Control
Slaughter testing
Most countries require some form of inspection of swine
carcasses at slaughter for the presence of cysticerci. If
cysticerci are found, carcasses may be condemned or are
passed for cooking. Methods of inspection vary from visual to
invasive and are dependent, in part, on the relative prevalence
of the parasite. Some authors suggest that, unlike beef
cysticercosis, there are few light infections with T. solium (25),
so visual inspection of the tongue (a predilection site) and
other exposed and cut surfaces is sufficient. Other authors
believe that most infections are missed by traditional detection
methods (42,49). In one direct comparison, 75% of carcasses
which gave positive results by extensive necropsy were also
detected by visual examination and palpation of the tongue
(23). In some countries, an incision in the region of the triceps
muscle is also performed as part of the inspection for
cysticerci. Observations suggesting the presence of cysticerci
should be confirmed by additional cuts of the carcass to verify
the presence and extent of infection.
Processing
Relatively little information is available on the inactivation of
T. solium cysticerci in pork, but some data on the effects of
cooking and freezing on T. saginata may be relevant.
Cooking
Heating to a temperature of 56°C will inactivate cysticerci in
beef (1, 25). This temperature is considerably lower than that
required for processing or home cooking to protect against
trichinae. Thus processing by heating should render meat safe
from infection with T. solium cysticerci.
Freezing
Time and temperature combinations which kill cysticerci in
beef include -5°C for 15 days, -10°C for 9 days and -15°C for
6 days (24). Shorter freezing times have been demonstrated to
be effective for T. solium cysticerci held at -15°C for 75 min or
-18°C for 30 min (41). Many countries require that carcasses
found to contain cysticerci be frozen at -10°C for 14 days to
kill cysts.
Curing
No conclusive information is available on curing methods
which inactivate cysticerci of T. solium.
Irradiation
Treatment of T. solium cysticerci with doses of 20-60 kilorad
did not prevent evagination or partial development of
tapeworms (48). Tapeworms appear to be much less sensitive
to ionising radiation than Trichinella or Toxoplasma.
Therefore this is not a viable alternative for control of
cysticercosis in pork.
Prevention
Prevention of infection in swine is strictly a sanitation issue.
The only mechanism whereby pigs can become infected is
through the introduction of eggs passed by humans carrying
the adult tapeworm. Direct introduction of human faeces into
pig breeding areas or the introduction of contaminated water
or soil are the most common sources for pigs to become
infected. Control of infection in pigs in endemic areas should
be approached in two ways. Firstly, a programme for the
elimination of tapeworm carriers should be employed to
reduce the risks of environmental contamination. Secondly,
pig-rearing facilities should be located and constructed so as
to minimise incidental contamination; workers should be
instructed in proper sanitation with respect to pig facilities. In
developed countries, modem pig facilities pose little risk of
exposure to infection with T. solium cysticerci.