Other Irritating Arthropods (Beetles, Bugs, Centipedes, Etc.)

Since the late 1990s, bed bugs of the species Cimex lectularius and Cimex hemipterus have undergone a worldwide resurgence. These bed bugs are blood-sucking insects that readily bite humans. Cutaneous reactions may occur and can start out as small macular lesions that can develop into distinctive wheals of around 5 cm in diameter, which are accompanied by intense itching. Occasionally, bullous eruptions may result. If bed bugs are numerous, the patient can present with widespread urticaria or eythematous rashes. Often, bites occur in lines along the limbs. Over 40 pathogens have been detected in bed bugs, but there is no definitive evidence that they transmit any disease-causing organisms to humans. Anemia may result when bed bugs are numerous, and their allergens can trigger asthmatic reactions. The misuse of chemicals and other technologies for controlling bed bugs has the potential to have a deleterious impact on human health, while the insect itself can be the cause of significant psychological trauma. The control of bed bugs is challenging and should encompass a multidisciplinary approach utilizing nonchemical means of control and the judicious use of insecticides. For accommodation providers, risk management procedures should be implemented to reduce the potential of bed bug infestations.

The ecological phenomenon of arthropods with defensive hairs is widespread. These urticating hairs can be divided into three categories: true setae, which are detachable hairs in Lepidoptera and in New World tarantula spiders; modified setae, which are stiff hairs in lepidopteran larvae; and spines, which are complex and secretion-filled structures in lepidopteran larvae. This review focuses on the true setae because their high density on a large number of common arthropod species has great implications for human and animal health. Morphology and function, interactions with human tissues, epidemiology, and medical impact, including inflammation and allergy in relation to true setae, are addressed. Because data from epidemiological and other clinical studies are ambiguous with regard to frequencies of setae-caused allergic reactions, other mechanisms for setae-mediated disease are suggested. Finally, we briefly discuss current evidence for the adaptive and ecological significance of true setae.

Centipedes are among the oldest extant terrestrial arthropods and are an ecologically important group of soil and leaf litter predators. Despite their abundance and frequent, often painful, encounters with humans, little is known about the venom and venom apparatus of centipedes, although it is apparent that these are both quite different from other venomous lineages. The venom gland can be regarded as an invaginated cuticle and epidermis, consisting of numerous epithelial secretory units each with its own unique valve-like excretory system. The venom contains several different enzymes, but is strikingly different to most other arthropods in that metalloproteases appear to be important. Myotoxic, cardiotoxic, and neurotoxic activities have been described, most of which have been attributed to high molecular weight proteins. Neurotoxic activities are also unusual in that G-protein coupled receptors often seem to be involved, either directly as targets of neurotoxins or indirectly by activating endogenous agonists. These relatively slow responses may be complemented by the rapid effects caused by histamines present in the venom and from endogenous release of histamines induced by venom cytotoxins. The differences probably reflect the ancient and independent evolutionary history of the centipede venom system, although they may also be somewhat exaggerated by the paucity of information available on this largely neglected group. Copyright © 2011 Elsevier Ltd. All rights reserved.