Arthropod pests of public health significance in Australia Preface



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Arthropod pests

of public health significance in Australia

Preface

Humans have shown great ingenuity in adapting to life in every corner of the globe, which has, in turn, been of great benefit to many arthropod pests. These creatures have taken advantage of us, either exclusively or on an 'as need be' basis, for both food and shelter. Whether it is feeding on our blood, food, homes or garbage, many arthropods have adapted to a life in close contact with humans. For our part, we have moved our homes, businesses and holiday activities into areas that arthropods call home and it should come as no surprise that contact between people and pests will continue to increase as our population grows.

In Australia, we are fortunate to be free of some of the nastiest arthropod pests and the disease-causing microorganisms (pathogens) they transmit, particularly potentially fatal mosquito, tick and louse-borne diseases. However, we still boast an impressive list of insects, ticks, mites and spiders that can bite, sting and irritate us in our homes, workplaces and while we are enjoying the great outdoors. Besides nuisance biting and irritation, Australia also has pathogens that, while rarely causing fatalities, can be seriously debilitating and a significant cost on the local community and economy.

Climate change and globalisation represent new and potentially significant influences on the activity of arthropod pests and vector-borne disease. The predicted rises in temperature and rainfall in some regions may seem ideal for increased insect populations. However, predicting population change in our local pest populations and the activity of arthropod-borne disease is extremely difficult, with a wide range of biological, ecological, economic and sociological factors all playing a part in determining risks to public health. The rapid movement of people and their belongings around the world, facilitated by quick and affordable air travel, represents an equally important factor in future public health risks associated with local and exotic arthropods.

Sometimes it is not the insects that spread disease or that are present in large numbers that cause the greatest concern. The occasional cockroach scuttling along the kitchen floor or the tiny spider up in the corner of the bedroom can be a significant psychological threat to many self-confessed entomophobes. For those who suffer a fear of insects and other arthropods, access to the worldwide web has opened up a new world of myths and misinformation that does little to alleviate these fears, and probably does a lot more to intensify them.

Whether alleviating the fears of entomophobes or addressing the risks of arthropod-borne disease in Australia, the key to success is knowledge. Along with correctly identifying the pests, knowledge of their biology, ecology and association with disease will go a long way towards achieving effective control in a timely manner.

This document is designed to provide up-to-date information on the most important arthropod pests of public health concern in Australia. The content has been updated and expanded from the 1999 version, Guidelines for the Control of Public Health Pests - Lice, Fleas, Scabies, Bird Mites, Bedbugs and Ticks, and now represents a key resource for those agencies and other groups, workplaces and individuals dealing with infestations of arthropod pests.

Dr Cameron E Webb

Acknowledgments

This document was prepared for enHealth by Cameron E Webb, Stephen L Doggett and Richard C Russell

The following people and organisations are also gratefully acknowledged for their contribution to the development and review of this document:

Biotext Pty Ltd, Canberra

Rick Atwell, University of Queensland

Stephen Barker, University of Queensland

Clive Easton, Tweed Shire Council, New South Wales

Merilyn Geary, Department of Medical Entomology, University of Sydney and Westmead Hospital

Geoff Isbister, Menzies School of Health Research, Northern Territory

Danuta Knihicki, Industry and Investment, New South Wales

Garry Levot, Industry and Investment, New South Wales

Glenis Lloyd, Environmental Health Branch, New South Wales Department of Health

Peter Miller, University of Technology Sydney

Mike Muller, Brisbane City Council

Chris Orton, Pest Information, Appraisal and Consulting Services

Bryce Peters, University of Technology Sydney

Bill Pettit, Department of Medical Entomology, Department of Health and Families, Northern Territory

Peter Whelan, Department of Medical Entomology, Department of Health and Families, Northern Territory



Introduction

Scope

This document provides an overview of Australia's major arthropod pests of public health importance, focussing on their relative public health significance, recommendations for first aid, personal protection measures, and pest management. The term 'arthropod' refers to a wide classification of animals which includes insects, mites and ticks, arachnids (spiders) and crustaceans (such as lobsters, crabs and prawns). Many arthropod pests have complicated biological and ecological requirements and, for example, the conditions that trigger pest infestations in southern areas of the country may be different to those that trigger infestations in tropical regions.

This document is not designed to be a comprehensive guide to the biology, ecology or control of arthropod pests, or as a primary source of first aid information. It does not present an exhaustive list of arthropods with nuisance potential. There will always be situations where a unique combination of environmental and climatic conditions combines with human activity to allow a seemingly innocuous arthropod to rise to pest status. The key to solving pest problems is to correctly identify the pest causing the problems.

How to use this document

For each pest, the following series of subtitles highlight the key issues surrounding each arthropod:



  • Description—introductory information on the pest, including a brief description of its physical appearance to help identification and other relevant background on its current pest status.

  • Biology and ecology—a brief overview of the life cycle, and key biological and ecological traits that may help to avoid or manage the pest. The habitats of the pest and its host preference are discussed where appropriate. Some pests listed may have a diverse range of species and detailed information on each species is beyond the scope of this document.

  • Public health importance—information on the public health risks, if any, posed by the pest. These risks may include skin irritation, nuisance biting, poisoning (toxicosis) or the transmission of disease-causing microorganisms (pathogens).

  • First aid—basic information on treating the clinical symptoms of bites, stings, irritation or infestation. If any adverse reaction develops, or if people are concerned about a possible arthropod bite or sting, they should seek medical advice and not rely solely on the information in this document.

  • Personal protection—strategies for people to avoid contact with the specific pest. These may apply to potential exposure indoors, outdoors, or from existing infestations or infested individuals. Strategies can include physical or chemical barriers, changing behaviour to avoid the pest, or modifying buildings and property to minimise the risk of exposure to the pest.

  • Managing the pest and its impacts - strategies to control pests or minimise their effects. Specific information on insecticides and methods of application are not included. Only products registered by the Australian Pesticides and Veterinary Medicines Authority (APVMA) can be used to control infestations and a professional pest manager may be needed to eradicate the pest.

  • References—some pest-specific references are included. This is not intended to be a comprehensive list of references relating to the individual pests. Relevant general resources (i.e. books covering a wide range of pests) are listed in 'Further reading and resources' at the end of this document.

Public health risks associated with arthropods

Although only a very small proportion of Australia's arthropods pose a public health risk, those risks can often be very serious. Risks vary between arthropods, but may include nuisance biting, allergic reactions, skin infestations, the transmission of diseases, stings, envenoming bites and food contamination.



Nuisance biting

Humans can often be a target for bloodsucking insects and even a single insect bite can be enough to cause pain. Besides allergic reactions or the transmission of diseases, many insect bites can cause serious discomfort and annoyance. Nuisance biting can have indirect impacts on human behaviour, such as limiting outdoor activity. Sleep patterns can be disrupted and general anxiety about the risk of insect bites can cause psychological trauma. Many insects need the protein from a blood meal to complete their life cycle and, although humans are not always the specific target, our proximity when pests invade houses, backyards and urban areas means people can be affected by nuisance biting.



Allergic reactions

Humans can have various allergic reactions to arthropods from exposure to their bite, inhalation of airborne materials or physical contact. These reactions can sometimes be severe and occasionally result in anaphylactic shock or death. Some arthropods, especially dust mites, can trigger asthmatic reactions. A person's sensitivity and the severity of their reaction will vary with exposure to different pests and can often change over time with repeated exposure to particular pests. In some cases, repeated exposure may lead to desensitisation, but it can also result in extreme sensitivity in some people.



Skin infestations

Very few arthropods actively invade human tissue, but those that do can cause serious pain or discomfort. In Australia, scabies mite is the main pest in this category, and attachment of ticks to human skin can also cause serious discomfort.



Infectious diseases

The transmission of pathogens is a serious public health concern. Viruses, bacteria, rickettsia, protozoa and nematode parasites are all known to be transmitted to humans via arthropods (known as vectors) in various parts of the world. The public health risks associated with these pathogens and the severity of the diseases they cause can vary greatly, depending on the interactions between the specific arthropod vector, the pathogen, the natural hosts and the environment. Arthropods typically transmit pathogens either biologically or mechanically. The most common mode of transmission is biological, where the vector picks up the pathogen from an infected host (human or other animal), the pathogen undergoes some form of growth within the vector and is then transmitted to a human via the infected arthropod's bite. Mechanical transmission is less common and involves pathogens moving from infected to uninfected hosts through the contamination of the arthropod's body, typically the external mouthparts.



Stings and envenoming bites

Some arthropods inject venom when they bite or sting, which may lead to more severe reactions compared to a nonvenomous insect bite. The symptoms of an envenoming bite can vary greatly, ranging from mild irritation to severe pain to potentially life-threatening reactions. Venom is most commonly injected via an arthropod's sting, but some can excrete toxins in their bodily fluid or through body hairs.



Food contamination

Just as arthropods can transmit pathogens directly through their bites, many can pass on diseases by spreading contaminants from unhygienic areas to food storage or preparation areas. Insects that feed on contaminated material may either regurgitate, defecate or physically transfer pathogens to foodstuffs. In addition, when pest populations are high, arthropods or their body parts may contaminate stored products and be accidentally consumed, leading to allergic reactions or other human illness.



General annoyance

Under favourable conditions, many arthropods can reproduce to exceptionally large numbers. Even if these pests do not directly affect humans through biting or irritation, the sheer number of insects can cause annoyance in daily activity. In some cases, infestation of a home or property can result in severe psychological reactions, where anxiety and panic may be triggered by the perceived health risks or social stigmas associated with some pests. Some people have a strong fear of insects, known as entomophobia.



Personal protection strategies

Avoidance

One of the most reliable ways to minimise the risk of exposure to pest arthropods is to avoid their natural habitats (e.g. known mosquito or tick habitats) or limit their ability to infest a house or workplace (e.g. bed bugs or bird mites). This relies on knowledge of the pest, their natural habitats and environmental triggers for activity or population increases. For many pests, these factors may change depending on their geographic distribution across Australia.



Insect repellents

Insect repellents are usually applied to the skin to stop biting insects identifying the person as a potential blood meal. Repellents are often used against biting midges, mosquitoes and ticks, although they can sometimes be used against other blood-feeding arthropods (e.g. bed bugs, bird mites). Although the specific mode of action for many repellents is not fully understood, they usually stop the arthropod from biting by either blocking the cues that identify the host as a potential blood meal or providing an odour that overrides that of the host. There is a wide range of repellents available, classified as either synthetic or botanical in nature.



Synthetic repellents

This term generally applies to chemically produced or synthesised repellents. The most effective and widely used repellent internationally is DEET (diethyltoluamide). Developed by the United States Army in the 1950s, DEET is now used by many millions of people around the world and is available in a wide range of application formulations (e.g. roll-ons, lotions, aerosols, pump-sprays and wipes) and concentrations. Generally, repellents containing less than 10% DEET will offer up to two hours' protection from biting arthropods and are suitable for general use. Repellents that contain up to 80% DEET are more suitable for long periods of exposure to biting arthropods in areas of endemic vector-borne disease.

Picaridin is another widely available active ingredient found in commercial insect repellents in Australia. This product was developed more recently, is generally thought to have a more pleasant scent than DEET and has lower toxicity to humans (making it more appropriate for use on children). Scientific studies have shown that this product is equally effective at preventing insect bites as DEET.

Botanical repellents

There are a large number of plants whose essential oils or extracts may provide protection against biting insects. The most common products come from strongly aromatic plants, such as eucalypts or tea-tree, and commercial products often contain a blend of extracts. Many scientific studies have compared botanical and synthetic repellents and, although botanical products may provide some protection, products such as DEET and picaridin provide substantially greater and longer term protection, even at low concentrations. Some natural products offer protection for only a few minutes, leaving users unprotected and exposed to disease-carrying vectors. However, research on repellents with botanical-based active ingredients is continuing and these products may be useful under some circumstances.



Coils, sticks and other gadgets

Burning plant material to repel biting insects has been used by many cultures for thousands of years. Today, the tradition continues in the form of mosquito coils and sticks. The mosquito coil is the most popular form of personal protection from biting insects over the past 100 years. These devices are made of materials impregnated with insecticide (e.g. synthetic pyrethroids, such as allethrin) that burn slowly (some coils burn for up to eight hours) and may provide up to 80% protection. Some formulations are also available with botanical active ingredients, but these are generally less effective. Coils are cheap to produce and easy to operate, although the smoke produced may present a health risk when used indoors. There is also a number of electronic units available (for both indoor and outdoor use) that release insecticides from slow-release mats or liquids. These units can be very effective, as the pyrethroids kill mosquitoes rather than simply repelling them.

A wide range of products claim to repel biting insects in formulations other than topical repellents. Products containing synthetic or botanical active ingredients can include patches and wrist bands that claim to provide a degree of protection. However, scientific studies have shown that these products offer substantially less protection than topical repellents.

Repellent safety

All repellents used in Australia, whether synthetic or botanical, must by law be registered with the APVMA and the approval number must be listed on the label.

There is often a perception that synthetic repellents, such as DEET, are unsafe. However, despite the widespread use of DEET-based products internationally, there are very few cases of adverse reactions. Most of these cases involve serious misuse, most commonly applying too much of the product (especially on young children), eating it or exposing the eyes to the product. Botanical-based products can also cause irritation. The risk of an adverse reaction from using a repellent is very low and failing to use repellents in some locations will almost certainly result in insect bites and the real possibility of acquiring an infectious disease.

Regardless of the active ingredient, all repellents should be applied according to the instructions on the label.



Insecticides

All insecticides must be registered with the APVMA for use in Australia. Detailed discussion of the most suitable products for controlling specific pests is beyond the scope of this document and professional pest managers may be needed to treat serious infestations. However, in many cases, household insecticides (either knockdown aerosols or long-lasting residual surface sprays) may be a cost-effective solution to lessen the short-term effects of some biting arthropods. The one notable exception to this is for bed bugs, as household products are generally ineffective and can cause the infestation to spread, making eradication more difficult and expensive.



Barriers

Physical and chemical barriers against pests are often very effective. Screened windows, doorways and balconies, and bed nets provide protection from flying insects, and insecticide applications to the building or surrounding vegetation may provide further protection. Some vertebrate animals, such as bandicoots, rodents and birds can carry arthropod pests; barriers that stop these animals from entering properties are often the best way to minimise the risks of exposure to these arthropods.



Electronic devices

Many electronic (e.g. ultrasonic) devices are available that claim to repel invertebrate and vertebrate pests, but these have repeatedly been shown to be ineffective. These devices continue to be adapted to new technologies with options available for mobile phones, portable music players and other digital devices but, unfortunately, no new advances in their actual repellent properties have been made.



Traps and lures

A wide variety of traps and lures are designed to control arthropod pests. These traps and lures vary greatly, not only in their design and mode of action (e.g. electrocuting lights, carbon dioxide-baited suction traps, sticky paper, shelter providers), but also in their effectiveness in controlling pests. Although many of these devices collect pest arthropods, few offer complete protection from pest effects, long-term population control or eradication. However, they may be an important component of integrated pest management strategies and can be a useful tool in monitoring pest populations.



Knowledge

One of the most effective tools to assist personal protection is knowledge. Information about locally important pests and their biology, ecology and potential health impacts will allow the individual to better avoid exposure to the pests' bites, stings and disease-causing microorganisms. It is hoped that this document will go some way towards improving the availability of knowledge on many of Australia's most important arthropod pests.



Further reading

Antwi FB, Shama LM and Peterson RKD 2008. Risk assessments for the insect repellents DEET and Picaridin. Regulatory Toxicology and Pharmacology 51:31-36.

Barnard DR 1999. Repellency of essential oils to mosquitoes (Diptera: Culicidae). Journal of Medical Entomology 36:625-629.

Curtis C 1986. Fact and fiction in mosquito attraction and repulsion. Parasitology Today 2:316-318.

Fradin MS 1998. Mosquitoes and mosquito repellents: a clinician's guide. Annals of Internal Medicine
128:931-940.

Fradin MS and Day JF 2002. Comparative efficacy of insect repellents against mosquito bites. New England Journal of Medicine 347:13-18.

Frances SP and Cooper R D 2007. Personal protective measures against mosquitoes: insecticide-treated uniforms, bednets and tents. ADF Health 8:50-56.

Greive KA, Staton JA, Miller PF, Peters BA and Oppenheim VMJ 2010. Development of Melaleuca oils as effective natural-based personal insect repellents. Australian Journal of Entomology 49:40-48.

Maguranyi SK, Webb CE, Mansfield S and Russell RC 2009. Are commercially available essential oils from Australian native plants repellent to mosquitoes? Journal of the American Mosquito Control Association 25:292-300.

Novak RJ and Gerberg EJ 2005. Natural-based repellent products: efficacy for military and general public uses. Journal of the American Mosquito Control Association 21:7-11.

Strickman D, Frances SP and Debboun M 2009. Prevention of Bug Bites, Stings and Disease, Oxford University Press, New York.

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