Biological Agents

ZoonosesZoonoses are animal infections which may be transmitted

to people in the course of their work. Common examples include:BrucellosisQ FeverOrfPsittacosisAnthraxGlanders

Brucellosis

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

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

Psittacosis

A virus-like bacterium of poultry, game and other birdsCan be fatal to man if untreated Illness sets in suddenly after an incubation period of 2 to

3 weeks with fever, headache and lethargyPulmonary symptoms follow in a few days and mortality

may be as high as 20%, particularly in the elderly

Anthrax

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

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 faceLasts up to 4 months but is treatable with modern antibiotics

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

Zoonose Control Strategies

First stage of control strategy is to assess those people at risk

Factors to consider include:work being carried outsusceptibility to infection of the workershow infections might occurhow likely exposure to infection is

Zoonose Control StrategiesFirst 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

Zoonose Control StrategiesWhere 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 necessaryClean & hygienic animal living conditions and disinfection of

stalls will also ensure better hygiene in factory premises and will reduce probability of infection

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

Legionnaires Disease 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 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 Water systems potentially at risk include:

Cooling towersEvaporative condensersHot/cold water services where occupants are susceptible, I.e. health

care premisesHumidifiers and air washers creating a spray of water droplets above

20oCSpa baths & pools

Legionnaires Disease 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

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:

Avoiding water temperatures between 20-45oC Avoiding water stagnation & slimesAvoiding use of materials which provide nutrient for the organismsKeeping the system clean and preventing a build-up of sedimentsUsing appropriate water treatment chemicals

Sick Building Syndrome

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 buildingsVictims tend to be in low status repetitive jobs and have little or

no control over their working environment

Sick Building Syndrome

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

Other factors include inadequate ventilation and low humiditySeveral “temporarily sick buildings” have been “cured” by

increasing ventilation, amongst other measuresOverall 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 Leptospira icterohaemorrhagiae

Rats are the primary cause of the diseaseFound in the kidneys of rats and is excreted in urine

Leptospirosis - Weil’s Disease

There is evidence that the spirochaete can pass through intact skin Persons at risk include:

canal workerssewer workersagricultural workers rat catcherspig workersbutchers

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

Leptospirosis - Weil’s Disease

It is essential that people subject to potential risk are:aware of the causes and symptomsgiven 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 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 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

Hepatitis

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

AIDSAcquired Immune Deficiency SyndromeCaused by Human Immunodeficiency Virus (HIV), which

attacks the immune systemVirus 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

AIDSOccupational 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

AIDSMany 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