Biological Agents

Biological Agents

Zoonoses • 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 • 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 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

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 face • Lasts 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 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

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

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 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 • 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 & 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 • 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 • 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 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 Leptospira icterohaemorrhagiae • Rats are the primary cause of the disease • Found 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 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

Leptospirosis - Weil’s Disease • 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 • 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

AIDS • 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 • 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 • 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

Biological Agents