TUNGIASIS:
overview
Tungiasis
is an infestation by the burrowing flea Tunga penetrans or
related species.
The
flea has many common names, being known in various locations as the chigger
flea, sand flea, chigoe, jigger...
The
flea is indigenous to the West Indies/Caribbean/Central America region, but it
has spread to Africa, India, Pakistan, and South America.
TUNGIASIS:
Patophysiology
The
main habitat for T. penetrans is warm, dry soil and sand of
beaches, stables, and stock farms.
To
reproduce, the flea requires a warm-blooded host. In addition to humans,
reservoir hosts include pigs, dogs, cats, cattle, sheep, horses, mules, rats,
mice, and other wild animals.
Upon
contact, the flea invades unprotected skin. The most common site of
involvement is the feet (interdigital skin and subungual area). The flea has limited
jumping ability.
TUNGIASIS:
Patophysiology
The
flea expands, often reaching 1 cm in diameter. The head is down into the
upper dermis, feeding from blood vessels, while the caudal tip of the abdomen
is at the skin surface, often forming a punctum or an ulceration. In many
cases, this is described as a white patch with a black dot.
During
her gestation the jigger causes a considerable amount of irritation. Pus may
form around her distended abdomen, which now raises the integument into a
pea-like elevation.
Very
heavy infestation may cause ulceration and fibrosis that may result in secondary
infections, such as bacteremia, tetanus, lymphangitis, and gas gangrene.
These infections may follow attempts to extract the flea. Autoamputation of
digits or other extensive soft tissue debridement is also a possibility.
Over
1-2 weeks, more than 100 eggs, which fall to the ground, are
individually released from the exposed orifice.
Afterwards,
the flea dies and is slowly sloughed by the host. The eggs hatch on the
ground in 3-4 days, go through larval and pupal stages and become adults in 2-3
weeks. The complete life cycle lasts approximately 1 month.
TUNGIASIS:
signs and symptoms
Infestation
in its simplest form is manifested by the appearance of a white patch with a
black dot.
More
advanced infestation manifests as:
•
crusted,
erythematous papules;
•
painful,
pruritic nodules;
•
crateriform
lesions;
•
secondary
infections, including lymphangitis and septicaemia.
Lesions
can range from asymptomatic, to pruritic, to extremely painful.
Pain
or itching and papular or nodular eruptions, are usually on the feet, but they
can occur on any area of the body to which the flea has access (no part of the
body escapes especially when sleeping on the soil).
TUNGIASIS:
management
Extraction
of the gravid flea using a sterile needle or dissecting forceps is diagnostic
and therapeutic.
Following
surgical extraction of the flea, thoroughly cleanse and cover the remaining
crater with a topical antibiotic cream to prevent secondary infection.
A
skin biopsy of a suspected papule or nodule may be performed.
In
general, no laboratory studies are indicated other than a histologic
examination of excised tissue to confirm the presence of the flea, but we
normally never do it because local people know the infestation very well.
No
imaging studies are indicated unless
there is a secondary infection with a complication such as gas gangrene.
Conditions
to consider in the differential diagnosis of tungiasis include the following:
•
Cercarial
dermatitis
•
Creeping
eruption due to Ancylostoma species
•
Scabies
•
Tick bite
•
Flea bites
•
Myiasis
(Dermatobia hominis)
•
Fire ant bites
•
Ingrown toenails
TUNGIASIS:
topical treatment
Topical
ivermectin, metrifonate, and thiabendazole have been reported as effective.
Occlusive
petrolatum suffocates the organism.
20%
salicylated petroleum jelly (Vaseline) applied 12-24 hours in profound
infestations caused the death of the fleas and facilitated their manual
removal.
However,
these treatments do not remove the flea from the skin, and they do not
result in quick relief from painful lesions.
The
insect repellant Zanzarin, a lotion consisting of coconut oil, jojoba oil,
and aloe vera, was shown to reduce the number of newly embedded fleas and
skin lesions, as well as to almost completely reverse the cutaneous pathology,
when applied twice daily.
In
areas with a high endemicity of sand fleas, daily application of Zanzarin was
found to be very efficacious at preventing tungiasis.
Dr
Giuseppe Gaido
Dr
Nadia Chiapello
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