Follow Ups | Post Followup | Back to Discussion Board | VegSource

From: TSS (216-119-136-100.ipset16.wt.net)
Subject: Occupational risk factors for the sporadic form of Creutzfeldt-Jakob disease (FULL TEXT)
Date: November 29, 2003 at 5:18 pm PST

-------- Original Message --------
Subject: Occupational risk factors for the sporadic form of Creutzfeldt-Jakob disease (FULL TEXT)
Date: Sat, 29 Nov 2003 13:09:20 -0600
From: "Terry S. Singeltary Sr."

{please note, scanned, copied, and corrected, could be errors..TSS)

La Medicina del Lavoro
Med Lav 2003; 94,4:353-363

Occupational risk factors for the sporadic form of
Creutzfeldt-Jakob disease

PL. Cocco, A. CAPERNA*, F. VINCI*

Dipardmento di Sanita Pubblica, Sezione di Medicina del Lavoro, Universita di Cagliari
* Isdtuto di Medicina del Lavoro, Facolta di Medicina e Chirurgia A. Gemelli, Universita Cattolica del Sacro Cuore, Roma

KEYWORDS

Creutzfeldt-Jakob disease; epidemiology; occupational health

SUMMARY

Some case reports among European farmers and a few case-control
studies suggested the hypothesis of an increased risk of the
sporadic form of CJD (sCJD) associated with livestock farming or
work as a butcher. Also, the discovery of the possibility of
transmission of the disease via blood or by contact following
corneal or dura madre transplant suggested that health
occupations might also run higher sCJD risks. However, a
meta-analysis of three case-control studies and a multicentre
European study did not find any positive association between
sCJD and health-related jobs or occupational contact with
livestock, such as cattle and sheep, or animal products. To
explore possible occupational risk factors for Creutzfeldt-Jakob
disease (CJD), we used a publicly available US database including
about 6 million deaths in 24 states during 1984-95. Cases were
636 deaths (300 men and 336 women) with CJD (ICD-9 code 046.1)
as the underlying cause of death. Controls were 3,180 deaths
randomly selected from among those who died from all other
diseases except those affecting the central nervous system.
CJD cases represented a wide variety of occupations (159) and
industries (147). Among occupations and industries, for which
previous reports suggested potential exposure to a transmissible
spongiform encephalopathy (TSE) agent, the OR for CJD was
significantly increased among butchers (OR=6.8, 95% C.I. 1.5,
30.1, based on 4 cases and 3 controls), and persons working in
offices of physicians (OR=4.6, 95% C.I. 1.2, 17.6 based on 5
cases and 4 controls). Nine other occupations and seven other
industries, for which no previous suggestion existed in the
literature, also showed significant associations. Overall, our
results suggest that occupational exposures are not an important
source of sCJD infection. However, as the excess among butchers
and some workers in health occupations was consistent with
previous reports, more indepth research is warranted to address
the hypothesis.

RiASSUNTO

«Fattori di rischio professlonale per la forma sporadica della
malattia di CreutzfeIdt-Jakob». L'epidemia delta cosiddetta
"nuova variante" della malattia di Creutzfeldt-Jakob (CJD) in
Gran Bretagna, e la sua dimostrata associazione con l'epidemia
di encefalopatia spongiforme bovina (BSE) in quello stesso Paese,
hanno ridestato l'in-

Pervenuto il 28.11.2002 - Accettato il 15.1.2003

Corrispondenza: Diparrimento di Sanita Pubblica, Sezione di
Medicina del Lavoro, Universita di Cagliari, via San Giorgio 12,

09124 Cagliari - Tel. 070-60285278 - Fax 070654350 -
E-mail: coccop@pacs.unica.it

Comunicazione orale alia XXV Riunione Annuale dell'Associazlone
Italiana di Epidemioloeia, Venezia 4 Ottobre 2001

354

COCCO ET AL

teresse nei confronti di tutte leforme di questa rara malattia e
del suo possibile rapporto con alcune esposizioni in amblto
lavorativo. La descrizione di alcuni casi di CJD in contadini
europeifece ipotizzare che attivita quail l'all-evamento di
bovini o l'abbattimento degli stessi in mattatoi potessero
comportare un aumento del rischio di CJD. Inoltre, la possibility
di una trasmissione per via ematica o per contatto con materiali
biologici, successivamente ai trapianfi di dtira madre o di
cornea, fece sospettare che anche le professioni sanitane potessero
comportare un aumento del rischio di CJD. Tuttavia, una
meta-analisi di tre studi caso-controllo non dimostro una
associazione tra forma sporadica di CJD ed attivita sanitarie o
contatto con bovini ed ovini, ed uno studio multicentrico Europeo
non trovb akuna associazione con I'esposizione professionale ad
animali o pelli, mentre itrischio risultava elevato perfrequents
esposizlone a cuoio ed esposizione a fertilizzanti contenenti
zoccoli e coma. La dispombilita di un data-base pubblicamente
accessible, contenente i dati di circa 6 milioni di certificati
di morte in 24 Stati degli Stati Uniti nel periodo 1984-95, ha
consentito I'esplorazione dei rischi occupazionali di CJD in
questo Paese. Sono stati individual in tutto 636 casi (300 uomini
e 336 donne) di decessi per CJD (ICD-9 046.1). Come controlli
sono stati selezionati 3180 soggetti deceduti per altre patologie,
ad esclusione di quelle a carico del sistema nervoso centrale,
accoppiati in rapporto di 5:1 ai casi per area geografica'di
residenza, sesso, razza edeta. Tra le occupaziom sospettate a
priori di un'associazione, i macellai mostravano un OR di 6,8
(I.F. 95% 1,5, 30,1, basato su 4 casi e 3 controlli), ma un
risultato simile veniva osservato anche in altre nove occupazioni
non sospettate a priori di un'associazione. Il rischio non
risultava elevato per Ie attivita agricole nel complesso, o nelle
Industrie alimentan, mentre un OR di 4,6 (I.F. 95% 1,2, 17,6,
basato su 5 casi e 4 controlli) era associate al lavoro in
ambulaton medici, ma non in ospedali o altri servizi sanitari.
Altre sette attivita industriali, non sospettate a priori di
un'associazione, mostravano un significative aumento del rischio
di CJD. La dispersione dei casi di CJD in una grande varieta di
occupazioni induce a ritenere che le esposizioni professionali
contribuiscano scarsamente all'eziologia della forma sporadica di
CJD. D'altro canto, i risultati positivi potrebbero essere genera
ti dal caso data la molteplicita di con-fronti effettuati.
Tuttavia, appare opportuna la pianificazione di indagini
multicentriche piu approfondite che testino l'ipotesi del ruolo di
esposizioni professionali nell 'attivita di abbattimento degli
animali, insieme ad altri possibili fattori di rischio,
nell'eziologia di questa rara malattia.

INTRODUCTION

The UK epidemics of the new variant form of
Creutzfeldt-Jakob disease (nvCJD), and its link
with bovine spongiform encephalopathy (BSE)
(46, 47) has raised interest in searching for etiolog-
ical clues for the more commonly seen, classic
forms of CJD. Classic CJD is a neurological disor-
der, classified in the group of transmissible spongi-
form encephalopathies (TSEs), that has been esti-
mated to affect approximately 1x10-6 persons per
year worldwide. It is invariably fatal, with a mean
illness duration of 5 months (47), and a median age
at death of 68 years (20). Some TSEs in humans
have been shown to be associated with mutations
in the prion protein (PrP) gene (PRNP) on chro-
mosome 20 (32), and a few are classified as familial
CJD. In patients affected by the non-familial spo-
radic form of classic CJD (about 85% of CJD cas-
es), a significantly increased prevalence of homozy-

gosity for methionine or valine at PrP codon 129
has been reported (25, 28, 37, 40). Based on the
scarce geographical variation in the occurrence of
sporadic CJD over long time periods, it has been
proposed that there is no environmental source of
infection (16, 31) and that the vast majority of cas-
es rather result from de novo spontaneous genera-
tion of a transmissible agent consisting of an ab-
normal form of a host-encoded glycoprotein (31).
This transmissible agent was given the name of
"prion" in 1982 (30). However, a 5-fold inter-re-
gional variation in the crude CJD mortality rate
occurred within Italy in 1993-99 (8). Also, the pro-
portion of polymorphism at codon 129 among
sCJD cases is more similar to that observed among
persons with iatrogemc CJD, than to that in the
general population, which suggested that simple
stochastic events would not fully explain SCJD
(33). Also, sCJD cases are tipically elderly, with
cortical symptoms, and abnormal PrP, but not

CJD AND OCCUPATION

355

amyloid, deposits in the synapses, On the other
hand, nvCJD typically affects young people; it is
not associated with codon 129 polymorphism and
it does present amyloid plaques in the brain (47).

A substantial body of evidence supports the hy-
pothesis of blood transmission of the sCJD agent
in various animal species (41), depending on the
tissue level of PrP infectivity, the species barrier,
and the route of administration (33). However, the
risk of CJD transmission by transfusion remains
theoretical, since no confirmed cases have ever
been causally attributed to the receipt of a blood
transfusion, nor has any case developed in recipi-
ents of clotting factor concentrates, or pooled plas-
ma derivatives, to which a donor, who subsequently
developed CJD, had contributed (15, 27, 41). Also,
no known cases of CJD were attributable to the
reuse of percutaneous transluminal coronary angio-
plasty (PTCA) equipment contaminated by blood
(15). While the potential exists for blood transmis-
sion of the disease, thus far human epidemiological
evidence suggests that such an occurrence would be
rare, as only a small fraction of the general popula-
tion carrying codon 129 and codon 200 polymor-
phisms might be susceptible to infection, and most
transfusions might not contain infective doses suf-
ficient to cause the disease (33). On the other
hand, the hypothesis of a transmissible agent, pos-
sibly with blood, is supported by numerous clinical
reports of iatrogenic CJD consistently identifying
surgical procedures as a risk factor. Although such
a possibility was ruled out in an early study among
French cases occurring in 1968-77 (4), CJD cases
have been described after dura madre or corneal
transplants from infected donors (14, 21, 24, 26,
27, 29), neurosurgery of stereotactical encephalog-
raphy with contaminated instruments (3, 49), use
of GH hormonal extracts from cadavers (2), and
three epidemiological studies showed a higher
sCJD risk following general surgery (9, 22, 43).
However, while Australian authors interpreted the
evidence as an indication of the possibility of dis-
ease transmission (9), German authors suggested
stress as the relevant risk factor (22). Due to the
exceptional resistance of the infecting agent to
common sterilising agents, autoclave and sodium
hypochloride or hydroxide treatment, or formic

acid treatment of infected materials and instru-
ments has been suggested to prevent occupational
and/or iatrogenic transmission of the disease (34,
36), while formadehyde was not effective in pre-
venting transmission (33).

If blood transmission were important, occupa-
tional contact with animal blood, organs, and other
animal products would be a plausible co-factor in
sCJD etiology. In the pre-nvCJD-epidemic era, the
hypothesis of CJD as a zoonotic disease was raised
(23). As early as 1986, such a hypothesis was again
raised in a small French study (11). Occupational
contact with animals such as deer, monkeys, and
squirrels was associated with a non-significant 9-
fold increase in risk, while the excess risk of similar
degree associated with non occupational contact
with deer or rabbits was statistically significant.
Exposure to animal organs was also significantly
associated with CJD (OR=20.9; p<0.005) (11).
Following the nvCJD epidemics in the UK, clinical
reports of sCJD cases among livestock farmers and
butchers have been repeatedly published (17, 35,
44, 48), further suggesting that - if the link were to
be confirmed in analytical studies — transmission
via the blood or skin contact through skin lesions
with infected materials and/or instruments would
be important (19). Analytical studies have been less
numerous, and they are reported in table 1. A
meta-analysis of three case-control studies on
sCJD published at that time concluded that a non
significant association existed with livestock farm-
ing and with health related occupations (45). The
study of 662 sCJD deaths in 1970-96 in the Unit-
ed Kingdom found a significant excess risk among
livestock farmers (6 observed deaths versus 2.4 ex-
pected), although the interpretation was limited to
the absence of any link with the nvCJD epidemics
(10). All the observed cases were livestock farmers,
four of whom (0.6 expected) occurred in farms
where BSE cases had been reported. No cases were
observed among veterinarians (0.03 expected), or
butchers. (0.15 expected). A matched case-control
study of 206 sCJD cases and controls did not iden-
tify any association with a priori suspected occupa-
tions (38). However, 21 cases (10%) e 14 controls
(7%) occurred in subjects with occupational contact
with animal products (p=0.17). The authors did

356

COCCO ET AL

Fable 1 - Studies of sCJD and occupation

Author

Type of study Health Raising Butchers,

occupations cattle/sheep abattoir workers

Wientjens et al, 1996

Cousens et al, 1997

UK Nat CJD Surv Unit, 1997

Van Duijn et al, 1998

Aylin et al, 1999

UK Nat CJD Surv Unit, 2001**

Meta-analysis
Cohort

Case-control

Case-control

Trend in proportional mortality

Case-control

snip...not available...tss

* contact with animal products; ** combining nvCJD and sCJD cases

not explore this finding in detail. We conducted a
crude calculation based on the published data, and
we found instead an Odds Ratio of 1.6 (95% confi-
dence interval 1.18,2.15).

A European case-control study was conducted
by interviewing next-of-kins of 405 CJD cases and
405 hospital controls, excluding patients suffering
from dementia (42) .The authors reported a signifi-
cant excess risk associated with the use of fertilizers
containing substances derived from hoofs and
horns, and with contact with skin and fur not as
garments. Among individual occupations, only
butchers showed a non-significant increase in the
Odds Ratio. A proportional mortality analysis of
deaths from dementia in England and Wales dur-
ing 1979-96 did not find a consistently increasing
temporal trend in occupations suspected a priori of
being at risk, such as farmers, butchers and abattoir
workers, and veterinarians (1). Another prelimi-
nary combined case-control analysis of 102 nvCJD
cases and 197 sCJD cases, compared to 195 con-
trols, found no excess risk among health related oc-
cupations, butchers and abattoir workers, and other
occupations involving contact with animal products
(39). Eight out of 114 identified cases in Slovakia
had health related occupations (25).The authors
excluded a link between occupational factors and
CJD risk, although no formal analysis was con-
ducted in this regard, nor any information was pro-
vided on which were the occupations of the other
106 cases.

It is possible that, in the studies conducted thus
far, the small number of subjects in the occupations
at risk limited the exposure assessment to ever hav-
ing held a job considered a priori at risk, indepen-
dently of the period in the lifetime, duration, type
of animals, and actual job content. The methods
section of these papers do not explain whether
complete work histories were included in the ques-
tionnaire, or whether only one or more main occu-
pational titles or the last were collected. A further
problem in these studies is that information for
cases always relied on next-of-kin reporting, whilst
the same study subjects provided the information
in about half the hospital controls and in all popu-
lation controls.

Overall, the results of the studies conducted thus
far stress the fundamental requirement of having
experts in occupational epidemiology, agricultural
work technology and veterinarian hygiene par-
ticipating in planning and analyzing occupational
data.

To examine the possible association of CJD with
occupational risk factors, we accessed a large pub-
licly available database, including death certificate
from 24 US states in 1984-95, to analyze the occu-
pations of the 636 deaths due to CJD therein re-
ported in comparison to 3,180 controls deceased
from other selected causes of death, in a country
thus far not affected by the nvCJD epidemics.

METHODS

The 24 US states death certificates database we
used consists of several million coded death certfi-
cates from 24 US states, covering the years 1984-
95. The 24 states are: Colorado, Georgia, Idaho
(from 1988), Indiana (from 1986), Kansas, Ken-
tucky, Missouri (in 1984-86), Maine, Nebraska (in

CJD AND OCCUPATION

357

1984-85), Nevada, New Hampshire, New Jersey
(from 1988), New Mexico (from 1986), North
Carolina (from 1987), Ohio (from 1985), Okla-
homa, Rhode Island, South Carolina, Tennessee
(in 1985-88), Utah (from 1985), Vermont, West
Virginia (from 1988), Washington (from 1989),
and Wisconsin. In addition to standardized coding
procedures, information on usual occupation and
kind of business or industry, reported in the death
certificate for each decedent, was included in the
database provided to the National Center for
Health Statistics (NCHS) (7). The information on
occupation and industry was coded according to
the 1980 US Bureau of the Census classification
(6). The underlying cause of death was coded ac-
cording to the International Classification of Dis-
eases - 9th revision. No further details, such as du-
ration of employment or concurrent diseases, are
available from this database. Among subjects 25
years of age or more at death, 636 cases of CJD
(ICD-9 code 046.1) were identified. Table 2 shows
the case distribution by age, and gender. Only 22
subjects were indicated as non-whites in the data
base. As we did not see any reason why a gross def-
inition of genetic background, such as the demo-
graphic concept of "race", should affect sCJD risk,
we included all subjects in the analysis. Eligible
controls were subjects who died from all other dis-
eases, except mental disorders (ICD-9 codes
290.0-319.9), diseases of the central nervous sys-
tem (ICD-9 codes 320.0-349.9), cerebrovascular
diseases (ICD-9 codes 430.0-438.9), unspecified
atherosclerosis (ICD-9 code 440.9), and ill defined
conditions and symptoms involving the central
nervous system (ICD-9 codes 780.0-781.9). We

Table 2 - Deaths from Creutzfeldt-Jakob disease in 24 US
states in 1984-95 by age, and gender

Age group Men Women
25-39 3 4
40-49 11 16
50-59 47 46
60-69 126 121
70-79 92 117
80 + 21 32
All ages 300 336

randomly selected five controls per each case with-
in the set of controls with the same geographic re-
gion, race, gender, 5-year age group, and year of
death as the index case. The Odds Ratio (OR) as-
sociated with a given occupation or industry cate-
gory was expressed relative to an unexposed refer-
ence group including all other occupation or indus-
try categories.

Odds Ratios (ORs) and their 95% confidence
intervals (95% C.I.) were derived from the respec-
tive log odds obtained with logistic regression
modeling, using the GMBO feature of the Epi-
cure® software. ORs were calculated for selected
demographic variables. We first calculated OR for
those occupations and industries for which litera-
ture reports suggested a potential association with
CJD. For occupations, these prior hypotheses were
livestock farmers, veterinarians, butchers and other
food-related occupations, pathologists and other
health professionals. For industries, those consid-
ered as prior hypotheses were livestock tanning,
slaughterhouses and meat processing plants, hospi-
tals and other health facilities. Secondly, we calcu-
lated OR for all occupations and industries for
which there were three or more exposed cases. Co-
variates in the logistic regression model for occupa-
tion and industry were age (5-year age categories),
marital status (never-married versus ever-married),
and socioeconomic status (SES) (five categories).
The SES indicator was obtained by categorizing
the Greens Standardized Scores for Specific Occu-
pations (13,18), as follows:

- low SES (score 21-39);

- medium-low SES (score 40-49);

- medium SES (score 50-59); 4. medium-high
SES (score 60-64);

- high SES (score >65).
Introducing gender as a covariate in the logistic
regression model did not change the risk estimates.

RESULTS

In the present study population, female cases are
more numerous than male, and more than 94 per-
cent of the cases died at age 50 or older (table 2).
Subjects who died from CJD were less likely to have

COCCO ET AL

never been married and to have lived in the South,
and slightly more likely to have resided in metropol-
itan areas (not shown in the tables). The OR for
CJD increased with higher SES (test for trend,
p<0.001). This association persisted within strata of
latitude, geographic region, race (although numbers
were very small among African Americans), gender,
age, and marital status (not shown in the tables).

Overall, 159 occupation and 147 industry cate-
gories were represented among CJD cases, with 52
of the occupation and 54 of the industry categories
composed of at least three cases. A statistically sig-
nificant association with CJD was observed for
10/52 occupation categories (19%) and 8/54 indus-
try categories (15%), including disparate activities
such as financial managers, mechanical engineers,
teachers, military personnel, and persons working
in manufacture of toys, amusement, and sporting
goods, telephone utility companies, beauty shops,
and financial services (table 3). These associations
varied very little after limiting the analysis to sub-
jects aged 40 years or older.

Among food handling occupations, a prior hy-
pothesis in this study, a statistically significant asso-
ciation was observed for butchers (OR=6.8, 95%
C.I. 1.5, 30.1, based on 4 cases and 3 controls). The
OR was non-significantly elevated for miscella-
neous food preparation occupations (Census code
444: OR=3.2, 95% C.I. 0.9, 10.7, based on 4 cases
and 9 controls), a heterogeneous category which in-
corporates food preparation occupations other than
those with specific codes (such as cooks, waiters, or
bartenders). When we combined all food prepara-
tion occupations, no association was observed
(OR=1.1; 95% C.I. 0.5,2.3, based on 9 cases and 41
controls), suggesting that the observed excesses
were restricted to butchers and miscellaneous food
preparation occupations. No cases or controls were
coded as non-farm animal caretakers. One case and
no controls were classified as a hunter or trapper.
When examined by industry grouping (table 3) the
ORs were non significantly elevated in the meat
products industry (OR=3.8, 95% C.I. 0.8, 17.3,
based on 3 cases and 4 controls).

CJD was not associated with agricultural work.
The occupation of non horticultural farmer showed
a non significant 20% increase in risk. Among in-
dustries, a similar result was observed for crop pro-
duction (OR=1.2; 95% C.I. 0.6, 2.4, based on 12
cases and 73 controls), and livestock farming
(OR=1.2, 95% C.I. 0.3, 4.2, based on 3 cases and
17 controls).

Health-related occupations and industries were
also a prior hypothesis in this study. The excess ob-
served among physicians was not statistically sig-
nificant (OR=4.6, 95% C.I. 0.7, 29.0, based on 3
cases and 2 controls). No excess was observed for
nurses (occupational codes 095 and 207 combined:

OR=0.8, 95% C.I. 0.4, 1.5; based on 12 cases and
55 controls), or for all health related occupations
combined (OR=0.8; 95% C.I. 0.5, 1.5, based on 13
cases and 72 controls). No pathologists were re-
ported among cases. No veterinarians were report-
ed among cases versus one among controls.

Among health-related industries, a significant
association was observed for persons working in
offices of physicians (OR=4.6, 95% C.I. 1.2, 17.6,
based on 5 cases and 4 controls), but not for those
working in hospitals (OR=1.0, 95% C.I. 0.6, 1.7,
based on 22 cases and 95 controls), or health ser-
vices not elsewhere classified (OR=1.1, 95% C.I.
0.3, 3.8, based on 3 cases and 13 controls).

For the occupations and industries shown in
table 3, being a prior hypothesis of this study did not
increase the likelihood of a significant association
with CJD (1/6 or 17% significant findings among
prior hypotheses versus 9/46 or 20% among the other
occupations, and 1/7 or 14% among prior hypotheses
compared with 7/47 or 15% among the other in-
dustries).

DISCUSSION

In this death certificate based case-control study,
we observed a statistically significant association of
CJD with work as a butcher and with employment
in the office of a physician, occupation and indus-
try categories for which previous literature reports
suggested potential exposure to a TSE agent.
However, other occupations and industries for
which the same hypothesis was raised, such as
work on a livestock farm, were unassociated with
CJD. The positive associations with the occupation

CJD AND OCCUPATION

of butcher and employment in physician's offices
cannot be conclusively interpreted because of the
small numbers and lack of information on the type
and extent of exposure to potentially infectious
material. Also, other generally smaller studies of
CJD in Europe have not found specific associa-
tions with livestock farming or other specific occu-
pations, including health care workers (1,42).

In our study, significant associations were found
for CJD with 19 percent of the occupations and 15
percent of the industries composed of at least three
cases, and these proportions did not vary according
to being a prior hypothesis in this study or not. A
proportion of positive findings (about 5%) would
be expected to occur by chance. Relative differences
in ascertainment may also have contributed to pos-
itive findings for some high SES employment cate-
gories, such as financial managers, engineers,
teachers, drafting occupations, or work in insurance
firms and financial industries. In this data set, risk
for other neurological diseases, including
amyothrophic lateral sclerosis, multiple sclerosis,
and Parkinson's disease, also showed this pattern
(data not shown), suggesting a generalized diag-
nostic bias related to SES in diseases requiring a
more sophisticated diagnostic evaluation. The pos-
sible under-ascertainment of CJD deaths in the
lower SES categories may also explain some of the
deficit in CJD mortality previously reported among
African Americans compared to whites in the USA
(20). Therefore, as described in the methods sec-
tion, we adjusted by SES all risk estimates. The in-
crease in CJD risk for butchers and employees in
physicians offices persisted in the unadjusted
analysis or when the analysis was restricted to the
SES category they belonged.

An important limitation in our study is that it
was based on the one occupation and industry
combination on the death certificate of study sub-
jects, and no further details, such as duration of
employment, were available. This should be con-
sidered when interpreting our findings. One
strength of our study is the large number of CJD
deaths available for analysis (636 cases), as we uti-
lized the largest database possible to evaluate the
relationship of CJD with occupational risk factors.
Still, the numbers for specific occupations and in-
dustries are quite small, and chance could account
for the increases in risk observed in our study.

Disease misclassification was likely to be a mi-
nor problem in this study, as death certificates have
been shown to be a reasonably specific source for
ascertaining CJD cases (5, 12), and control subject;

were selected after excluding deaths linked to diag-
nostic codes conceivably including misdiagnosed
CJD cases. However, as it is not possible to distin-
guish familial from non-familial CJD cases within
a data base of coded death certificates, we cannot
assess whether and to what extent individual find-
ings may have been biased by poor diagnostic in-
formation.

While chance could account for the associations
we observed, their consistency with other pub-
lished clinical and epidemiological reports indicate
that further in-depth studies are warranted to eval-
uate the findings among butchers and employees in
physician's offices before concluding for a CJD ex-
cess in these jobs. The rarity of the sCJD has pre-
vented substantial progress in the knowledge of its
etiological factors. The international multicentre
approach, and a detailed occupational exposure as-
sessment performed by experts, would be crucial in
successfully identifying candidate risk factors...

CJD AND OCCUPATION

Table 3 - Odds Ratio for Creutzfeldt-Jakob disease associated with selected industries
and occupations (at least 3 exposed cases)

Census/Code...............Cases/Controls..........OR(95%C.I.)

007 - Financial managers 6/5 4.2 (1.2-14.8)
019 - Managers and administrators, n.e.c. 36/151 0.9 (0.5-1.3)
023 - Accountants and auditors 6/24 0.9 (0.4-2.4)
056 - Industrial engineers 3/3 3.0 (0.6-15.6)
057 - Mechanical engineers 7/4 6.0(1.6-22.2)
084 - Physicians 3/2 4.6 (0.7-29.0)
095 + 207 - Registered nurses & licensed practical nurses 12/55 0.8 (0.4-1.5)
156 - Teachers, elementary school 16/63 1.0(0.5-1.8)
157 - Teachers, secondary schools 3/4 2.8 (0.6-12.8)
159 - Teachers, n.e.c. 5/6 3.5 (1.0-11.8)
176 - Clergy 3/14 1.1 (0.3-3.9)
185 - Designers 3/8 1.4 (0.4-5.5)
217 - Drafting occupations 3/4 3.8 (0.8-17.2)
243 - Supervisors and proprietors, sales occupations 22/97 1.1 (0.7-1.8)
253 - Insurance sales occupations 5/11 1.8 (0.8-5.3)
254 - Real estate occupations 3/9 1.3 (0.3-4.8)
259 - Sales representatives, mining, manufacturing, wholesale 7/16 1.7 (0.7-4.2)
263 - Sales workers, motor vehicles and boats 4/9 2.2 (0.7-7.0)
274 - Sales workers, other commodities 8/59 0.7 (0.3-1.4)
313 - Secretaries 14/73 1.0 (0.5-1.7)
337 - Bookkeepers, accounting, and auditing clerks 8/30 1.3 (0.6-2.9)
379 - General office clerks 10/30 1.7 (0.8-3.4)
407 - Private household cleaners and servants 9/39 1.7 (0.8-3.8)
417 - Firefighting occupations 3/7 2.1 (0.5-8.1)
435 - Walters and waitresses 4/22 1.1 (0.4-3.4)
436 - Cooks, except short order 5/30 1.1 (0.4-2.8)
444 - Miscellaneous food preparation occupations 4/9 3.2 (0.9-10.7)
447 - Nursing aides, orderlies, and attendants 3/39 0.5 (0.1-1.6)
449 - Maids and housemen 3/7 2.8 (0.7-11.0)
453 - Janitors and cleaners 5/50 0.7(0.3-1.7)
458 - Hairdressers and cosmetologists 6/8 3.7 (1.3-10.7)
473 - Farmers, except horticultural 14/87 1.2 (0.6-2.3)
518 - Industrial machinery repairers 3/3 5.2 (1.0-26.1)
529 - Telephone installers and repairers 3/2 7.2 (1.2-43.4)
558 - Supervisors, n.e.c. 3/17 0.9 (0.2-2.9)
563 - Bnckmasons and stonemasons 3/4 5.0(1.1-22.7)
567 - Carpenters 4/41 0.6 (0.2-1.7)
575 - Electricians 4/15 1.3 (0.4-4.0)
633 - Supervisors, production occupations 10/40 1.2 (0.6-2.5)
637 - Machinists 6/22 1.3 (0.5-3.3)
653 - Sheet metal workers 3/4 3.8 (0.8-17.2)
686 - Butchers 4/3 6.8 (1.5-30.1)
744 - Textile sewing machine operators 5/28 1.2 (0.4-3.1)
757 - Separating, filtering &, clarifying machine operators 3/2 7.2 (1.2-43.4)
779 - Machine operators, not specified 10/25 2.0 (0.9-4.2)
783 - Welders and cutters 3/20 0.9 (0.3-3.2)
785 - Assemblers 9/31 1.9 (0.9-4.2)
804 - Truck drivers, heavy 7/62 0.7(0.3-1.5)
844 - Operating engineers 3/7 2.1 (0.5-8.1)
877 - Stock handlers and baggers 3/8 2.0 (0.5-7.6)
889 - Laborers except construction 16/93 1.3 (0.7-2.5)
905 - Military 10/23 2.2 (1.0-4.6)

Table 3 - continued

Census/Code Cases/Controls OR (95% C.I.)

Industries

010 - Agricultural production, crops 12/73 1.2 (0.6-2.4)
O11 - Agricultural production, livestock 3/17 1.2 (0.3-4.2)
060 - Construction 26/179 0.8 (0.5-1.2)
100 - Meat products 3/4 3.8 (0.8-17.3)
142 - Yarn, thread and fabric mills 10/49 1.2 (0.6-2.4)
151 - Apparel and accessories, except knit 3/23 0.8 (0.2-2.6)
160 - Pulp, paper, and paperboard mills 4/12 1.7 (0.5-5.3)
172 - Printing and publishing, except newspapers 4/20 0.9 (0.3-2.8)
181 - Drugs manufacturing 3/5 3.0 (0.7-12.7)
192 - Industrial and miscellaneous chemicals 3/14 1.1 (0.3-3.9)
200 - Petroleum refining 3/11 1.2 (0.3-4.6)
270 - Blast furnaces, steelworks, rolling, and finishing 9/27 1.7 (0.8-3.7)
280 - Other primary metal industries 3/6 2.6 (0.6-10.3)
320 - Metal working machinery manufacturing 3/4 3.6 (0.8-16.4)
331 - Machinery except electrical, n.e.c. 5/20 1.1 (0.4-3.0)
342 - Electrical machinery, equipment and supplies 4/24 0.8 (0.3-2.4)
351 - Motor vehicles and motor vehicle equipment 13/43 1.7(0.9-3.1)
352 - Aircrafts and parts 6/16 1.8 (0.7-4.5)
371 - Scientific and controlling instruments 3/7 1.9 (0.5-7.5)
390 - Toys amusement, and sporting goods 3/1 18.3 (1.9-177)
392 - Not specified manufacturing industries 11/57 1.1 (0.6-2.1)
400 - Railroads 4/31 0.6 (0.2-1.8)
410 - Trucking service 9/51 1.0 (0.5-2.0)
441 - Telephone (wire and radio) 10/17 2.7 (1.2-5.9)
552 - Wholesale trade of petroleum products 3/4 3.8 (0.8-17.1)
601 - Grocery stores 4/33 0.6 (0.2-1.8)
612 - Motor vehicle dealers 9/25 1.8 (0.8-3.9)
620 - Auto and home supply stores 3/5 2.9 (0.7-12.1)
621 - Gasoline service stations 6/12 2.8 (1.0-7.4)
630 - Apparel and accessories stores, except shoe 4/17 1.1 (0.4-3.3)
641 - Eating and drinking places 13/70 1.0(0.5-1.8)
682 - Miscellaneous retail stores 3/13 1.1 (0.3-3.9)
691 - Not specified retail trade 3/25 0.6 (0.2-1.9)
700 - Banking 6/14 1.7 (0.7-4.6)
710 - Security, commodity brokerage, & invest, companies 3/4 3.5 (0.8-15.8)
711 - Insurance 17/29 2.6 (1.4-4.7)
712 - Real estate 9/30 1.3 (0.6-2.7)
742 - Business services, n.e.c. 3/18 0.8 (0.2-2.6)
751 - Automotive repair shops 4/18 1.3 (0.4-3.9)
760 - Miscellaneous repair services 3/15 1.1 (0.3-3.7)
761 - Private households 9/46 1.4 (0.7-3.1)
772 - Beauty shops 6/10 3.0(1.1-8.3)

812 - Offices of physicians 5/4 4.6 (1.2-17.6)
831 - Hospitals 22/95 1.0(0.6-1.7)
832 - Nursing and personal care facilities 3/21 0.8 (0.2-2.6)
840 - Health services, n.e.c. 3/13 1.1 (0.3-3.8)
842 - Elementary and secondary schools 34/128 1.2(0.8-1,8)
880 - Religious organizations 3/23 0.7 (0.2-2.3)
890 - Accounting, auditing, and bookkeeping services 4/9 1.9 (0.6-6.1)
901 - General government, not elsewhere classified 6/37 0.8 (0.3-1.8)
910 - Justice, public order, and safety 8/34 1.1 (0.5-2.5)
921 - Public finance, taxation, and monetary policy 4/3 5.5 (1.2-24.8)
931 - Administration and economic programs 3/10 1.4(0.4-5.0)
942 - Armed Forces 10/22 2.3 (1.1-4.9)

Note: N.e.c. = not elsewhere classified

REFERENCES

1.AYLIN P, BUNTING J, DE STAVOLA B, COLEMAN
MP: Mortality from dementia in occupations at risk
of exposure to bovine spongiform encephalopathy:
analysis of death registrations. Br Med J 1999; 318:
1044-1045

2. BILLETTE DE VILLEMEUR T, DESLYS JP, PRADEL A, et
al: Creutzfeldt-Jakob disease from contaminated growth
hormone extracts in France. Neurology 1996; 47: 690-
695

3. BROWN P: Environmental causes of human spongiform
encephalopathy. In Baker H, Ridley RM (eds): Methods
in Molecular Medicine: firion diseases. Totawa (NJ): Hu-
mana Press Inc, 1996:139-154

4. BROWN P, CATHALA F, GAJDUSEK DC: Creutzfeldt-
Jakob disease in France: III. Epidemiological study of
170 patients dving during the decade 1968-1977. Ann
Neurol 1979;6:438-446

5. BRUTON CJ, BRUTON RK, GENTLEMAN SM, ROBERTS
GW: Diagnosis and incidence of prion (Creutzfeldt-
Jakob) disease: a retrospective archival survey with im-
plications for future research. Neurodegeneration 1995;
4: 357-368

6. BUREAU OF THE CENSUS: Alphabetical Index of Indus-
tries and Occupations. Washington (DC): US Depart-
ment of Commerce, PHC80R3,1982

7. BURNETT CA, MAURER J, DOSEMECI M: Mortality by
occupation, industry, and cause of death. 24 reporting states,
1984-1988. Cincinnati (OH): US Department of
Health and Human Services, Centers for Disease Con-
trol, National Institute for Occupation Safety and
Health, 1997 (DHHS - NIOSH publication No 97-
114)

8.CAPERNA A, TANZILLI P, CANNAS M, VINCI P:

Creutzfeldt-Jakob disease e rischio occupazionale. Folia
Medica 2000; 71:177-185

9. COLLINS S, LAW MG, FLETCHER A, et al: Surgical
treatment and risk of sporadic Creutzfeldt-Jakob dis-
ease: a case-control study. Lancet 1999; 353: 693-697

10. COUSENS SN, ZEIDLER M, ESMONDE TF, et al: Spo-
radic Creutzfeldt-Jakob disease in the United King-
dom: analysis of epidemiological surveillance data for
1970-96. BMJ 1997; 315:389-395

11. DAVANIPOUR Z, ALTER M, SOBEL E, et al: Transmissi-
ble virus dementia: evaluation of a zoonotic hypothesis.
Neuroepidemiology 1986; 5: 194-206

12. DAVANIPOUR Z, SMOAK C, BOHR T, et al: Death cer-
tificates: an efficient source for ascertainment of
Creutzfeldt-Jakob disease. Neuroepidemiology 1995;
14:1-6

13. DOSEMECI M, HAYES RB, VETTER R, et al: Occupa-
tional physical activity, socioeconomic status, and risks
of 15 cancer sites in Turkey. Cancer Causes Control
1993;4: 313-321

14. ESMONDE T, LUECK CJD, SYMON L, et al: Creutzfeldt-
Jakob disease and lyophilised dura mater grafts: report
of two cases. J Neurol Neurosurg Psychiat 1994; 56:
999-1000

15. FAGIH B, EISENBERG MJ: Reuse of angioplasty
catheters and risk of Creutzfeldt-Jakob disease. Am
HeartJ 1999; 137:1173-1178

16. GAJDUSEK DC: Infectious amyloids: subacute spongi-
form encephalopathies as transmissible cerebral amyloi-
doses. In Fields BN, Knipe D, Howley PM, et al (eds):
Virology, 3rd ed. Philadelphia (PA): Lippincott-Raven,
1996:2851-2900

17. GORE SM: More than happenstance: Creutzfeldt-
Jakob disease in farmers and young adults. Br Med J
1995; J.U:1416-1418

18. GREEN L: Manual for scoring socioeconomic status for
research on health behavior. Public Health Rep 1970;
85: 815-827

19. HOFMAN A, WIENTJENS PWM: Epidemiological evi-
dence concerning possible causal link. Br Med J 1995;
311:1418-1419

20. HOLMAN RC, KHAN AS, BELAY ED, SCHONBERGER
LB: Creutzfeldt-Jakob disease in the United States,
1979-1994: Using national mortality data to assess the
possible occurrence of variant cases. Emerg Infect Dis
1996:2:333-337

21.LANG CJ, HECKMANN JG, NEUNDORFER B:
Creutzfeldt-Jakob disease via dural and corneal trans-
plants. J Neurol Sd 1998; 160:128-139

22. LASK.E C, GEFELLER 0, PFAHLBERG A, et al: The ef-
fect of stress on the onset and progression of
Creutzfeldt-Jakob disease: results of a German pilot
case-control study. EurJ Epidemiol 1999; 15: 631-635

23. MASTERS CL, HARRIS JO, GAJDUSEK DC, et al:
Creutzfeldt-Jakob disease: patterns of worldwide occur-
rence and the significance of familial and sporadic clus-
tering. Ann Neurol 1979; 5:177-188

24. MASULLO C, POCCHIARI M, NERI G, et al. A retro-
spective study of Creutzfeldt-Jakob disease in Italy
(1972-1986). EurJ Epidemiol 1988; 4: 482-487

25. MITROVA E, BELAY G: Creutzfeldt-Jakob disease in
health professionals in Slovakia. Eur J Epidemiol 2000;
16: 353-355

26. NAKAMURA Y, ASO E, YANAGAWA H: Relative risk of
Creutzfeldt-Jakob disease with cadaveric dura trans-
plantation in Japan. Neurology 1999; 53:218-220

27. NAKAMURA Y, OKI I, TANIHARA S, et al: A case-con-
trol study of Creutzfeldt-Jakob disease in Japan: trans-
plantation of cadaveric dura mater was a risk factor. J
Epidemiol 2000; 10: 399-402

28. PLAITAKIS A, VISKADOURAKI AK, TZAGOURNISSAKIS
M, et al: Increased incidence of sporadic Creutzfeldt-
Jakob disease on the island of Crete associated with a
high rate of PRNP 129-methionine homozygosity in
the local population. Ann Neurol 2001; 50:227-233

29. PRICHARD J, THADANI V, KA.LE R, et al: Rapidly pro-
gressive dementia in a patient who received a cadaveric
dura mater graft. MMWR Morb Mortal Wkly Rep
1987; 36:49-50

30. PRUSINER SB: Novel proteinaceous infectious particles
cause scrapie. Science 1996; 216:136-144

31. PRUSINER SB: Prions. In Fields BN, Knipe DM, How-
ley PM, et al (eds): Virology, 3-' ed. Philadelphia (PA):
Lippincott-Raven, 1996: 2901-2950

32. PRUSINER SB, HSIAO KH: Human prion diseases. Ann
Neurol 1994; 35: 385-395

33-RICKETTS MN, CASHMAN NR, STRATTON EE,
ElSAADANY S: Is Creutzfeldt-Jakob disease transmitted
in blood? Emerg Infect Dis 1997; 3:155-163

34. RUTALA WA, WEBER DJ: Creutzfeldt-Jakob disease:

CJD AND OCCUPATION

363

recommendations for disinfection and sterilization.
Clin Infect Dis 2001; 32:1348-1356

35. SMITH PEM, ZEIDLER M, IRONSIDE JW, et al:
Creutzfeldt-Jakob disease in a dairy farmer. Lancet
1995;346: 898

36.TAYLOR DM: The effect of formic acid on BSE and
scrapie infecrivity in fixed and unfixed brain tissue. Vet
Microbiol 1997; 58:167-174

37. THE EUROCJD GROUP: Genetic epidemiology of
Creutzfeldt-Jakob disease in Europe. Rev Neurol 2001;
157: 633-637

38. THE NATIONAL CJD SURVEILLANCE UNIT:
Creutzfeldt-Jakob Disease surveillance in the UK. Sixth
Annual Report 1997. London (UK): Department of In-
fectious and Tropical Disease, London School of Hy-
giene and tropical Medicine, 1997

39. THE NATIONAL CJD SURVEILLANCE UNIT:
Creutzfeldt-Jakob Disease surveillance in the U.K. Tenth
Annual Report 2001. London (UK): Department of In-
fectious and Tropical Disease, London School of Hy-
giene and tropical Medicine, 2001

40. TYLER KL: Risk of human exposure to bovine spongi-
form encephalopathy. Br MedJ 1995; 311:1420-1421

41. VAMVAKAS EC: Risk of transmission of Creutzfeldt-
Jakob disease by transfusion of blood, plasma, and plas-
ma derivatives. J Clin Apheresis 1999; 14:135-143

42. VAN DUIJN CM, DELASNERIE-LAUPETRE N, MASULLO
C, et al: Case-control study of risk factors of
Creutzfeldt-Jakob disease in Europe during 1993-95.
European Union (EU) Collaborative Study Group of
Creutzfeldt-Jakob disease (CJD). Lancet 1998; 351:
1081-1085

43. WARD HJ, EVERINGTON D, CROES EA, et al: Sporadic
Creutzfeldt-Jakob disease and surgery; a case-control
study using community controls. Neurology 2002; 59:
543-548

44. WEIS J, KRETZSCHMAR HA, WINDL 0, et al: Fatal
spongiform encephalopathy in a patient who had han-
dled animal feed. Lancet 1996; 348:1240

45. WIENTJENS DPWM, DAVANIPOUR Z, HOFMAN A, et
al: Risk factors for Creutzfeldt-Jakob disease: a reanaly-
sis of case-control studies. Neurology 1996; 46: 1287-
1291

46. WILL RG, IRONSIDE JW, ZEIDLER M, et al: A new
variant of Creutzfeldt-Jakob disease in the UK. Lancet
1996;347: 921-925

47. WORLD HEALTH ORGANIZATION CONSULTATION
GROUP: Public health issues and clinical and neurologi-
cal characteristics of the new variant of Creutzfeldt-
Jakob disease and other human and animal transmissi-
ble spongiform encephalopathies: memorandum from
two WHO meetings. Bull World Health Organ 1996;
74: 453-463

48. YOUNG GR, FLETCHER NA, ZEIDLER M, et al:
Creutzfeldt-Jakob disease in a beef farmer. Lancet
1996; 348: 610-611

49. ZERR I, BRANDEL JP, MASULLO C, et al: European sur-
veillance on Creutzfeldt-Jakob disease: a case-control
study for medical risk factors. J Clin Epidemiol 2000;
53: 747-754

=============

Re: Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States [FULL TEXT] - TSS 9/10/03
(0)

http://www.vegsource.com/talk/madcow/messages/1072.html

TSS

• Re: Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States [FULL TEXT] - TSS 9/10/03

Follow Ups:

• Re: Occupational risk factors for the sporadic form of Creutzfeldt-Jakob disease (FULL TEXT) TSS 11/30/03 (0)

Post a Followup