402 ◾ Fundamental Food Microbiology
trichinella spiralis 25
Trichinella spiralis is a roundworm and can be present in high frequencies in pigs and causes trichinosis or trichinellosis in humans and animals. Eight species of the genus Trichinella are recognized
as zoonotic pathogens worldwide. It is also found quite frequently among game animals. A person
is infected by consuming raw or insufficiently cooked meat of infected animals. The infected meat
contains encysted larvae. Once the meat is consumed, the cysts dissolve in the GI tract, releasing
the larvae, which then infect the GI tract epithelium. Here, the parasites mate and deposit larvae
in the lymphatic system. Through lymphatic circulation, the larvae infect other body tissues. In
the United States, between 1973 and 1987, 128 incidents of trichinosis infecting 843 people were
recorded. Although many types of foods were involved, the highest incidence (55) was from pork.
Almost all incidences were a result of improper cooking.
The symptoms of trichinosis appear in 2–28 days following ingestion. Initial symptoms are
nausea, vomiting, and diarrhea, followed by fever, swelling of eyes, muscular pain, and respiratory
difficulties. In extreme cases of infection, toxemia and death may result.
The prevention methods consist of not raising pigs on garbage and cooking meat thoroughly
[140°F (60°C) and above]. Microwave cooking may not be effective in killing all the larvae.
Freezing meat for 20 days at –20°C (home freezer) or in liquid nitrogen for several seconds also
kills the parasite. Irradiation is generally effective in inactivating Trichinella in meats.
Anisakis simplex
The nematode Anisakis simplex is a parasite in many fish, particularly of marine origin. Human
infection, called anisakiasis, results from the consumption of raw, infected fish. Inadequately
cooked, brined, or smoked fish has also been implicated in some cases. Symptoms appear after a
few days and generally include irritation of throat and digestive tract. Anisakiasis is predominant
in countries where raw fish is consumed. Proper cooking, salting, or freezing at –20°C for three
days can be used as a preventative measure.
taenia Species
Taeniasis is a tapeworm disease caused by Taenia solium from pork and by Taenia saginata from
beef. The illness results from the ingestion of raw or improperly cooked meat contaminated with
larvae (taeniasis) or the adult tapeworms (cysticercosis). Symptoms appear within a few weeks and
are digestive disorders and severe abdominal pain. If an organ is infected by the larvae, especially
a vital organ, the consequences can be severe.
toxoplasma gondii 26
The zoonotic infection toxoplasmosis is a tissue protozoan disease transmitted to humans from
the consumption of undercooked and raw meat and raw milk contaminated with oocysts of
Toxoplasma gondii (Figure 28.3). Toxoplasma gondii was first reported in 1908, and its lifecycle
was not discovered until 1970. Drinking water contaminated with cat feces was thought to be
responsible for several outbreaks worldwide. Unwashed hands after contact with pet cats, fruits
and vegetables washed in contaminated water, and eating of undercooked meat (pork, lamb) are
considered to be potential sources for this parasite. Cats serve as the primary host. Cats become
infected by consuming infected prey. The cyst in a cat is dissolved in the digestive tract and
trichinella spiralis 25
Trichinella spiralis is a roundworm and can be present in high frequencies in pigs and causes trichinosis or trichinellosis in humans and animals. Eight species of the genus Trichinella are recognized
as zoonotic pathogens worldwide. It is also found quite frequently among game animals. A person
is infected by consuming raw or insufficiently cooked meat of infected animals. The infected meat
contains encysted larvae. Once the meat is consumed, the cysts dissolve in the GI tract, releasing
the larvae, which then infect the GI tract epithelium. Here, the parasites mate and deposit larvae
in the lymphatic system. Through lymphatic circulation, the larvae infect other body tissues. In
the United States, between 1973 and 1987, 128 incidents of trichinosis infecting 843 people were
recorded. Although many types of foods were involved, the highest incidence (55) was from pork.
Almost all incidences were a result of improper cooking.
The symptoms of trichinosis appear in 2–28 days following ingestion. Initial symptoms are
nausea, vomiting, and diarrhea, followed by fever, swelling of eyes, muscular pain, and respiratory
difficulties. In extreme cases of infection, toxemia and death may result.
The prevention methods consist of not raising pigs on garbage and cooking meat thoroughly
[140°F (60°C) and above]. Microwave cooking may not be effective in killing all the larvae.
Freezing meat for 20 days at –20°C (home freezer) or in liquid nitrogen for several seconds also
kills the parasite. Irradiation is generally effective in inactivating Trichinella in meats.
Anisakis simplex
The nematode Anisakis simplex is a parasite in many fish, particularly of marine origin. Human
infection, called anisakiasis, results from the consumption of raw, infected fish. Inadequately
cooked, brined, or smoked fish has also been implicated in some cases. Symptoms appear after a
few days and generally include irritation of throat and digestive tract. Anisakiasis is predominant
in countries where raw fish is consumed. Proper cooking, salting, or freezing at –20°C for three
days can be used as a preventative measure.
taenia Species
Taeniasis is a tapeworm disease caused by Taenia solium from pork and by Taenia saginata from
beef. The illness results from the ingestion of raw or improperly cooked meat contaminated with
larvae (taeniasis) or the adult tapeworms (cysticercosis). Symptoms appear within a few weeks and
are digestive disorders and severe abdominal pain. If an organ is infected by the larvae, especially
a vital organ, the consequences can be severe.
toxoplasma gondii 26
The zoonotic infection toxoplasmosis is a tissue protozoan disease transmitted to humans from
the consumption of undercooked and raw meat and raw milk contaminated with oocysts of
Toxoplasma gondii (Figure 28.3). Toxoplasma gondii was first reported in 1908, and its lifecycle
was not discovered until 1970. Drinking water contaminated with cat feces was thought to be
responsible for several outbreaks worldwide. Unwashed hands after contact with pet cats, fruits
and vegetables washed in contaminated water, and eating of undercooked meat (pork, lamb) are
considered to be potential sources for this parasite. Cats serve as the primary host. Cats become
infected by consuming infected prey. The cyst in a cat is dissolved in the digestive tract and