Case 5 Geographic Movement

A female 22 years of age returned from an archaeology field school held in Belize during the months of June through July 2000. She had been working at a relatively remote although secure site in the jungle for a period of 4 weeks. During this period

Fig. 14.6 Scalp of student showing locations of two D. hominis larvae
Fig. 14.7 Left shoulder of student showing partially expressed larva of D. hominis

of time, she was living is somewhat primitive conditions. Although the students were aware of the presence of Dermatobia hominis and the possibility of infestation, a number did acquire the bots. On her return to California, the student was aware of 2 larvae in her scalp (Fig. 14.6) and one on her left shoulder (Fig. 14.7). Initially she was not disturbed but as the larvae matured, she became more aware of their feeding activities and requested that they be removed. The larvae were expressed with no adverse effects to the student (Fig. 14.8).

The life cycle of D. hominis is quite unique and deserves some brief comment. The adult fly is somewhat similar in appearance to a bluebottle fly and is a forest-dwelling insect. The adults are non-feeding. The adult female does not oviposit directly on the host animal. Instead, another arthropod is captured and

Fig. 14.8 D. hominis larva removed from left shoulder of student

eggs deposited on its external surface. Guimaraes and Papavero (1999) list 55 species of arthropods in nine families as vectors for D. hominis eggs. While the majority are obligate blood-feeding species, several are not. When the egg vector comes in contact with the vertebrate host, the eggs hatch and the emergent larva falls onto the host skin. These larvae may penetrate the skin at the point of first contact or migrate to another part of the body. Once the skin is penetrated, the larva encysts and remains at that site. There is no migration through the host, characteristic of many myiasis causing species, although not those typically encountered in forensic situations. The site of penetration will take the form of a boil, with an opening to the outside maintained to enable the larva to breath. Development to the puparial stage varies, depending on the host and can range from 5 to 10 weeks (James 1947). Once the larva has matured, it leaves the site and drops to the soil to pupariate. The emergence most frequently takes place during the early morning hours. Guimaraes and Papavero (1999) indicate that the adult life span is variable, ranging from 2 to 9 days, depending on temperature.

Guimaraes and Papavero (1999) list 17 different countries in which D. hominis larvae have been recovered from individuals returning from trips to areas of Central and South America where D. hominis is present. While none of these reports has a specific forensic nature, given the current ability for travel and transport, D. hominis and other myisasis-causing Diptera have the potential to serve as evidence for geographic movement of individuals in criminal cases.

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