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Fieldwork Safety
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This is the Mandatory Operational Code of Practice for
Field Safety produced by the Field Studies Council.
FSC OPERATIONAL CODES OF PRACTICE
No. 1 : FIELD SAFETY
Appendix 2 : Leptospirosis
1. Causes and Infection Route of Disease
- The disease is caused by the bacteria Leptospira. Various species
/ strains [known as serovars] of the bacteria are carried by mammals
with each serovar tending to be associated with particular species
of mammalian or maintenance host. This point is important only in
that the severity of the disease in humans depends upon the particular
bacterial serovar involved.
- The bacteria are found in the urine of their maintenance host. The
infection pathway to humans is by direct contact with the infected
urine or by contact with materials or objects which have been contaminated
by infected urine. The bacteria do not survive for long in dry conditions
but will remain alive [ie infective] for some considerable period
in moist or wet conditions. This is important in that, whilst water
bodies [streams, ponds, etc. containing infected urine] are generally
recognised as potential 'secondary sources of infection', the disease
may also be contracted through handling or touching such items as
farmyard manure' or even farm buildings and implements which have
remained moist because of rainfall.
- The bacteria require moisture to survive outside their host and
can live for four weeks in fresh water and six months in urine-saturated
soil. The latter has obvious implications in relation to farmyard
visits. Comment has been made in relation to infected material being
washed from rat holes, following heavy rainfall, and entering waterbodies.
The survival of the bacteria in fresh water is, therefore, important
when the waterbody involved is stagnant or slow moving because the
bacteria may be retained in the waterbody for some considerable time
and may still be infective. In a waterbody which has a reasonable
discharge rate [under normal conditions], the risk of infection [from
flushed out bacterial is lessened because they will be carried away
from the 'entry point' by the normal flow of the stream or river.
Although killed by seawater within 24 hours, the bacteria can survive
in estuaries and the tidal reaches of rivers for longer periods because
of the reduced salinity levels.
The bacteria are readily destroyed by drying, ultraviolet radiation,
heating above 60C and exposure to disinfectants and detergents.
- The bacteria enter the human body through breaks in the skin such
as cuts, blisters and abrasions or via the lining of the nose, mouth
or alimentary tract or through the moist surfaces [conjunctiva] of
the eye.
- There are 202 serovars found world-wide, but only 16 have been isolated
in the UK.
The most commonly encountered species in the UK is Leptospira
sejroe serovar hardjo which is associated with cattle.
A vaccine is available which is effective in preventing the disease
in cattle.
Leptospira icterohaemorrhagiae also occurs and is particularly
associated with rats.
Leptospira sejroe serovar saxkoebig has been
isolated from wood mice and voles.
Leptospira canicola, previously associated with dogs,
has probably been eliminated from the UK following widespread immunisation
of dogs.
Certainly no cases of the disease caused in humans by this serovar
have been reported since 1985.
It should be noted that infected maintenance hosts usually remain
well and continue to carry active bacteria in their urine for several
years.
2. Symptoms of the disease
- The incubation period is usually between 7 - 12 days after being
infected, although it may occasionally be as short as 2 days or as
long as 30 days.
- The disease may produce no symptoms at all [so-called subclinical
infection]. In these cases, the infected person recovers fully without
ever being aware that they have been infected, unless this is revealed
by subsequent blood tests.
- If symptoms are presented, the early symptoms are similar to those
of flu and their severity [as with flu itself] can vary between individuals
:
- Fever [may last for about five days]. NB : patient will exhibit
an elevated body temperature, but may still complain of feeling cold
or shivery.
- Muscular aches and pains [particularly in leg and calf muscles].
- Loss of appetite.
- Vomiting with prostration.
- The patient's condition may deteriorate significantly
when the fever subsides and as secondary symptoms occur:
- Bruising of the skin
- Sore eyes
- Nose bleeds
- Jaundice
- Urine production reduced or ceases.
- The disease is known generally as leptospirosis. Its severest
form is caused by the bacterial serovar contracted from rats. It is
this form of the disease which is known as Weil's Disease or Sewerman's
Disease.
Other forms of leptospirosis, whilst serious and capable of causing
severe illness, are rarely fatal, a statement which must be viewed
in the context of a disease for which prognosis [successful treatment]
is very good even in the severest form of the disease [see section
4.3. of this Appendix].
3. Diagnosis and Treatment of the Disease
- The initial symptoms of the disease may be overlooked or mistaken
by the patient because of their similarity to those of flu and because
they may in any case be mild. Even if the patient consults a doctor
and particularly if the patient has a 'clean' occupation, the symptoms
may still be mistaken for those of flu and the possibility of leptospirosis
overlooked by the doctor.
- It is therefore essential that any individual who experiences any
of the initial symptoms, after any activity during which they may
have been infected and within the incubation period, must consult
a doctor and specifically tell the doctor of the possibility of a
leptospiral infection.
It is vital, in terms of the FSC's Safety Management System [see
section 5 of this Appendix], that all visitors who undertake any
activity during which they may come in contact with a source of
infection, are made aware of this position. In the case of young
persons, this specific advice must also be given in / included in
any general advice and information on the disease provided, in writing,
to group organisers and the parents / guardians of the young people.
- Diagnosis of the disease is confirmed by laboratory blood tests.
Blood samples should be sent directly to the Leptospira Reference
Unit [See section 6 of this Appendix for address] where they will
be tested within 24 hours. Testing by laboratories at a local hospital
is not advised because this may take undue time. It must however be
noted that the test will only become positive after about the 6th
day of illness and should only be used for confirming an initial clinical
diagnosis and not for the purposes of deciding whether or not to commence
treatment.
- Treatment of the disease at this stage is relatively straight forward
[using antibiotics] and effective. The bacteria are still multiplying
within the body and the treatment kills the bacteria, thus preventing
further multiplication
- Treatment, once the secondary symptoms have developed, is more complicated
and difficult. By this stage, bacterial growth has been enormous and
the dead, solid remains of the bacteria and their action on the body
can cause kidney failure [hence decline in urine production and jaundice]
and internal bleeding [hence the skin bruising]. Whilst further bacterial
multiplication can be prevented by antibiotics, it is the rectification
of the kidney failure [and its associated complications] and the internal
bleeding which presents the medical difficulties.
- There is no vaccine for humans available in the UK
4. Incidence of bacteria and of cases of leptospirosis
in the UK
- Little is known of the incidence of the bacterial pathogen in the
UK.
With regard to Weil's Disease, information suggests that in excess
of 50% of rats carry the bacteria. However somewhat alarmist reactions,
linking this incidence rate to the fact that the rat population
of the UK is increasing, must be treated with caution in terms of
implying that it will lead to an increase in leptospirosis cases
[see section 4.3. of this Appendix].
Given that other mammals, such as cattle and rodents, also harbour
their own serovars of the bacteria, it is probably true that the
bacteria is widely distributed throughout the UK- However, there
is no evidence to suggest that there are 'hot spot' areas in the
UK where the incidence of the bacteria [in their maintenance host
species] is unusually high. The risk to humans of infection is related
more to the presence and the numbers of the maintenance host in
an area. In this respect, the risk of infection may be almost site
specific. eg. the risk of contracting bovine leptospirosis is essentially
nil on an exclusively sheep farm; on the same farm, the risk of
contracting Weil's Disease as a result of working in a fast-flowing
stream in open moorland could be regarded as 'possible but highly
unlikely' because the location would not be conducive to the presence
of rats ; however, around the actual farm buildings, the risk of
Weil's Disease would be higher because that particular location
could well provide the ideal habitat [ shelter, food supply, etc.]
where rats would congregate, survive and possibly multiple.
- Care must also be taken in interpreting data on numbers and location
of actual cases of leptospirosis.
In the past, it was almost exclusively an 1 occupational disease,
eg nearly all cases of bovine leptospirosis occurred in farmworkers,
the connection between Weil's Disease and sewerworkers is equally
obvious. In recent years, there has been a decline in Weil's Disease
amongst sewage water workers because the workers are more aware
of the risk [and consequently take adequate precautions], and both
the workers and their doctors are more alert to the symptoms [resulting
in early diagnosis an treatment.]. There does not seem to have been
a similar decrease amongst farmers. Indeed, they are now the main
group at risk from leptospiral infections, accounting for 47% of
all reported cases between 1980 and 1993.
However, there has been a concurrent increase in 'non-occupational'
cases. Many of these have been amongst people indulging in 'leisure
activities' which expose them to infection, eg. cavers, canoeists,
but cases have also occurred in more unusual circumstances eg. by
drinking beer straight from bottles which have been stored in cellars
infested by rats.
Even so, when considering water related cases [recreational and
occupational exposure] the numbers of reports accounted for only
16% of cases over the period 1980 - 1993. Certainly the risks of
accidental drowning from such pursuits are much higher.
Consideration must also be taken of the fact that, where a relatively
large number of people are entering a 'risk site', there is going
to be a statistically greater chance that infection will occur even
if the actual risk is fairly low. Thus, more cases could be notified
from that site than from a site where the risk was much higher [ie
more maintenance hosts present] but which was visited / used by
fewer people.
- It must be stressed that, even allowing for some under-reporting
of mild cases, leptospirosis is a relatively uncommon disease in the
UK. Over the decade 1985 -94, there was an average of 51 cases per
year of all forms of leptospirosis confirmed in the UK. This represents
less than one case per million of population per annum. The number
of reports have, in fact, fluctuated from year to year but with no
consistent pattern. No increasing trend in incidence of the disease
has been observed over this period. In particular, there has been
no increase in L. icterohaemorrhagiae infections which have averaged
16 per year. There is no evidence, therefore, to support the view
that increasing rat populations are giving rise to an increased incidence
of leptospirosis.
In the early 1950's, deaths from leptospirosis ranged between 5
- 44 a year. Nowadays, fatal outcomes are rare - averaging 2 - 3
per year since 1980 -which is about the same risk as being killed
by lightning.
5. Safety Management System for Leptospiral Infections
- It is important that staff recognise that
- The risk of leptospiral infection, as a result of undertaking activities
normally associated with fieldwork on FSC courses, is intrinsically
low.
- The safety management techniques, recommended by the FSC, will further
reduce the risk of infection occurring.
- If an infection occurs, early diagnosis and treatment is extremely
effective.
- The safety management procedures, recommended by the FSC, will assist
in ensuring that diagnosis and treatment is achieved at an early stage
in the disease.
- Whilst not detracting from the potential seriousness of the disease,
prognosis is good and, with appropriate medical treatment, complete
recovery occurs in the majority of cases.
- It is important that staff, in advising visitors [together
with group organisers and parents, if appropriate] of the FSC's safety
management system for this disease, give appropriate emphasis to the
points outlined in section 5. 1. above- Not to do so may well cause
unnecessary alarm both to individual visitors and to other people
who may have responsibilities towards or for such visitors.
- It is recommended that the safety management system, utilised by
Units, should consist of three elements :
- Advice and information given to visitors [and other appropriate
people] in order to raise their awareness of
- The disease and the risks of infection,
- The safety techniques which will be utilised to reduce the risk
infection.
- The symptoms of the disease so as to ensure early treatment.
With regard to advice and information provided to the visitors themselves,
it is recommended that this is done immediately prior to the undertaking
of a fieldwork activity which may involve the risk of infection. It
is recommended that the normal procedure of alerting visitors to potential
hazards during the activity briefing session and on arrival at the
fieldwork site itself is a suitable opportunity [see FSC MP No. 1,
section 4.4.].
With regard to advice and information provided to other appropriate
people [such as group organisers and, in the case of young people,
parents or guardians], it is recommended that this is done
- For group organisers, prior to the course as part of the more
general information issued.
- For people, at the time of the course and only then if they have
actually undertaken an activity in which they may have been exposed
a risk of infection.
It is recommended that such advice and information is in the form
of an open letter or information sheet whose content and style would
indicate that its distribution is a routine part of a Units normal
procedure of course information provision. In this way, the function
of 'raising awareness without causing alarm' may be more easily achieved.
Exemplars of such letters are given in section 7 below.
- An assessment and evaluation of every fieldwork site,
prior to any fieldwork activity being undertaken at a site, in which
a major consideration is the actual occurrence of maintenance hosts
or the potential for their occurrence [see section 4. 1. above for
explanation].
On the basis of this assessment and evaluation, recommendations
should be made as to the use of a site for particular fieldwork
activities.
The UM is responsible for:
- Ensuring that such assessments and evaluations are undertaken
by appropriate staff.
- Making recommendations as to the use of a site.
- Ensuring that appropriate records are kept of the assessments
and evaluations, together with the UM's recommendations for site
usage.
- Ensuring that such records are available to and utilised by appropriate
staff
- Ensuring that sites are reassessed and evaluated as appropriate
and necessary.
It is accepted that the possibility of increased infection risk does
not preclude a site from use for fieldwork activities, eg. studies
of the agriculture in an area may include an actual visit to a farm,
including its buildings, provided that appropriate safety management
techniques are implemented.
However [regardless of the safety management techniques used] it
could be considered irresponsible to carry out fluvial studies on
a small slow-moving stream, which derived directly from a farmyard
and when rats had been seen around the farm buildings and in the streamway,
merely because the stream was near to the Unit and there was easy
access to it.
- Practical safety management techniques implemented during
or as part of a fieldwork activity in order to reduce the risk of
infection. By way of example, recommendations 1 comments for three
typical 'fieldwork activities' are now given:
- Small Mammal Studies
The risk of infection would be classified as 'high' given the
possibility of direct contact with infected urine and infection
through existing cuts or cuts arising as a result of an animal
biting the person handling them. Limiting the handling of animals
to 'by staff only' may not be practical [eg. in studies where
large numbers of traps are being used and / or traps are being
examined frequently] nor educationally desirable [eg. students
frequently have a natural enthusiasm / wish to handle the animals
and the studies also provide an ideal opportunity for students
to practice the 'best handling techniques' in terms of animal
welfare].
Strict adherence to the wearing of suitable rubber gloves will
eliminate the risk of infection through existing cuts and will
do much to prevent cuts occurring if an animal attempts to bite.
If an animal's bite does result in a cut [even through gloves],
strict adherence to a procedure of the incident being reported
to FSC staff and automatic subsequent consultation of the Unit's
doctor will ensure that, if appropriate, diagnosis and treatment
is ensured at the earliest possible stage.
Strict adherence to the wearing of gloves should also be followed
when:
- Examining traps for possible 'successful catches` because contact
may be made with the inner surface of the trap or with bedding
material in the trap, both of which represent potential infection
sources.
- Cleaning / washing traps at the end of an activity.
- Disposing of soiled bedding material taken from traps or from
plastic bags which have been used to examine animals [by opening
/ emptying traps into the bags].
All soiled bedding and used plastic bags should be subjected to
appropriate 'final disposal' [in sealed refuse sacks] so as to eliminate
the risk of them being mistaken for 'fresh' [ie. uninfected] items
and reused without adequate safety precautions being taken.
Gloves have to be removed. This provides the opportunity to demonstrate
and practice techniques of removing gloves in a manner which will
reduce contact with potentially contaminated outer surfaces of the
gloves. Strict adherence to these techniques and to the washing
of hands after the gloves have been removed will further reduce
the possibility of infection.
It is not necessary to be constantly issuing new gloves provided
that gloves are disinfected and allowed to dry after use and before
they are used again. It is to be recommended that FSC staff 'actually
carry out this procedure [in order to ensure that it is done properly
and safely] and that they also ensure that 'being cleaned' gloves
are kept separate from 'cleaned and dried' gloves, preferably in
a location to which students do not have ready access.
Food must not be eaten whilst actually emptying traps or handling
any animals. All the people so involved must be advised to wash
or clean their hands thoroughly before eating any food. [Whilst
there is nothing better than copious supplies of soap and hotwater,
this may not be a practical possibility in relation to certain fieldwork
sites or activities. Thorough cleaning with antiseptic wipes or
gels may then be an acceptable substitute.]
- Visits to farmyards and buildings
NB : Visits to refuse tips and active quarries also present
the risk of infection because of the likely presence of rats.
Such visits present the possibility of infection leading to both
Weil's Disease and to other forms of leptospirosis. However, knowledge
of both the infection route and the maintenance hosts will suggest
measures which can be taken to reduce the risk of infection. In
general terms, such measures will involve
- Avoiding contact with areas, objects, materials, etc. which
may be contaminated with infected urine.
It is not necessary for all members of a party to be issued
with and to wear gloves. However, people with scratches, cuts
or sores on their hands must use waterproof plasters to cover
such injuries.
Some possibilities are relatively obvious eg. not touching
machinery which will almost certainly be contaminated with farmyard
effluent and animal manure ; not handling animal feed or feed
containers because of rats being attracted to such 'food sources';
not touching farm animals.
Other possibilities may not be so obvious. Rats tend to move
around an area along the junctions between walls and floors
; students crouching or sitting down against a wall may well
touch a contaminated area when standing up. In wet weather,
waterproof clothing can become contaminated and may then be
touched by the wearer.
- All food must be wrapped and no food must be eaten until a person
has thoroughly washed / cleaned their hands.
- Students must be advised to wash their hands on returning to
the Unit after the farm visit.
- Due consideration of possible infection, if contact does occur,
so as to determine subsequent actions
- Activities involving water bodies
NB : This includes visits to caves and activities on water,
such as canoeing / rafting, as well as more traditional activities
carried out by groups on biology and geography field courses
The covering of cuts, etc. on hands by plasters only is not recommended.
There is no guarantee that such plasters are 'waterproof' ie provide
an effective barrier to infection. In any case, they are frequently
and inadvertently dislodged, often without being noticed particularly
in activities such as caving. Plasters should be used by people
with cuts but the hands of all group members must be covered by
appropriate rubber gloves, thus reducing the possibility of sustaining
an injury whilst actually working in the waterbody.
Similar consideration applies to a strict insistence that suitable
footwear must be worn in order to prevent infection via existing
or new injuries to feet.
With regard to gloves and wellingtons, there is little point
in insistence on them being worn if the water depth or the activity
is such that water will get inside these items. If this is likely
to occur, the 'secondary barrier' of plasters must be used by
people with known injuries on their hands or feet. This precaution
must be further extended in cases where site assessment and evaluation
has indicated an 'increased infection risk'. In this situation,
it is recommended that individuals with known injuries to hands
or feet must not undertake any part of an activity which would
knowingly bring them in contact with the water or knowingly place
in a situation where such contact was likely.
With activities on water, there is also the added problem that
a person may become totally immersed in water, either accidentally
or deliberately [practising capsize drill], or may be subjected
to more extensive 'splashing' than would be associated with activities
such as freshwater invertebrate studies. Sites used for such activities
must be subjected to the most rigorous assessment and evaluation
process. There must be more careful consideration of the undertaking
of such activities by people with known injuries.
Further, it is recommended that all people undertaking such activities
must be advised to wash or shower after completion of the activity.
All food must be wrapped and no food must be eaten until a person
has thoroughly washed / cleaned their hands.
6. Testing for leptospirosis
If the disease is suspected by a doctor, blood samples should be
sent direct to:
The Leptospira Reference Unit
Public Health Laboratory
County Hospital
Hereford
HR1 2ER
Tel : 01432 277707
Fax : 01432 351396
7. Specimen Letters [see section 5.3.a. above]
- To the Organiser of groups
attending a course at
Unit Name
Current Date
The risk of infection with one of the waterborne diseases as a
result of attending a field course
Dear Organiser
Examination syllabuses specifically mention topics such the effects
of pollution on freshwater communities, farming practices, etc. Attending
a field course provides an ideal opportunity to study such topics
at first hand. However, such work exposes people to the perceived
risk of a bacterial infection known as Leptospirosis. [When the disease
is associated with rats, it is known as Weil's Disease or Sewerman's
Disease.]
I must say, at the outset, that I regard the risk of such an infection
as slight. [There are only some 50 cases of Leptospirosis reported
per year throughout the whole of the country ie. less than 1 case
per 1,000,000 people in the population.] If any student undertakes
work or visits a site where there could be a possibility of infection,
they will be advised of and use precautions which would in fact be
appropriate to a much more hazardous situation. Each student will
also be given a letter [copy enclosed] to take home with them.
The purpose of this letter is to advise you of this situation. You
may wish to discuss it further [when you are arranging the course
programme] with the tutor who will be taking your course, so that
you may provide suitable advice and guidance to your students and
their parents or guardians prior to the course.
Yours sincerely
UM's signature and name
- To Parents and Guardians
of students attending a course at
Unit Name
Current Date
The risk of infection with one of the waterborne diseases as a
result of attending a field course
Dear Parent or Guardian
Examination syllabuses specifically mention topics such the effects
of pollution on freshwater communities, farming practices, etc. Attending
a field course provides an ideal opportunity to study such topics
at first hand. However, such work exposes people to the perceived
risk of a bacterial infection known as Leptospirosis. [When the disease
is associated with rats, it is known as Weil's Disease or Sewerman's
Disease.]
I must say, at the outset, that I regard the risk of such an infection
as slight. [There are only some 50 cases of Leptospirosis reported
per year throughout the whole of the country ie. less than 1 case
per 1,000,000 people in the population.] If any student undertakes
work or visits a site where there could be a possibility of infection,
they are advised of and use precautions which would in fact be appropriate
to a much more hazardous situation.
This letter is part of those precautions and its purpose is to alert
you to the very faint possibility of infection and to advise you to
consult your family doctor, mentioning the possibility of Leptospirosis,
if your child develops any of the following symptoms within four weeks
of his / her return from the field course
- A feeling of having a 'flu-like.' illness
- Above normal temperature and / or a feeling of chill
- Pains in joints and muscles - calf muscle pains often being particularly
noticeable.
Treatment by antibiotics in the early stages is completely effective.
Yours sincerely
UM's signature and name
8. References
I.R. Ferguson Leptospirosis surveillance : 1990 - 1992 Communicable
Disease Report, Vol 3 Review No.3, 26 February 1993.
National Canoeing Association Weil's Disease
Downloadable from: http://web.ukonline.co.uk/nca/weils.htm
Copies to be kept in Unit's Safety Information System.
9. Acknowledgements
This appendix was written with the invaluable advice and information
provided by T J Coleman and M Palmer [Leptospira Reference Unit] and
A Wood [National Canoeing Association].
The contents of this appendix, particularly its recommendations for
safe working procedures to be undertaken by FSC staff, remain the
responsibility of the FSC.
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