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The Food Insects Newsletter

Allergies Related to Food Insect Production and Consumption
July 1995. Volume 8, Issue #2.
By Joel Phillips & Wendell Burkholder
USDA-ARS Stored-Product Insects Research Laboratory
Department of Entomology
University of Wisconsin-Madison
Madison, Wisconsin 53706

Editor's Note: This is the third in a series of invited articles on potential hazards that could be posed by indiscriminate or careless consumption or handling of insects. We are grateful to the authors for generously agreeing to prepare the article under severe time constraints.

The cultural practice of entomophagy is old and well-established especially in non-industrialized regions of the world. Thanks to this newsletter, along with occasional anecdotes in the electronic and print media, human consumption of insects is a growing novelty in the U.S. and other nations not usually associated with the custom. Latter-day food insect devotees may simply want to sample species considered delicacies in other cultures, or they may be interested in the reputed nutritional or medicinal qualities of certain food insects. Regardless of motivation, initiates must first overcome the wide spread cultural taboo against the practice, that is, the idea that consuming insects is generally unhealthy. Proper methods of selection and preparation can largely nullify the health concerns associated with eating food insects. However, one matter will continue to nag the practice, and that is the possibility of allergies to insect derived foods. Virtually any food item can be allergenic. Yet, other arthropods such as shellfish (i.e., shrimp, lobster, crayfish) are particularly well-known for their ability to induce mild to severe allergic reactions in susceptible individuals. Thus, the risk can not be taken lightly. The following is a brief review of the potential health risks associated with the production and consumption of food insects.

The popular image of insect allergies is that associated with the bites and stings of venomous species like bees, ants, and wasps (injectant allergens). Over one-hundred deaths per year in the U.S. are attributed to fatal reactions to arthropod venoms. These accounts make hot news, although the vast majority of victims suffer little more than short-term itching, burning and swelling. More common allergic reactions attributable to insects include those caused by contacting body parts or waste products (contactant allergens) or inhaling microscopic dust particles composed of pulverized carcasses, cast skins and excreta (inhalant allergens). Allergies caused by contacting or inhaling insect material can have significant health consequences in the home or work environment with symptoms ranging from eczema and dermatitis, to rhinitis, congestion and bronchial asthma. In severe cases, sensitivity to insect material is heightened to the extent that the victim can experience anaphylactic shock, a potentially life-threatening condition often involving rapid swelling, acute respiratory distress, and collapse of circulation. If possible, it is incumbent upon the sufferer to recognize and avoid insect allergens long before the onset of extreme sensitivity.

Since most insect allergies are of the contactant and inhalant type, it would be reasonable to assume that the greatest health risk associated with food insects would be to workers involved in their production. Owing to the small and obscure nature of the food insects industry, especially in the U.S., virtually nothing is known of such problems. However, there are many records of insect-induced allergies among workers in other enterprises. Workers shelling and cleaning walnuts in Bulgaria developed eczema, dermatitis and intense itching of the skin associated with exposure to the larvae and excreta of the Indianmeal moth. Although they are not insects, mites that infest cheese, bran, dried fruits, jams and sugars are known to cause transient dermatitis among workers when body fluids are re leased upon crushing. Records of inhalant allergies in the workplace make up the majority of case histories. In a NIOSH survey of USDA labs that rear insects, nine orders of insects plus mites and spiders were named as sources of the inhalant allergens. In his 1980 survey of insectary workers, Wirtz found that 67% of his respondents linked their allergy symptoms to direct or airborne exposure to lepidopteran (moth and butterfly) scales with emphasis on respiratory problems. Two labs had 53% and 75% of their personnel develop allergies to scales despite the use of exhaust hoods and protective masks and clothing. Case histories of asthma among Lepidoptera workers are numerous.

Reactions to Orthoptera (grasshoppers, crickets, locusts, cock roaches, etc.) are also common. In 1969 LeClercq reported that workers rearing locusts suffered rhinitis, itching skin, bronchitis and ultimately asthma in general sequence. Wirtz recounted one study of migratory locusts where all of the workers became allergic to the insect. The authors know of a researcher who suffered dyspnea (labored breathing) during a prolonged session of grinding crickets into meal to supplement chicken feed. Ominously, the three cases of anaphylactic shock reported by Wirtz involved orthopterans.

Workers exposed to the obligate beetle and weevil (Coleoptera) pests of stored grains and milled products have also been affected. Reports of skin itching, hives, rhinitis, dyspnea, and bronchial asthma are numerous and well-documented. Flies and midges (Diptera) as well as mayflies (Ephemeroptera) and caddisflies (Trichoptera) have likewise been implicated as allergenic hazards in the workplace. The above reports as well as others too numerous to mention in this article highlight the fact that insects and related arthropods pose a very real occupational health threat to workers repeatedly exposed to them. Coping with this problem can be an annoying inconvenience that has both economic and health consequences for the worker and employer. Although good ventilation, protective clothing, gloves and masks are common sense preventive measures (as well as being mandated by OSHA), reassignment of the sensitized victim to a non-threatening work environment is often the only viable remedy to the problem.

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 most 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 utilized dialized 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), Indianmeal moth (Plodia in terpunctella), sawtoothed grain beetle (Oryzaephilus surinamensis), 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 dialized 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 Indianmeal moth extract eliciting the most positive reactions followed by the extracts of red flour beetle larvae, red flour beetle adults, rice weevils, fruit flies, confused flour beetles, sawtoothed 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 Indianmeal moth and its relatives, for example, can be persistent and notorious pests wherever candy is 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 cornmeal 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?

Perhaps there are processes that largely diminish the potential threat of food allergies. One school of thought suggests that insect allergens in food are deactivated by cooking, yet, when five of the aforementioned insect extracts were heated at 100C for one hour, positive skin reactions were again observed, although they were deemed less vigorous than those of the unheated treatments. In a 1964 study, Bernton and Brown heat-treated the extracts of cock roaches at 100C for one hour and found that these allergens likewise resisted deactivation. The idea that insect allergens are deactivated in the highly acidic environment of the stomach is also appealing until one considers the number of normally eaten foods that have been identified as potentially allergenic and whose allergens obviously survive digestion and cooking.

For most people, working with or eating food 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. The person with known insect or arthropod allergies would be wise to exercise some caution. Cross-reactivity among related as well as taxonomically dispersed groups of insects has been established. There is also evidence for cross-reactivity among distantly related members of the Arthropoda suggesting the existence of common allergens within the phylum. So, if you are allergic to shellfish, you might want to reconsider the urge to "down " a plate of fried meal worms. As with anything, a little knowledge and common sense should keep you out of trouble.

Further Reading
Bauer, M. and R. Patnode. 1983. NIOSH, HETA, Report No. 82 002-1312. 36p.
Bellas, T.E. 1990. Occupational inhalant allergy to arthropods. Clinical Reviews in Allergy. 8: 15-29.
Brenner, R.J., K.C. Barnes, R.M. Helm, and L.W. Williams. 1991. Modernized society and allergies to arthropods. American Entomologist. 37(3):143-155.
Bernton, H.S., and H. Brown. 1967. Insects as potential sources of ingestant allergens. Annals of Allergy. 25:381-387.
Gorham,R.J. 1976. Insects as food. Bulletin of the Society of Vector Ecology. 3: 11 -16.
LeClercq, M. 1969. Entomological Parasitology. Pergamon Press, New York. 158 pp.
Phillips, J.K. and W.E. Burkholder. 1984. Health hazards of insects and mites in food, pp. 279-292, in F.J. Baur (ed.), Insect Management for Food Storage and Processing. American Association of Cereal Chemists, St. Paul, MN.
Wirtz, R.A.1980. Occupational allergies to arthropods - documentation and prevention. Bulletin of the Entomological Society of America. 26(3):356-360.


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