The infestation of living vertebrates by the
larvae of flies called myiasis, is derived from the Greek, ‘myia’ means a fly. The
condition although very common in domestic and wild
animals all over the world but is also observed occasionally among humans inhabiting rural
and slum areas where domestic animals are in their close contact (1). Human myiasis is an outcome of increased fly
populations due to ever-increasing garbage dumps and poor hygienic conditions. The condition is more frequent in tropical climates than in sub-tropical
and temperate ones. India being a tropical country fulfills all the favourable
conditions for the abundant growth of myiasis causing flies and their larvae.
In human myiasis the usual events is oviposition by flies in open neglected
wounds or foul smelling purulent discharge from natural body openings like
mouth, nose, ear, vagina, rectum etc. followed by hatching of eggs. The
explicit chemosensory components that are accountable for attracting flies for
oviposition are not known, but presence of pus and odour of decay in the wounds
had been reported to intensify the attractiveness of wounds as oviposition
sites. It is possible that any organ accessible to the flies could be
involved. Thus depending upon the organ involved myiasis may be oral, nasal,
aural, vaginal, rectal, cutaneous and so forth (2). Prolonged
infestations among children may lead to malnutrition, weight loss, stunted
growth and reduction in physical and mental activity.
Infestation by larvae of Chrysomya bezziana has
been reported to cause myiasis in man and domestic animals in the oriental
region. The occurrence of myiasis due to Old World screwworm fly, C. bezziana, the only known obligatory
producer of myiasis in humans is well known. The adult female lays about 150-500
eggs at a time on neglected wounds or foul smelling natural body openings. The
eggs hatch after 18-24 hours. The larvae feed for 3-4 days on surrounding
tissue and then drop to ground and pupate. The adult flies emerge after 7-9
days in tropical conditions and 8 weeks in subtropical winters (3).
A 3-yaer-old female from
a rural area was brought to Kuashalya Devi Government Hospital, Patiala (Punjab)
India, with a traumatic wound on her scalp. The patient was suffering from high
fever, severe pain and nibbling sensation in her wound. On questioning, her
parents revealed that she had sustained an injury on her scalp about a week ago
but they didn’t sought any medical care due to their low socio-economic status.
The wound was kept open and neglected during that period. Examination revealed
a bone deep wound full of foul smelling purulent discharge along with numerous
maggots, but the skull was intact (Fig 1). Haematological examination revealed
RBC count of 410 x 104/mm3, WBC count of 11,200 /mm3
and Hb 6.5 g/dl. The data indicated that the patient had slight
leukocytosis and anaemia. About 50 maggots were removed with the help of
forceps and the wound was cleaned properly with hydrogen peroxide and dressed.
Turpentine liniment plug was used to evacuate the maggots from the wound as
they come out of the wound following suffocation. A broad spectrum antibiotic
was prescribed and was asked to revisit the hospital after two days for antiseptic
dressing. While dressing the wound on her next visit 15 creamish white maggots
were recovered from the wound (Fig 2). The maggots were
identified as third instar larvae of Old World Srewworm fly- Chrysomya
bezziana belonging to the family Calliphoridae. The patient was given a
course of broad spectrum antibiotic together with anti inflammatory drugs and
with regular antiseptic dressing the wound healed within two weeks.
The dipteran larvae usually infest humans when the
conditions favour their enormous multiplication as in foul smelling wounds and
natural body openings. Oviposition is encouraged by discharges from diseased
tissues. Some other major factors for the onset of myiasis are necrotic lesions
such as due to adenocarcinoma; squamous cell carcinoma; basal
cell carcinoma; wounds of diabetic patients and trauma or surgical wounds. It
has also been remarked that debilitated persons such as newborns and patients
who are mentally disturbed or in comatose condition are vulnerable to fall
victims to myiasis. In majority of cases of human myiasis, local factors such
as traumatic lesions, inflammatory and malignant diseases play an important predisposing
The larvae of the Old World Screwworm (OSW) fly – Chrysomya bezziana Villeneuve is known to be the predominant species
for causing myiasis among man and domestic animals in tropical regions all
over. The fly had been reported as world-wide pest of domestic animals which
occurs throughout Africa, India, Arabian Peninsula, and
Southeast Asia (5). The maggots of C.
bezziana had been confronted in the wounds on majority of animals and may
be imputed to the aspect that the larvae of the fly are well known obligatory
parasites and unable to develop in dead and decaying organic matter. Consequently
the fly has to complete its larval development by parasitizing live animals. Cases of myiasis are more frequent during the months of June to November since optimum
humidity and temperature, which are the favourable conditions for the flies to breed,
are available in this period.
In the present study, the patient had a severely
infected pus filled wound, which had originated a week ago. The scalp wound had
been totally neglected and left uncovered. Moreover the hygienic condition of
the patient was very poor as the hairs were full of lice and their eggs. This
had attracted gravid flies to lay eggs and the flies in abundance were known to
be present in the vicinity as the patient lived in rural area with poor
sanitary conditions and close association of domestic animals. After hatching,
the larvae tend to penetrate deep into the tissue for feeding and the severe
pain reported by the patient might be due to the approach of the larvae to the periosteum.
The present study is reported to be the case of severe neglected hygiene and
ignorance among masses about the onset of myiasis.
It is noteworthy that myiasis is quite uncommon in
children and when it occurs, one could expect a predisposing lesion of the type
that would have attracted flies for oviposition such as purulent discharge or
open neglected wounds as in the present case. At the same time hygienic factors
could also be speculated to contribute to myiasis in fly infested areas. It is
emphasized that the parents of the child patients should not neglect their
wounds and should take proper medical care so as to avoid myiasis. Besides, there
is urgent need to create awareness among masses about the problem. Control of
fly populations and reduction of odour of decomposition are some of the
effective means of prevention of myiasis in third-world countries.