Stephen L. Doggett, Merilyn J. Geary & Richard C. Russell
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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 Authors: Stephen L. Doggett, Merilyn J. Geary & Richard C. Russell Presenter: Stephen L. Doggett 5/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. Safety & Pest Biology, 2008 8.1 Biology in the Management of Biting Arthropods S.L. Doggett, M.J. Geary & R.C. Russell This case study demonstrates several key points; 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. 8.2 Safety & Pest Biology, 2008 S.L. Doggett, M.J. Geary & R.C. Russell Biology in the Management of Biting Arthropods 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 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. Safety & Pest Biology, 2008 8.3 Biology in the Management of Biting Arthropods S.L. Doggett, M.J. Geary & R.C. Russell 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 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.