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Parasitic Infestations of Surgical Importance in Children 147

develop in the subcutaneous tissue in 12 days. Dogs and small rodents
are a particularly important reservoir for the parasite; humans are
infected accidentally. Children, because of their daily habits and liking
for pets, are especially prone to developing the disease. Under normal
circumstances, the fly larvae that have penetrated the skin remain in
the subcutaneous tissue below the skin orifice until they reach maturity
without migrating to deeper structures. However, there have been two
reports of fatal cases of cerebral infestation caused by migration of the
larvae through the open fontanelles in children.
Ultimately, the larvae emerge from the swellings, which may be
situated on the forearm, scrotum, and other parts of the body (Figure
23.3) and fall to the ground to pupate in 36 hours.
Clinical Presentation
The clinical presentation is usually simple and includes swelling of the
part of the body involved, pain, and itching. The history may suggest
recent handling of infested pests from which similar larvae may have Figure 23.3: Penile myiasis (arrow) with fly larva exiting lesion after it was
squeezed out with gloved hands (courtesy of Dr UE Usang, Calabar, Nigeria).
been extracted. The child may be unkempt.
A boil-like lesion may be seen with a tiny opening at the top from
which the motile tip of the larva may be observed. Application of water
on the lesion activates the indwelling larva, making the diagnosis obvious.
Investigation
Diagnosis is clinical. However, the extracted larva should be submitted
for parasitological identification (Figure 23.4).
Treatment
The larvae may spontaneously exit from the lesion, which then subsides
unless secondarily infected. Alternatively, obstructing the cutaneous
orifice by pouring water, oil, or liquid paraffin suffocates the larva,
which wriggles out and can be squeezed out gently with the gloved
hands. Topical antibiotic creams may be applied to prevent secondary
infection. Rarely, larvae that have burrowed through the subcutaneous
or deeper tissues may require surgical removal.
Hydatid Disease
Hydatid disease is a common problem in the developing countries. Figure 23.4: Fly larva of Cordylobia anthropophaga extracted from a 12-year-old
The cause of the disease in human beings is the hydatid cyst, which is child with penile myiasis (courtesy of Dr UE Usang, Calabar, Nigeria).
a larval form of Echinococci. There are three species of Echinococci
that may cause hydatid disease: E. granularis, E. multilocularis, and E. scolices have a sucker and hooklet and are infective. Multiloculated
olgiettas. The clinical presentation and management of various forms cysts are formed by infestation with E. multilocularis. After the death
of hydatid disease are similar with only minor differences. Hydatid cyst of the animal in the wild or the feeding of infected organs to the dogs
is the most common cestodes infection in the world, with cosmopolitan by butchers, dogs and other canines ingest hydatid cyst-infested tissue.
distribution. It is especially prevalent in sheep- and cattle-raising areas The scolices, using their hooks, settle in the proximal small intestine
where canines such as dogs, wolves, jackals, and foxes are present.
and grow into mature worms. Human beings are accidental hosts and
Pathophysiology do not complete the life cycle. In endemic areas, the parasite may cause
The adult echinococcus is a small tapeworm, 3–6 mm long. It has a infection in early childhood, but it takes a long time before the child
life-span of about 5 months. Canines (dogs, wolves, jackals, and foxes) may become symptomatic. Sometimes the disease may manifest 20–30
are the definitive hosts. It resides in the upper small intestine of the host years after initial infection.
and lays eggs that are passed in the faeces of the canine and infect soil, Epidemiology
water, and the bodies of the dogs and other animals. Cattle, sheep, and Hydatid disease has a worldwide presence. It is seen in the countryside
other animals get infected by ingesting these eggs and are intermediate where cattle, sheep, dogs, and humans live in close association. In
hosts. Humans get infected by ingesting raw vegetables and water, and rural areas, especially in developing countries, animals are slaughtered
by close association with dogs. After ingestion, either by human beings in open areas and the infected tissue is fed to the street dogs, which
or an intermediate host, the embryo is liberated in the small intestine, may get infected and may also transmit the disease to humans. In
which then penetrates the intestinal mucosa to reach the portal circula- adults, the liver and lungs are involved in 90% of the cases, and liver
tion. It may settle in the liver and form a hydatid cyst. The embryo may hydatid is seen in nearly 75% of the cases. In children, lung hydatid
pass the portal circulation and enter into the general circulation, where is more common.
it can form a hydatid cyst in virtually any organ and tissue of the body,
such as the lung, brain, and bones. Clinical Presentations
The hydatid cyst is the larval form of Echinococcus and consists of In humans, hydatid disease manifests as a hydatid cyst. Usually there
an inner germinal layer and outer laminated membrane. Compressed is a single hydatid cyst, but there may be multiple cysts. The organs
host connective tissue forms the false capsule around the cyst. The of predilection are the liver and lung, but it may involve virtually any
germinal layer forms bulblike projections in the lumen called brood tissues or organs of the body, such as bones, brain, spleen, heart, and
capsules. Inside the brood capsules, small invaginations occur that form peritoneum. The clinical presentation of a hydatid cyst depends on the
the scolices, which are the future heads of the mature worms. These organ involved and is either by its presence in the organ, its local pres-