Introduction

Myiasis has been defined variously by numerous different authors over the years. The term itself was first coined by Hope in his 1840 paper entitled "On insects and their larvae occasionally found in the human body" although there were some earlier accounts by other authors. Subsequently there were additional treatments but not with equal restrictions. Possibly the most enduring and practical definition is that of Zumpt in his 1965 work entitled "Myiasis in Man and Animals in the Old World." In this work myiasis is defined as: "the infestation of live human and vertebrate animals with dipterous larvae, which, at least for a certain period feed on the host's dead or living tissue, liquid body-substances, or ingested food." A similar definition was followed by Guimaraes and Papavero in their 1999 work on myiasis in the Neotropics. Based on the system of classifying parasites developed by Patton (1922), Zumpt divides these myiasis-causing larvae into Obligatory Parasites and Facultative Parasites. Diptera larvae within the obligatory group develop in the living tissues of the host and this is, in fact, a necessary part of their life cycle. By contrast, the facultative group includes species that are normally free-living, feeding on decaying material, such as animal carcasses, fecal material, and even decaying vegetable materials. Under some While some species included in this category, such as Phaenicia sericata, may frequently act as parasites for all or part of their larval development, more commonly, species in this classification are associated with dead tissues present in a wound and do not actually feed on living tissues. Another situation, termed "Pseudomyiasis or Accidental Myiasis," occurs when Diptera larvae are accidentally ingested with

Forensic Sciences Program, Chaminade University, Hawaii, USA C. P. Campobasso

Department of Health Sciences, University of Molise, Italy M. Gherardi

Forensic Pathologist, Private Practice, Milano, Italy

J. Amendt et al. (eds.), Current Concepts in Forensic Entomology, 313

DOI 10.1007/978-1-4020-9684-6_14, © Springer Science + Business Media B.V. 2010

food materials and pass through the digestive tract. Keep in mind that this passage is most often passive and may result in the death of the larva. Their presence in the gut of the animal will often trigger various gastric problems, as noted by (e.g. Kenny, 1945). These infestations are not to be confused with the obligatory infestations of mammal digestive tracts by species in the subfamily Gasterophilinae (Colwell et al. 2006).

As a result of the medical/veterinary implications of myiasis, for clinical and practical reasons, there has been an additional subdivision into several different grouping, based primarily on location of the infestation. A comprehensive treatment of these is given in Hall and Farkas (2000). Additional, more recent, accounts include: sanguini-vorous myiasis, cutaneous myiasis (Suite and Polson 2007), Auricular myiasis (Rohela et al. 2006), oral myiasis (Droma et al. 2007; Kamboj et al. 2007), traumatic myiasis (Franza et al. 2006), nasopharyngeal myiasis (Gelardi et al. 2009), umbilical myiasis (Duro et al. 2007), intestinal myiasis and urogenital myiasis (Makarov et al. 2006). In many respects these subdivisions do not have any relevance to the type of myiasis or the Diptera species involved, only to the location of the infestation, although the majority would be classified as traumatic myiasis.

From an evolutionary standpoint, myiasis presents an interesting situation. There have been two routes proposed for the origin of the lifestyle by Zumpt (1965): Saprophagous and Sanguinivorous. The saprophagous route appears to begin with a relatively unspecialized larva feeding on carrion or in a benign manner on necrotic tissues associated with wounds. This habit progresses to feeding on healthy tissues adjacent to the necrotic tissues and finally results in an obligatory feeding on healthy tissues with a detrimental effect. In like manner, there appear to be three steps in the evolution of myiasis via the sanguinivorus route. In this route, the larvae begin as blood-feeding predators of other arthropods feeding on fecal material or carrion. From this the habit shifts to feeding on the vertebrate as a blood feeder and finally to the obligatory condition. A similar pattern has been suggested for the parasitic mites in the families Laelaipdae and Macronyssidae by Radovsky (1967). In this pattern, the nest is viewed as a mechanism for bringing the various elements (predators, necrophages, parasites, and hosts) together. A similar situation has not been observed for myiasis in mammals. Most species involved in forensic concerns have probably originated through the saprophagous route.

In the forensic context, myiasis is most frequently associated with the facultative parasites in the Families Calliphoridae, Sarcophagidae and Muscidae. However, some use may be made of species demonstrating the obligatory state, such as Dermatobia hominis (Cutrebridae). If not fully appreciated, myiasis can be a significant point of confusion for the forensic entomologist, appearing to give an estimate of the postmortem interval far longer than the actual period of time since death. In other instances, particularly in cases involving the living, an understanding of myiasis may prove to be a significant factor in resolving the case. In this chapter, several different situations involving myiasis will be demonstrated using case studies. Although myiasis is involved in both human and veterinary aspects of forensic investigations, in this treatment, only human involvement is presented.

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