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Dispatch
Myiasis during Adventure Sports
Race
Mikko Seppänen,* Anni Virolainen-Julkunen,*† Iiro Kakko,‡ Pekka Vilkamaa,§
and Seppo Meri*†
*Helsinki University Central Hospital, Helsinki, Finland; †University
of Helsinki, Helsinki, Finland; ‡Sports Institute of Eerikkilä, Tammela,
Finland; and §Finnish Museum of Natural History, Helsinki, Finland
Suggested citation
for this article:
Seppänen M,Virolainen-Julkunen A, Kakko I, Vilkamaa P, Meri S. Myiasis
during adventure sports race. Emerg Infect Dis [serial online] 2004
Jan [date cited]. Available from: URL: http://www.cdc.gov/ncidod/EID/vol10no1/02-0825.htm
Travelers who have
visited tropical areas may exhibit aggressive forms of obligatory myiases,
in which the larvae (maggots) invasively feed on living tissue. The
risk of a traveler’s acquiring a screwworm infestation has been considered
negligible, but with the increasing popularity of adventure sports and
wildlife travel, this risk may need to be reassessed.
Case Report
In November 2001, a 41-year-old Finnish man, who was participating in
an international adventure sports race in Para (a jungle area in Brazil),
tripped at night over a loose rock while he was riding a bicycle. He received
a bruised, lacerated wound on his left dorsal antebrachium, which he quickly
wiped with paper. The remaining gravel, dirt, and three unidentified winged
insects were removed, and the wound was thoroughly rinsed 3 hours later
by medical personnel. Petrolatum was applied topically and the wound bandaged.
The patient continued the jungle race for the next 108 hours, during which
the wound was hastily cleansed and rebandaged twice. The patient repeatedly
swam in the Amazon Basin. At the race’s finish, the wound appeared purulent
and was cleansed with tap water, soap, and a brush. Numerous attached
ticks were removed from his skin.
The arm became tender, and the patient had bouts of intensified local
pain. A possible, round entry wound, about 1 mm in diameter, was noted,
at the bottom of which the patient observed motion. Five days after the
accident, a physician explored the wound with scissors at a breakfast
table. No larvae were found. Sugar was applied topically and cefalexine
prescribed. Twenty hours later, the bouts of pain recurred with increasing
frequency. The patient believed that something left in the wound “ate
his flesh.” Nine days after the accident, at the Frankfurt Airport, Germany,
the patient found a larva (Figure, part a) and an
exit site wound (Figure, part b) under the bandage.
The bouts of tenderness subsided. The patient’s wound was reexamined 1
day later and was found to be largely healed; the forming scar remained
somewhat tender and itchy for 2 months. The maggot was sent to the Finnish
Museum of Natural History, Helsinki, Finland, and identified as a third-stage
larva of Cochliomyia hominivorax (Coquerel), the New World screwworm
fly. In addition to the New World screwworm fly, an important Old World
species, Chrysoimya bezziana, is also found in tropical Africa
and Asia.
Conclusions
Myiasis is the infestation of live humans and vertebrate animals by fly
larvae. These feed on a host’s dead or living tissue and body fluids or
on ingested food. In accidental or facultative wound myiasis, the larvae
feed on decaying tissue and do not generally invade the surrounding healthy
tissue (1). Sterile facultative Lucilia larvae
have even been used for wound debridement as “maggot therapy.” Myiasis
is often perceived as harmless if no secondary infections are contracted.
However, the obligatory myiases caused by more invasive species, like
screwworms, may be fatal (2). The screwworms are capable
of penetrating through minor cracks in the skin, entering body openings,
and migrating from wounds to living tissue. Most often this is initiated
when the flies, attracted by the wounds, lay their eggs in necrotic, hemorrhagic,
or pus-filled lesions. Infestation and penetration of the ocular, nasopharyngeal,
paranasal, and auricular cavities are frequently described (3).
The female flies colonize the wounds with bacteria like Providencia
spp., which in turn attract more flies by the distinct odor of the bacterial
mass. Secondary bacterial infections are common. All conditions compromising
the integrity of skin (like tick bites and skin diseases) predispose to
the infestation (4). The eggs of Cochliomyia hominivorax
are laid in batches. Hundreds of maggots of both sexes can be found in
a wound. Screwworms can thus be introduced to new areas by just one index
patient. Considerable risk exists of reintroducing C. hominivorax
into areas from which it has been eradicated. Within 24 hours of hatching,
the larvae begin feeding and cause extensive tissue destruction, pain,
and even death. The larvae possess powerful oral hooks and can invade
cartilage and bone (5). After feeding for 4 to 8 days,
the larva leaves the wound to pupate in the soil (6,7).
The pest is viable year round in areas with temperatures constantly >16°C.
C. hominivorax was first found to be infesting people in the penal
colony of Devil’s Island in French Guiana in 1858. It was originally distributed
from the southern United States to Argentina between the 35o
north latitude and the 35o south latitude. Due to a massive
sterile male fly release program, C. hominivorax was eliminated
from North America. C. hominivorax is an important insect pest
of livestock in the neotropical regions and has caused substantial losses
to the livestock industries of the Americas (7). It is
classified as a restricted animal pathogen in the United States. At present,
populations of C. hominivorax are found in Central and South America
and in certain Caribbean Islands (4,6,7). Human infestations
remain an important health problem, primarily affecting the severely debilitated
or persons with no access to healthcare. In the largest published study,
the fatality rate was 2.8% (7). Isolated reports of infestations
in the United States and Mexico are often traced to the importation of
infested animals. Between 1969 and 1988, 39 human cases were reported
(7). The potential for the introduction of C. hominivorax
into new areas is ever present. In 1988, the screwworm appeared in Libya,
most likely imported by infested livestock. It overwintered and became
for the first time established outside the Western Hemisphere, where it
infected 3,000 livestock and >200 persons. From Tripoli, it spread
rapidly approximately 200 km and threatened to spread further to the savannas
of sub-Saharan Africa. This possibility presented a potential threat of
enormous proportions to the livestock, wildlife, and human populations
of a large part of the Eastern Hemisphere. After a large-scale campaign,
the screwworm was successfully eliminated from the area in 1991 (7,8).
In humans, the most common sites of C. hominivorax infestation
are the nose, eyes, and skin. The manifestations depend on the anatomic
region affected but are usually characterized by local pain, intense pruritus,
cutaneous nodules, and larvae emerging from wounds or cavities (7,9).
Massive infestations can result in the death of the host, usually attributed
to “massive toxic shock” or to penetration of viscera or cavities, especially
in the head and neck area (6,8). Infestation of paranasal
sinuses often goes undetected for long periods. When infestation is suspected,
a careful search for a larval infestation of eyes, nose, paranasal sinuses,
or wounds should be performed, if necessary with the help of computed
tomography or magnetic resonance imaging (7). Radiographic
studies may only show edema. No effective antimicrobial therapy is available,
although doramectin and ivermectin have been investigated for prophylactic
use in cattle. Treatment involves removal of the larvae (reviewed in [5]
and [6]). Irrigation with either chloroform or ether
is advocated. Surgery is often required. For identification, the larvae
should be hatched to adult flies, or first killed by immersion in nearly
boiling water, then cooled and preserved in 80% ethanol. Secondary bacterial
infections should be treated with local wound care and administration
of antimicrobial agents.
In industrialized countries wound myiasis is a sign of neglected wound
care, with mostly facultative myiases seen. The patients are often debilitated,
of lower economic status, homeless, or substance abusers. The main focus
is in treating secondary bacterial infections and in proper debridement.
The risk of a traveler’s acquiring C. hominivorax is thought to
be negligible (3). With the increasing popularity of
adventure and wildlife travel, the risk may need to be reassessed. Travelers
can contract aggressive obligatory myiases. This is the third report of
C. hominivorax infestation in a tourist in 3 years (4,9).
Also, a previous case was reported in a U.S. Army ranger who was wounded
in action in Panama (5). In particular, medical personnel
who treat patients who have participated in adventure sports events should
recognize the intensity of the exposure to even the most exotic infectious
diseases.
Acknowledgments
We thank Pasi Ikonen
for providing the photograph in Figure A.
Dr. Seppänen is a
specialist in infectious diseases and internal medicine and a consultant
at Helsinki Central Hospital, Helsinki, Finland. His current research
interests include primary immunodeficiencies, complement deficiencies,
and the immunology of herpes simplex virus infections.
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