Diptera Nematocera and Brachycera

■ Many dipteran species act as vectors of pathogens. Their bites also cause local reactions, and fly maggots may even penetrate into and colonize the skin, wounds, or natural orifices, thereby causing considerable tissue damage._&

Role as vectors. Many species of Nematocera are significant vectors of pathogens, e.g., Anopheles mosquitoes transmitting the malaria parasites, Aedes aegypti which is the principal vector of the Dengue virus, or Phlebotomus sandflies (Fig. 11.1e) transmitting the causative agents of leishmanioses (see Chapter 9). Nematocera also transmit many other pathogens—not only in the tropics, but in central Europe as well.

The same applies to numerous fly species e.g., Glossina flies, the vectors of the sleeping sickness agents. Flies can also disseminate various pathogens mechanically (e.g., bacteria, parasites).

Bite reactions. The bites of Nematocera and flies can cause more or less pronounced primary dermal reactions (e.g., mosquitoes of the genus Aedes or blackflies of the family Simuliidae) or allergic skin reactions.

Table 11.4 Important Forms of Myiasis in Humans

Type of infestation

Larvae form focal skin swellings with central small hole

Form of myiasis

Cutaneous myiasis ■ Furuncular myiasis

■ "Creeping eruption"

■ Wound myiasis

Larvae tunnel in epidermis and induce focal skin swellings

Deposition of eggs or larvae in wounds

Infesting flies (genera, selection)

Dermatobia, Cordylobia, Cuterebra

Hypoderma, Gasterophilus

Sarcophaga, Calliphora, Musca, Wohlfahrtia, Lucilia, Cochliomyia

Other forms

■ Nasopharyngeal, Deposition of eggs or larvae Sarcophaga, Calliphora, ocular, auricular, and in nasal orifices, eyes, Musca, Wohlfahrtia, Lucilia urogenital myiasis auricular orifices, vulva, etc.

Myiasis. Larvae (maggots) of various fly species can penetrate and colonize the skin, skin lesions, and body orifices, thereby causing the type of tissue damage known as myiasis. There are various forms of myiasis, the most important of which are summarized in Table 11.4. Cases of imported myiasis and autochthonous wound myiasis have increased in central Europe in recent years. Diagnosis: inspection and identification of the larvae. Therapy: mechanical removal of the parasites, control of secondary infections, if required oral therapy with ivermectin (extralabel drug use).

The maggots of certain fly species (Lucilia spp.) raised under sterile conditions are sometimes used for treating patients with necrotizing or non-healing dermal lesions. In many cases, the maggots are able to clean such wounds in short order.

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