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July 19, 2001 A report by Public Citizen and the Government Accountability Project
July 19, 2001
Secretary Ann M. Veneman
U.S. Department of Agriculture
14th & Independence Ave., SW
Washington, DC 20250
Fax:
202-720-2166
Dear Secretary
Veneman:
As you know, Americans are understandably
concerned about the possibility of mad cow disease or bovine
spongiform encephalopathy (BSE) occurring in this country. Having
witnessed the public health, social and economic devastation
wrought by the disease in Europe, they are anxious not to see
similar scenarios occur here.
While there have been no
cases of either BSE or its human equivalent, variant
Creutzfeldt-Jakob disease (vCJD), in this country, over 100
people, primarily in Europe, have been diagnosed with vCJD and
most of them have already died.
One line of defense is surveillance:
systematic sampling by the USDA of cow brains from around the
country. In the
accompanying report, Public Citizen and the
Government Accountability Project examine the current U.S.
surveillance system for BSE.
Our premise was that, because
there is no reason to expect BSE to be significantly more likely
to appear in one part of the country or another, testing rates
should be approximately equal in all states.
We used data from the USDA to compare the
cattle testing rates between states for the period August
1997-December 2000.
The testing rate ranged from 1,004
brains per million cattle slaughtered (New York) to 0.5 brains
per million cattle (Kansas), a 2,000-fold difference. The
median testing rate was 21 brains per million cattle. Attempts
to adjust for the age of the cattle slaughtered or their feed do
not account for the massive variations in testing rates between
states.
Based on these findings, the report made
five recommendations:
1.
Increase the transparency of the testing
2.
Develop clear criteria for the selection
of animals for testing
3.
Randomly select slaughterhouses for
testing of downer cattle
4.
Monitor state testing rates to identify
states with low rates
5.
Conduct unannounced inspections to
monitor compliance with the
testing requirements
Please review the attached report and
indicate whether and how you plan to order compliance with our
recommendations. We are
willing to meet with you to discuss
them further.
Yours sincerely,
Peter Lurie, MD, MPH
Deputy Director
Public Citizen’s Health Research Group
Felicia Nestor
Food Safety Project Director
Government Accountability Project
Patricia Lovera
Researcher
Public Citizen’s Critical Mass Energy and Environment
Program
Sidney M. Wolfe, MD
Director
Wenonah Hauter
Director
Public Citizen’s Critical Mass Energy and Environment
Program
USDA’s Mad Cow Disease
Surveillance
Program:
A
Comparison of State Cattle-Testing Rates
Health
Research Group: www.citizen.org/hrg and
Critical Mass Energy and Environment Program: www.citizen.org/cmep
and
the Government Accountability Project
www.whistleblower.org/www/safefood.htm
July 19, 2001
1.
Increase the transparency of the testing
system
2.
Develop clear criteria for the selection of animals for
testing
3. Randomly select slaughterhouses for testing of downer cattle
4.
Monitor state testing rates to identify states with low
rates
5.
Conduct unannounced inspections to monitor compliance
Research for
this report was
conducted by Peter Lurie, MD, MPH of Public
Citizen’s Health Research Group, Felicia Nestor of
the Government Accountability Project and Patricia Lovera
of Public Citizen’s Critical Mass Energy and
Environment Program
Bovine
spongiform encephalopathy
(BSE) or “mad cow disease” is a degenerative,
irreversible, invariably fatal neurological disease that
was first identified in British cattle in 1986. Since
then, cases of the disease have been diagnosed in cattle
in over a dozen European countries, including France,
Germany and Italy.[1]
BSE is widely assumed to have caused a related fatal
disease in humans, variant Creutzfeldt Jakob disease
(vCJD), which was first detected in Britain in 1996.
Approximately 100
people in Britain, France, Ireland[2]
and now Hong Kong have fallen ill, and most have already
died. The cases
in Ireland and Hong Kong are
thought to have resulted from exposure while the patients
were living in England.
To date, there have been no
cases of vCJD diagnosed in the U.S.
In order to
protect U.S. consumers
from BSE, the federal government has implemented several
protective measures.
These include a ban on imports
of ruminants and feed from Europe and a ban on the
feeding of most types of ruminant protein to other
ruminants. In
addition, a surveillance program that
tests cattle brains for signs of the disease was
initiated in May, 1990 by the Animal and Plant Health
Inspection Service (APHIS) of the U.S. Department of
Agriculture (USDA).
As of March 31, 2001 the
surveillance program had tested 12,341 bovine brains.
None of these tested positive for BSE.[3]
In recent
years, the surveillance
program has expanded substantially, although so far not
to an extent we believe adequate. Between 1990 and
1992, fewer than 100 brain submissions per year were
received by the National Veterinary Services Laboratory
(NVSL), the main agency doing BSE testing in the U.S.
From 1993 to 1995, NVSL recorded between 400 and 500
tests per year.
Since then tests have steadily
increased, with approximately 2,300 in 2000.3
The USDA has stated that it plans to increase the number
of tests to 5,000 in 2001.
For the
purposes of detection of
BSE, there are three populations of cattle that might be
tested: 1. Cattle suffering from central nervous system
disorders (e.g., tumors, listeria); 2. Cattle that are
unable to ambulate (“downer” cattle); and 3.
Normal cattle.
Logically, one would first assure
that all cattle with central nervous system signs are
tested, since neurological symptoms are a hallmark of
BSE. The number
of such cattle tested has remained
stable at about 400 per year. While it is not
necessarily true that cattle with neurological symptoms
are being sampled consistently temporally and
geographically, the similar numbers of such cattle tested
per year provide a measure of assurance that this is
approximately so.
Next, one
would begin to test downer
cattle. The
total number of downer cattle tested
has increased from almost 200 in 1994 to about 1,900 in
2000.
Particularly because there is no clear
definition of what constitutes a downer animal, any
variations in overall BSE testing rates (either
geographically or temporally) would most likely be
predominantly the result of variability in downer cattle
testing rates.
The annual number of downer cattle
slaughtered in the U.S. is usually estimated at 100,000.
No normal
cattle are tested in the
U.S. at the present time. Western European
countries, which are considered to generally have BSE,
are now conducting tests of normal cattle. A total
of 76 positive tests occurred in 1.8 million healthy
cattle tested in these countries between January and
April 2001, for a rate of 0.004%.[4]
The USDA
claims that the
surveillance program has included all cattle with
neurological symptoms and a “random sampling of
… ‘downer cattle’ at slaughter.”3
Presumably, this means that any one downer
animal is as likely as any other to be selected for
testing. This is
an appropriate goal, because one
would want any surveillance system to be about as likely
to detect the disease wherever it arose.[5]
A truly
random sampling scheme should, all
things being equal, produce approximately equal testing
rates across states.
The purpose of this study was
to determine if this is true.
METHODS
The goal of the research was to
compare cattle testing rates across states. To
determine testing rates, one needs a numerator (the
number of cattle tested) and a denominator (the number of
cattle slaughtered) for each state.
The analysis was restricted to the period between August 1997 and December 2000. We excluded the period prior to 1997 because the numbers of cattle tested have increased substantially in recent years. See below for further justification for the August cutoff.
Data on cattle tested
There are
three components to the
USDA’s active surveillance system.3
First, there are the state Veterinary Diagnostic
Laboratories (VDLs), which accounted for 36% of brain
samples collected between May 1990 and March 31, 2001,
and 23% of brain samples during the study period. These
are primarily from animals suspected of having rabies or
other domestic diseases, primarily in the field (not in
slaughterhouses), and are not ordered primarily for the
detection of BSE.
Second, the largest source (62%
of brain samples) is APHIS’s National Veterinary
Services Laboratory (NVSL). NVSL conducts brain
biopsies on cattle presented for slaughter with signs of
central nervous symptom disorders, downer cattle and
cattle in which domestic diseases such as rabies had been
ruled out. Over 70% of NVSL testing has occurred
since 1997.
Finally, a small fraction (1%) of
brains have been tested by the Centers for Disease
Control and Prevention (CDC). The CDC project involved
BSE surveillance associated with rabies diagnosis, but
was discontinued prior to the period of study here.
The USDA does not provide data for testing broken down by
the various categories of cattle (stags, heifers,
etc.).
This analysis
focuses on the NVSL
data.[6]
NVSL is probably more likely to detect a case of BSE than
VDL because it tests the highest-risk animals. Moreover,
because the NVSL is a federal program, it is more
susceptible to federal policies to rectify any
disparities in BSE testing rates. In addition,
because the rates of suspected rabies or other domestic
diseases (the indication for many of the VDL tests) may
vary by state, the NVSL-only testing rates should, in
theory, be essentially independent of geography, for any
category of cattle.
In 1997, the Government
Accountability Project (GAP) submitted a Freedom of
Information Request to the USDA asking for BSE-testing
information, broken down by state, and received data
covering the period from May 1990 through July 31, 1997.
Until recently, USDA’s website3 provided
testing data only for the period May 10, 1990 to December
31, 2000. We therefore determined the number of tests
conducted between August 1997 and December 2000 by
subtracting the GAP data from the USDA website data.
Data on cattle slaughtered
Data on
bovines slaughtered at
federally inspected establishments in each state, broken
down by year and category of bovine, are available at the
USDA’s National Agriculture Statistics Service
website.[7]
In those few states where data were missing for
some part of the study period, data were generated by
extrapolation from the months for which data were
available. We
conducted three separate analyses: 1
All cattle, excluding calves[8]
(steers,[9]
heifers,[10]
all cows,[11]
bulls[12]
and stags[13]);
2. “Old animals” (cows, bulls and stags); and
3. Dairy cows.
In 2000, for example, the total
number of cattle slaughtered was 35.6 million, of which
6.0 million (16.9%) were old animals. In that same
year, 2.6 million dairy cows were slaughtered (7.3% of
all cattle and 43.3% of old animals).
We also paid
attention to older
animals because they are more likely than younger animals
to show the clinical symptoms of BSE, are more likely to
show evidence of the disease at autopsy and are likely to
be more infectious than younger animals. It is
possible that USDA might have focused its testing in that
population of cattle.
The higher prevalence of BSE
in older animals is in part due to the long incubation
period of the disease and in part because older animals
have had more opportunity to be exposed to the BSE
agent.
We also
looked at dairy cows because
they also tend to be somewhat older than beef cows (or
any other category of cattle) at slaughter, a reason to
focus disproportionately on this group for testing.
Moreover, dairy cows may have been more likely to have
been fed meat and bone meal which could have included
– intentionally or by accident – ruminant
protein (which increases the fat and protein content of
milk) prior to the feeding ban. For each of the
three cattle categories, we selected the 20 states with
the highest numbers of animals slaughtered.
We then
divided the number of brains
tested from that state (the numerator) by the number of
animals slaughtered in that state (the denominator).
We did this analysis for the three different populations
of animals slaughtered (all cattle, old animals, and
dairy cows) and then ranked the states by their testing
rates. The data
were entered into an Excel 97
spreadsheet and analyzed using Stata Version 6.
RESULTS
The primary outcome of interest
was the ratio between the testing rate in the state with
the highest testing rate to the testing rate in the state
with the lowest testing rate among the 20 states with the
highest number of slaughtered animals in that category.
A.
All cattle (see Table 1)
The top 20 cattle states
accounted for 98% of all cattle slaughtered during the
study period.
The median number of cattle
slaughtered in these states during the study period was
3.2 million (range: 250,000 (New York) – 26.6
million (Kansas)).
The median number of brains
tested was 23 (range: 2 (Michigan) – 1,533
(Texas)).
There was enormous variation in
the rates of testing by state. While the highest
rate of brain testing was 1,004 per million cattle in New
York, it was 0.5 per million cattle in Kansas, an
approximately 2000-fold difference (median testing rate:
21 per million cattle for all 20 states). Although
New York’s testing rate was considerably higher than
for the state with the second-highest testing rate
(California with 199 brains tested per million cattle),
even this second-place rate was 400 times higher than
Kansas’s rate.
There was no correlation
between the number of cattle slaughtered in a state and
its testing rate (Kendall’s J = -0.26; p = 0.12).
B.
Old animals (see Table 2)
The top 20 old animal states
accounted for 95% of all old animals slaughtered during
the study period.
Seventeen of the top 20 old
animal states were also in the top 20 all cattle states.
The median number of old animals slaughtered in these 20
states was 603,000 (range: 129,000 (Missouri) to 3.3
million (Texas)).
Again, huge variations between
the testing rates in these states were apparent. The
highest-ranking state (New York with 1,184 brains tested
per million old animals) had a testing rate about 400
times that of the lowest ranking state (Minnesota with 3
per million old animals). The median testing rate
was 58 per million old animals. There was no
correlation between the number of old animals slaughtered
in a state and its testing rate (Kendall’s J =
-0.06; p = 0.72).
C.
Dairy cows (see Table 3)
The top 20 dairy cow states
accounted for 88% of all dairy cows slaughtered during
the study period.
Sixteen of the top 20 dairy cow
states were also in the top 20 all cattle states. The
median number of dairy cows slaughtered in these 20
states was 168,000 (range: 41,000 (Florida and New
Mexico) to 2.5 million (Wisconsin)).
Once more, huge variations
between the testing rates in these states were apparent.
The highest ranking state (Texas with 4,034 brains tested
per million dairy cows) had a testing rate almost 600
times that of the lowest ranking state (Minnesota with 7
brains tested per million dairy cows). The median
testing rate in the 20 states was 162 tests per million
dairy cows.
There was no correlation between the
number of dairy cows slaughtered in a state and its
testing rate (Kendall’s J = -0.17; p = 0.31).
CONCLUSIONS
This report clearly demonstrates
that there are enormous variations in the BSE testing
rates between states.
States with the highest rates
of testing had rates 400 to 2,000 times those of the
lowest states.
This enormous variability suggests
that the USDA’s testing program is being
administered in a haphazard fashion. Moreover,
USDA’s claim that there have been no cows detected
with BSE in the U.S. is not very compelling for states
with low testing rates.
Alternative
explanations for these
findings are essentially ruled out by the data. Because
extremely large variations between states persist even
when older animals and even dairy cows are used as the
denominator, it is not likely that targeting testing at
older cattle explains these findings. (The findings
are fairly similar across the three cattle categories;
six states are among the 10 states with the highest
testing rates in all three categories.) Nor do
differences in state laboratory practices explain the
data, because we focused on the federal NVSL data. High
testing rates in smaller cattle states (one can get very
high ratios when dividing by small numbers) are also not
the cause of the findings, because in each category of
cattle, we looked only at the 20 states with the largest
numbers of cattle slaughtered. Moreover, in each
category of cattle, there was no correlation between the
number of cattle slaughtered and the testing rate. Testing
variations are also not attributable to surveillance
targeted according to feeding practices. The
northeastern states are probably most likely to have used
animal protein feeds because plant protein is less
available there, but these states represent only a
minority of cattle slaughtered and their testing rates
are not much higher than other states’ testing
rates. Aside
from variations in feeding practices
and the categories of cattle farmed (and hence their
ages), there is no reason to expect BSE to be more likely
to appear in one part of the country than in another.
Although high or low rates of testing by large plants in
small states might explain some of the findings, they
cannot explain the overall variations. The basic
finding is this: The variations between states, even
after all these considerations, are so large that none of
these alternative explanations is viable.
We believe
that much of the
variability is in the testing of downer cattle. Even
as the total number of cattle tested has increased
substantially in the past several years, the number of
cattle with neurological symptoms tested has remained
essentially stable.
The USDA has stated that it
will increase the number of cattle tested annually to
5,000, presumably by expanding testing in the downer
cattle population, but even this would represent only
approximately 5% of this population. Particularly
when small percentages of populations are being tested,
it is important that each animal be as likely as any
other to be selected for testing.
But all of
the evidence presented
here suggests that current practices are not well
coordinated.
USDA has no definition of exactly what
constitutes a downer animal, and so slaughterhouse
veterinarians inevitably rely upon subjective judgments.
On top of this problem, there may be other cattle that
would be good candidates for BSE testing that are simply
never presented to slaughterhouses by the farmer (and
thus cannot be reflected in our data) or slaughtered in
smaller plants where a veterinarian is not always on
duty.
The analyses
for old animals and
dairy cows represent our attempt to adjust for the
possibility that USDA has conducted its testing
disproportionately among these higher-risk animals.
However, the USDA does not make available brain testing
data that are broken down by category of cattle. It
is for this reason that we have placed most emphasis in
this report on the testing rates for all cattle. However,
regardless of the method used, we always found interstate
variations far above anything that could be considered
vaguely acceptable.
The data
presented here are
presented by the state in which the animal was
slaughtered and tested (these will be the same). However,
cattle may be transported to another state for slaughter
and, of course, are likely to be consumed in states other
than the state in which they were slaughtered. For
this reason, the data presented are not intended to
provide consumers with guidance as to more or less safe
states in which to consume cattle products.
This report
does not address the
question of what the correct testing rate is. It
simply documents enormous inconsistencies in the way the
current surveillance program is being applied. We
note that during the study period only three states (New
York, California and Pennsylvania) tested all cattle at
rates higher than the USDA is currently proposing (5,000
tests for 35.6 million cattle slaughtered in 2000, or a
rate of 140 tests per million cattle slaughtered). Although
we welcome the increase in BSE testing USDA has promised,
this increase will be of only limited value if the
testing is not spread more uniformly (in terms of the
rate of brains tested per million cattle slaughtered)
across the country than it has been to date. Indeed,
especially for the states with lower testing rates,
spreading testing more evenly across the country, even
with the current number of cattle tested, will have a
bigger impact in raising testing rates than increasing
the national testing rate by the amount contemplated by
the USDA.
RECOMMENDATIONS
[1]
European Union. Bovine Spongiform
Encephalopathy.
Available at: http://europa.eu.int/comm/food/fs/bse/index_en.html.
Downloaded on July 16, 2001.
[2]
Department of Health. Monthly Creutzfeldt-Jakob Disease
Statistics. Available at: http://www.doh.gov.uk/cjd/stats/jul01.htm.
Downloaded on July 16, 2001.
[3] USDA. BSE Surveillance. Available at: http://www.aphis.usda.gov/oa/bse/bsesurvey.html. Downloaded on June 13, 2001.
[4]
Donnelly C. Mathematical modeling of potential BSE
exposures in various BSE countries. Presented at U.S.
Food and Drug Administration Transmissible Spongiform
Encephalopathy Advisory Committee meeting, June 28,
2001.
[6]
We conducted similar analyses using the NVSL combined
with the VDL data.
These generated similar results
to the NVSL-only analyses, but are not presented here.
The results can be obtained from Public
Citizen.
[7]
National Agricultural Statistics Service. Published
Estimates Data Base. Available at: http://www.nass.usda.gov:81/ipedb/.
Downloaded on July 16, 2001.
[8]
Bovines that are generally less than six months old
(about 3% of all bovines slaughtered annually).
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