Page 108 - parasitology for medical and clinical laboratoryprofessionals

88 CHAPTER 4

infected meat, by ingestion of fecal matter of a cat that
has itself recently been infected, or in some cases by
Source: Centers for Disease Control and Prevention (CDC) have been shown as a major reservoir of this infection.
transplacental transmission from the mother to her fetus
(Figure 4-9). It should be understood, however, that cats

The prevalence of toxoplasmosis is considerable
around the world. According to various statistics based
on testing of blood donors, perhaps as many as one-
third of the world’s population may carry evidence of a
Toxoplasma infection. The CDCP established rates in
the United States based on random specimens collected
by the National Health and Nutritional Examination
Survey (NHANES) during a five-year period of 1999 to
FIGURE 4-8 Culex tarsalis mosquito, known to spread 2004. The infective rate for the general population was
encephalitis, begins feeding on human host 10.8 percent, and for women of childbearing age (15 to
44 years), the rate was 11 percent (Jones, et al., 2007).
partly from poor compliance or incomplete treatment During the first few weeks, the infection typically causes
regimens. More than a dozen vaccines are currently
under development to possibly immunize large segments
of individuals in endemic areas against this serious disease.

TOXOPLASMA SPP.,
TOXOPLASMOSIS, AND INFECTIONS
CAUSED BY RELATED ORGANISMS

Toxoplasmosis is one of the most common and wide-
spread parasitic infections but is relatively little known
because in the majority of cases, infections are asymp-
tomatic. The disease is usually a self-limiting infection
due to a parasite called Toxoplasma gondii, and is often
a recurrence of a mild infection that may be subclinical
in that no signs or symptoms are apparent. However, for
a fetus and for an immunodeficient person, it can be a
serious cause of mortality and morbidity. The parasite
that causes the infection, T. gondii, was discovered inde-
pendently by the French parasitologists Charles Nicolle
and Louis Herbert Manceaux while looking for a reser-
voir host for the organism that causes Leishmania in a
North African rodent, the gundi, a natural host. Gundis Source: Centers for Disease Control and Prevention (CDC)
are found in rocky outcroppings in desert-like environ-
ments of the northern parts of Africa. They first came to
the notice of Western naturalists in Tripoli in 1774 and
were given the name gundi mice (Cox, 2002).
The toxoplasmosis parasitic disease is capable of
infecting almost all species of warm-blooded animals, FIGURE 4-9 Pregnant woman feeding her cat “canned”
including humans, but the primary host is the various cat food, in order to prevent infection with the parasite,
members of the cat family. Animals are infected by eating Toxoplasma gondii