Vol 10 Part 14. An introduction to the immature stages of British Flies ...

doubt many more cases occur than are diagnosed and recorded. Where myiasis is a
normal way of life for fly larvae in animals this is described under the particular Diptera
family concerned. The types of myiasis can be further classified as follows.
1. Blood-sucking maggots. E.g. Calliphoridae (Auchmeromyia senegalensis
Macquart( = luteola Fabricius), the Congo floor-maggot (Afro-tropical)); Tabanidae
(in paddy fields in Japan); Therevidae (fig. 161, Smith, 1979a, 1986a, British cases);
Protocalliphora on birds.
2. Dermal and subdermal myiasis. Larvae penetrate unbroken skin or enter wounds
or form boils or other lesions, either at the site of entry or elsewhere, e.g. Calliphoridae,
Gasterophilidae, Hypodermatidae, Muscidae and Sarcophagidae.
Oldroyd (1964) reports 'I have known a female Sarcophaga to fly to a coat, the sleeve
of which had been soiled with blood from a shot pheasant and immediately lay a batch
of young larvae upon it'. Lucilia sericata (Meigen), a common green bottle, is also the
sheep maggot fly (fig. 809), the causal agent of sheep strike. Larvae of Lucilia and
Calliphora may occur in cases of wound myiasis in man and animals. Calliphorid larvae
(Lucilia sericata, L. caesar (Linnaeus) and Phormia regina (Meigen) have been used
to clean wounds of necrotic tissue on the battlefield (Hinman, 1933, Imms, 1939,
Greenberg, 1973) and may even exude an antibiotic (Pavillard & Wright, 1957). Osteomyelitis
and other kinds of non-healing wounds have also been treated in this manner,
e.g. heat burns, X-ray burns, varicose and diabetic ulcers, etc. (see also below under
Musca domestica).
First ins tar larvae of Gasterophilus can cause a creeping myiasis in man, usually on
the face and buttocks (Zumpt, 1965) but I know of no British cases. Hypoderma
may also be incriminated in this category (Smart, 1939) but is usually involved in
nasopharyngeal myiasis (see below).
Musca domestica larvae may occur in cases of human myiasis where urine is
involved: e.g. in neglected cots or napkins of infants (Mumford, 1926, Chapman, R. K.,
1944); in the feet and footwear of incontinent geriatric patients (see also urogenital
myiasis). M . domestica has also been used to clean gangrenous wounds as the larvae do
not attack healthy tissue (as other genera will- see above). Healing can commence
48 hours after treatment begins (Imms, 1939).
3. Nasopharyngeal myiasis. This includes invasion of the nasal fossae, frontal
sinuses, pharyngeal cavities, eyeballs, eye-sockets and (aural myiasis) ears, e.g. Calliphoridae,
Cuterebridae (non-British), Gasterophilidae, Hypodermatidae, Mycetophilidae,
Oestridae, Phoridae, Psychodidae, Sarcophagidae and Scenopinidae.
Lucilia has been involved in a case of human aural myiasis in the U.K. (Smart, 1936)
and several other cases are known from Europe and North America. Occasionally first
instar larvae (fig. 693) of Hypoderma (mostly lineatum Villers) (warble flies of cattle)
have been found in the orbit or eyeball of man, which they will completely destroy if
they are not extracted quickly. I know of only two British cases involving H . lineatum,
one in Devon (Style, 1924)and the other in the Hope Valley of Derbyshire in 1945 when
this locality suffered 'the worst "gadfly" epidemic for many years' (Smith, A. &
Greaves, 1946) (the term 'gadding' of cattle is properly used in connection with their
response to the attention of the blood-sucking adult Tabanidae). The larvae of Oestrus
ovis Linnaeus (the sheep nasal bot fly, fig. 684) may also occur in the human eye, but are
far less serious than Hypoderma since they do not survive beyond the first instar.
Anderson (1935) found a dead first instar larva of Gasterophilus intestinalis (De Geer)
in the eye of a patient (in the U.S.A.).It is possible that an egg was transferred by wiping
the back of the hand across the eye. Zumpt (1965) records (in Africa) seeing G. intestinalis
repeatedly ovipositing on the backs of human hands when held with the palms
over horses' lips.
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