Transcript Section 12 day 3 Biological Hazards

BASIC PRINCIPLES IN
OCCUPATIONAL HYGIENE
Day 3
12 - BIOLOGICAL HAZARDS
BIOLOGICAL HAZARDS
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Biological Hazards - bacteria, viruses or moulds have
the ability in the right conditions to rapidly replicate
themselves.
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Focus on control is not only avoidance of contact with
the agent but also on ensuring that conditions
favourable for growth of the organism are prevented.
BIOLOGICAL HAZARDS
The three main categories of biological agents:
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Bacteria - single celled micro organisms that live in soil, water and air.
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Viruses – tiny parasitic organisms that can only reproduce within living
cells.
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Fungi – simple plants lacking chlorophyll and normal plant structures
(e.g. leaves, stems etc).
Dividing Escherichia coli bacteria
Source: Wikimedia Commons
Exposure to micro-organisms
Individual to exposure to micro-organisms depends on state of
immunity:
– whether the individual has already experienced a particular illness
– immunisation levels
– individual resistance
– fatigue
– age.
Legionella pneumophila multiplying inside a cultured human lung fibroblast
Source: Wikimedia Commons
CONTROL DEPENDANT ON RISK GROUP
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Risk Group 1 - (low individual and community risk). An organism that is
unlikely to cause human or animal disease.
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Risk Group 2 - (moderate individual risk, limited community risk). A
pathogen that may cause human or animal disease and which might be a
hazard to laboratory workers, but is unlikely to spread to the community,
livestock or the environment.
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Risk Group 3 - (high individual risk, low community risk). A pathogen
that can cause serious human disease but does not ordinarily spread
from one individual to another.
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Risk Group 4 - (high individual and community risk). A pathogen that
usually produces serious human or animal disease and may be readily
transmitted from one individual to another, directly or indirectly.
Biosafety levels
Four Biosafety levels which give the containment precautions:
– Biosafety Level 1 – Little contaiment or segragation, precautions such as
seperation and labelling of waste materials.
– Biosafety Level 2 – Staff have specific training in handling pathogenic
agents, restriocted access, sharps protection, biological cabinets for
certain activities
– Biosafety Level 3 – Bbiological safety cabinets or other physical
containment devices, personal protective clothing and equipment. Doubledoor access zones.
– Biosafety Level 4 – Separate building/ controlled are. Controlled
ventilation maintining it under negative pressure. All activities are carried
out in Class III biological safety cabinets, or Class II biological safety
cabinets with one-piece positive pressure personnel suits ventilated by a
life support system.
Legionella
X5000 Magnification of a large grouping of Gram-negative Legionella pneumophila bacteria
Source: Wikimedia Commons
Legionella
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1976 - an outbreak occurred among delegates attending an American
Legion convention.
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Two patterns of disease in humans;
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Pontiac Fever (a mild flu-like illness)
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Legionnaires Disease. (pneumonia and flu-like symptoms. It is fatal
in about 10 - 15% of cases).
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It enters into the body when fine droplets of contaminated water are
inhaled. The bacterium is not transmitted from person to person.
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Legionella are widespread in natural fresh water including rivers, lakes,
streams and ponds.
Legionella
Areas most at risk include:
– Cooling towers
– water storage tanks and calorifiers
– hot and cold water services in premises where occupants are
particularly susceptible (homes for the elderly, hospitals etc.)
– humidifiers and or washers that create a spray of water
droplets and in which water temperature exceed 20°C
– spa baths and pools
– fire sprinkler systems and fountains.
Legionella
Factors affecting growth include:
• Water temperature - Temperatures in the range of 20-45°C favour
growth (optimum temperature 37°C). Proliferation of the bacteria
is unlikely below 20°C, and the organism does not survive above
60°C.
• Water being stagnant favours multiplication.
• The presence of sediment, scale and sludge.
• The presence of other micro-organisms (algae, amoeba and
bacteria) or a biofilm (a layer of micro-organisms contained in a
matrix which may form a slime on surfaces).
Legionella
Control – prevent growth of bacteria and production of aerosols
• Minimise the release of water spray
• Avoid water temperatures between 20°C and 45°C
• Avoid water stagnation
• Avoid use of materials that can harbour or support the growth of
bacteria and other organisms
• Keep the system clean
• Use of suitable water treatment systems including biocides
• Ensure that the system operates safely and correctly and is well
maintained.
• Sampling to assess water quality.
Humidifier Fever
• Associated with exposure to many different types of microorganisms including various bacteria and fungi found in humidifier
reservoirs and air-conditioning units.
• The micro-organisms have been found in both large ventilation
systems as well as in small units.
• Significant concentrations of these organisms can be dispersed
into the environment in the aerosol mist generated by the
humidifiers during normal operation.
• Flu-like illness with fever, chills, headache, muscle ache and
fatigue.
• Controls by ensuring that the bacteria and fungi do not multiply.
Blood Borne Diseases
The risk of occupational acquisition of a blood borne virus relates to:
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The prevalence of the virus in the patient population
The efficiency of virus transmission after a single contact with
infected fluid / tissue
The nature and frequency of occupational blood contact
The concentration of the virus in the blood.
Protection comes from avoidance of blood to blood contact by
precautions including:
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Wearing protective gloves and face masks
Covering cuts and wounds with a waterproof dressing
Care with sharps
Ensuring all equipment is appropriately sterilized
Safe disposal of infected material
Control of surface contamination
Good hygiene.
Blood Borne Diseases
• Hepatitis B
• Hepatitis C
• HIV - (Human Immuno-deficiency Virus).
Zoonoses
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Zoonoses are infections that are naturally transmitted from animal to
humans.
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There are over 150 known zoonoses which range from ring worm to
anthrax and rabies.
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Zoonoses primarily affect people who work closely with animals i.e. farm
workers, laboratory workers, vets, forestry workers.
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Infection can occur through contact with:
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Animal and animal products (meat, bone meal, fur, feathers, skins, wool)
Animal tissue & body fluids (blood, saliva etc)
Birth products (placenta etc)
Waste products (urine, dung, faeces)
Contaminated materials (ground, fencing, clothing etc).
Infection may occur via inhalation, ingestion or through broken skin or
contact with mucous membranes.
Anthrax
• The disease is caused by the spore forming bacteria
Bacillus anthracis.
• Many animals may carry the anthrax bacteria or
spores including cattle, horses, goats and sheep.
• Spore remain viable in animal products for long
periods.
• Cutaneous anthrax - (a skin disease).
• Pulmonary anthrax (affecting the lungs).
• The main occupations at risk include agricultural
workers, abattoirs, animal by product processing,
vets and the wool and tanning industries.
Source: Wikimedia Commons
Leptospirosis
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The main form of leptospirosis is Weil’s
disease which is a potentially life
threatening illness caused by the
Leptospira bacteria passed from rats via
urine.
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Symptoms include flu-like symptoms
such as fever, headache, vomiting,
muscle pains, pneumonia and possible
kidney failure and death.
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The disease may be transmitted through
contact with rat’s urine or watercourses
contaminated with it.
Source: Wikimedia Commons
Salmonellosis
• Salmonellosis is the name given to an infection caused by any of
the Salmonella group of bacteria.
• Salmonella bacteria may be carried by most types of farm animal.
• Symptoms develop suddenly about 12 to 24 hours after infection
and include malaise, headache, nausea, abdominal pain,
diarrhoea and fever.
Pandemics
An epidemic of an infectious disease that spreads over a wide
geographic area and affects a large proportion of the population.
A pandemic can start when the following conditions occur:
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Emergence of a disease, or a particular strain of a disease, new to a
population
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The agent affects humans, causing serious illness
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The agent spreads easily and sustainably among humans.