Page 181 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-6 Infectious Diseases

Parasitic Diseases
Necatoriasis and Ancylostomiasis
CUTANEOUS LARVA MIGRANS

Reported causes of
Cutaneous larva migrans is a tropically acquired skin Cutaneous Larva Migrans
disease caused by the aimless wandering of a nematode
larva. This disease has also been termed “creeping erup- Ancylostoma braziliense*
tion” because of the slow, methodical movement under- Ancylostoma caninum*
neath the skin, which subsequently manifests with the Uncinaria stenocephala
classic cutaneous findings. The most frequent cause of Ancylostoma ceylanicum
cutaneous larva migrans is the larva of Ancylostoma bra- Ancylostoma tubaeforme
ziliense or Ancylostoma caninum. The cutaneous findings Ancylostoma duodenale
are similar among the various species that can cause Necator americanus
disease. Treatments are effective for this condition, Bunostomum phlebotomum
which causes more psychological than physical harm. Gnathostoma spinigerum
Establishment of the specific larva responsible for the Strongyloides myopotami
disease is not routinely attempted, nor is it practical or Strongyloides westeri
cost effective. Cutaneous Larva Migran Strongyloides procyonis
Clinical Findings: The larvae gain entrance into is frequently encountered Strongyloides papillosus
the epidermis through tiny abrasions, cuts, or any dis- on the feet. It is acquired Dirofilaria repens
ruption of the normal epidermal layer. The larvae are by barefoot walking *Account for the vast majority
frequently obtained during a barefoot walk on a con- in infested areas. of cases
taminated beach or from a similar environment. Trav-
elers to Central and South America often acquire the
larvae on the beach while lying on or playing in the Larvae ascend trachea
sand. The initial entry of the larvae goes entirely to pharynx and
unnoticed. It is not until days to weeks later that are swallowed Secondary
the human host begins to develop cutaneous signs of anemia
the disease. The first evidence is a pink to red, edema- Larvae reach lung via
tous eruption that begins to take on a serpiginous pulmonary artery, then
course. The involved skin appears as red, squiggly penetrate alveoli 9 to 11 mm
lines. If only one larva is present, only one serpiginous and enter bronchi 7 to 9 mm
line will be present. The line meanders and slowly Mature worms
elongates over days to weeks until the patient Necator develop in
seeks medical advice. Patients who are infected with americanus duodenum
multiple parasites have multiple serpiginous areas of (adult worms) and jejunum,
involvement, with some in a criss-crossing pattern. bite into mucosa,
Pruritus is universal, but pain is infrequent. The Larvae enter blood and suck blood
lesions are typically elevated but can become vesicular stream and are causing variable
in nature. carried to heart degrees of anemia.
Pathogenesis: Cutaneous larva migrans is caused by Fertilized
penetration of the epidermis by one of the various larvae ova Ancylostoma
duodenale
known to cause disease. The larvae are derived from discharged
eggs that are laid in the intestines of an infected animal, in feces
such as a dog, and then released in the stool. When the
animal defecates, the eggs are readily passed into the Final larval forms pene- Rhabditiform Mouth parts
soil, where they hatch into larvae. The human is an trate human skin causing larvae
incidental or dead-end host, because the larva is unable “ground itch” develop
to replicate or complete its life cycle in humans. This in ova in
is very much different than infections with the gastro- 24 hours
intestinal parasites Ancylostoma duodenale and Necator
americanus, which require the human host to replicate. Rhabditiform
The larvae wander around the epidermis, unable to larvae escape
penetrate the basement membrane zone and therefore Larvae molt twice developing from egg Copulatory bursae
unable to enter the dermis. If the condition is left into filariform larvae
untreated, the larvae die in the skin within a few months.
The larvae have been shown to secrete enzymes that
help them travel throughout the epidermis, but they
lack an enzyme to penetrate the dermal-epidermal
junction.
Histology: The histopathology is nonspecific unless
the actual larva is biopsied. This is highly unlikely,
because the larva is typically an estimated 2 to 3 cm the most frequently used medications. Oral ivermectin pharmacist can compound these agents into a topical
ahead of the leading edge of the serpiginous rash, and is well tolerated and works equally as well as the others. solution to apply to the affected area. Other therapies
most biopsies are taken from the serpiginous region. Ivermectin binds to glutamate-gated chloride channels that have been attempted include cold therapy with
The biopsy specimen shows a lymphocytic dermal infil- in the parasites, allowing free passage of chloride and topical liquid nitrogen, which is no longer advocated.
trate with eosinophils. Occasionally, a space is seen eventually death of the cell. Thiabendazole and alben- The larvae have been shown to survive at subfreezing
within the spongiotic epidermis, which indicates the dazole work by inhibiting microtubule polymerization temperatures, and because one cannot predict with high
area through which the larva passed. in the parasite, ultimately leading to its death. Thiaben- certainty the location of the larva, a large area of skin
Treatment: The mainstays of treatment are the dazole and albendazole can cause severe gastrointestinal must be treated with liquid nitrogen for the treatment
anthelmintic agents. Albendazole and ivermectin are side effects, and they are best used topically. A to be effective.

THE NETTER COLLECTION OF MEDICAL ILLUSTRATIONS 167