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116 CHAPTER 4

SUMMARY

The varieties of parasites that infect cells of the blood headaches, nausea, flulike sensations, and bone pain in
are many. In addition, their life cycles are complex for more advanced cases. Fevers may cause shaking chills,
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many of them, and some stages may be lived outside followed by a fever of up to 40 C or 104 F. The fever
the host and in the intermediate host. Examination of a cycle, along with blood smear examinations are useful in
stained smear with a combination of Wright-Giemsa or identifying species of malaria.
with Giemsa stain alone will yield the best information. Babeosis is also a disease in which a number (more
Remember, the morphology of parasites is best seen with than 100) of various species exist. Only a few species,
Giemsa stain, as the definition and clarity is not as good however, are responsible for the majority of disease from
with Wright stain, which is best for blood cell morphol- this organism, and vary by region. Babesia microti is pri-
ogy. These stains are useful for detecting various species marily the species found in the northeast, the Midwest,
of malaria (Falciparum), Babesia, Trypanosoma, Leish- and a couple of West Coast states. Another substantial
mania, and some species of microfilaria. Wet mounts are contributor to this infection is blood transfusions and a
useful for certain characteristics observed in intracellular few cases of intrauterine, transplacental transmission to
parasites, but permanent, fixed stains are also necessary fetuses. Babeosis is passed to humans through the bite
for definitive identification. Thick smears, where the red of the deer tick, and symptoms are sometimes so mild as
blood cells are destroyed, are followed by stained, thin to be ignored, but fever, joint myalgia, arthralgia, nausea,
smears for most of these parasites. and vomiting may be present.
Blood and other tissue flagellates include Leish- Filarial worms and lymphatic filariasis sometimes
mania and Trypanosoma, but these are quite different cause a condition called elephantiasis. The superfamily
from the flagellated amoebae that may inhabit the in- Filarioidea contains a number of nematodal organisms
testines. A major difference is that a vector, an insect, is that reside in tissues of the human body, of which the
necessary for the transmission of these two organisms. species Wuchereria bancrofti is the major infection caus-
Trypanosoma cruzi is the major organism of this genus ing the presence of microfilaria, or small roundworms.
and may include intracellular organisms in macrophages, The larvae transmit the disease to humans most often
liver cells, spleen cells, and bone marrow. Three major through mosquito bites, but may also be transmitted by
species of Leishmania exist, based on their geographic sand gnats, tabanid flies, blackflies, and other insects.
location. Dogs and various species of rodents are the res- Another dreaded organism with widespread impact
ervoir hosts, whereas sandflies of two different genera are is that of the organism Dracunculus medinensis, which is
capable of transmitting the organism. known as the guinea worm. This parasite is common in
Malaria is the major category of parasitic infections the subcutaneous tissues and muscles of mostly humans
that occur in the blood. These four species are prevalent and dogs. Dracunculiasis is a disease that causes cuta-
based on their location, with Plasmodium falciparum neous nodules which become open ulcers. At this time
as the major causative organism for the infection of hu- the caudal or tail end of the adult female worm begins to
mans. It should be remembered that there are many protrude from the host animal’s body, most often involv-
species of malaria, some of which are found in certain ing the feet and lower limbs. The infective stage of the
birds and animals, and are species from which humans offspring of this organism is released into water, where
possess natural immunity. The clinical symptoms of ma- the parasites can find new hosts.
laria are significant, with paroxysms of fever that include