population per gram of dust is believed to be from 100 to 500, but can be up in the thousands. Egg-laying female
mites can increase the population by 25 to 30 every three weeks. Mites are equipped with sticky pads on the ends of their
feet, so they are able to burrow deep in carpet fibres and furniture where they hang on and are able to survive vacuuming.
Proteins in the dust mite droppings, called Der P1 and Der F1, are severe instigators of allergic response. When these
floating pellets are inhaled, they cause problems in the mite-allergic person. Even after the mite’s death its faecal particles
remain in the home, and the mite’s disintegrating body parts are still allergenic and easily airborne.
Although no environment is free of dust mites, there are specific steps you can take to reduce the number of these
creatures in your home. Many of these emanate from old wives’ tales, but have their basis in fact:
Mattresses, box springs and pillows should be encased in non-allergenic, plastic-zipped casings. The zips should be
covered with adhesive tape. Wipe with a damp cloth or vacuum weekly. If there is more than one bed in a room, each
mattress should be encased. If bunk beds are used, the allergic child should sleep on the top bunk. Avoid using canopy
beds.
Use washable blankets, spreads and polyester or dacron pillows. Avoid feather pillows, down or padded comforters, wool
blankets and chenille spreads. Wash all bedding frequently in hot water (over 60 degrees centigrade). Don’t use an
economy wash as mites survive in warm water, and you just end up with clean mites!
Ants
Understanding Ant Music
The ability to communicate through infochemical means, including pheromones, is at its highest among insects which live
in homogeneous communities – social insects. The ant in particular is distinguishable by its numerous exocrine glands
and the various chemicals it secretes as it relays information among its groups.
The largest ants have eyes located about 5mm from the ground whilst the smallest have eyes less than 1mm above the
ground and are unable to see beyond anything more than 5mm tall. Eyesight then, is not their strongest point. Ants
evolved from bees and they have developed acute olfactory senses which enable them to forage for food even in the
darkest situations. The ant senses environmental chemicals such as odours or non-volatile matter through physical
contact via its antennae. It then reacts according to the information the chemicals convey.
Chemical signals for species recognition
Insect species consist entirely of males and females with a male and female from each species reproducing. Sex
pheromones facilitate mating encounters however, how does an insect ascertain that the potential mate belongs to the
same species?
Dr Ryohei Yamaoka, of the Kyoto Institute of Technology has evaluated the important role infochemicals play in individual
identification among ants by observing their behaviour in their fascinating world. The team sampled cuticular waxes,
particularly hydrocarbons, from more than 500 species of insects including ants. They discovered that the composition of
these substances was species specific for all the insects sampled. They also discovered what happens when two ants
from different species meet and fight savagely. Only when the antennae of one ant actually touches its opponent’s body
will the fighting begin. No matter how closely the two pass, unless the antennae of one touches the body of the other, no
fighting will occur. Ants do not recognise their opponents by vision, but by non-volatile chemicals on their bodies and they
also seem to confirm membership of the same species by detecting like-for-like hydrocarbons in the same way.
Different species of ants can live together
In order to live together, different species must change their previous recognition of their cohabitants as belonging to
different species. Slave maker ants (Polyergus samurai) invade nests where so-called hill black ants (Formica japonica) or
forest black ants (Formica sp.) live, attack and steal pupae and cocoons from them and bring their booty back to their
own nest. They attend to the pupae and cocoons until they hatch as well as nurturing the slave maker queens’ eggs. In
the nest, slave maker ants avoid productive activity. They walk about lazily prompting slave ants to feed them.
Dr Yamaoka’s team sampled cuticular hydrocarbons from two species of ants which live harmoniously in the same nest
as previously mentioned and discovered that slave maker ants can barely synthesize hydrocarbons natural to their own
species and receive the cuticular hydrocarbons they possess from slave ants through bodily contact. Accordingly, slave
maker ants take on the same hydrocarbons as those of their slave ants and are thus chemically camouflaged, rendering
them recognisable as cohabitants by their slave ants.
Signals which allow ants to identify mates from the same nest
The chemical discrimination ability of the ant is so great that it can distinguish not only ants of different species, but ants
from different nests (colonies). Cohabitants from the same nest are generally offspring of the same queen ant and share
the same kinship. However, other ants, even those from the same species, share no common kinship when they inhabit
different nests. Instead, they are intense rivals, competing for common food sources.
Ants from a given nest are believed to use individual or group odours, distinctive to the nest they inhabit, although the
composition of the chemicals involved remains undetermined. However, the composition of the hydrocarbons, which act
as a signal for species recognition, must be identical between residential and visiting ants, as they are members of the
same species… you would think.
The tests the team conducted bore interesting results. The profiles of composite hydrocarbons showed great variety from
one colony group of ants to another, or were distinct in each type of ant tested. There was also diversity in ants from a
queen-less nest. But samples taken from ants in the same nest with a queen were identical. This is due to the queen which
will entice nearby worker ants around her by use of a pheromone. In approaching, the workers initiate physical contact.
Accordingly, cuticular hydrocarbons are exchanged among a swarm of individual ants, leading to chemical consistency
of ants in the same colony.
Grooming
Grooming also plays a major part in “spreading” the same hydrocarbons among ants in the same colony. They use two
methods. One is to remove cuticular hydrocarbons from the partner by licking, then storing them in a special gland. The
other is to secrete them from the same gland for use in coating and grooming its own body.
Psocids
Psocids
“Sosids,” as the proper pronunciation is, are booklice and there are over 3000 species of them to be found across the
world, although less than 50 are associated with human activities, including food storage and processing. But, their
significance as pests has increased over the last 35 years, which has been a matter of considerable interest to the Society
of Food Hygiene Technology, which ultimately led them to sponsor a survey among their members.
The results were published in 1984 and, although they helped to define the problem, they highlighted the need for further
research, as many questions about them still remain unanswered.
Psocids are widely distributed and typically favour dark places. They infest domestic premises, raw material stores,
manufacturing, distribution and retail premises; museums have also been infested and a wide variety of commodities may
be infested, including those which are of animal and vegetable origin, particularly farinaceous materials.
A four-fold problem
Nuisance – Psocids are a nuisance in industry because they interfere with production and threaten the integrity of
products, so reducing the quality and wholesome nature of the food.
They are typically associated with newly completed homes – damp building materials, plaster, etc., foster the growth of
mould on which the insects feed. Also, they are regularly encountered in food cupboards where they infest cereals, flour,
sugar, gravy thickener, etc..
Direct feeding damage – Psocids are not usually associated with damage caused by feeding activities, but direct
damage to commodities is possible and particular problems may be experienced when valuable articles, such as furs,
books, etc., become infested.
Transmission of micro-organisms – Micro-organisms and their spores will survive passage through the psocid gut and
may be carried on the surface of their bodies. Psocids may therefore, disseminate spoilage organisms, or even possibly
pathogens.
Health hazard -There is no evidence that psocids are vectors of disease. Nevertheless, they may eat tapeworm eggs
and harbour their larvae and so act as intermediate hosts for such parasites. Despite this, there is increasing evidence
that the insects may be a source of environmental allergens. The main impact of psocid infestations in homes is regarded
as psychological, with reactions which are occasionally disproportionate to any real threat.
Major Pest Species – L. bostrychophila is the major psocid pest encountered in domestic premises, accounting for over
90%, and is usually associated with consumer complaints. It is not generally found in commercial food handling
situations. The various psocid species tend to be associated with particular situations.
Environmental Factors – Psocids are vulnerable to dessication at humidities specific temperature and humidity data, coupled with data for the intrinsic rate of increase were considered, L.
bostrychophila ranked amongst other major stored food pests in terms of adaptability and pest potential. Egg laying
ceases at temperatures L. bostrychophila thrives on a yeast diet which is typically regarded as a rich diet. It is generally accepted that psocids
are most successful on a diet in which micro-organisms are present in moderation. The fact that L. bostrychophila is
parthenogenetic means that under suitable environmental and dietary conditions, populations develop rapidly and
certainly much faster than those species restricted to sexual reproduction.
Monitoring – Effective methods for monitoring psocid infestations are essential if prevention and control strategies are to
be successfully implemented. They can be monitored by visual examination, trapping, filth tests and the pallet “knock-
out” test.
Control – Psocids are difficult to control because they are small and can hide in cracks and crevices, so avoiding pesticide
treatments. They can survive long periods without food and are ubiquitous. An integrated approach to control is desirable
which uses all suitable techniques in a compatible manner.
The aim should be to manipulate the environment to the maximum detriment of the insects by denying them access to
some essential requirement. Little can be done to proof buildings and denying them harbourage is difficult although this
can be an option in small kitchens. They don’t like cold, dry conditions and cannot survive at humidities application of dry heat with temperatures of 50-60oC will control psocids. As already said, freezing will kill them. Clearly,any reduction in humidity will also deter moulds which are a significant food source.
Control can be effected by the use of fumigants, space and surface spray treatments and a wide range of pesticides have
been shown to be effective for the control of psocids. Products based on the synthetic pyrethroids permethrin and
deltamethrin and the carbamate bendiocarb are well established in the control of psocids. However, there is evidence that
certain strains of L. bostrychophila featuring mixed function oxidase enzyme systems, which can detoxify and reduce the
effectiveness of some pyrethroid insecticides. This can be overcome by the use of the synergist piperonyl butoxide. PCOs
must therefore, be alert to possible variability in the control achieved using synthetic pyrethroids.
Conclusions
Psocids are ubiquitous pests which have the potential to cause a considerable nuisance, damage stored products and
pose a hazard to health, especially in sensitive individuals.
Evidence shows that complaints to the food industry have increased over the last 35 years, although the reasons are still
unclear. It is likely that psocids will continue to pose significant problems to householders and the food industry, but much
has been achieved in recent years developing a better understanding of the pest which must contribute to improved
control in the future.
Pests and Allergy problems
Other pests which cause allergy problems
Fleas
Heska in Orlando, Florida announced in 1997 a revolutionary breakthrough in flea allergy dermatitis (FAD) testing. Heska’s
team of immunologists has been carefully studying flea biology – the result is the development of novel diagnostic
reagents and detection technology.
The HESKATM Flea Allergy Dermatitis Test is the first test specifically developed for detecting IgE antibodies against flea
salivary antigens as well as whole-body flea antigens.
Flea allergy dermatitis is a common dermatologic disease, and has been traditionally defined as an allergic reaction to flea
bites caused by injection of saliva as the flea feeds. Insect-associated dermatitis is a hypersensitivity to whole-body flea
antigens. Cross reactivity has been shown between whole-body flea allergen and black fly, black ant and cockroach
antigens. Redness, inflammation and itching are caused by the various protein components in flea saliva that can
stimulate an allergic response. The clinical signs related to FAD depend on the degree of immunologic sensitivity and the
level of flea exposure.
Wasps and Bees
A few people are very allergic to things such as insect stings. When exposed to these items they may have a severe
allergic response, also known as anaphylaxis.
In North America and Europe, nearly 100 people a year die from insect stings. Death usually comes within the first hour
after a sting and is attributed to insect allergy and not the toxic effect of the venom. It is thought that heat stroke or heart
attack may be given as a cause of death when actually it was the result of a sting. More children are stung but in older
persons with complicating health problems such as coronary heart disease or chronic bronchitis, death occurs more
frequently. Most of the victims of fatal insect sting have evidence of specific IgE antibodies.
The severity of the reaction depends on, among other things, the amount of venom injected and the degree of
sensitisation. Some sting victims have been reported as suffering 2000 stings and surviving while others receive a single
fatal sting.
In general, honey bee venom allergens are distinct from wasp allergens. Several more suspected potent allergens have
been found solely in Vespula and Dolichovespula (the so-called Euro- or super-wasp). Clinical presentations include large
local reactions which may extend to the limbs, with disfigurement and swelling.
Highly aggressive honey bees from Africa were mistakenly released in Brazil during the 1950s. These bees colonised
nests of the native honey bees. Africanised honey bees are very much a threat in South and Central America and it is
predicted that they will be colonising the southern United States. In one study, venoms were compared biochemically and
immunochemically. These investigations concluded that the higher morbidity after sting by the Africanised bees was due
to their more offensive behaviour.
Honey bees are the only stinging Hymenopteran that nearly always leaves its fluked sting in the skin of the victim. The
venom continues to pump into the victim until the venom sac is exhausted or the sting removed.
Wasp stings are often more cause for concern. Among the Vespula species, Vespula vulgaris (the common wasp) is
responsible for inflicting the greatest proportion of stings and has a nasty disposition. They live in large colonies, with 500-
5000 individuals. When a colony is disturbed, the sentry wasps fly out, find the intruder and begin to sting. The venom
contains an alarm substance which tells the other wasps the location of the first sting. Then they continue stinging around
that site.
Whether stung by a bee or wasp, within moments susceptible people may have anxiety, a tight throat, shortness of breath,
and low blood pressure. These serious symptoms require prompt medical care, as breathing may stop and death could
occur. If you see someone having these problems, seek help by calling the emergency services. Watch and assist the
victim’s breathing if needed.
If people have ever had such a reaction, it may recur if they become exposed again. It is wise for them to wear an ID
bracelet to alert doctors. The use of anti-histamine tablets will help in the short term, but further treatment should be
sought.
Birds
Allergic reaction to birds is also possible. Pigeon fancier’s lung (PFL) is a form of extrinsic allergic alveolitis (EAA) – an
allergic reaction of the lungs to some external allergen. In PFL it is believed that small particles of dust containing pigeon
proteins cause the allergic response.
Professor Chris Feare of Wild Wings Bird Management in the UK said, “The allergens may emanate from both the pigeons’
droppings and also from the copious quantities of dust produced as pigeons shed wax from their feather sheaths, and
that any concentration of pigeons can be a source of allergens”.
There are two distinct but overlapping phases of EAA, namely an “acute” phase, which may or may not be followed by a
“chronic” phase. The acute phase is the most common and as the name of the condition suggests, is principally of
concern to pigeon fanciers. However, anyone who is exposed to a high level of “pigeon material” is at risk – so pest
controllers involved with pigeon proofing or guano clearance should take note.
Typically sufferers experience intense ‘flu-like symptoms of fever, chills, muscle ache, cough and/or breathlessness, four
to eight hours after exposure. The symptoms usually pass within 48 hours, but may persist for a week or more. Although
this attack will probably pass without treatment, it is important to visit the doctor whilst symptoms are still present,
preferably on the day of onset, as if you delay there may be no visible symptoms for the doctor to investigate.
It is important that the condition is identified as early as possible to prevent progression to the more serious chronic stage
of PFL. If detected and appropriate measures are taken early enough, acute PFL is reversible. If not detected (or ignored),
the acute phase may be followed by the chronic phase which is characterised by a type of irreversible lung damage
doctors call pulmonary fibrosis. This is very serious and in extreme cases may be fatal. The major symptoms are
breathlessness on exertion, coughing and weight loss, which can be considerable.
It can be seen that many of the symptoms are general to a number of “chesty” conditions, so it is important for sufferers
to recognise that there may be a possible link with pigeons and mention this to the doctor.
Chris Feare emphasises a further complication – similar ‘flu-like symptoms may be produced by a pathogen commonly
carried by pigeons (and other birds) and also present in their droppings. This is Chlamidia psittaci, the cause of ornithosis
in man, and it is therefore important that the diagnosis of the “‘flu” is correct. Like a number of other conditions passed
from birds to man, in most cases the symptoms can be passed off as “‘flu” and recovery is quick and complete. However,
if you happen to be one of the unfortunate few who are susceptible, things could get very serious indeed. It’s not just pest
controllers who are at risk. Even those whose houses, flats or shops have resident populations of pigeons are in danger.
All encounters with high levels of “pigeon material” must be regarded as potentially highly hazardous and precautions
should be taken to minimise the production of dust and suitable personal protective equipment should be worn at all
times when handling such material.
Stored Product Pests
Many stored product insects can produce allergies. Even the humble grain weevil (Sitophilus granarius) can produce
allergic responses, although the importance of allergy to grain weevil in grain to dust asthma has not been fully evaluated.
Grain farmers can become sensitized and develop asthma because of one or more of the organic allergens in their
environment. In the literature, at least three cases of asthma in laboratory workers were described due to the grain weevil.
This brings us to the topic of ingestant allergens, that is, eating or unintentionally swallowing allergenic insect material.
Since we are not a nation accustomed to dining on “bugs”, direct evidence for allergies to food insects is practically
nonexistent.
Nonetheless, entomologists are sometimes treated to nebulous accounts of people getting sick after deliberately eating
insects. Since almost everyone can name at least one food that turns their stomach, it is not clear what role, if any,
psychological factors may have played in these illnesses. We can, however, gain some insight from controlled
experiments on human subjects done with preparations of common food-infesting insects.
A classic study by Bernton and Brown in 1967 utilised dialised extracts of seven of these insects in skin sensitivity tests
of subjects with and without known allergies. Test extracts included those of the rice weevil (Sitophilus oryzae), fruit fly
(Drosophila melanogaster), Indian meal moth (Plodia interpunctella), saw-toothed grain beetle (Oryzaephilus
surinamensis), rust red flour beetle larvae and adults (Tribolium castaneum), confused flour beetle (Tribolium confusum),
and lesser grain borer (Rhyzopertha dominica).
Of the 230 allergic patients, 68 (29.6%) reacted positively to one or more of the dialised insect extracts. Surprisingly, of
the 194 non-allergic subjects, 50 (25.8%) showed sensitivity to at least one extract. A total of 333 positive reactions were
observed. The degree of overall sensitivity was practically the same for both groups, with the Indian meal moth extract
eliciting the most positive reactions followed by the extracts of rust red flour beetle larvae, rust red flour beetle adults, rice
weevils, fruit flies, confused flour beetles, saw-toothed grain beetles, and lesser grain borers.
The question arises as to where upwards of 25% of the general population might have acquired sensitivity to these
insects. At one time or another, most people have had to clean out their cupboard as a result of an infestation by one or
more stored-food pests. If the problem is bad enough (and recurrent), sensitivity could be related to inhalant or contactant
allergens of insect origin.
More likely, however, these allergies are the result of ingesting small quantities of insect material in food over a lifetime.
Despite proficient methods of production and storage, trace amounts of insect material are going to find their way into
our food. The Indian meal moth and its relatives, for example, can be persistent and notorious pests wherever sweets are
manufactured or stored. Stored-product moths will also attack flour, pasta and dried fruit. Grain beetles and weevils are
a constant threat to stored whole grain, and who hasn’t opened a box of cake mix or corn meal, only to discover flour
beetles infesting the contents?
We are not inclined to eat food showing obvious signs of insect contamination, but we are more than likely getting
occasional small doses of insect material in food we consider wholesome. For most people this level of exposure is
medically inconsequential. For people with known allergies, especially those of the food and insect varieties, the matter
becomes problematic. In the case of food insects, does the sensitized person exercise strict avoidance of this novel
cuisine or take his or her chances?
For most people, working with or accidentally eating insects would pose little if any health risk, especially if they have no
history of allergy to insects or other arthropods. Nonetheless, since sensitivity can be acquired with repeated exposure to
an allergen, a measure of vigilance is in order. Any person with known insect, arthropod or bird allergies would be wise to
exercise some caution.
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