S.L. Doggett, M.J. Geary & R.C. Russell Biology in the Management of Biting Arthropods
THE ROLE OF BIOLOGY IN THE MANAGEMENT OF BITING ARTHROPODS
Stephen L. Doggett, Merilyn J. Geary & Richard C. Russell
4/Sep/2008
Department of Medical Entomology, University of Sydney and ICPMR, Westmead Hospital, Westmead, NSW 2145
Tel: 02 9845 7265 Fax: 02 9893 8659 Email: [email protected]
Introduction
Aims of this paper are; • To highlight the importance of biology in the management of biting arthropods through the provision of case studies, • To discuss the medical implications of biting arthropods, • To discuss the biology and management of the most common biting arthropods, • To discuss those arthropods that often causes unnecessary worry, • To examine other causes of bite-like reactions, • To review the condition known as ‘Delusionary Parasitosis’, • To provide a information that may assist in the identification of an unknown infestation of biting arthropods, • To consider if an insecticide application should be undertaken in the absence of any biting arthropods pests, • To provide reference sources for further information.
Case Studies
The importance of biology can be demonstrated by the following case studies.
Case Study 1: A resident complained of chronic attack caused by a tiny insect-like creature. They had collected specimens, which were sent by the pest manager to a government agricultural entomological laboratory. These were identified by the entomologist as bird mites, Ornithonyssus bursa. Understandably on the basis of this, the pest manager implemented a bird mite control program; the roof void was sealed to prevent access by birds and the roof cavity was treated with various insecticides. However, the problem did not go away and persisted for several weeks, despite repeated insecticidal application for bird mites. Eventually the specimens were sent to a specialist Medical Entomology laboratory who described the mites not being bird mites, but rather rat mites, Ornithonyssus bacoti. A rodent control program was intiated and the problem was promptly resolved.
This case study demonstrates several key points;
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1. Accurate identification of the pest is critical (and the basis of Integrated Pest Management). 2. That no entomologist can be expected to be able to identify every insect species; after all there are only several million species in the world! Thus there are specialist medical, urban, agricultural, veterinary, and forestry entomologists, to name but a few groups, and each speciality is further subdivided into certain disciplines. Always ensure that any specimen is sent to the appropriate expert group. 3. Without appropriate knowledge of the biology of the pest, control is unlikely to be achieved.
Case Study 2: A group of girls in a private boarding school were all suffering with bite- like reactions around the lower abdomen and groin area. The immediate response of the Headmaster was to suggest having the girls treated for pubic lice. The folly of this proposal is evident when the biology of pubic lice is considered. Pubic lice are transmitted through sexual contact and access to dorms is strictly controlled meaning that outside contact is limited. Outbreaks of pubic lice within a group would only occur with the mass sharing of partners, and this is just not probable in a boarding school. Thus public lice are highly unlikely. One group of pests that commonly afflicts large numbers within the school environment are urticating caterpillars. As the rash was confined to a limited body area, this suggested that the students were not directly or generally exposed to urticarial hairs of the caterpillars, rather just the clothing. An inspection of the laundry area revealed that the clothes lines were situated directly under a Eucalyptus tree that was infested with Mistletoe, which was in turn infested with the caterpillar of the Brown-tailed Mistletoe moth, a noted species causing urticarial rash. Removal of the Mistletoe (and the entire tree in this instance) solved the problem. As in the case study above, it was knowledge of the biology of biting insects that led to a positive resolution and ensured the wrong control path was not followed.
Medical Significance of Biting Arthropods
Worldwide, biting arthropods are responsible for considerable mortality and morbidity, and impinge on human health in numerous ways;
Nuisance biting; the bite from many arthropods can be painful and uncomfortable, Some insects can even do physical damage to the host through their bites (e.g. Stable flies on dogs).
Allergic reactions haematophagus (i.e. bloodsucking) arthropods inject saliva during feeding, which contain a variety of proteins that can produce an allergic reaction in the host. This can be quite variable, some people may show no reaction, while others may develop a small lump at the bite site with some localised irritation, while others could have produce intensely itchy wheals that can last for days to even weeks. Some highly sensitised people can have such a severe anaphylactic reactions that a bite/sting can be life threatening. Bullous eruptions (i.e. boils) can occur with some insect bites (e.g. bed bugs), while scabies infection can result in a generalised allergic rash in areas of the body where the mite is not present. As bite reactions vary from individual to
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individual, it is usually not possible to determine the pest from the bite, all the distribution of bites may help. Any insect bite can become infested with bacteria as a result of scratching the bite site, which may lead to further complications.
Toxicosis some arthropods when they bite or sting can inject venom, which may cause a severe toxicosis. This may also result in a life threatening anaphylactic response in sensitised people. In the case of the Paralysis tick, this species injects a powerful neurotoxin that can cause paralysis, which may in turn lead to respiratory failure.
Infectious agents many of the biting arthropods are vectors of disease and can transmit a variety of pathogens, including viruses, bacteria, rickettsia and protozoans. The most important group are the mosquitoes, which transmits malaria and many different viruses (termed ‘arboviruses’). It is estimated that for malaria alone, there are over 300million cases and 1million deaths annually.
Mental Trauma some people are entomophobic, i.e. have a natural fear of insects, and exposure to insects can cause them considerable mental hardship. Some people are traumatised when they have to pay the control costs associated with certain urban insects, notably termites and bed bugs. While some people can develop the disturbing mental illness known as ‘Delusionary Parasitosis’.
The Biting Arthropods
The Acarines; Ticks & Mites
Ticks: in Australia there are around 70 species of ticks, several of which are important veterinary pests. Fortunately, few attack humans and the species that is responsible for the vast majority of tick bites is the Paralysis tick, Ixodes holocyclus (Fig. ). This species occurs along the along the narrow coastal strip east of Australia, from Victoria to far north Queensland. Even in this region, its distribution is limited to localised bushlands, principally wet sclerophyll forests and rainforests, where it requires a native host for its blood meals. The main host are bandicoots, and if bandicoots are present, then usually so too is the Paralysis tick. The main tick problem areas around Sydney include the northern beaches from Manly to Palm Beach, the green belt from the northern beaches across St Ives to Dural, and around Bundeena in the south.
There are four main life stages of the tick; the egg, six-legged larvae, and the eight- legged nymph and adult. The larvae stage, nymphal stage and the adult female all require a blood meal for development, or as in the case of the adult, the production of eggs. The life stages show distinct seasonality, with the numerous larval stage being most common during the autumn months, the nymphs mid-year and the adults towards the spring (Fig. ).
The Paralysis tick has important medical implications. As the name implies, the species can cause paralysis and the adult female injects a powerful neurotoxin when it bites. Between the 1920’s and 1940’s there were 20 human deaths, mostly children. With modern supportive medicine and the development of antivenene, no deaths have been
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recorded since then, however life threatening cases of paralysis in children sometimes are seen during the spring months. The bite of the tick can produce a variable reaction between individuals, including mild urticaria (often called ‘scrub itch’ with larval ticks) to a severe allergic response including anaphylaxis. The paralysis tick can also transmit the infectious disease, Queensland Tick Typhus, which is occasionally fatal (Doggett 2004).
The control of ticks is via host exclusion, habitat modification and insecticide application. For a detailed description of Paralysis tick control, see Doggett (2005).
Mites. Broadly speaking there are three categories of mites that affect humans. This includes the ‘Anthropophilic’ mites, the ‘Zoophilic’ mites and the ‘Stored Product’ mites. Excluding scabies, which can only be seen with a compound microscope, most of the mites are visible to the naked eye, albeit very small. However, mites are often blamed for the cause of just about any skin irritation, particularly in patients suffering with Delusionary Parasitosis. Contrary to popular opinion, most mites do not burrow into the skin (only Scabies, Demodex and the scrub itch mites do) and many ‘test’ bite in the search for their usual host.
Anthropophilic, or the ‘people loving’ mites, are those that have humans as a host, or rely on human matter for a food source. Probably the most famous example of the latter group are house dust mites, which consume shed human skin. Other anthropophilic mites include scabies and Demodex.
Scabies is a medical condition caused by the microscopic mite, Sarcoptes scabiei (Fig. ). Scabies mite live in the upper skin layer and their tunnelling activities can be indicated by grey lines similar to pencil marks. Typical symptoms in infested individuals include a generalised skin rash on various parts of the body and intense itching. Identification of scabies is via skin scrapings which must be examined microscopically for the presence of mites. Unfortunately, many general practitioners use the term scabies as a catch phrase for various unexplained skin reactions and often fail to confirm the disease with the required skin scrapings despite prescribing treatments. In reality, scabies is fairly uncommon in the general community and tends to be more of an issue in displaced persons camps, aboriginal communities and nursing homes. The life cycle of the mite is around 10-14 days and the transmission is through prolonged body contact. The symptoms can take time to manifest and in the meantime such individuals can be infective to others. Treatments involves the application of various acaricides, such as permethrin based creams, and in severe scabies (often called ‘crusted’ scabies) than oral ivermectin may need to be given, and all contacts with the patient need to be treated. It is important to note that scabies is a medical condition and should not be dealt with by pest managers.
Demodex mites are common commensal mites that live on many people. They infest the hair follicles of the eyelashes and eyebrows, and generally the infestation is benign and causes no medical problem.
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House Dust mites belong to the genus Dermatophagoides and live in the dust of homes where they feed of such things as shed human skin. The mites themselves do not bite, but their faeces and cast skins can trigger severe allergic reactions and asthma in sensitised people. They have a worldwide distribution and tend to be more common in warm humid regions, and within the bed rooms of homes. Control of dust mites involves making an environment which is less favourable for survival (e.g. lowered humidity, removal of carpets and soft furnishings), and improvements in housekeeping to reduce minimise the population and to reduce the presence of allergens (e.g. regular vacuuming and hot washing of bed linen).
Zoophilic mites are those that have a vertebrate animal as a host and if the host is absent, then these mite will bite humans. Generally however, the mites will not live on humans and tend to only ‘test’ bite in their search for the usual host.
Bird mites (Ornithonyssus bursa, Fig. ) are a commonly encountered biting arthropod during the spring months. They are typically associated with exotic species of birds, such as Indian Mynahs and pigeons that readily breed within the roof cavities of homes or on the ledges of office buildings. The mites become a problem after the young bird has left the nest; without a ready blood source the mites begin to disperse and search for a new host, where they then encounter humans, producing a painful bite. One nest can be infested with thousands to even tens of thousands of mites and the result is that the resident can be bitten many, many times. Contrary to the belief of some, bird mites can not live away a bird host for long and eventually the infestation will die off after some days to a few weeks. Bird mites are often blamed as the cause of unexplained bites, particularly by patients with Delusionary Parasitosis, who often claim that the mites are living under the skin, or been present for years. Control of bird mites is through the prevention of birds roosting in the roof cavity, treating and removing nesting, and insecticide application of roof cavities and possibly walls.
Rat mites (Ornithonyssus bacoti), as noted in the first Case Study, are extremely similar in appearance to the common bird mite and requires expert entomological skills to differentiate. Like bird mites, they inflict painful bites that can produce raised red itchy wheals. It is not uncommon for rat mites to be especially problematic following rodent control measures. Despite their name, rat mites will live on mice as well and control (like bird mites) involves removal of the host (i.e. rodent control) and the judicious use of insecticides.
Chigger mites can produce two clinical conditions; scrub itch and scrub typhus. The former condition is the bite reaction associated with large numbers of mites, while scrub typhus is an infectious disease transmitted by chigger mites. The disease is caused by the rickettisia, Orientia tsutsugamushi, and if not treated with antibiotics is often fatal. The chigger mites themselves are the larval stage of mites belonging to the family Trombiculidae (Fig. ), which are parasitic on wild and feral rodents. They will burrow into the skin in areas on humans where clothing is restricted (such as the around the waist and groin along the underwear line) and the bites form extremely itchy papules. The mites tend to be encountered in disrupted rainforest areas, particularly grassy areas where native rodents frequent, and are largely tropical in distribution. It is rare for any
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control measures to be undertaken against this mite, and avoiding the mite through the use of repellents or not going into high risk areas are the only option.
Stored product mites are those that infest food of humans or livestock. are found in association with stored products (e.g. grains, flours, cheeses, packing materials, mulches), and the moths and beetles that may infest them. The mites feed on the products, the moulds that grow on them, and the insects that also feed on them. Contact with infested products leads to contact with the mites, which can result in dermatitis or itchy bites. Generally, this involves a range of mites and these can be specific to the type of stored product; historically, these have been occupational conditions, e.g. grocer’s itch, baker’s itch, copra itch and straw itch.
Pyemotes, Aleuroglyphus, etc
For more information on medically important Acarines, see Russell (2001).
Biting Flies – the Disease Carriers (Vectors)
Mosquitoes - big push for the pest control industry to undertake mosquito control, particularly harbourage treatments – knowledge of biology (&identification) is essential in achieving control
Sandflies (Ceratopogonidae) or 'sand flies' are very small and often difficult to see when biting. The bite reaction often develops hours later. Travelers or new residents of not only coastal areas but also inland locations, often encounter the painful itchy bites. Some individuals can be hospitalized as a result of severe bite reactions and others can develop hypersensitivity. Applying a repellent, wearing suitable clothing and staying away from known infested areas (mostly estuarine coastal regions), and staying indoors at peak biting times maybe the only solution as total control is difficult. Habitat modification may be the only long-term solution to a biting midge problem. Newly retired people to an area may be forced to sell resulting in loss of money. Often female partners tend to be more disadvantaged as they can suffer from an intense bite reaction forcing them to be house bound creating further problems. There are areas in Tweed Heads shire where real estate operators open homes for inspection only in non-biting times. Homes in these areas have a huge turn over rate.
Non-disease carriers (non-vectors) Stable Flies (Stomoxys calcitrans) looks similar to a house fly but has a painful bite when seeking a blood meal. It is a common pest in urban environments attacking dogs and humans throughout the summer months. Local breeding occurs in compost heaps and piles of animal manure that are often used as mulch on garden beds.
Horse/March flies (march or horse flies) can deliver a painful bite, these flies are often associated with semi rural areas that may have stock animals and creeks and dams where breeding occurs in mud flats. One species of tabanid in Queensland has been reported to cause severe skin ulceration at the site of their bite. Another biting fly is the
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Spaniopsis, which is similar in appearance to a tabanid and can inflict a bite; bush walkers can be troubled with this particular fly.
Lice Head Pediculus humanus capitis Creamy brown, 1-4mm Wingless, do not fly, jump Head to head – major trans. route No pathogen transmission Most common childhood comm. dis. (ex. colds) Motility reduced in wet hair
Body Pediculus humanus
Similar to head lice
Do not live on body
Very rare today
Vector of: Epidemic typhus Rickettsia prowazekii Relapsing fever Borrelia recurrentis
Pubic Pthirus pubis
Most contagious sex. dis., 1990’s most common Transmission mainly sexually
Mainly pubic/perianal, beards/eyebrows Control, Similar to head lice Synthetic pyrethroids Sexual partners treated
Here’s an interesting anecdote from history; in Sweden during the Middle Ages, any man who wished to be Mayor would place their chin on a table. A louse was released in the middle, and whosever beard it would walk onto would then be the Mayor!
The Hemipterans
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Bed bugs; only those pest managers living in ignorance bliss would not be aware of the worldwide resurgence in bed bug infestations over the last five years, with numerous reports in industry magazines and the popular press. In Australia alone, a survey of pest managers in 2006 indicated that bed bug infestations had risen by over 4,500% since the year 1999 (Doggett & Russell, 2008). In this country we have two problem species, the common bed bug, Cimex lectularius, which occurs south of the Queensland/New South Wales border, and the tropical bed bug, Cimex hemipterus, which occurs north of the border. Bed bugs are being commonly encountered by travellers who often unknowingly bring them home in the luggage. Bed bugs are secretive insects that hide in narrow cracks and crevices during the day and come out to bite their warm blooded bed partner at night. The result are irritating itchy wheals. The resurgence has largely been due to insecticide resistance and very few of the insecticides currently on the market can effectively control an infestation, with most having virtually no residual effect. Bed bugs are now considered one of the most challenging, if not the most difficult, urban insect pest to control. This prompted the development of a Code of Practice for their control (Doggett 2007), which can be freely downloaded from www.bedbug.org.au.
Fleas are a common source of irritation and many homeowners with pets may experience flea problems that are difficult to control. The flea responsible is usually the cat flea Ctenophelaide felis. Visible to the eye, these brown fast moving insects can readily be observed hopping up and down against a light coloured background. Fleas will attack humans usually around the ankles, leaving a small itchy raised red welts. There have been no diseases attributed to this flea species but some individuals may become hypersensitive. Elderly people and sight-impaired individuals may not be able to detect this insect as the source of their continued irritation. Other species of fleas may be associated with other animals and bite humans when host animal dies. Concentration of the immature stages (eggs & larvae) of the flea will be found where pets rest and feed; control measures should be targeted at these specific areas.
Urticating Caterpillars Caterpillars of a number of species are capable of causing severe skin dermatitis from the small sharp hairs that cover their body. The hairs that are shed by the caterpillars can fracture and penetrate human skin. Contact with any surface that the caterpillars may have moved across, or with other life stages including the pupae, adults or even eggs may result in contact dermatitis. Often people handling wood stored under a tree that has had a past infestation of caterpillars develop skin rashes. Hanging washing near an infested tree may contaminate the clothing items with air-borne hairs. Severe skin reactions in family members can be difficult to explain. Telltale signs of a caterpillar infestation are amount of frass, cast skins or silken webbing at the base of host tree, and defoliation of the upper tree/shrub canopy.
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To relieve symptoms, adhesive tape applied to the affected skin and removed quickly can reduce the effect of the irritation. Use of analgesics, steroid creams, and antihistamines can relieve the discomfort.
Bigger species of caterpillar, such as the White Stemmed gum moth (Chelepteryx collessi) can also pose a health risk with their large spines that penetrate skin after inadvertently handling or treading on the caterpillar or their cocoon. Contact with these caterpillars may result in hospitalization for children.
Other caterpillars, such as many cup moth species, have raised areas of retractable strong spines on their body that carry a toxin, and contact with these spines that can cause swelling, pain and irritation.
The scales covering the wings and bodies of many moths and butterflies are known to cause respiratory allergies in some persons with frequent exposure.
Miscellaneous
Beetles (Coleoptera) There are several species of beetle that, when handled, can release chemicals that may damage human skin. These species of beetle typically are encountered outside the home, although they can be attracted by house lights and indoor contact cannot be excluded in high-risk areas. Blister beetles (family Meloidae) contain the compound cantharidin, which results in blistering of the skin. The Rove beetles (Family Staphylinidae) have also been associated with blistering of skin and pain.
There is an irritating eye condition known as ‘Christmas eye’ or ‘harvesters eye’, which has been attributed to a beetle seasonally active in rural areas, but the causative agent has not been identified and there may be alternative explanations.
Domestic beetles are rarely of concern, although the larvae of carpet beetles possess many sharp hairs, and in situations where a large infestation exists the hairs from the shed skins may cause skin irritation.
Collembola or springtails and amphipods are common pathology specimens that are received as the suspected source of ongoing skin irritation. These arthropods are particularly common in homes with a slab floor constructions surrounded by thick leaf mulch and ongoing wet weather.
Wasps/Bees/Ants (Hymenoptera) This order of insects contains many species that are medically important. Many bees, ants and wasps are capable of severe stings. Some individuals who are sensitized to their venom can develop severe reactions to the stings and life-threatening anaphylactic shock if medical attention is not forthcoming. There are many incidences where a small
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species of wasp or ant can sting and leave the scene before being spotted, so identification of the species responsible is not always possible.
The Worriers Moth Flies (Family: Psychodidae, Fig.), also known as ‘Drain’ flies, are very common insects around 2mm in length and grey to brown in colour. They are particularly hairy, being superficially similar in appearance to moths and hence the name. The adult flies are often found in the damp parts of the home, particularly on the walls of bathrooms and outside toilets. The flies themselves are largely innocuous as they do not bite and rarely cause any medical issue. Occasionally if they are in exceptionally large numbers, allergic reactions may occur in sensitised individuals. The adult flies lay their eggs in slime layers, which can occur in drains, under toilet lips, cisterns and shower rosettes. It is in the slime layer where larvae feed and develops. The larval stage is worm-like in appearance and can be dislodged from the slime layer of cisterns and toilet lips by the flushing action of the toilet. The appearance of worm-like creatures (Fig. ) in the toilet bowl understandably causes concern and people often believe that they are infested with some mysterious and probably lethal parasite. Control of moth flies is through the physical removal of the slime layer by cleaning or via the use of biological detergents.
Rat-tailed maggots (Family: Syrphidae, Fig. ) are the larval stage of hover flies belonging to the genus Eristalis and breed in highly polluted environments such as sceptic tanks. The cream coloured larvae are quite large with a body of up to around 4cm in length and a tail that is much longer than the body (this is actually a breathing siphon). Like the larval stage of moth flies, rat-tailed maggots causes worry to individuals who notice them amongst their night soil.
Miscellaneous Worriers, almost any insect can instil fear in certain circumstances, even if the individual person is not particularly entomophobic (i.e. have a fear of insects). Pests that have a high public profile through exposure on news and current affairs programs can lead to unnecessary concern. For example, the horror of people being bitten in bed at night while asleep makes a great headline and many media groups have jumped on the news bandwagon with the recent resurgence of bed bugs. As a result our Department has received numerous insect specimens, particularly nymphal cockroaches, thought to be the bed bugs. To the untrained eye, nymphal cockroaches do have a superficial appearance to bed bugs, with a similar body shape and colouration (Fig. ). The biology and control of these insects is however very different.
A very common group of insects that are often the cause of worry is the group known as Thaumastocorids. These are sap sucking insects belonging to the order Hemiptera (this order also includes aphids and cicadas) and feed on various native trees. These insects often drop onto the hair, and being of similar size to head lice, the result is that many parents believe that their child has become reinfested. Thaumastocorids however, do not bite and have no medical implications.
Misnomers
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The basic tenet of Integrated Pest Management is the accurate identification of the pest. Inaccurate identification will lead to control failure. This means it is important to use the proper name of the pest for communication purposes. Unfortunately when it comes to biting insects, many pest managers bandy about all sorts of names, some of which are misguided and some represent mythical creatures. This includes terms such as ‘Bird Lice’, ‘Book Lice’ and ‘Paper Mites’. In the case of Bird Lice, these do exist but do not bite humans and are generally uncommon. When pest managers use the term ‘Bird Lice’, presumably they are referring to ‘Bird Mites’. ‘Book Lice’ is a term used for the order of insects called Pscoptera (or commonly ‘Pscocids’). These are common insects that feed on moulds on paper and other plant based materials, but do not bite humans. Finally, there is no such thing as ‘Paper Mites’ and when pest managers use this term, it indicated that they have no clue as to the problem. The use of any of these false names appears amateurish and gives the appearance of a very unprofessional organisation.
Other Causes of Bite-Like Reactions
Most people when they receive what they believe to be a bite immediately suspect an insect as being the cause; however this is often not the case. In fact when our Department has been involved in investigations of unknown biting insects, an entomological cause has been identified in only around 20% of cases. There are literally hundreds of different items that can produce a bite-like sensation. These are broadly categorised below.
Environment: within the immediate environment (especially in workplaces where large amounts of dust can be produced from such materials as paper) there can be fibres and various dust particles which can produce skin irritation and bite-like sensations. Certain circumstances can make these more apparent such as during periods of low humidity where the build up of static electricity, particularly in carpeted areas, can result in the fibres and dust particles being attracted to the skin. This condition is sometimes referred to as ‘cable bug’. During summer months if the factory or workplace is not air- conditioned and physical activity results in heavy sweating, then fibres and other particles will stick to the skin. The implementation of good housekeeping using vacuums fitted with HEPA filters can assist, antistatic sprays on carpets can reduce the build up of static electricity along with the raising of the humidity levels.
Many plants are known skin irritants, including native Grevilleas, spores from ferns, the stiff hairs on the seeds of Plane trees (Platanus spp.), to name but a few. Exposure to these can produce bite like reactions in which insects are often blamed and determining that plants are the cause can be difficult to establish. In one case within a nursing home, several residents and staff complained of constant bites. During a site inspection, it was noticed that large ferns had been planted next to the air conditioning intake and dust samples revealed large numbers of fern spores. Removal of the ferns resolved the issue. In another situation, a home owner complained of ongoing bites, however they occurred on one arm only. When the pest manager interviewed the resident, it was
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found that they checked for mail every day and in the process rubbed against a Grevillea bush. Removal of this plant halted the problem.
Chemicals: daily we are exposed to hundreds to even thousands of different chemicals. These include pollutants, cosmetics, cleaners, paints, and even insecticides. Many are known skin irritants.
Medical Conditions: many pathogens (e.g. fungi, Staphylococcus) and infectious diseases (e.g. chicken pox) can produce urticarial skin reactions and insect may be blamed. Such conditions can be readily diagnosed via the culturing of skin scrapings and the patient needs to seek expert dermatological advice (usually the general practitioner is not sufficiently skilled). Certain physiological conditions are known to have a bite-like or crawling sensation as a symptom. In post-menopausal women, there is a decline in the natural hormone oestrogen, which can result in skin shrinkage and a feeling that is described as akin to ants crawling on the skin. This medical condition is termed ‘Formication’ (named after ants, which belong in the family Formicidae) and can be readily treated with hormone replacement therapy. Allergic reaction to various environmental stimuli can produce hives and other skin irritations and bite-like feelings. Some medicines and medical treatments (e.g. radiotherapy) can result in skin irritations and urticarial reactions. Certain drugs of addiction can produce tactile hallucinations, for example some users of the drug Ice report of a sensation of having insects crawling under their skin. Naturally it would be inappropriate and unprofessional for a pest manager to discuss or suggest possible medical conditions to a client. All such conditions need to be managed by clinicians.
Power of suggestion: give a presentation on head lice to an audience and within seconds someone will start scratching! Likewise in the workplace, if one individual starts scratching and complaining of bites, then others are likely to begin as well and this can escalate to the point where OH&S staff are forced to become involved. In one recent case, such an OH&S incident begun as a result of one staff member being infested with pubic lice; soon many others began scratching (although the original staff had not spread their infestation within the office)!
Delusionary Parasitosis
This condition is known by various names including ‘Delusions of Parasitosis’ and ‘Ekbom’s syndrome’. Delusionary Parasitosis (DP) is a persistent and irrational fear of insects and affected people believe that they have a chronic infestation. Patients suffering SP can often be linked back to an initial infestation of biting arthropods. For example, there was a case where a woman who had had previously experienced a bed bug infestation would wake up in the middle of the night and stuff her pillow into the freezer and another who would routinely spray her mattress with insecticide (Doggett 2005). Often the patients are women in the age group of 50-70 (suggesting possible ‘Formication’) and tend to live alone. DP patients tend to have multiple pest controllers, grossly overuse insecticides and often applying products directly onto their own skin. Some will self mutilate in the process of scratching their itch. In one sad case, a woman was convinced she had mites along the hairline on her head. She had a special tool
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made to help her dig at the alleged infested site and eventually penetrated the skull resulting in a cerebral haemorrhage. DP patients will ‘Doctor shop’ and move from one clinician to the next when nothing is found, hoping to find a doctor that will confirm their misguided belief. These people can not be easily convinced and often state that the insect is new to science. Their irrationality is often fuelled by bizarre and unscientific web sites that describe all sorts of imaginary bugs as being fact. DP patients will describe weird life cycles; one patient believed that everyone who scratched their ears with keys where infested with snake mites. Statements are often made such as; “it only comes out at night”, “you can not see it”, “they are hard to catch”, “they produce fibres under the skin”, and various other equally bizarre comments. Patients will collect copious amounts of samples, often picking scabs off their own skin. Our Department has received such delightful specimens as contents of nose pickings from over several months (the patient thought they had a nose mite acquired while travelling through Asia) and used tampons.
The reality is that DP patients are suffering from a mental illness and yet it is virtually impossible to convince them that they need psychiatric assistance, even though they are desperate for a solution. Various anti-psychotic drugs such as can be prescribed to these patients.
The reality is that DP patients are difficult to handle, they are generally highly emotional and quite irrational. Many even threaten health professionals and pest managers with going to the press if they can not find the solution. If a pest manager suspects that the patient may have DP, then it is important to ignore this and keep an open mind, and undertake a thorough inspection and investigate all possible biting arthropods.
For more information on DP, see Goddard (2004).
Identifying the Cause
The first stage in the control of any unknown and mysterious biting arthropod is proper identification of the pest. Finding the pest can be extremely challenging and may take considerable detective skills. A sound knowledge of the biology of biting arthropods will naturally assist in achieving a successful outcome. Even before a site inspection, asking the client the right question may lead to the identification of the cause (for example, case study 2 in the introduction above was solved over the phone). Naturally the identity of the pest needs to be confirmed in a site inspection before any control program is implemented. If the initial suspicions prove incorrect than it is important to keep an open mind and explore various possibilities. The following questions may be of assistance;
Where do you live? Certain insect pests are restricted to certain habitats; for example ticks only occur around bushy areas. Mosquitoes and sandflies are particularly problematic near estuarine environments. Some insects are more common in certain locations; for example bed bugs are more frequent close to the city and eastern suburbs within Sydney.
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What time of the year is it? Most insects tend to be more problematic during the warmer months of the year, although some tend to be very seasonal. The larvae of ticks are the most numerous stage and are particularly troublesome during the autumn months. Many urticating caterpillars are also most abundant during this time of the year. Bird mites represent a problem during the spring months, when young birds fledge and leave the nest.
What part of the house is the problem? If it is in the bedroom then bed bugs are a real possibility. In pet areas, then possibly fleas. In a certain room, then possibly bird mites. If outside, the pest could be mosquitoes, sand flies or other biting flies.
Where on the body are the bites occurring? Fleas tend to bite on the legs, likewise larval ticks. Bed bugs tend to bite on the torso, arms and legs, while biting flies attack the exposed parts of the body, notably the arms and legs. Urticating caterpillars often drop their hairs onto clothing and so the clothed parts of the body are often afflicted.
Is there a distinctive bite mark? Most biting insects will leave some mark, even if very temporary. As individuals vary tremendously between bite reactions, it is usually impossible to identify the cause from the bite alone. However, bed bugs often bite in lines, particularly on the torso and can be a good indication of the pest. If the client states that they can feel the bite, but there is no reaction, then it is likely the cause is non-entomological.
How many are affected? If a large number of individuals are affected, such as a group of students, then urticating caterpillars may be responsible. If a couple are affected amongst a group of residents, then the mysterious insect could be bed bugs. If most of the household are impacted then it could be various mites or fleas.
Have you recently travelled? If they have travelled recently, particularly to a popular tourist location or a major city then bed bugs are always a possibility. Just remember that people’s memory can be notoriously bad and the word ‘recently’ can mean different time frames to different people.
Can you see the pest? Describe the size, shape and colour? Unfortunately the descriptive powers of clients are generally poor; all insects look much the same to the uninitiated. It is however worth pursuing this line of questioning and may lead to the pest’s identification. Just be sure to let the client objectively describe the pest and try not to lead the them into describing what you may think it is.
Do you have samples? Having the client do the work, will hopefully make life a lot easier. Ask them to collect samples and place them into a plastic crush proof jar, such as a urine pot or a film canister (which are becoming rare in our digital age). Try to have them send it to you before the site inspection in case a microscope is needed for examination. If the suspected creature is small, then sticky tape can be used to collect it for later examination.
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Do you have pets? Fleas are always a possibility with cats and dogs, although fleas have become less common with the highly effective flea products on the market. If the pets are birds, then bird mites are a possibility.
Birds in the roof area? Then bird mites are likely.
Do you work with stored products or animal feeds? A stored product pest such as Pyemotes may be the culprit.
How long has this problem been occurring? If the problem has been occurring for many months or even years, then an entomological cause is unlikely and may even be delusionary.
Have you had this problem treated by other pest controllers or yourself? If multiple pest controllers have been involved then the problem is most likely delusional, however treatment failure by a number of pest control companies with bed bugs is not uncommon.
The Use of Glue Boards/Sticky Traps
A standard approach in biting arthropod investigations is the placement of glue boards or sticky traps in locations where people claim to be bitten. These are often employed if the cause was not readily apparent on the initial site inspection. The reality is however, glue boards have little direct benefit and rarely result in the identification of the culprit. Glue boards also require a very extensive examination under a compound microscope which most pest control companies do not have, and entomological experience at indentifying any trapped insect, which again most companies do not have. Rather for many pest managers, glue boards have a psychological benefit; the client sees that the pest manager is active in looking for a solution, and if the problem is in a work environment, then staff can see that management is not sitting on their laurels. Some pest managers even notice a ‘placebo effect’, i.e. that the problem abates with the placement of glue boards, particularly if the situation is in a workplace environment. Glue boards may collect large amounts of fibres and dust particles suggesting that the irritation may be caused as a result of poor cleaning practices. In this case, the recommendation would be to implement a thoroughly hygiene regimen utilising vacuum cleaners with HEPA filters.
Should you Spray?
Investigations involving a mysterious biting insect will reveal no apparent arthropod cause. Despite this, many pest managers will still undertake an insecticide application with the belief that they are being helpful to the client. There are however good reasons not to;
• False expectations: the clients will be of the understanding that the insecticide will stop the problem. If the problem is not insect related, then it will continue. This is
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likely to result in call backs with even more insecticide applications that will do nothing other than make the pest manager appear amateurish, damage the reputation of the company, and possibly even cost the company more than what the job was worth. It is unlikely that spraying will produce a ‘placebo effect’ and stop the biting problem. • Create more difficulties for those that come after: spraying gives the false impression to the client that the pest has been correctly identified. As the problem is unlikely to stop, other pest managers are probably going to be involved who will then be forced to convince the client of the earlier errors (“the last guy sprayed for paper mites, why won’t you?”). • Make the problem worse: the synthetic pyrethroids are known to cause contact dermatitis and more insecticide may only exacerbate the problem. • Insecticide resistance: the misuse and overuse of insecticides can lead to resistance. Already there are too few insecticides available in the arsenal of pest control; we do not want to loose any of those we have left. • It is illegal: an insecticide can only be legally applied according to label instructions and only against those insects that are stated on the label. This means that using an insecticide against an unidentified insect is breaking the law.
After extensive investigations, if no arthropods are found, then the pest manager must not spray. It should be stated in the client report that insects and other biting arthropods are unlikely to be the source of the problem and the client should consider other possible causes.
Conclusion
For further general information on biting arthropods see, Goddard (1993, 2004), Russell (1987) and Russell & Kay (2004).
References & Further Reading
Balit C.R., Geary M.J., Russell R.C. and Isbister G.K. (2003). Prospective study of definite caterpillar exposures. Toxicon 42: 657-662.
Balit C.R., Ptolemy H.C., Geary M.J., Russell R.C. and Ibister G.K. (2001). Outbreak of caterpillar dermatitis caused by airborne hairs of the mistletoe browntail moth (Euproctis edwardsi). Medical Journal of Australia, 175: 641-643.
Doggett S.L. (2007). A Code of Practice for the Control of Bed Bug Infestations in Australia. 2nd Edition. Department of Medical Entomology & The Australian Environmental Pest Managers Association, Westmead Hospital, Sydney. 56pp. ISBN 1740800974.
Doggett S.L. (2005). Chap 5. Tick ecology and control. in Pests of Disease and Unease. Synopsis of Papers. Westmead. 163pp.
Doggett S.L. (2004). Ticks: Human Health and Tick Bite Prevention. Medicine Today, 5: 33-38.
8.16 Safety & Pest Biology, 2008 S.L. Doggett, M.J. Geary & R.C. Russell Biology in the Management of Biting Arthropods
Doggett S.L., Dwyer D. and Russell R.C. (2008). Summer scourges. Medical Observer, 22 Feb: 29-31.
Doggett S.L., Geary M.J. and Russell R.C. (2004). The resurgence of bed bugs in Australia, with notes on their ecology and control. Environmental Health, 4: 30-38.
Doggett S.L. and Russell R.C. (2008). The Resurgence of Bed Bugs, Cimex spp. (Hemiptera: Cimicidae) In Australia: Experiences from Down Under. Sixth International Conference on Urban Pests, Budapest, Hungary, 13-16th July 2008.
Geary M.J., Knihinicki D.K., Halliday R.B. and Russell R.C. (2000). Contact dermatitis associated with the storage mite Aleuroglyphus ovatus (Troupeau) (Acari: Acaridae) in Australia. Australian Journal of Entomology, 39: 351-352.
Goddard J. (2004). Itches, Illusions & Phobias. in Hedges S.A. (ed.). Mallis Handbook of Pest Control. GIE Media.
Goddard J. (1993). Physician’s Guide to Arthropods of Medical Importance. CRC Press, Florida.
Le Messurier J. (2005). Control of Stomoxys calcitrans in urban and rural areas. Bulletin of the Mosquito Control Association of Australia, 17(3): 38-47.
Pinto L.J., Cooper R. and Kraft S.K. (2007). Bed Bug Handbook: The Complete Guide to Bed Bugs and their Control. Pinto & Associates, Maryland.
Russell R.C. (2001). The medical significance of Acari in Australia. In Halliday R.B., Walter D.E., Proctor H.C., Norton R.A. and Colloff M.J. Proceedings of the 10th International Congress of Acarology. CSIRO Publishing, Melbourne. Pgs 535-546.
Russell R.C. (1996). A Colour Photo Atlas of Mosquitoes of Southeastern Australia. Published by the Department of Medical Entomology, Westmead Hospital and the University of Sydney. 194pp.
Russell R.C. (1987). Common Pests and Public Health in New South Wales. Revised Edition. NSW Dept of Health Publ. (HP) 87-019, pp. 55.
Russell R.C. and Kay B.H. (2004). Medical Entomology: changes in the spectrum of mosquito-borne disease in Australia and other vector threats and risks, 1972-2004. Australian Journal of Entomology, 43: 271-282.
Scholz A., Russell R. and Geary M. (1993). Investigation of caterpillar dermatitis in school children. NSW Public Health Bulletin, 4(6): 65-66.
Service M.W. (2000). Medical Entomology for Students. 2nd Edition Cambridge University Press. (3rd Ed 2004 now available).
Webb C.E., Doggett, S.L., Geary, M.J. and Russell R.C. (2004). The biology and control of bird mites. Professional Pest Manager, 9(1): 21-22.
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