Page 191 - The Netter Collection of Medical Illustrations - Integumentary System_ Volume 4 ( PDFDrive )

Plate 6-16 Infectious Diseases

CLINICAL FINDINGS AND MANAGEMENT OF LICE
Clinical findings

Intense itching in pubic area
(often nocturnal) is a hallmark
of parasitic infection, and
excoriations are common.
LICE (Continued)

be present on the clothing, particularly in small hiding Bluish skin discolorations
spaces such as the seams. Along with the lice, many eggs (maculae ceruleae) are often
and larvae may be seen. seen with Phthirus pubis infestations.
The body louse has been shown to be a carrier of the
bacterial agents that cause relapsing fever, trench fever,
and epidemic typhus: Borrelia recurrentis, Bartonella
quintana, and Rickettsia prowazekii, respectively. The Secondary infection of
louse carries the bacteria within its gut. excoriations or bites may
B. recurrentis is responsible for causing the disease yield impetiginized lesions.
relapsing fever. It is transmitted from one human to
another when the fecal material of a human body louse
gains entry into the bloodstream. This bacterium is
unique in that it can rearrange its surface proteins. This Examination of pubic area and pubic
is believed to be the reason for the relapsing and recur- hair may reveal ova and parasites.
rent fevers: The host immune system reacts in a peri-
odic manner to the changing surface of the bacteria.
B. quintana is a bacterium that is transmitted through
the feces of the louse. After a louse defecates on a
patient’s skin and the patient scratches, the stool and
the bacteria are implanted into the skin, which causes
infection. Also, the louse often bites after defecating
and causes skin trauma that transfers the bacteria into
the skin. B. quintana is the etiologic agent of trench
fever, bacillary angiomatosis, and peliosis and has also
been shown to cause endocarditis. B. quintana infections
are most commonly seen in patients who are infected
with the human immunodeficiency virus and in home- with
less individuals. E. Hatton
R. prowazekii is an obligate intracellular parasite that Phthirus pubis Phthirus pubis egg case (nit) on pubic
is transmitted to humans through the feces of the hair. The egg case is firmly attached.
human body louse. The natural environmental reser-
voir for this bacterium is the flying squirrel (Glaucomys Management
volans). The infected louse feeds on the human, and the
fecal material that contains the R. prowazekii bacteria is Insecticide
deposited into the fresh wound, allowing for infectious
transfer. This infection is most frequently seen during
times of war, when individuals are in close contact with
one another for significant periods. Signs and symp-
toms of epidemic typhus include fever, rash, pain, delir-
ium, and other constitutional symptoms.
Pathogenesis: P. humanus capitis affects humans and
has a high propensity to infest the scalp. These lice live
on the host and periodically take a blood meal from the
scalp or neck area. In patients with very long hair, the
blood meal may be taken from the back or any area of
skin that is in contact with the hair. The lice are able
to reproduce rapidly. The females, which are a bit larger Increased general hygiene and treatment of General house cleaning
than the males, lay eggs that hatch and develop into household members and all sexual partners with emphasis on disinfection and
adults capable of reproducing within 4 weeks. with insecticide shampoos and creams laundering of underclothing and bedding
Histology: The histological findings on skin biopsy
are similar among all forms of louse bites. Histological
evaluation cannot differentiate a louse bite from any
other insect bite with certainty. Skin biopsies are rarely Treatment: Therapeutic agents to treat lice are of lindane has decreased because of its potential neuro-
performed in these cases, because the diagnosis is made similar among all species of human lice. The most toxicity. Malathion and oral ivermectin show excellent
clinically. Biopsy specimens show a nonspecific, mixed commonly used therapies are based on permethrin; efficacy. Oral ivermectin needs to be repeated in 1
superficial and deep inflammatory infiltrate with eosin- when used appropriately, they show good cure rates. week, because it does not kill the developing larvae
ophils. This may suggest a bite reaction. Unlike tick These treatments should be used in conjunction with within the nits.
bites or scabies, in which occasionally tick parts or an agent that helps remove the nits from the hair Therapy for body lice also requires complete disin-
scabies mites are seen in a biopsy specimen, a biopsy shafts, and physical removal with a lice hair comb is a fection of the household or living areas. Overtly infested
from a patient with a lice infestation will never show must. Therapy should be repeated on a weekly basis. clothing should be thrown away. Professional fumiga-
mouth parts or other elements of the louse. Bedding and clothing need to be disinfected. The use tion should be considered.

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