Database Reference
In-Depth Information
Chapter 9
Toxoplasmosis
1
9.1 Introduction
Toxoplasmosis is a parasitic infection caused by the protozoan
Toxoplasma gondii
.
Humans can become infected by ingestion of raw or undercooked meat that con-
tains tissue oocysts (the reproductive cell), or by direct contamination from the en-
vironment contaminated by infected cat feces. Although toxoplasmosis is most often
asymptomatic in humans, it can cause serious illness in immune-compromised in-
dividuals and in fetuses. At this time, there is no cure for the disease; prevention is
the only method of control.
This model examines the principal factors that influence the spread of the disease
from animals to humans on a case study of 43 Illinois swine farms. Most of the data
for this model were obtained from
2
,
3
, and
4
. Some of the references are given in the
model variable icons.
The main questions we wish to answer with this model are: How is the prevalence
of
Toxoplasma gondii
in people on swine farms in Illinois affected by exposure to
cats, ingestion of infected food, and the handling of dirt? Which one of these factors
affects the prevalence most? How would the prevalence be affected if we vaccinated
the cats, and which rate would be optimal?
1
This chapter is condensed from the work of Nohra Mateus-Pinilla, Illinois Natural History Survey,
Champaign, IL.
2
Frenkel, J.K. et al., 1981. “Endemicity of Toxoplasmosis in Costa Rica,”
Am. J. Epidemiology,
v113:254-269.
3
Smith, J.L 1993. “Documented Outbreaks of Toxoplasmosis: Transmission of
Toxoplasma gondii
to Humans,”
J. Food Protection,
v56:630-639.
4
Weigel, et al., 1997. “Risk Factors for Infection with
Toxoplasma gondii
for Residents and Work-
ers on Swine Farms in Illinois,” Vet. Biosciences Dept., University of Illinois, Urbana IL, unpub-
lished.
