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From: Terry S. Singeltary Sr. (216-119-136-100.ipset16.wt.net)
Subject: Natural Rubber, Latex Gloves, Condoms and TSEs aka MAD COW DISEASE
Date: November 6, 2003 at 11:12 am PST
-------- Original Message --------
Subject: Natural Rubber, Latex Gloves, Condoms and TSEs aka MAD COW DISEASE
Date: Thu, 6 Nov 2003 11:13:44 -0600
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy
To: BSE-L@uni-karlsruhe.de######## Bovine Spongiform Encephalopathy ######### OPINION OF THE SCIENTIFIC COMMITTEE ON MEDICINAL PRODUCTS AND
MEDICAL DEVICES ON
“THE PROTECTION OFFERED BY NATURAL RUBBER LATEX MEDICAL DEVICES (MEDICAL
GLOVES
AND CONDOMS) AGAINST TRANSMISSIBLE DISEASES”
Adopted by the SCMPMD during the 24th plenary meeting
of 16 October 2003 snip... 1. Introduction to the problem
The changing characteristics of the risk of infection by blood borne
pathogens with respect to clinical
procedures has resulted in a number of discussions about the
effectiveness of protective equipment and
materials, including natural rubber latex products such as medical
gloves, designed to have this barrier
function (Anonymous 1987, CDC 1988, Fay and Dooher1992, Fay 1996, FDA
1999, Gerberding et al
1995, Rabussay and Korniewicz 1997, Stringer et al 2001). In addition,
the low quality of some surgical
and examination gloves, considering the importance of the barrier
effectiveness, has been a concern in
the past (Fay and Dooher 1992). This was particularly so in the 1980’s
when the increased use of
gloves placed an increased demand on industry, resulting in some low
quality gloves on the market (Fay
and Dooher1992). The perception of additional risks of infectivity with
respect to the Transmissible
Spongiform Encephalopathies (TSE) such as Bovine Spongiform
Encephalopathy (BSE) and variant
Creutzfeld-Jacob-Disease (vCJD) have also raised the level of concern.
In addition, a series of
alternative materials have been made available to clinicians, arising
from the apparent increased levels
of allergies to latex products. Similar concerns exist for these
alternatives, leading to a greater degree of
uncertainty over barrier effectiveness from one product to another. snip... 2. Mandate
The SCMPMD is asked to make a general review of the protection offered
by natural rubber latex
medical devices such as condoms, diaphragms and surgical gloves against
blood borne diseases with
particular reference to TSE agents and HIV. snip... 5. Background information on TSE
The TSEs are a group of diseases which affect the brain. After a
prolonged asymptomatic phase,
clinical signs of neurological dysfunction develop and death inevitably
ensues. TSEs are found as
scrapie in sheep and goats, BSE in cattle and Chronic Wasting Disease
(CWD) in three American
species of deer. In humans the disease occurs sporadically as sporadic
Creutzfeldt-Jakob Disease
(sCJD), or in families as familial CJD (fCJD), Gerstmann Straussler
Disease etc., and iatrogenically.
Variant CJD (vCJD) is thought to be the human version of BSE. Although
the primary cause of the
diseases remains controversial, a transmissible agent can almost always
be detected, even in those
cases of apparent genetic or sporadic causality. A series of reviews are
available in a recent issue of the
British Medical Bulletin (Br Med Bull, 2003).
The epidemiology of TSEs varies widely. Both scrapie and CWD transmit
naturally from animal to
animal. In sheep there is a wide range of genetic susceptibility to
infection, controlled primarily by the
gene that encodes the protein PrP. The mechanisms of transmission are
not known. By contrast, BSE
does not spread horizontally from animal to animal directly but seems to
have been caused by
consumption of contaminated feed. Natural mechanisms of transmissions in
humans are not known.
However, iatrogenic infection has occurred through transplantation of
infected tissue (e.g. corneas and
dura mater), through an electrode implanted in the brain (Bernoulli et
al 1977) and through
contaminated hormonal preparations (Brown et al 2000a). There are major
concerns about the
possibility of transmission by surgical instruments after their use on
known or suspect CJD cases, since
these instruments may become contaminated. Normal cleaning and
sterilisation processes do not
completely eliminate or inactivate TSE agents (Taylor 1991, 2002).
Infection has probably also occurred
through ingestion of BSE in the case of vCJD.
In humans there are major concerns about potential iatrogenic
transmission of human TSEs, including
sporadic CJD, familial forms of CJD, variant CJD and iatrogenic CJD. In
all forms of TSE, neural tissue
contains high levels of infectivity late in the disease. In some types
of TSE disease other tissues,
primarily but not exclusively lymphoid tissue, can have high levels of
infectivity, sometimes at an early
stage after infection (Brown et al 2000b). However, this is not true for
all TSEs, e.g. sCJD has little
peripheral involvement. There are very low levels of infectivity in
blood in some TSE diseases (Brown,
2003). Nevertheless there are concerns about potential TSE transmissions
from blood and blood
products.
Distribution of TSE infectivity through organs of the body is dependent
on host, TSE agent, route of
infection and elapsed time since infection occurred. In TSE models where
TSE infectivity is widely
distributed, low levels of TSE infectivity have been detected in blood.
It is possible that cerebral spinal
fluid, lymph and saliva also contain low levels of TSE infectivity since
their associated organs can
6
contain significant levels of infectivity. There is no evidence of TSE
infectivity in milk although it has
been difficult to assay sufficiently large volumes of milk directly.
Epidemiological studies suggest that
transmission via milk is unlikely. There is no direct evidence of TSE
infectivity in urine.
The structure of the causal agents of TSE diseases remains to be
resolved. TSE agents, however, are
small in comparison to viruses. They are highly resistant to all known
methods of sterilisation. It is
thought that a host protein PrP in an abnormal conformation is a
component of these agents, but
whether it is the sole component remains to be determined (Somerville 2002).
6. Barrier effectiveness of gloves
6.1 General principles. snip... 6.5 Passage of TSE infectivity through latex gloves
There is no information about the transmission of TSE infectivity
through latex gloves. Theoretically
transmission through latex depends on size and properties of the agent.
Most experimental estimates of
TSE agent particle size, made from filtration experiments, are > 15 nm,
though smaller sizes cannot be
ruled out. Some theoretical considerations suggest a much smaller size.
For example the prion
hypothesis suggests that monomeric or oligomeric PrP (MW 25,000 to
33,000) may be infectious.
However, there is little experimental evidence to support such a small
value for infectious particles.
10
TSE agents are poorly soluble and adhere tenaciously to surfaces. Such
properties may affect the
ability of the TSE infectivity to pass through latex. Detergents, which
are widely used in TSE research,
may affect the permeability of latex to TSE infectivity. Other areas
where latex gloves may be used
where there is a possibility of exposure to TSE infection include
operating theatres and surgical
instrument washing and sterilisation units, where detergents are also
used, often in alkaline solutions.
There are no reports of experiments testing the transmissibility of TSE
infection through condoms.
However there is no evidence of TSE transmission via sexual intercourse
so this question may not be of
material concern. Vertical/maternal transmission occurs in some types of
TSE disease, notably scrapie
in sheep, but transmission is thought to occur later, probably perinatally. snip... 7. Risk assessment including populations at risk
The risk of health care workers for blood borne exposure and infection
is highest in operating room
settings, the most likely means of transmission being percutaneous
injuries (Fay and Dooher 1992,
Stringer et al 2001, Wright et al 1991). Prevention is mainly provided
by the use of the so-called
universal precautions (CDC 1988). Glove use should reduce the incidence
of contamination of hands,
but they cannot prevent penetrating injuries due to needle or other
sharp instruments. It should be noted
that there is an increase in glove leakage during surgical and dental
procedures (Albin et al 1992,
Douglas et al 1997, Driever et al 2001, Fay and Dooher 1992, Fiehn and
Westergaard 1989, Korniewicz
et al 1990, Kotilainen et al 1989, Rego and Roley 1999). For example
Driever et al (2001) found during
an examination of 953 gloves worn during cardiac surgery, 26% of those
worn by the operator were
punctured, as were 38 % of those worn by the theatre nurses. Limiting
the time of the surgical
procedure reduces glove barrier failure, as glove failure increases in
time (Fay and Dooher 1992,
Gerberding et al 1990, Quebbeman et al 1991).
The use of the double glove method in surgery gives an additional level
of protection against blood
borne infections and greatly reduces the risk of glove penetration, as
discussed by Gerberding et al
(1990) and Quebbeman et al (1992) a number of years ago. Recently there
have been a number of
studies published that strongly support and advocate the use of double
gloving as the major risk
management factor in the control of the transmission of disease in a
clinical setting. In gynaecological
surgery, Murta et al (2003) found that 10.4 % of single gloves
perforated during use, as did 9.8 % of the
outer double gloves whereas there was no perforation of any inner double
glove. In general surgery
Laine and Aarnio (2001) found a 6.2 % incidence of puncture of the inner
of a double glove compared to
an overall 18.3% of total operations resulting in perforation. In open
lung surgery, Hollaus et al (1999)
reported a 78 % incidence of perforation of gloves, but the inner glove
only perforated in 1.1%, double
gloving effectively protecting against cutaneous blood contact. It is
recognised that double gloving may
not always bring benefits (Avery et al 1999), that many surgeons are not
in favour of it (St Germaine et
al, 2003) and that care has to be taken not to reduce manual dexterity
and increase discomfort (Alrawi
et al, 2002), but a recent major systematic review of the evidence
(Tanner and Parkinson 2002) makes
it very clear that wearing two pairs of latex gloves significantly
reduces the number of perforations of the
glove in contact with the skin and reduces the risk of surgical cross
infection.
Although the risk for infection with TSE is largely unknown, certain
assumptions for the possibility of
infection can be established. The United Kingdom (UK) is at this moment
the only country with a major
infected population. Up to August 2003, 133 people have died of definite
or probable vCJD in the UK,
the total number of patients diagnosed being 137. In France 6 people
were diagnosed with vCJD, while
in some other countries only single cases were noted so far. A major
difficulty here is that people may
be infected and unknowingly be in the incubation phase of the disease at
the time of a clinical
procedure, this phase possibly lasting several years. This necessitates
rather severe prophylactic
measures. The route of infection is not known, but could be ingestion of
BSE contaminated food.
11
Health care workers are one of the populations at risk, of which those
working in the operating theatre
(surgeons, nurses) have the highest risk, especially when surgery on the
brain is performed.
Considering the rather limited number of patients with TSE, and the
professional measures which can
be used to avoid contamination/infection, the actual risk to anyone is
very limited. For those patients
with a known TSE infection (CJD, vCJD) proper measures can be instigated
to protect the health care
workers. The use of natural rubber latex medical gloves is one of them.
In view of the limited number of humans infected with vCJD, the general
risk for health care workers for
infection with vCJD even in the UK is marginal at most. As stated for
specific cases, specific measures
can be instigated to reduce the risk of infection. The risk for
infection with vCJD (or BSE) by food
consumption is unknown, and is largely reduced by various EU
regulations, but is probably higher than
the risk introduced by patient contact.
For viral infections (HIV, Hepatitis) the situation is quite different.
The risk especially for health care
workers for infection with a viral infection can be rather high.
However, this risk can be reduced to
almost zero by proper preventive measures such as using protective
clothing and natural rubber latex
medical or examination gloves.
An overview of the estimated risks for transmission of infectious agents
through natural rubber latex
medical devices i.e. gloves and condoms, along with risk management
procedures is presented in Table
2.
8. Conclusions/recommendations
For TSE it is unknown whether the agents can pass through an intact
latex membrane. The estimated
size of these agents lies below that of viral simulants which cannot
pass the latex membranes, so,
theoretically, TSE passage cannot be excluded. However, in view of the
known physical and chemical
characteristics of TSE agents and natural rubber latex, it seems
unlikely that TSE can actually pass
through intact latex. This is probably also true for alternative
materials. So far, no infections with TSE in
health care settings could be attributed to the barrier failure of latex
medical gloves. Moreover, the
population at risk for TSE infection in health care settings is very
low, even in the UK. For condoms
there is no indication of risk for TSE infection as there are no
indications for sexual transmission of
TSE’s.
Both natural rubber latex medical gloves and condoms offer good
protection against transmission of
viral infections including HIV. However, the protection may diminish
during use, especially when the
glove material is aged or damaged. By far the greatest risk for
transmission of infectious agents, is
encountered when a glove is torn or punctured during a medical
procedure. In order to prevent this,
more detailed instructions on use of latex medical gloves would be
warranted in terms of factors such as
the duration of use and the use of double gloves. It should be
emphasized that medical gloves and
condoms are single use devices.
It is known that some chemicals can penetrate natural rubber latex and
affect the physical properties of
the product. It is, however, unknown as to whether this process can
influence transmission of infectious
agents, either positively or negatively.
In general, in terms of leakage properties, no alternative material has
been found to be superior to
natural rubber latex.
9. References snip... http://europa.eu.int/comm/food/fs/sc/scmp/out48_en.pdf TSS ########### http://mailhost.rz.uni-karlsruhe.de/warc/bse-l.html ############
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