738 Modern Food Microbiology
of 600 cases were recorded in 8 countries outside the U.K. with 256 (42.7%) in Switzerland.
9 ) Since
1996, 4.5 million cows have been destroyed. Between 1986 and November 2003, 183,634 cattle were
diagnosed with BSE in the U.K. with 4,469 in 22 other countries.
29 Around 84 human deaths were
recorded in the U.K. in the year 2000. The first confirmed case in Japan occurred in September 2001,
and about 9 cases were seen through 2003. The first case confirmed in North America was announced
on May 20, 2003, and the animal was a cow in Alberta, Canada. The first confirmed case in the United
States occurred in December 2003, in a Holstein downer cow in Moses Lake, Washington. The cow
was 6.5 years old and, thus, might have consumed currently banned feed that contained animal matter.
Around 35 million beef animals up to age 24 months are slaughtered in the United States annually,
with an additional 6 million or so of older dairy cows.
Testing for prion proteins consists of an immunohistochemistry method (considered to be the gold
standard), a conformation-dependent immunoassay (CDI) method (developed in 2003), a screening test
developed by the Bio-Rad Corporation (TeSeE), another method developed by the IDEXX Laboratories
(Herdchek
R ), and 5 to 6 other postmortem tests for central nervous system tissue of cattle. The two
latter tests were approved early in 2004 by the U.S. Department of Agriculture for animal testing.
Several of the available methods are ELISA based.
Creutzfeldt-Jakob Diseases (CJD, vCJD)
Since humans are susceptible to the prions that cause CJD, the early concern was whether humans
could contract BSE from cattle. In March 1996, a new variant of CJD (nvCJD, vCJD) was reported in the
United Kingdom in a small group of people, all of whom were much younger than most individuals
with CJD. This prompted speculation that vCJD had been contracted from cattle. Normally, CJD
appears in persons around age 60 or older, but in the U.K. vCJD was found to afflict individuals in the
late teens to the early 40s. It has been concluded that vCJD is the human equivalent of BSE,
115 and
the agents for BSE and vCJD appear to be the same based on studies using mice.
11
Between February 1994 and October 1995, 10 persons in the United Kingdom were found to have
the new variant form of CJD, and 8 died. Most were under age 30 (in the United States, most CJD
victims are over age 55; see below). For the years 1995–1998, there were 39 cases of vCJD.
14 Through
2003, around 150 vCJD cases were seen in humans throughout Europe with about one-third in the
United Kingdom.
For the 5-year period 1991–1995, 94 CJD deaths were recorded in the United States and 9 were
below age 55.
21 None conformed to vCJD. Over 85% of CJD patients in the United States die within
one year of onset. Between 1991 and 1995, the average annual death rate from CJD in the United
States was 1.2/1 million population.
7 BSE is thought to have been contracted by cattle through specified
bovine offal (that contained brain, spinal cord, and the like) from infected animals, a practice that was
banned in 1989. Using a mouse assay, prions could not be detected in beef muscle and milk from
infected cattle.
9 The incubation period for BSE is between 1 and 15 years.
Regarding the heat destruction of the prions of vCJD, studies are wanting. However, data on scrapie
and CJD have been presented and summarized.
15 The latter investigator suggested that the brain tissue
of a TSE-infected cow can be expected to contain about 10
11 prions per gram. Assuming that the nerve
tissue is ground with muscle tissue, about 10
8 prions per gram may be expected in ground beef, or
10
10 prions in a 100-g portion. To effect a 12-D reduction, 22D is required (10 + 12 = 22). Thus, some
of the times in minutes needed to achieve a 22D were calculated as follows: D 160 ◦ C = 1.0; D 140 ◦ C =
11.0; D 120 ◦ C = 110.
15 It has been suggested that there is a need for new processing or packaging
of 600 cases were recorded in 8 countries outside the U.K. with 256 (42.7%) in Switzerland.
9 ) Since
1996, 4.5 million cows have been destroyed. Between 1986 and November 2003, 183,634 cattle were
diagnosed with BSE in the U.K. with 4,469 in 22 other countries.
29 Around 84 human deaths were
recorded in the U.K. in the year 2000. The first confirmed case in Japan occurred in September 2001,
and about 9 cases were seen through 2003. The first case confirmed in North America was announced
on May 20, 2003, and the animal was a cow in Alberta, Canada. The first confirmed case in the United
States occurred in December 2003, in a Holstein downer cow in Moses Lake, Washington. The cow
was 6.5 years old and, thus, might have consumed currently banned feed that contained animal matter.
Around 35 million beef animals up to age 24 months are slaughtered in the United States annually,
with an additional 6 million or so of older dairy cows.
Testing for prion proteins consists of an immunohistochemistry method (considered to be the gold
standard), a conformation-dependent immunoassay (CDI) method (developed in 2003), a screening test
developed by the Bio-Rad Corporation (TeSeE), another method developed by the IDEXX Laboratories
(Herdchek
R ), and 5 to 6 other postmortem tests for central nervous system tissue of cattle. The two
latter tests were approved early in 2004 by the U.S. Department of Agriculture for animal testing.
Several of the available methods are ELISA based.
Creutzfeldt-Jakob Diseases (CJD, vCJD)
Since humans are susceptible to the prions that cause CJD, the early concern was whether humans
could contract BSE from cattle. In March 1996, a new variant of CJD (nvCJD, vCJD) was reported in the
United Kingdom in a small group of people, all of whom were much younger than most individuals
with CJD. This prompted speculation that vCJD had been contracted from cattle. Normally, CJD
appears in persons around age 60 or older, but in the U.K. vCJD was found to afflict individuals in the
late teens to the early 40s. It has been concluded that vCJD is the human equivalent of BSE,
115 and
the agents for BSE and vCJD appear to be the same based on studies using mice.
11
Between February 1994 and October 1995, 10 persons in the United Kingdom were found to have
the new variant form of CJD, and 8 died. Most were under age 30 (in the United States, most CJD
victims are over age 55; see below). For the years 1995–1998, there were 39 cases of vCJD.
14 Through
2003, around 150 vCJD cases were seen in humans throughout Europe with about one-third in the
United Kingdom.
For the 5-year period 1991–1995, 94 CJD deaths were recorded in the United States and 9 were
below age 55.
21 None conformed to vCJD. Over 85% of CJD patients in the United States die within
one year of onset. Between 1991 and 1995, the average annual death rate from CJD in the United
States was 1.2/1 million population.
7 BSE is thought to have been contracted by cattle through specified
bovine offal (that contained brain, spinal cord, and the like) from infected animals, a practice that was
banned in 1989. Using a mouse assay, prions could not be detected in beef muscle and milk from
infected cattle.
9 The incubation period for BSE is between 1 and 15 years.
Regarding the heat destruction of the prions of vCJD, studies are wanting. However, data on scrapie
and CJD have been presented and summarized.
15 The latter investigator suggested that the brain tissue
of a TSE-infected cow can be expected to contain about 10
11 prions per gram. Assuming that the nerve
tissue is ground with muscle tissue, about 10
8 prions per gram may be expected in ground beef, or
10
10 prions in a 100-g portion. To effect a 12-D reduction, 22D is required (10 + 12 = 22). Thus, some
of the times in minutes needed to achieve a 22D were calculated as follows: D 160 ◦ C = 1.0; D 140 ◦ C =
11.0; D 120 ◦ C = 110.
15 It has been suggested that there is a need for new processing or packaging