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108 CHAPTER 4

and D. insignis. D. insignis is a species of this genus,
MICROSCOPIC DIAGNOSTIC which primarily infects dogs and wild carnivores. But

FEATURE D. medinensis is the organism that has the greatest im-
pact on the health of humans, and this section primar-
ily relates to D. medinensis. These parasites received
General their respective names when it was seen by a European
Classification—Microfilaria
traveler in natives along the coast of West Africa, but the
Organism Brugia malayi, B. timori disease is prevalent today in India, Iran, Pakistan, and a
Specimen Required Blood or lymphatic large portion of Africa. It is also alleged to be the fiery
aspirate serpent alluded to in the Bible. This parasite is also on
Stage Microfilariae the list of those slated for eradication by 2020, by efforts
of the Carter Center, the Bill and Melinda Gates Founda-
Size Average for B. malayi
is 310 μm, 250 μm for tion, and other national and international organizations.
B. timori
Shape Round and elongated DRANCUNCULUS MEDINENSIS
with pointed tail
Nucleus(i) Distinct pair of nuclei The Drancunculus medinensis, worms, members
in the tail of the taxonomic order Spirurida, are long and thin
Other Features Stained microfilariae worms that are often confused with other microfilarial
for both species ap- worms, previously presented. D. medinensis worms
pear “sheathed” but belong to the order Camallanida and the suborder
stain poorly in B. timori Camallanina.
Time for collection
for some species is at Morphology
night, whereas others
are subperiodic (mod- Dracunculiasis is widely known as the guinea worm
ified circadian rhythm
where the periods of disease. The condition is caused by the larvae that
appearance are not penetrate the stomach and duodenum where they are
clear-cut) circulated through the body and the large female of the
nematode invades the tissues of the body. The organism
emerges slowly and painfully from the skin, from sites
usually on the lower limbs. The disease can infect ani-
SUBCUTANEOUS FILARIASIS mals but the animal cycles that occur in North America
and Central Asia but do not act as reservoirs of human
Four species of filarial parasites primarily infect the tis- infection. Adult female worms may measure from 70 to
sues beneath the epidermis of the human host. But other 120 centimeters but are only about 2 millimeters in di-
organs may be infected by specific species of those para- ameter. The male worm is but 2 centimeters in length
sites producing subcutaneous signs and symptoms. The and 0.4 millimeters in diameter.
four species that are considered as subcutaneous para-
sites are: Oncocerca volvulus, Loa loa, Mansonella strep-
tocerca, and Drancunculus medinensis. Symptoms
Redness and inflammation may occur at the site where
DRACUNCULIASIS the adult worm emerges from the skin. No symptoms as-
sociated with the copecod vector occur until the blister
The organism Dracunculus medinensis, better known as forms where emergence will occur. At this time, fever
the guinea worm disease, dates back to at least the 1400s and allergic reactions appear with intense itching and
as documented in Egyptian writings. Two species of the sometimes asthmatic symptoms may occur. Periorbital
organism of the genus Drancunculus exist: D. medinensis swelling may become obvious along with nausea and