[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 9 The Filariae
227
tion of granulomatous lesions, lymphangitis,
and lymphadenopathy. Bacterial infections with
Streptococcus may also occur. Elephantiasis or
swelling of the lower extremities especially the
legs develop due to obstruction of the lymphatics.
The genitals and breasts may also be involved.
On the death of the adult worms, calcification or
the formation of abscesses may occur.
Treatment
Medications that have known effectiveness
against W. bancrofti include diethylcarbamazine
(DEC) and ivermectin (Stromectol) when used in
combination with albendazole. DEC and ivermectin
kill microfilariae. Increased doses are necessary
to kill adults. Surgical removal of excess
tissue may be appropriate for the scrotum but is
only rarely successful when performed on the
extremities. The use of special boots, known as
Unna’s paste boots, as well as elastic bandages
and simple elevation, have proven successful in
reducing the size of an infected enlarged limb.
Prevention and Control
Prevention and control measures for W. bancrofti
include using personal protection when entering
known endemic areas, destroying breeding areas
of the mosquitoes, using insecticides when appropriate,
and educating the inhabitants of endemic
areas. Avoiding mosquito infested areas is ideal.
Mosquito netting and insect repellants are more
practical and useful in endemic areas.
Notes of Interest and New Trends
The origin of W. bancrofti is thought to date
back as far as the second millennium BC. This
parasite appears to have been spread via people
around the world exploring and relocating over
the years. For example, early explorers of the
17th and 18th centuries learned about bancroftian
filariasias when they visited Polynesia.
Circa 1930, an epidemic caused by W. bancrofti
died out in Charleston, South Carolina. It
is suspected that the infection was brought to the
United States by African slaves who were sent to
Charleston.
Quick Quiz! 9-4
Diagnosis of infection with Wuchereria bancrofti is
best accomplished by: (Objective 9-8)
A. Examination of stained peripheral blood taken
during the night
B. Examination of stained tissue biopsy taken during
the night
C. Use of serologic testing with blood taken during
the day
D. Examination of stained lymph fluid taken during
the day
Quick Quiz! 9-5
Which of the following, in combination with albendazole,
has proven to be an important drug for the
treatment of Bancroft’s filariasis? (Objective 9-9C)
A. Doxycycline
B. Ivermectin
C. Metronidazole
D. None of the above
Brugia malayi
(broog’ee-uh/may-lay-eye)
Common name: Malayan filaria.
Common associated disease and condition
names: Malayan filariasis or elephantiasis.
Morphology
Microfilariae. The typical Brugia malayi
microfilaria ranges in length from 200 to 280 µm
(Figs. 9-4 and 9-5; Table 9-2). This organism,
like W. bancrofti, possesses a sheath, rounded
anterior end, and numerous nuclei. The characteristic
that distinguishes it from the other
sheathed organisms is the presence of two distinct
nuclei in the tip of the somewhat pointed
tail. These two nuclei are distinct and separated
from the other nuclei present in the body of the
organism, as shown in Figure 9-4.