Myiasis, a noun derived from Greek (mya, or fly), was first proposed by Hope to define diseases of humans caused by dipterous larvae, as opposed to those caused by insect larvae in general (161). Myiasis has since been defined as the infestation of live vertebrates (humans and/or animals) with dipterous larvae (371). Recognized in ancient times, flies causing myiasis are still some of the world’s most devastating insects, responsible for severe losses in animal husbandry, with significant economic losses, including reduced milk production, weight and fertility issues, and reduced hide quality (371). In mammals (including humans), dipterous larvae can feed on the host’s living or dead tissue, liquid body substance, or ingested food and can cause a broad range of infestations, depending on the body location and the relationship of the larvae with the host (250). Implications of the Use of the Myiasis for Nurse and Patient Essay. The distribution of human myiasis is worldwide, with more species and greater abundance in poor socioeconomic regions of tropical and subtropical countries. In countries where it is not endemic, myiasis is an important condition, where it can represent the fourth most common travel-associated skin disease (59).

MYIASIS CLASSIFICATION

There are two main systems for categorizing myiasis: anatomical and ecological classifications. The anatomical system of classification, first proposed by Bishopp, is considered useful for practical diagnosis and to classify the infestation in relation to the location on the host (172, 269, 371). Since a single species can be assigned to more than one anatomical location, and the same location can be infested by different species, a classification system based on the degree of parasitism shown by the fly is also used.

TAXONOMIC CLASSIFICATION OF THE DIPTERA (TRUE FLIES)

The order Diptera is a large order of insects that are commonly known as true flies. The presence of a single pair of functional wings with a reduced hind wing, termed halteres, distinguishes true flies from other insects (226, 227). Flies are ubiquitous and abundant, with approximately 150,000 species in 10,000 genera and 150 families. This order contains most of the insects vectoring diseases in humans.

The order Diptera is divided into two suborders, the Nematocera and the Brachycera. The Nematocera contain most families of blood-feeding flies that serve as vectors for a variety of viral, protozoan, and helminthic diseases, especially the Culicidae (115). Rarely, agents in this suborder can cause accidental myiasis (Table 3). The Brachycera are composed of infraorders. The infraorder Muscomorpha or “Cyclorrhapha” (term used in nonphylogenetic classifications) contains all species that cause specific myiasis and most of the species responsible for facultative myiasis, especially the species within the Calyptratae.

Figure 1 summarizes the taxonomy of the Diptera, and Fig. 2 presents the taxonomic division of the Calyptratae. Both were designed to include the agents related to human myiasis. Table 3 shows the species outside the Calyptratae reported to cause human myiasis. Implications of the Use of the Myiasis for Nurse and Patient Essay. Tables 4 to ​to88 summarize the most important aspects of the species within the Muscoidea, Oestroidea, Calliphoridae, and Sarcophagidae that cause human myiasis.

LARVAL PRESERVATION AND IDENTIFICATION

When treating a patient with myiasis, it is critical to make the correct identification of the larva. It helps not only to understand how the infestation was acquired but also to plan the treatment and to promote preventive measures.

After removal, the maggot should be killed by immersion for 30 s in very hot (enough to produce vapor) but not boiling water, which prevents decay and maintains the natural color. Larvae should then be preserved in a solution of 70% to 95% ethanol. The above-described method best preserves larval length and morphology. Killing of the larvae directly in a preservative will putrefy and shrink them. If a solution of 70% ethanol is not available, 70% isopropyl alcohol can be used instead. Formalin solutions should not be used, because they cause an excessive hardening of the larval tissues, making them difficult to process (229).

Identification can be very challenging and demanding. Specific knowledge of the morphological aspects of the larva is necessary for the identification of the maggot’s species, a task usually done by a trained entomologist. Several aspects of the larva must be analyzed before the final species is determined, which is not possible in some cases. Implications of the Use of the Myiasis for Nurse and Patient Essay. Body shape, aspects of the papillae, the posterior spiracles (position, shape, openings, and structures), pigmentation of the dorsal tracheal trunks, the body surface (spines), the anterior spiracles, the cephalopharyngeal skeleton, and clinical behavior are all taken into account when the offending maggot is analyzed. An excellent Internet resource to help identify the species when a trained expert is not present is the Natural History Museum (London, United Kingdom) website (http://www.nhm.ac.uk/research-curation/research/projects/myiasis-larvae/intro-myiasis/index.html), using the option, “launch the key to myiasis-causing larvae.”

MYIASIS AND TRAVEL MEDICINE

Increasing international travel, both for tourism and for business, raises the need for physicians to cover a large spectrum of diseases, especially those caused by infectious agents. Skin diseases, together with systemic febrile illness and acute diarrhea, are the leading causes of health problems in travelers and account for 8% to 12% of all tourists medical problems (160). Myiasis is usually among the five most common dermatologic conditions, representing 7.3% to 11% of cases (212, 290).

Travel clearly raised the importance of myiasis knowledge, especially in countries where the infestation is unusual, rare, and, in some cases, reported as being exotic (120, 124, 150). Even physicians unfamiliar with this condition can easily diagnose cases in which maggots are visible. On the other hand, furuncular, migratory, and cavitary cases and pseudomyiasis pose a diagnostic challenge, especially to those doctors unacquainted with myiasis and its possibilities. For the correct diagnosis, several aspects should be determined: the region where the patient visited, climate conditions, and the species habits of the region visited.

An accurate and timely diagnosis is important not only to alleviate the patient’s symptoms but also to prevent the establishment of myiasis-causing flies in regions where they are not endemic, a phenomenon that is already happening with the movement of farm animals. In many cases, the patient receives unnecessary oral antibiotics, increasing the development of bacterial resistance (150). Implications of the Use of the Myiasis for Nurse and Patient Essay.

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CLINICAL MANIFESTATIONS

Myiasis is considered, in most cases, an embarrassing and repugnant disease to patients and to health care professionals. Poor hygiene and low socioeconomic status are the most important risk factors for acquiring myiasis (111, 220). Another important factor is an abundance of exposed preexisting suppurative lesions that attract and stimulate the deposit of eggs by the female insect. For specific species, habits of the population, such as sitting or lying on the ground and some religious rites, and climatic conditions influence the occurrence of myiasis (117).

The real importance of human myiasis is unknown, and identification of the species responsible for a case of myiasis is rarely done. Epidemiological data on human myiasis are scant, and registration of the cases is not usually obligatory. Health care professionals judge myiasis to be a disease of minor importance, leading to an inadequate registration of the case: the larva and dressings are normally discarded without further examination. In some countries, domestic and empirical treatments of the patients are made by family members, reducing the number of the cases seen in medical facilities. Access to entomologists with expertise in dipteran classification is usually difficult, especially in developing regions, where myiasis can be a real problem of public health.