Transcript Biological Agents

Biological Agents
Zoonoses
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Zoonoses are animal infections which may
be transmitted to people in the course of
their work. Common examples include:
– Brucellosis
– Q Fever
– Orf
– Psittacosis
– Anthrax
– Glanders
Brucellosis
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Caused by the bacterium Brucella abortus, which
may infect people handling cattle or pigs or their
carcasses in abattoirs
Not very severe but involves loss of appetite,
headache, insomnia and slight fever
In the UK a policy of eradication has been pursued
since the 60’s by destroying any infected cattle
Q Fever
Known to occur in farm workers, abattoir
workers and veterinary surgeons
 The causative agent, Coxiela burnetii, has
been found in cows and sheep
 Not as serious as Brucellosis and takes the
form of cold or `flu-like symptoms
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Orf
A contagious pustular dermatitis of viral
origin, mainly affecting farm workers,
shepherds, sheep shearers, butchers
and abattoir workers
 Lesion enlarges and often becomes
ulcerated, exuding fluid and pus
 Complete recovery occurs in about 3
weeks
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Psittacosis
A virus-like bacterium of poultry, game
and other birds
 Can be fatal to man if untreated
 Illness sets in suddenly after an
incubation period of 2 to 3 weeks with
fever, headache and lethargy
 Pulmonary symptoms follow in a few
days and mortality may be as high as
20%, particularly in the elderly
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Anthrax
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An acute infectious disease of farm animals caused
by a bacterium
Transmitted to man by contact with infected hair,
hides, excrement or products such as bonemeal
Fatal without treatment
Initial lesion rapidly becomes ulcerated
Treatment is by penicillin
Inhaling the pathogen causes pulmonary anthrax
which is usually fatal in 3 or 4 days
Glanders
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An infectious disease of horses, donkeys and
mules caused by the pathogen
Pseudomonas mallei
Transmitted to humans by nasal or mouth
secretions from the infected animal
 Abscesses appear on hands, arms or face
 Lasts up to 4 months but is treatable with
modern antibiotics
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Zoonose Control Strategies
Most common route of entry is via the
skin, by way of open cuts, sores or
abrasions which provide direct entry to
bloodstream
 Other routes include inhalation of
contaminated dusts, contact with
conjunctiva of eyes, direct injection by
cuts from infected animals or animal
bites, and direct ingestion via hands
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Zoonose Control Strategies
First stage of control strategy is to
assess those people at risk
 Factors to consider include:
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– work being carried out
– susceptibility to infection of the workers
– how infections might occur
– how likely exposure to infection is
Zoonose Control Strategies
First priority for preventing occupational
exposure to zoonoses is to eliminate the
infections from the animal stock, usually by
protecting exposed animals through
immunisation and improvement of their
environment
 Workers should be protected by suitable
environmental hygiene controls and wearing
protective clothing including hand, arm, foot
and leg protection
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Zoonose Control Strategies
Where animal products likely to emit infected
dust are handled (e.g. wool, skin, hides,
pelts), LEV and possibly RPE should be
provided to prevent airborne infection
 Specific immunisation of workers may be
necessary
 Clean & hygienic animal living conditions and
disinfection of stalls will also ensure better
hygiene in factory premises and will reduce
probability of infection
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Zoonose Control Strategies
Automation to reduce human contact and
enclosure of aerosol-producing activities
will reduce exposure to infection
 Finally, medical checks, training and
information, procedures, instruction and
records will give added protection to
workers
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Legionnaires Disease
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Caused by the bacterium Legionella pneumophilia
A type of pneumonia affecting the lungs and other
organs
A number of conditions have been found to affect
rate of growth:
– Water temp. in the range of 24-45oC. It does not survive
about 60oC. Organisms may remain dormant in cool water
– Sediment, sludge, scale and organic material in water
systems can act as a source of nutrients, as can
organisms such as algae, amoebae and other bacteria
– Incorporation of Legionella in slime on surfaces can
protect the organisms from biocides
Legionnaires Disease
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Infection caused by inhaling airborne droplets or
particles containing Legionella, which are small
enough to pass deep into the lungs and be
deposited in the alveoli
People at greatest risk include smokers, alcoholics
and patients with cancer, chronic respiratory or
kidney disease
Initial symptoms include high fever, chills, headache
and muscle pain. A dry cough soon develops and
most patients suffer difficulty with breathing
Legionnaires Disease
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Water systems potentially at risk include:
– Cooling towers
– Evaporative condensers
– Hot/cold water services where occupants are
susceptible, I.e. health care premises
– Humidifiers and air washers creating a spray of
water droplets above 20oC
– Spa baths & pools
Legionnaires Disease
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Employers should manage the risk of Legionella
by:
– Identifying and assessing sources of risk, taking into account
potential for drop formation, water temperature, exposure
probability and adequacy of control
– Implementing and managing precautions and keeping
records of the precautions
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Particular attention should be paid to populations
which contain a high proportion of susceptible people
(hospitals or nursing homes) and situations where
there is a large number of such people at risk
Legionnaires Disease
Main aim of control measures is to avoid
conditions where Legionella can proliferate and
to avoid creating sprays or aerosols
 Growth of Legionella can be inhibited by:
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– Avoiding water temperatures between 20-45oC
– Avoiding water stagnation & slimes
– Avoiding use of materials which provide nutrient for the
organisms
– Keeping the system clean and preventing a build-up of
sediments
– Using appropriate water treatment chemicals
Sick Building Syndrome
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Occupants suffer from measurably higher incidence
of illness than would be expected, for no readily
identifiable reason
Symptoms may include ear, nose and throat
irritation; skin rashes; lethargy; headaches;
respiratory infections and nausea
Occurs predominantly in air conditioned buildings
Victims tend to be in low status repetitive jobs and
have little or no control over their working
environment
Sick Building Syndrome
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Symptoms are more frequent in offices with large
numbers of employees, and are also reported with
greater frequency in the afternoons than in the
mornings
Cause is likely to be due to a number of factors,
some of which may be biological, others not
Airborne contaminants may cause SBS symptoms
through several mechanisms, including toxicity,
irritations, infection and allergy
Sick Building Syndrome
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Other factors include inadequate ventilation and low
humidity
Several “temporarily sick buildings” have been
“cured” by increasing ventilation, amongst other
measures
Overall conclusion is that SBS is a complex
phenomenon with a number of causes, possibly
influenced by the victims reaction and attitude to
the working environment
Leptospirosis - Weil’s Disease
An infectious jaundice with symptoms of
fever, jaundice, liver enlargement,
haemorrhages and feverish relapses
 Causative organism is a spirochaete called
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Leptospira icterohaemorrhagiae
Rats are the primary cause of the disease
 Found in the kidneys of rats and is excreted
in urine
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Leptospirosis - Weil’s Disease
There is evidence that the spirochaete can
pass through intact skin
 Persons at risk include:
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– canal workers
– sewer workers
– agricultural workers
– rat catchers
– pig workers
– butchers
Leptospirosis - Weil’s Disease
Primary control is through systematic
destruction of rats in infested areas
 Prophylactic immunisation offers the best
solution in sewer workers
 All “at risk” workers should carry a card
warning of the dangers, stressing personal
cleanliness and hygiene, explaining the need
for protective clothing and alerting doctors to
the possibility of the disease
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Leptospirosis - Weil’s Disease
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It is essential that people subject to potential
risk are:
– aware of the causes and symptoms
– given instruction in suitable first-aid precautions
(e.g. covering existing skin wounds, cleaning and
disinfecting all fresh wounds), notifying a GP if
`flu-like symptoms occur and notifying public
authorities if rat infestation is noticed in a work
area
Fungi
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Cause ill-health through inhalation of contaminated dust.
Examples include:
– Extrinsic Allergic Alveolitis is a type of pneumoconiosis of
biological origin caused by exposure to organic dusts of vegetable
and animal origin
– Bagassosis is a similar disease to farmer’s lung resulting from
exposure to spores present in the cellulose fibres of cane-sugar
after the sugar has been extracted
– Aspergillosis is an all-embracing term to describe the types of
extrinsic allergic Alveolitis (asthma) caused by the spores of the
Aspergillus fungus, found as a mould on cellulosic fibres such as
hay, straw, jute, flax, hemp, sugar-cane
Fungi
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Farmer’s Lung is a specific disorder caused by
exposure to spores from mouldy hay.
– The disease is result of hypersensitivity due to an antigen
present in the dust.
– Symptoms are often mistaken for `flu, with extreme
shortness of breath on exertion
– Recovery is swift following removal of the individual from
the dust source
– However, with seasonal exposures the disease becomes
chronic, leading to pulmonary fibrosis, emphysema and
bronchiectasis, by which time it may be irreversible
Hepatitis
Those at risk include doctors, surgeons,
nurses and porters
 Infection amongst health workers is a result
of contact with blood or excreta of patients
suffering from viral hepatitis or in whom the
disease is still in its incubation stage
 Porters and refuse disposal are at risk from
carelessly discarded syringes and other
sharps - the problem is becoming worse with
the increase in drug addiction
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Hepatitis
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Course of disease is similar to Weil’s Disease, but is
usually much less severe and normally self-limiting
with recovery in about 6 weeks
In about 5% of cases, chronic infectious hepatitis
follows, leading to cirrhosis and possibly death
Persons exposed to risk can be protected with
injections of gammaglobulin
In all cases, protective disposable gloves should be
worn and hands and arms washed regularly with
disinfectant
AIDS
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Acquired Immune Deficiency Syndrome
Caused by Human Immunodeficiency Virus
(HIV), which attacks the immune system
Virus is found in most body fluids but is delicate
and relatively easy to kill with heat and
chemicals
It has low infectivity and transmission is thought
to be more likely with repeated exposure to
infection rather than to a single contact
AIDS
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Occupational risk comes from accidental
inoculation or contamination of a cut or
abrasion with blood or body fluids of an infected
person
Doctors, nurses, dentists, laboratory and
hospital staff are at some risk, since they may
come into close contact with body fluids
Other workers possibly at risk might include
community, welfare, custodial and emergency
service workers and first aiders
AIDS
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Many of the precautions taken against other
infections, especially Hepatitis B, will be equally
effective against HIV. They include:
– Prevention of puncture wounds, cuts and abrasions
in the presence of blood and body fluids; and the
protection of existing wounds and skin lesions
– Control of surface contamination by containment and
disinfection
– Safe disposal of contaminated waste, especially
sharps