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Blood (Intracellular) and Other Tissue Protozoa 79

fatigue, muscular aches, chills, and fever accompanied weeks to several months of incubation and symptoms
by sweating. No periodic episodic fever cycle is found in of fever, chills, headache, sweats, myalgia, arthralgia,
infections by Babesia, as is the case in various species of nausea, and vomiting may be so mild as to be ignored in
malaria. some victims. As in malaria, thick and thin blood films
stained with Giemsa or Romanowski stains are used
Life Cycle for diagnosis. A polymerase chain reaction is also used
for confirmation of the diagnosis.
Babesiosis is similar to malarial infections except for The parasites of the Babesia species must repro-
a fever cycle, and some call the disease the “malaria of duce in red blood cells, and are therefore called obli-
the northeast.” As in malaria, the parasites of the Babe- gate organisms. There they can be seen as cross-shaped
sia species reproduce inside red blood cells. There they inclusions where four merozoites are asexually bud-
can sometimes be cross-shaped inclusions where four ding but are attached together to form the previously
merozoites are asexually budding but are attached to- mentioned configuration of a Maltese cross, that results
gether to form a figure similar to that of a Maltese cross. in hemolysis of the red blood cells which produces
This distortion of the red blood cells results in hemolysis anemia in a manner similar to that of malaria. Careful
(destruction) of the red blood cells, which produces ane- scrutiny of multiple blood smears may be required, as
mia in a manner similar to that of malaria. Asexual repro- Babesia microti may be easily overlooked because the
duction takes place in human or other mammalian hosts organism typically infects fewer than 1 percent of the
and sexual reproduction occurs in the vector (several spe- circulating red blood cells.
cies of the ixodid tick). Because the sexual reproductive
stage takes place within the tick, this is where the infec-
tive sporozoites are formed. The infective stage involv-
ing sporozoites are then injected into the host during the MICROSCOPIC DIAGNOSTIC
blood meal of the tick. These injected organisms spread FEATURE
throughout the circulatory system and invade RBCs (red
blood cells) where they undergo asexual reproduction
and form intracellular ring forms that approximate those General
of the Plasmodium (malarial) genus. However, gameto- Classification—Protozoan
cytes are not visible in the peripheral blood in the man- Organism Babesia microti
ner they are in malarial infections. Specimen Required Blood smear
Stage Merozoite stage is
Disease Transmission diagnostic
Size Ring forms may mea-
Babesia organisms are spread chiefly by the ixodid tick sure 1.0–5.0 μm
Ixodes scapularis, the same vector for Lyme disease, Shape May appear as ring
although a number of species are capable of transmit- forms and Maltese
ting the Babesia organisms. A tick must be embedded cross shapes (tetrads)
for at least 12 hours before transmission takes place, so Motility None
daily body surveys are necessary to avoid infection. The Nucleus(i) Chromatin dot as
disease is rarely fatal and is usually resolved without nucleus
treatment.
Cytoplasm Parasites appear as
cytoplasmic rings
Laboratory Diagnosis Other Features May resemble P. faci-
parum, except for
Just as in the case of the better-known Lyme disease, the absence of stippling
organism for babesiosis, regardless of species, is spread and enlargement of
chiefly by deer ticks except for blood transfusions from the infected red cells
asymptomatic carriers. The disease requires several