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204 CHAPTER 9

against trichinosis. If the Trichinella parasite is discov- in ancient times. References to such cysts in animals
ered early, in the intestinal phase, albendazole (Albenza) that were slaughtered in religious rituals are found in
or mebendazole is usually effective in eliminating the the Babylonian Talmud. Approximately 400 years
intestinal worms and larvae before considerable damage before the birth of Christ, Hippocrates mentioned
to skeletal muscles occurs. these phenomena in animals butchered for food, and
The adult trichina also lives in the intestinal subsequently by several other investigators over the next
lining of many meat-eating animals as wild swine, several centuries. Other ancient medical practitioners
bears, walruses, horses, rodents, and a number of other have also made references to cystlike structures in food
animal species including humans. The best defense animals.
against contracting trichinosis is accomplished through Descriptions of hydatid cysts in humans are found
proper food preparation. Humans should avoid in European medical texts, where references are made
undercooked meat by ensuring that the meat is cooked of structures described as enlarged glands or bags of
to an internal temperature of 170°F (77°C) before mucus, accompanied by blood vessels with abnormal
eating it. A food thermometer is preferable to ensure growth patterns, lymphatic varices (dilated veins), and
that meat is thoroughly cooked. Other methods exist accumulations of body fluids. A number of observant
for ensuring meat is safe by storing the meat for at least scientists appeared to associate these cysts as products
3 weeks or by the process of irradiation. Irradiation will of parasites, and more specifically as damage caused
by larval tapeworms. Although not credited with the
kill parasites in wild-animal meat, and deep-freezing
theory that E. granulosus was responsible for the
for 3 weeks kills Trichinella in some meats; however,
formation of hydatid cysts, Francisco Redi in the 1600s
Trichinella organisms in bear meat do not ordinarily
proposed this initial framework for the formation of
die by freezing. Neither irradiation nor freezing is
the cysts.
necessary if you ensure that the meat is thoroughly
cooked. Smoking or pickling of meat will not always The German clinician and natural historian Pierre
Simon Pallas showed a parasitic link to the cysts in
kill Trichinella in infected meat.
1766 (Cox, 2002). Carl von Siebold demonstrated in
1853 that Echinococcus cysts from infected sheep were
ECHINOCOCCOSIS the origin of adult tapeworms when raw meat was fed to
dogs (Cox, 2002). A demonstration by Bernhard Nau-
The causative organism for echinococcosis is the
nyn in 1863 definitively proved that adult tapeworms
Echinococcus granulosus tapeworm. This is one of
developed in dogs fed with hydatid cysts (Figure 9-5),
the most serious of human diseases that is caused by which were obtained from a human (Cox, 2002). The
a larval cestode. This condition may also be known as history of hydatid disease and the transmission of
hydatid disease, and frequently results from accidental
infection with the larval stages found in the canid species
(originating from a dog ancestor) tapeworm called
Echinococcus granulosus. The disease most often occurs
in adult dogs and as a larval cyst(s) particularly in sheep
but also in other species of both wild and domesticated
animals. The potential for echinococcosis to become
more prevalent in the United States certainly exists.
The canid species, includes carnivores such as wolves Source: Centers for Disease Control and Prevention (CDC)
and coyotes, which hunt and eat both domesticated and
wild animals, and could potentially aid in the spread of
the organisms from sheep-raising country in the western
United States and into other areas of the country where
cattle are raised.
The massive bladder-like hydatid cysts, FIGURE 9-5 Membrane and hydatid daughter cysts
particularly those found in the liver, were well known from human lung