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
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