Toxoplasmosis, a one-celled parasite found in many meats, can occur in South
Carolina deer, but venison is not the only source of the disease, says a state
Department of Natural Resources deer biologist.
"Many people concerned about eating venison, or deer meat, have called the
department asking about the likelihood of exposure to toxoplasmosis," said
Charles Ruth, statewide Deer Project supervisor for the Wildlife Management
Section of the S.C. Department of Natural Resources (DNR). "Although the disease
is often mentioned only in conjunction with venison, it can be found in many
domestic meats including beef, pork, and sheep. Once you become aware of how the
disease works, chances of exposure can be minimized, and venison can be safely
Toxoplasmosis is caused by a microscopic protozoan parasite, and it is one of
the most common diseases transmitted from animals to humans. Authorities
estimate that 30 to 60 percent of adults in the United States have been exposed
to the parasite, but the organism rarely causes disease. Although most human
infections are silent, there may be brief flu-like symptoms in some cases. The
greatest risk of real illness in humans would likely be in someone whose immune
system is already compromised.
Since white-tailed deer can be infected with the toxoplasmosis organism, there
is a chance that humans can become infected if the meat is not properly handled.
This is also true for common domestic meats as well.
Sportsmen can minimize their risks of toxoplasmosis infection by following these
guidelines with venison: 1) do not handle fresh carcasses or meat with wounds on
their hands; 2) freeze all meat before cooking because freezing kills the
majority of the parasites; and 3) cook venison thoroughly (150ºF).
Although toxoplasmosis normally does not cause illness in humans, women who are
pregnant or are planning a pregnancy should be particularly careful. The effect
of toxoplasmosis upon an unborn fetus can be severe.
If a woman is pregnant or planning a pregnancy, she should: 1) minimize contact
with cats and their litter boxes; 2) handle all meats carefully; 3) cook all
meats thoroughly before eating; 4) freeze all red meats prior to cooking; and 5)
minimize contact with soil or dirt when gardening.
In 1981, Karen Oertley, a student at the University of Georgia, completed a
study of toxoplasmosis in white-tailed deer. This effort also combined
information on the disease from other studies around the world. "Several points
of Oertley's toxoplasmosis study are of particular interest to deer hunters and
others who eat venison," Ruth said.
According to Oertley's study, the prevalence of toxoplasmosis in white-tailed
deer in the Southeast was 24.4 percent. On the other hand, surveys conducted at
commercial slaughter houses to determine the prevalence of this organism in
domestic meats indicated a great variance in occurrence, but infection rates as
high as 64 percent for sheep, 45 percent for swine and 38 percent for cattle
were found among animals to be used as human food.
Natural infections of toxoplasmosis have been reported in more than 200 species
of mammals, Oertley found in the study. Prevalence is naturally higher in
carnivores, or meat-eating animals, than in herbivores, such as cattle and deer.
According to the study, probably the greatest risk for human toxoplasmosis
infection is the presence of cats in and around homes. Members of the cat family
are the only suitable definitive host for the parasite. Cats kill and eat wild
rodents, which are also part of the parasite's life cycle, and shed the organism
in their feces. This in turn can contaminate the soil and/or water, which
increases the likelihood of exposure to other types of mammals and birds.
Although not a necessary part of the parasite's life cycle, herbivorous animals
like deer probably get the parasite from these contaminated soil or water
"It would be nearly impossible to totally prevent the risk of exposure to the
parasite because of its distribution in soil or water contaminated by cat
feces," Ruth said. "This, and the fact that the organism can be found in so many
types of meats, likely explains why such a high percentage of people have been
exposed to the organism."
According to Ruth, "The bottom line is that toxoplasmosis is not just related to
deer meat. Evidence suggests that the potential for contracting the disease from
venison is probably the same as it is from domestic meats. Healthy people in
general should not be overly concerned with the disease since there is a good
chance they have already been exposed to it. Precautionary measures are most
important for high-risk individuals such as pregnant women and people with some
pre-existing condition that has compromised their immune system."