1026 Int Diploma IB5 v2

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Element IB5:

Biological Agents

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Types and Properties of Biological Agents

55

Fungi 5 Fungi 5 Bacteria 6 Bacteria 6 Viruses 7 Viruses 7 Protozoa 7 Protozoa 7 Sources

Sources of of Biological Biological Agents Agents 88

Special

Special PropertieProperties s of of Biological Biological Agents Agents 1414

Assessment and Control of Risk

1616

Intentional

Intentional Work Work and and Opportunistic Opportunistic Infection Infection 1616

Diseases

Diseases Caused Caused by by Biological Biological Agents Agents 1717

Risk

Risk Factors Factors in in LaboratoLaboratory ry work work 4646

General

General Biosafety Biosafety Levels Levels Control Control Approach Approach for for Non-animal Non-animal Laboratory Laboratory Work. Work. 5151

References

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Types and Properties of

Biological Agents

The ILO Fact sheet 3 of Manual 4 of Health, Safety and Environment – a series of trades union education manuals for agricultural workers, 2004 denes biological agents:

“Any micro-organism, cell culture, or human endoparasite, which may cause any infection, allergy, toxicity or otherwise create a hazard to human health. These include viruses and bacteria which can cause infection and disease, dangerous plants and animals (for example parasites or insects), biologically contaminated dusts, or wastes from humans and animals.”

(ILO 2004)

An endoparasite is an animal or plant living inside the body and which draws nutriment directly from the human body.

The main types of biological agent are:

▪ Fungi;

▪ Bacteria;

▪ Viruses; and

▪ Protozoa

With the main sources of biological agents being:

▪ Human;

▪ Animal; and

▪ Environmental

Fungi

Fungi are plants but lack chlorophyll, the essential element for photosynthesis, and must have organic matter as part of their food. They include yeasts (ovoid in shape with budding cells) and moulds (growing as branching tubes).

They can cause disease in plants and animals and cause food to decay. They also have benets as food (mushrooms) and medicines (e.g. penicillin is produced from a genus of mould called penecilium).

Fungal spores (reproductive seeds) often cause respiratory diseases such as extrinsic allergic alveolitis. An example of extrinsic allergic alveolitis is farmer’s lung. It is caused by the inhalation of fungal spores from mouldy hay; also a condition known as bagassosis is caused from exposure to mouldy sugar cane.

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Bacteria

Bacteria are single-celled organisms and are found everywhere, in soil, on and in people and animals, in air, water and on / in food. Bacteria are microscopic, i.e. cannot be seen with the naked eye which can see objects of around 75µm, for example Salmonella bacteria have a length of about 3µm. A microscope with the ability to magnify up to around 1000 X would be needed to examine in detail such an object, if a housey were magnied to the same extent it would be around 9 m in length! (Sprenger,1991).

Bacteria come in many shapes and sizes; rod shaped known as bacilli, spherical shaped known as cocci and spiral shaped known as spirochaetes. Within the different groups of bacteria there are also a number of other characteristic features which dene the various bacteria, including the ability to survive and thrive in the absence of oxygen.

Bacteria are killed by antibiotics, certain viruses (bacteriophages) and sustained high temperatures. Many food products are heat treated (pasteurised) to kill off bacteria to improve its shelf life, e.g. milk is pasteurised at 72°C for 15 seconds and ultra-heat treated milk (UHT) is subjected to 132°C for 1 second, destroying much of the bacteria naturally present in the milk. Certain groups of bacteria, notably Bacillus anthracis, the causative agent of anthrax, have the ability to produce ‘spores’. This is a dormant state for the bacteria which effectively provides a protective jacket around the bacteria to protect it from adverse environmental conditions allowing the bacterium to survive high temperatures, disinfection and other destructive techniques. This allows the bacteria to survive long periods of time and return to an active state when conditions once again become favourable. The killing power of anthrax was demonstrated by British scientists during the Second World War when it was released on the tiny island of Gruinard, just off the mainland of Scotland. The ground was contaminated with anthrax during biological

warfare testing in 1942 and was deemed out-of-bounds for almost 50 years due to the likely presence of spores.

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Viruses

Viruses are smaller than bacteria and are visible only with an electron microscope. They are made up principally of genetic material (DNA or RNA) typically wrapped in a protein coat, and can only reproduce within a living cell. Each type of virus requires a specic host cell to infect and subsequently multiply. Once they have infected a cell they reproduce rapidly and spread to other cells, destroying them as they go. Antibiotics are not effective against viruses, although vaccines exist for some. Viruses can also be destroyed by disinfecting chemicals such as bleach. There are many different types of viruses known and they can cause a range of infections from those which are inconvenient, e.g. the common cold, to those which are deadly, e.g. Ebola infection, rabies, cancer, AIDS, etc.

Examples of types of virus signicant for occupational health include:

▪ Human Immunodeciency Virus (HIV), which is a blood borne virus and the causative

agent of Acquired Immunodeciency Syndrome (AIDS);

▪ Hepatitis A, which is a food or water borne viral infection associated with poor sanitation and living conditions; and

▪ Hepatitis B and C, which are blood borne viral infections with particular signicance in the health care sector.

Protozoa

Protozoa are single cell animals of relatively large size such as amoeba. Most are harmless and live in seas, soil, and sewage and on dead matter. Some, particularly those found in plants and animals can cause disease. Examples include:

▪ Cryptosporidium, often water borne, a parasitic infection of the gut; and

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Sources of Biological Agents

All biological agents have a place in the ecosystem. The natural place of biological agents is known as the reservoir. Where exposure to the reservoir of infection is such that an infective dose is received then the individual may suffer symptoms of the infection. Man is the natural reservoir for many types of bacteria which, if moved from their natural site, may become pathogenic, e.g. Escherichia coli (E-coli) is naturally present in the gut of humans but its presence on food can indicate faecal contamination and cause food poisoning symptoms by releasing an enterotoxin in the intestines. Other reservoirs include animals such as cattle and sheep for anthrax, aquatic environments for legionella bacteria and rats for leptospira bacteria.

Human Sources

The entire human body is a reservoir for all 3 main types of biological agent:

Fungi

Several fungi cause diseases in humans, some of them serious. For example, a disease of the lungs and spinal cord is caused by a fungus called Cryptococcus neoformans. This disease is serious in AIDS patients, and it is often spread in dust by currents.

Another human pathogen is Candida albicans. This organism causes disease of the oral cavity (thrush), as well as “yeast disease” of the reproductive tract. Normally the disease is mild, but in persons with HIV infection, it can be serious.

Other human fungal diseases include ringworm and athlete’s foot. Each is caused by fungi of various genera, and each is characterised by blister-like regions on the skin or in the webs of toes or ngers. Fungal diseases of the lung tissues include histoplasmosis, blastomycosis, and coccidioidomycosis.

Bacteria

Many of the human bacterial diseases are well known – Tuberculosis (the bacteria mycobacterium tuberculosis), Diphtheria (the bacteria Corynebacterium diphtheria), Whooping Cough or Pertussis (the bacteria Bacillus pertussis), Cholera (Vibrio comma), Leprosy (rod – shaped bacterium Mycobacterium leprae), Tetanus (Clostridium tetani), Pneumonia (Streptococcus pneumonia), Typhoid (Salmonella typhi) etc.

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Viruses

There is a wide range of human viral diseases – Common cold (rhinovirus), Inuenza ( from avian u to swine u), Chicken Pox (varicella-zoster virus), Rotavirus (rotavirus is the most common cause of severe diarrheal disease in infants and young children globally), Herpes (herpes is a sexually transmitted disease that affects one in ve adults in the U.S.), Hepatitis (types A through E are quite common, depending in what area of the world you live), Yellow Fever (spread by mosquitoes), Encephalitis (Encephalitis means swelling around the brain. This can be caused by a virus or by bacteria. Most of the viral sources are transmitted by the bite of a mosquito), HIV/AIDS, Human Papillomavirus (a common sexually transmitted disease) etc.

Transmission can occur through:

▪ Blood and other body uids;

▪ Human bodies;

▪ Human waste products such as faeces and urine;

▪ Respiratory discharges such as coughs and sneezes; and

▪ Skin contact.

Animal Sources

Animals are sources of biological agents of all 3 main types:

Fungi

Many fungal infections, or mycoses, of animals and also humans, affect only the outer layers of skin, and although they are sometimes difcult to cure, they are not considered dangerous. Athlete’s foot and ringworm are among the common supercial fungal infections.

Fungal infections of the mucous membranes are caused primarily by Candida albicans. It usually affects the mouth and the vaginal and anal regions.

The fungi that affect the deeper layers of skin and internal organs are capable of causing serious, often fatal illness.

Cryptococcosis is another fungal disease that may be localised in the lung or disseminated, especially to the central nervous system. It has a worldwide distribution, affecting men twice as often as women. The causative agent ( Cryptococcus neoformans) has been isolated in pigeon excretions.

Histoplasmosis, which is caused by spores of the fungal genus Histoplasma, is a severe infection that shows varied symptoms. In acute cases ulcers of the pharynx and enlargement of the liver and spleen are present. In other forms tubercularlike lesions of the lung occur. In its benign form no symptoms may be present. The fungus grows in soil contaminated with bird or bat droppings.

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Bacteria

Bacterial infections in animals include – Anthrax (the bacteria -Bacillus anthracis) there is cutaneous anthrax, pulmonary anthrax and intestinal anthrax, Leptospirosos (the bacteria -Leptospira), Anaplasmosis ( a type of tick fever caused by the parasite Anaplasma ovis), Tularemia (the bacteria - Francisella tularensis), Bovine tuberculosis the bacteria - (Mycobacterium bovis).

Viruses

Viral infections in animals include – Rhabdoviruses, e.g. rabies, Foot-and-mouth disease virus Pestiviruses (account for important diseases in animals such as swine fever), Inuenza (caused by RNA viruses affects birds and mammals),

Environmental Sources

The environment is a massive reservoir of all 3 main types of biological agent:

Fungi

Mould spores are a common component of household and workplace dust. However, when mold spores are present in abnormally high quantities, they can present a health hazard to humans, potentially causing allergic reactions, producing mycotoxins or causing fungal infection (mycosis). Health problems associated with high levels of airborne mould spores include allergic reactions, asthma episodes, irritations of the eye, nose and throat, sinus congestion, and other respiratory problems.

Sporotrichosis is an infection of farmers, horticulturists, and others who come into contact with plants or mud. The disease affects the skin and lymphatic system and, in rare cases, becomes disseminated.

Among the fungi that infect the deeper tissues is Coccidioides immitis which, causes coccidioidomycosis, sometimes called valley fever. The fungus resides in the soil and produces airborne spores when the rains come.

Blastomycosis is caused by a yeastlike fungus that reproduces by budding. Infection occurs by inhalation of the fungus from its natural soil habitat. The North American variety, caused by Blastomycosis dermatitidis, occurs more often in men and seems to be limited to the central and E United States and Canada. Wart like lesions appear most often on the skin, sometimes spreading to the bones and other organs.

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Bacteria

Bacteria are the pathogens that cause deadly illness and disease in their human hosts. Millions of people every year die because of these tiny living beings that multiply in our system and take advantage of any weaknesses they nd.

E. Coli

Virulent strains of E. coli can cause gastroenteritis, urinary tract infections, and neonatal meningitis. In rarer cases, virulent strains are also responsible for hæmolytic-uremic syndrome (HUS), peritonitis, mastitis, septicemia and Gram-negative pneumonia. Needless to say, this one little bacterium can cause severe disruption to the body’s functions.

It is one of the most commonly involved in product recalls as well. On the bright side, in developed countries, it is easily treated at the moment with antibiotics; unfortunately, it also quickly grows resistant, so combination therapies may be chosen. E. coli is not one of the devastating killers as a whole but deadly in areas without antibiotics or treatment.

Salmonella

Salmonella is deadly in two forms. Salmonella typhi causes typhoid fever, which is responsible for the death of 216,000 persons a year in endemic areas. It is spread through feces and urine contamination.

Tetanus

The good news about the tetanus bacteria is the development of a vaccine against it. For those who may have forgotten to get the vaccine - if you are injured where dirt-carrying spores might enter your system, the vaccine can be given then. Lockjaw and terrible spasms are the symptoms of the disease,

Staphylococcus

Staphylococcus is one of the largest groups of bacteria with 40 subspecies. It is normally found in small amounts on your skin, and a normal immune system can deal with it or antibiotics in most cases if the bacteria take a hold and make someone ill. Recently, however, antibiotic-resistant strains have appeared, called MRSA (Meticillin antibiotic-resistant Staphylococcus aureus),

Streptococcus Pneumoniae

This killer is responsible for numerous cases of pneumonia throughout the world, and equally as important, is the main cause of bacterial meningitis, a killer in its own right. The body has a normal amount of this ora in its respiratory system but when the immune system is compromised or something occurs to disrupt it, this transforms into a virulent bacteria capable of killing those affected.

Mycobacterium Tuberculosis

Tuberculosis has ravaged the world for centuries, also known as consumption. It has been found in the spines of mummies and “in 2007 there were an estimated 13.7 million chronic active cases, 9.3 million new cases, and 1.8 million deaths, mostly in developing countries” according to the WHO. The organisation has started a program that aims at saving 14 million lives between 2006 and 2015. There is no effective vaccine as yet and the disease often lies dormant for years in the respiratory system before being activated.

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Viruses

Viruses pass into the environment from clinically ill or carrier hosts; although they do not replicate outside living animals or people, they are maintained and transported to susceptible hosts. Population concentrations and movement, both animal and human, have been steadily increasing in this century, enhancing transmission of respiratory and enteric viruses and compounding the difculty of preventing environmental transmission. Studies on environmental survival factors of viruses have been most denitive for polioviruses, foot and mouth disease viruses and Aujeszky’s disease virus (a disease of pigs caused by a herpes virus).

Viruses enter the environment from animals, including humans – a major source being excretion. The virus can then enter the water systems – groundwater, rivers, lakes – from which it can then be ingested by animals and humans.

From the environment, allergic and toxic reactions can occur via moulds or mould spores, dust mites and pollen.

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Table 1: Summary of Sources of Biological Agents

Human Sources Animal Sources Environmental Sources

Fungi ▪ Cryptococcus neoformans

– causes a disease of the lungs and spinal cord. ▪ Candida albicans – causes

thrush of the oral cavity and ‘yeast disease’ of the reproductive tract. ▪ Also: ▪ Ringworm ▪ Athlete’s foot ▪ Histoplasmosis, blastomycosis and coccidioidomycosis – all cause lung disease

▪ Cryptococcus

neoformans – has

been isolated in pigeon excretions.

▪ Histoplasmosis – grows in soil contaminated

with bird or bat

droppings

▪ Mould spores –

common component

of household and

workplace dust, can cause allergic reactions

▪ Sporotrichosis –

infection of farmers, horticulturists etc who come into contact with plants or mud

▪ Coccidioidomycosis – present in soil, produces spores when it rains

▪ Blastomycosis – present in soil Bacteria ▪ Tuberculosis -mycobacterium tuberculosis ▪ Diphtheria – corynebacterium diphtheria ▪ Whooping cough – bacillus

pertussis

▪ Cholera – vibrio comma ▪ Leprosy – mycobacterium

leprae

▪ Tetanus – clostridium tetanii ▪ Pneumonia – streptococcus

pneumonia

▪ Typhoid – salmonella typhii

▪ Bacillus anthracis –

causes anthrax, from diseased animals. ▪ Leptospira – primarily

from infected rats

▪ Anaplasma ovis –

causes a type of tick fever, from infected ruminants

▪ Francisella tularensis – causes tularemia, from rabbits and aquatic rodents

▪ Mycobacterium bovis

– causes tuberculosis, from infected cattle

▪ Escherichia coli (E-coli)

– harmless strains

live in the human gut, virulent strains from

faecal contamination

eg. water

▪ Salmonella – can

cause enteritis and

typhoid, common in the

environment, spread

via faecal and urine contamination

▪ Clostridium tetanii – lives in the environment, causes tetanus

▪ Staphylococcus – live in soil, and on skin

Viruses ▪ Common cold – rhinovirus

▪ Chicken pox – varicella-zoster virus

▪ Rotavirus – most common cause of sever diarrhoeal disease in children

▪ Herpes – sexually

transmitted ▪ Hepatitis

▪ Yellow fever – spread by mosquitoes

▪ Encephalitis – can be viral (or bacterial)

▪ HIV – can lead to AIDS

▪ Human Papillomavirus –

sexually transmitted

▪ Rhabdoviruses eg

rabies, cause disease, from infected animals ▪ Aphthovirus – causes

foot and mouth disease ▪ Pestivirus – includes

swine fever ▪ Orthomyxoviridae

– causes inuenza,

affects birds and

mammals

Viruses do not replicate outside living animals

or people, although

some can survive in the environment. They enter

the environment from

animals and humans,

often from excretion and enter the water systems.

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Special Properties of Biological Agents

Cross Contamination

The bacterium S. aureus, is the most common cause of skin infections in humans. Suppose that one morning, an individual were to touch a surface, such as a doorknob, that was contaminated with Staphylococcus aureus. Another worker who had walked into the building just minutes beforehand had left the organism there, after grabbing hold of the same doorknob. Should the bacteria enter an open wound on the hand then an infection could occur which in its worst case could lead to a septicaemia (infection of the blood).

Rapid Multiplication

Even if only a single S. aureus cell were to make its way into the wound, it would take only 10 generations for that single cell to grow into a colony of more than 1,000 (2 10_{= 1,024), and}

just 10 more generations for it to erupt into a colony of more than 1 million (220_{= 1,048,576).}

For a bacterium that divides about every half hour (which is how quickly S. aureus can grow in optimal conditions), that is a high number of bacteria in less than 12 hours.

Rapid Mutation

S. aureus has about 2.8 million nucleotide base pairs in its genome. Where mutations within the genetic material occur then mutated bacteria are formed due to the rapid multiplication process. Consequently in just over a day each genome pair could have mutated more than once.

Where treatment is sought at a medical practitioner the doctor may prescribe antibiot ic treatment which in most cases would kill the bacteria causing the infection and the wound would heal quickly. However where the mutation causes the ability to resist the presence of the antibiotic then the bacteria is not killed and the resistant strain can develop freely.

Incubation Period

The incubation period is the amount of time between infection with a virus or bacteria to the start of symptoms. The incubation periods of several diseases are given below:

▪ Smallpox - 12 days

▪ Common cold - 2-5 days

▪ Measles - 8-12 days

▪ Chicken pox - 14-16 days

▪ Rubella (German measles) - 14-21 days

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Infectious

Infectious pathogens include some viruses, bacteria, fungi, protozoa, multicellular parasites, and aberrant proteins known as prions. These pathogens are the cause of disease epidemics, in the sense that without the pathogen, no infectious epidemic occurs.

The term infectivity describes the ability of an organism to enter, survive and multiply in the host, while the infectiousness of a disease indicates the comparative ease with which the disease is transmitted to other hosts.

Transmission of pathogens can occur in various ways including physical contact, contaminated food, body uids, objects, airborne inhalation, or through vector organisms.

Infectious diseases are sometimes called “contagious” when they are easily transmitted by contact with an ill person or their secretions (e.g., inuenza). Thus, a contagious disease is a subset of infectious disease that is especially infective or easily transmitted. Other types of infectious/transmissible/communicable diseases with more specialised routes of infection, such as vector transmission or sexual transmission, are usually not regarded as “contagious,” and often do not require medical isolation (sometimes loosely called quarantine) of victims. However, this specialised connotation of the word “contagious” and “contagious disease” (easy transmissibility) is not always respected in popular use.

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Assessment and Control of Risk

Intentional Work and Opportunistic

Infection

A distinction should be made between intentional work and opportunistic infections. Intentional work is where work with biological agents is deliberately undertaken such as in research and pathological laboratories, where tissue samples or biological cultures may be assessed.

Opportunistic infection occurs where organisms may develop due to their properties and lifestyle and the presence of favourable conditions, e.g. the growth of legionella bacteria in water systems in the presence of slime and scale at favourable temperatures. Exposure to biological agents is therefore incidental to the main activity being undertaken, e.g. the risk of leptospirosis (Weil’s disease) for construction workers or grounds maintenance personnel. Other types of workers who may be at a higher risk of exposure to biological agents include: ▪ Animal workers (e.g. agriculture, abattoir, veterinary);

▪ Health care workers;

▪ Mortuary workers;

▪ Emergency services and rst-aiders;

▪ Refuse collection workers;

▪ Laundry workers; and

▪ Sewerage / construction workers.

Where the individuals belong to a high risk group such as the elderly, the young, new and expectant mothers or immunosuppressed, the risk of opportunistic infection may be increased. The employer should have consideration of the relevant risk factors in their assessment of the work activities.

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Diseases Caused by Biological Agents

Zoonoses

A zoonose is any infectious disease that can be transmitted between species (in some instances, by a vector) from animals to humans or from humans to animals (the latter is sometimes called reverse zoonosis or anthroponosis). In a study of 1415 pathogens known to affect humans, 61% were zoonotic.

NB: In epidemiology, a vector is any agent (person, animal or microorganism) that carries and transmits an infectious pathogen into another living organism.

Arthropods (invertebrate animals having an external skeleton, a segmented body, and jointed appendages) form a major group of disease vectors with mosquitoes, ies, sand ies, lice, eas, ticks and mites transmitting a huge number of diseases. Many such vectors are haematophagous, which feed on blood at some or all stages of their lives. When the insects blood feed, the parasite enters the blood stream of the host. This can happen in different ways. The Anopheles mosquito, a vector for Malaria, Filariasis and various arthropod-borne-viruses, inserts its delicate mouthpart under the skin and feeds on its host’s blood. The parasites the mosquito carries are usually located in its salivary glands (used by mosquitoes to anaesthetise the host). Therefore, the parasites are transmitted directly into the host’s blood stream.

Pool feeders such as the sand y and black y, vectors for Leishmaniasis and Onchocerciasis respectively, will chew a well in the host’s skin, forming a small pool of blood from which they feed. Leishmania parasites then infect the host through the saliva of the sand y. Onchocerca force their own way out of the insect’s head into the pool of blood.

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Psittacosis (Ornithosis, Parrot Fever)

Psittacosis is a bacterial disease which mainly affects birds and poultry and is caused by the bacteria chlamydia psittaci.

Method of Infection

The organism is present in dusts from desiccated bird droppings and feathers. The main method of contracting the disease is via inhalation of infected dust. The organism may survive for many months in dry dust.

Signs and Symptoms

The disease produces u-like symptoms, i.e. fever, headache, chills and respiratory irritation often developing into pneumonia. The disease is rarely fatal and has an incubation period of around 4 to 15 days.

Workers at Risk

Poultry workers, pet shop staff, zoo workers, taxidermists and, to a lesser extent, building and maintenance workers who may have to enter spaces where there is an abundance of bird droppings and feathers.

Precautionary Measures

Removal of birds from the area may be appropriate in some situations, although for many workers exposure is unavoidable. Regular cleaning of infected areas will minimise accumulation and drying out of bird droppings. Suitable PPE such as dust masks may be appropriate as well as practising high standards of personal hygiene. There are clinical methods of detection and prophylaxis is readily available.

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Leptospirosis (Weil’s Disease)

A little over 100 years ago, Adolph Weil published his historic paper describing the most severe form of infection that would be later known as Weil’s Disease.

Leptospirosis is a bacterial disease that is caused by pathogenic spirochetes of the genus Leptospira. It is considered the most common zoonosis in the world. Leptospirosis has recently been recognized as a re- emerging infectious disease among animals and humans and has the potential to become even more prevalent with anticipated global warming. Leptospirosis is distributed worldwide but is most common in the tropics.

Method of Infection

This is an infection that is commonly transmitted from rats to humans via their urine, or water, which has been contaminated by it. Typically this occurs where an infected rat urinates in an area where a human comes into contact with that urine, or standing water where rats have inhabited. This could include construction sites, animal laboratories, lakes, canals or sh farms. The main route of entry for leptospirosis is via broken skin or mucous membranes. The bacterium remains active for 2-3 weeks in cold water, particularly where the water has not been exposed to strong sunlight. The bacterium is NOT active in seawater.

Signs and Symptoms

This condition usually has an incubation period of between 4 and 19 days. The disease produces u-like symptoms, i.e. sudden onset of fever, headache, chills, myalgia (aching muscles), rash leading to meningitis, pneumonia and may lead to jaundice and kidney failure. It is fatal in approximately 20% of cases.

The condition is often misdiagnosed as meningitis or encephalitis.

Workers at Risk

Any person who can come into contact with rat’s urine, an area which is frequented by rats or standing water is at risk. Examples of occupations at risk include canal workers, construction workers, animal laboratory staff, farmers, sewage workers and leisure / water sport workers. There is the potential for a serious outbreak in the event of sewage system failure or ooding of areas with a high water table.

Precautionary Measures

Improved pest control to minimise the incidence of rats in the vicinity thereby reducing the reservoir of infection, also good housekeeping and the elimination of food waste, etc. can reduce the likelihood of rats inhabiting an area. Good hygiene measures can minimise the likelihood of infection, i.e. frequently washing hands and exposed skin thoroughly after work and prior to eating, drinking or smoking. Covering up of any cuts or grazes with a waterproof plaster is also important; PPE such as rubber gloves and eye protection should be worn where appropriate. Education of staff in the risks, control measures and signs and symptoms of the disease is also important. The HSE has produced a pocket card listing signs and symptoms of the disease and precautionary measures. It is recommended that this is issued to ‘at risk’ workers. If they experience any of the early symptoms of the disease they should contact their doctor and show his or her pocket card. Early diagnosis of the disease is particularly important and often difcult due to the similarity of many of the symptoms with other infections.

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Cryptosporidiosis

This is a disease caused by cryptosporidium parvum, a protozoan organism which is found in a wide range of animal faeces.

Method of Infection

A common route of infection to humans is from calves. This can be by faecal-oral transmission or via contaminated drinking water or milk. Bottle feeding a newborn lamb is a particularly high-risk activity.

Signs and Symptoms

After an incubation period of 1 to 12 days, the victim suffers with acute diarrhoea and may also develop u-like symptoms, i.e. fever, headache, chills and respiratory irritation.

Workers at Risk

Farm workers, vets, laboratory personnel and anyone who handles young animals or may come into contact with animal faeces are particularly at risk. This could also include park workers and grounds maintenance staff as well as carers of infected persons.

Precautionary Measures

Good hygiene measures can minimise the likelihood of infection, i.e. frequently washing hands and exposed skin thoroughly especially after work and prior to eating, drinking or smoking. PPE such as rubber gloves should be worn where appropriate. Where water contamination is suspected then boiling drinking water will reduce likelihood of infection.

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Farmer’s Lung

Farmer’s lung is one of the more serious respiratory hazards to which farmers are exposed. Unfortunately, the number of farmers affected by farmer’s lung has been increasing in recent years. Farmer’s lung is a hypersensitivity pneumonitis induced by the inhalation of biological dusts coming from hay dust or mould spores or other agricultural products It results in a type III hypersensitivity inammatory response and can progress to become a chronic condition which is considered potentially dangerous.

Method of Infection

Farmer’s lung is a noninfectious allergic disease that is caused by inhaling mold spores in the dust from moldy hay, straw, or grain. This debilitating disease disrupts the normal function of the lungs, where oxygen enters and carbon dioxide exits the bloodstream.

Just as plants produce seeds for reproduction, molds produce tiny spores. These spores are less than 4 microns in size - so small that as many as 250,000 spores can t on the head of a pin. On the farm, molds tend to grow in stored hay, grain, or silage when moisture content is high (30%) and storage areas are poorly ventilated.

Mold spores attach themselves to airborne dust particles when farmers move or work with hay, grain, or silage materials in which mold spores have grown. As a result, farmers inhale both dust particles and mold spores. In fact, a farmer can inhale up to 750,000 of these spores per minute.

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Signs and Symptoms

General symptoms:

▪ Sudden illness that develops a few hours after handling mouldy crop material;

▪ Chronic cough; and

▪ General feeling of tiredness or depression

Farmers will develop specic symptoms of farmer’s lung based on the amount of dust and spores to which they have been exposed or the intensity of their body’s reaction to the dust and spores. Farmers are also likely to develop an increased sensitivity to mould exposure over time and will have more severe reactions with lighter exposures. In all cases, each additional exposure will aggravate the problem.

The symptoms of farmer’s lung may be most severe for a 12 to 48 hour period after exposure to mold spores. However, the symptoms may remain for as long as two weeks. Acute farmer’s lung is the short-term form of the disease. Farmers typically develop chronic farmer’s lung due to repeated exposure to mold spores over time, usually because they continue to ignore the symptoms of acute farmer’s lung. However, it is possible to develop chronic farmer’s lung even after one acute attack.

.

Delaying medical treatment for farmer’s lung often worsens the situation. Permanent damage has often occurred by the time a farmer sees a doctor. In some cases scar tissue (pulmonary brosis) has already developed, which further interferes with normal lung function.

The body has natural defence mechanisms (such as coughing and sneezing) that help prevent dust and other particles from entering the lungs. However, mould spores can often bypass these defences because of their small size and overwhelming numbers.

Mould spores move into, accumulate, and settle into the lower lungs. Since most gas exchange takes place in the lower lungs, toxins produced by the spores travel through the bloodstream with the oxygen. The body’s reaction to the toxins causes permanent scarring of the lung tissue, which affects the lungs’ ability to transfer oxygen into the bloodstream. Each exposure to mould spores increases the damage. The body’s last defence against these spores is to develop an allergic reaction that causes cold or pneumonia-like symptoms.

Workers at Risk

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Precautionary Measures

Farmers can control or even minimise the possibility of getting farmer’s lung by complying with

the following preventative measures:

▪

▪ Identify contaminants in the work environment;Identify contaminants in the work environment;

▪

▪ Minimise the amount and type of contaminants in the work environment;Minimise the amount and type of contaminants in the work environment;

▪

▪ Avoid Avoid exposure to exposure to contaminacontaminants nts and and mould mould spores and spores and dust dust from from decayed grains decayed grains andand

forages;

▪

▪ Limit exposure to all Limit exposure to all contaminancontaminants;ts;

▪

▪ Operate within a controlled environment whenever possible (e.g., cab, control room, etc.);Operate within a controlled environment whenever possible (e.g., cab, control room, etc.);

▪

▪ Use Use mechmechanicanical cal controntrols ols to rto remoemove ave air cir contaontaminaminants (nts (e.g.e.g., fan, fans, es, exhauxhaust bst blowelowers, rs, lterlterss

etc.);

▪

▪ Maximise ventilation in dusty areas;Maximise ventilation in dusty areas;

▪

▪ Move work outside whenever possible;Move work outside whenever possible;

▪

▪ AAvovoid id duduststy wy worork ik in cn cononnned ed arareaeas; s; anandd

▪

▪ Wear respirators, masks, or other protective equipmentWear respirators, masks, or other protective equipment

Respiratory protection must be selected to be appropriate for the task.

Management to prevent mould spore growth:

▪

▪ Use mould inhibitors;Use mould inhibitors;

▪

▪ Bale hay, store crops in silos , and harvest and store grain at recommended moistureBale hay, store crops in silos , and harvest and store grain at recommended moisture

contents;

▪

▪ Dry grain properly before storage;Dry grain properly before storage;

▪

▪ Properly ventilate storage buildings;Properly ventilate storage buildings;

▪

▪ Adequate Adequately ventilate croply ventilate crops to cool them s to cool them down; anddown; and

▪

▪ Always use a plastic sheet to cap open silos (not plan Always use a plastic sheet to cap open silos (not plant material) holding dot material) holding down the edgeswn the edges

with heavy weights (e.g., tyres);

If there is no option to working with mouldy material:

▪

▪ Wet down feed before transferring it to minimize dust;Wet down feed before transferring it to minimize dust;

▪

▪ Convert to mechanical or automated feeding or feed handling systems;Convert to mechanical or automated feeding or feed handling systems;

▪

▪ Wet down the top of the silo before uncapping material stored in silos;Wet down the top of the silo before uncapping material stored in silos;

▪

(25)

Hepatitis

This is a generic term for a range of viral infections that cause liver disease. The principal forms

are A, B, C and D.

Method of Infection

This varies between the different forms. Hepatitis A is food borne and can be transmitted

through faeces.

The other forms of hepatitis (B, C and D) are blood borne. The disease is spread by contaminat

The other forms of hepatitis (B, C and D) are blood borne. The disease is spread by contaminateded

blood entering the victim’s blood stream through broken skin or ‘needle-stick’ injury. Hepatitis B

may also be transmitted via sexual intercourse.

Signs and Symptoms

Inammation of the liver leading to abdominal discomfort, from which a full recovery can be

made, or the disease can be fatal, or lead to chronic life-long carrier status where the patient

is symptom free but can pass the condition on to contacts. Other symptoms include fever,

malaise, anorexia and nausea after an incubation period of 15 to 50 days for hepatitis A, 45 to

180 days for hepatitis B and 14 to 180 days for hepatitis C.

Workers at Risk

The main occupational groups are hospital, laboratory and health care staff for the blood borne

infections.

Cleaning and maintenance staff may also come into contact with contaminated body products,

e.g. wound dressings and contaminated sharps.

Precautionary Measures

Risk assessment should identify

Risk assessment should identify particular occupationparticular occupational hazards and help al hazards and help to develop effectiveto develop effective

systems of work to minimise the risk of infection. Disinfecting and sterilisation of any blood or

faecal spillage is important. In hospitals effective autoclave (sterilising) techniques should be

used to sterilise equipment as well as the appropriate use of disinfectants.

Cuts or abrasions should be covered with waterproof dressings and appropriate PPE used, e.g.

gloves, to avoid contact with blood and other body uids.

According to “vaccines today”

According to “vaccines today” (http://www(http://www.vaccinestoda.vaccinestoday.ey.eu) Hepatitis A can be u) Hepatitis A can be prevented byprevented by

vaccination and good hygiene. A vaccine against hepatitis B has been available since 1982

and is 95% effective in preventing infection and its chronic consequences. There is also a

combination A+B vaccine. The vast majority of countries in the WHO Europe Region have

implemented hepatitis B immunisation often incorporated in the routine vaccinations in infancy.

There are so far no vaccines against hepatitis C, D or E.

(26)

Human Immuno Deciency Virus (HIV) /

Acq

uir

ed

Imm

une

De

cien

cy S

ynd

rom

e (

AID

S)

This disease is caused by an organism known as the Human Immunodeciency Virus (HIV).

HIV can remain dormant with no clinical features in the infected person or may progress to the

clinical syndrome AIDS.

Method of Infection

From an occupational perspe

From an occupational perspective, infection is likely ctive, infection is likely to be similar to to be similar to hepatitis, i.e. via needle-stickhepatitis, i.e. via needle-stick

injury or splashes of infected body uids. There is the potential of a small risk of transmission

of HIV from infected workers where contact with bodily uids or open wounds is likely such as

may occur in the health care sector although the risk is low.

Signs and Symptoms

The HIV virus affects the human immune system making the body susceptible to infection. In

particular there is a greater risk of lung infections such as pneumonia and skin malignancy

(Kaposi’s sarcoma). Initial symptoms are non-specic and include weight loss, diarrhoea, fever

and fatigue. The incubation period for developing the syndrome is from around 2 months to 10

years or longer.

Workers at Risk

As

As for blood-borne hepatitis i.e. for blood-borne hepatitis i.e. those in those in the care the care industries and industries and those likely those likely to to come acrosscome across

infected material, e.g. rst aiders dealing with trauma incidents. The HIV virus is far less

infectious than hepatitis since the virus only survives for a short time outside the body.

(27)

Precautionary Measures

The lethal potential of HIV / AIDS requires that universal precautions be applied. This means that any suspected risk of exposure to a bodily uid is treated as a positive risk. Features of universal precautions include:

▪ Use of PPE (barrier methods), e.g. gloves, protective clothing, goggles; ▪ Controlled handling of sharps, e.g. scalpels, needles, etc.;

▪ Infection control techniques, e.g. covering open wounds;

▪ Effective decontamination and disposal protocols. These include cleaning and decontamination to remove all traces of bodily uids, etc. safe disposal of needles, sharps, etc. and sterilisation of equipment and the work place;

▪ Spillages should be absorbed into paper towels or cloths and disposed of in clinical waste plastic bags, the area of spillage should be cleaned with hot water and detergent and then disinfected;

▪ Laundry should be washed at 70°C;

▪ Sharps, needles, etc. should be either autoclaved or disposed of using suitable sharps receptacles;

▪ Reporting procedures to deal with any accidental exposure that requires appropriate testing; and

▪ Provision of information, training, instruction and supervision on the precautionary measures.

Universal precautions are also a prudent measure against hepatitis B.

Internal guidance on HIV infection for employees should be provided, which should be practical and non-alarmist and dispel any misconceptions about the virus and the methods of infection. It should give advice on the risk of contracting HIV, its latency period, how it is transmitted and associated health effects, e.g. pneumonia, skin cancer, AIDS, etc. Other aspects to be included within the guidance are:

▪ Risk assessment ndings of particular work activities, including the tasks involved, sources of HIV infection and identication of those at risk, e.g. clients (patients), social workers, care workers, injured persons, rst-aiders and ‘spillage’ of bodily uids;

▪ Control measures, e.g. use of protective clothing, treatment and disposal of clinical waste / sharps, ways to avoid contact with body uids and training; and

▪ Procedures for reporting after possible contact with body uids / infected material and HIV testing, including requirements for condentiality, counselling services.

Also health education is a key strategy to reducing the incidence of the disease in the population and therefore the risk of contracting the condition.

There is presently no effective vaccination or treatment for HIV / AIDS, although a number of drugs are available which can address some of the symptoms.

(28)

Legionnellosis (Legionnaires’ Disease)

This is the name given to a potentially fatal form of pneumonia caused by a bacterium known as ‘legionella pneumophila’. The organism was described following an outbreak of severe pneumonia, which resulted in the death of several American ex-Legion members who were attending a convention at the Bellevue Stratford Hotel in Philadelphia in 1976.

Method of Infection

The source of the rst known outbreak of the disease was traced to a naturally occurring bacterium that can be located in soils and pools of water. It causes lung diseases amongst victims, thus transmission occurs by inhalation of contaminated water droplets. Risk factors that increase the likelihood of infection include:

▪ Water between 20°C and 45°C, which provides the optimum conditions for propagation of the bacteria. The bacteria favour human body temperature, the rate of growth is most rapid at about 37°C. Above 46°C, the death rate exceeds the growth rate and the organism cannot survive above 60°C. Below 20°C the organism does not appear to multiply;

▪ Prevalence of stagnant water, which gives bacteria the opportunity to multiply. This could include water tanks or water pipes where water is not regularly drawn from, e.g. ‘dead legs’ where an installation has been removed and the pipe terminated;

▪ Dirty water which contains organic contaminants which can ‘feed’ the bacteria. These nutrients could include dead insects, algae, or even materials such as rubber and wood; ▪ Likelihood of aerosol formation. The organism is only infectious by inhalation; thus the

water needs to become airborne. Therefore any process which involves droplet formation presents a risk; and

▪ The presence of susceptible persons must be considered, e.g. at a hospital or care home the risk may be greater.

Signs and Symptoms

The incubation period is typically between 2 and 10 days when affected patients present with fever, non-productive cough, headache, myalgia, malaise, pneumonia and ultimately death. The disease tends to affect susceptible persons such as the aged, and hospital patients who are immunosuppressed.

The condition is fatal in around 12% of cases (HSC, 2004).

A similar condition called ‘Pontiac fever’ which is non-fatal, has also been associated with legionella bacteria. Recovery from this condition is spontaneous within 2-5 days.

Workers at Risk

Anyone who is at risk from the inhalation of contaminated water droplets, which could be workers, but more often are customers, or members of the public who could be in the vicinity of the source of infection.

(29)

Installations of Concern

Any installation that can cause infected water to become airborne is of some concern. Cooling towers and showers are obvious examples, but even water from a tap as it hits a surface can generate an aerosol which may be inhaled. One of the greatest risks is associated with cooling towers and evaporative condensers. These devices use water to assist with cooling, which results in water droplets being heated up, often to the ideal temperature for the bacteria as well as being in a form easily inhaled. In addition the water is often dirty due to contamination picked up from the air. Typically wet evaporative condensers for air conditioning plant are situated on the roofs of buildings. Water is sprayed onto cooling coils with risks arising from spray drift. The people at most risk are not the building occupants, but passers-by. Installations such as tanks where water is stored for extended periods are potential breeding grounds for bacteria. Mains water can generally be considered as treated and therefore legionella-free and it is generally delivered at less than 20°C. However, once in a storage tank, where dirt ingress is possible and temperatures increase, the risk of legionella becoming established increases.

Large hot water boilers may not always heat all of the water thoroughly leading to patches of lukewarm water.

During periods of high usage lukewarm water, with the greatest risk of contamination, is most likely to be drawn off.

Showers are a source of risk where warm water droplets are inhaled. The risk is particularly high where the showers are not frequently used and bacteria can reproduce in the stagnant pipework. Dead legs in water distribution pipe-work and intermittently used systems may provide an environment suitable for bacterial growth.

Other at-risk systems include atomising humidiers and spray-type air washers. Vehicle washes are a risk, particularly where the water is recycled. Decorative fountains are a source of risk. Spas and whirlpool baths can also present a risk of exposure to legionella.

Fire / sprinkler systems present a low risk in relation to the risk of re, although the testing of such systems should be designed to minimise the risk of aerosol generation and the numbers of persons exposed.

(30)

Precautionary Measures

Detailed information has been produced by the UK HSE in the form of an Approved Code of Practice and Guidance entitled ‘Legionnaires’ disease: The control of legionella bacteria in water systems’ (L8). Most of the advice relates to prevention by minimising as many of the risk factors as possible. A suitable and sufcient assessment of the risks must be undertaken for all workplace buildings and installations.

Cooling Towers

Cooling towers and evaporative condensers should be positioned as far away as is possible from air-conditioning and ventilation inlets. The risk from cooling towers and evaporative condensers can be minimised by good design and maintenance. The materials of construction should be such that they do not support microbiological growth.

Corrosion of steel should be inhibited as it may lead to conditions which encourage the growth of legionella. The design should allow disinfection, prevent spray drift and minimise dirt ingress. Drift eliminators, made of plastic or metal, should be installed in all towers. Rather than eliminate the drift of spray as their name suggests, drift eliminators are designed to reduce aerosol drift. The cooling tower sump should be sloping and tted with a drain valve.

The area above the cooling tower sump should be as well enclosed as possible to reduce the effects of wind. A full water treatment system should be integrated into the system design, with provision made for sampling, chemical dosing, bleed and drain points. Regular treatment of cooling water with a biocide is essential with regular testing of the water for total bacteria and legionella species. The composition of the make-up and cooling water should be routinely tested to ensure the effectiveness of the treatment programme. To ensure that dosage and bleed rates are correct the minimum recommended frequency is once a week. Microbiological activity should be tested at least once weekly. The most common method used to measure microbiological activity within a cooling system is to use a dip slide. Should the dip slides indicate a high result then water samples should be analysed by a UKAS accredited laboratory. The treatment and testing activities should be undertaken by specialists.

Disinfection followed by chemical and manual cleaning of cooling towers should be undertaken at least twice per year, but more frequent cleaning may be required depending on local environmental conditions. The system should be relled and chlorinated (disinfected) after cleaning.

Hot and Cold Water Services

Hot and cold water systems should be designed to aid safe operation by preventing or controlling conditions which permit the growth of legionella and to allow easy cleaning and disinfection. Low corrosion materials, e.g. copper, plastic and stainless steel should be used where possible. Materials to avoid in domestic water systems include natural rubber, hemp, linseed oil based jointing compounds and bre washers.

For water systems within buildings an effective regime of temperature control is the best means of ensuring that bacteria do not thrive. Cold water should remain below 20°C and hot water heated to above 60°C and delivered to outlets at above 50°C. Volumes of stored water should be minimised. As a general principle, no more water should be stored than can be used in 24 hours. Hot water systems should be designed to accommodate the normal daily uctuations in hot water use without any drop in temperature. The calorier (heat exchanger) should thoroughly heat all of the water to at least 60°C.

(31)

If the calorier is of excessive capacity for the installation, a smaller replacement should be considered, or ‘instant’ heaters installed at sink locations. Caloriers should be lagged (thermally insulated) and subject to an annual inspection, and if necessary regularly cleaned.

The hot water circulating loop should be designed to give a return temperature of 50°C or above. Where necessary a ‘shunt pump’ can minimise temperature stratication by circulating the water around the boiler.

Regular thermal disinfection should be considered where it cannot be guaranteed that all the water dispensed is above 50°C. This would typically involve heating water to 60°C for an hour a day (when the building is unoccupied).

The hot water distribution system should also be lagged. Extended non-circulatory hot water pipe runs should be avoided and any ‘dead legs’ removed back to the recirculation loop. Pipe branches of individual hot taps should be of sufcient size to allow the water in each tap to reach 50°C within 1 minute of turning on the tap. If this cannot be achieved, then trace heating should be provided in non-circulatory hot water distribution pipework.

Thermostatic mixing valves (TMVs) should be positioned as close as possible to the point of use. Multiple showers served by a single TMV by should be frequently ushed.

Cold water storage tanks should be situated in a cool place, covered, lagged and screened from insects and general dirt ingress. They should be inspected annually and regularly cleaned out. Piping should be insulated and kept away from heat sources to prevent a temperature rise of more than 2°C.

All water services should be routinely checked for temperature, water demand and inspected for cleanliness and use. The frequency of inspection, and maintenance, will depend upon the system and the risks it presents. All inspections and measurements should be recorded. Hot and cold water system plans should be checked annually to ensure that they are correct and up to date.

Biological monitoring of hot and cold water systems using dip slides is not necessary where the water is supplied from a potable source, i.e. drinking water. However biological monitoring should be carried out on a monthly basis in water systems that are treated with biocides where storage and distribution temperatures are reduced from the recommended levels. This frequency should be reviewed after a year and may be reduced when condence in the efciency of the biocide regime has been established.

Hot, and exceptionally, cold water services should be cleaned and disinfected if routine inspection shows it to be necessary, or if the system has been substantially altered or entered for maintenance purposes in a manner that may lead to contamination.

(32)

Other Risk Systems

Spas and whirlpool baths can present a risk of exposure to legionella. Careful attention to the design, maintenance and cleaning of equipment, e.g. lters, and regular water treatment to prevent / control the risk of legionella is required.

Atomising humidiers and spray-type air washers may use water from reservoirs or tanks where the water temperature exceeds 20°C. Unless regularly cleaned and maintained, they can become heavily contaminated, especially in industrial environments. The risk can be prevented by using humidiers which do not create a spray, e.g. steam humidiers.

Action in the Event of an Outbreak

As part of the outbreak investigation and control, the following requests may be made by the enforcing authority:

▪ Shut down the suspected process;

▪ Take water samples;

▪ Emergency disinfection;

▪ Provide staff health records to identify any further undiagnosed cases of illness and prepare case histories of the people affected; and

▪ Co-operate with the investigation, e.g. tracing pipework runs, provision of any records and providing statements, e.g. from operatives, managers and water treatment providers. If a cooling water system is implicated in the outbreak then the fan should immediately be switched off, water samples taken and the system decommissioned as soon as is practicable. People should be kept clear of the tower and the enforcing authority consulted before proceeding any further.

Typically, with the fan off, there follows a regime of chlorination and water circulat ion, biodispersant addition, de-chlorination and water draining, manual cleaning, relling, chlorination and water circulation, de-chlorination and water draining, relling and water circulation and nally taking water samples for testing. The system can only be re-commissioned when test results detect no legionella.

(33)

Malaria

Malaria is a potentially fatal tropical disease caused by a parasite known as Plasmodium. Malaria is one of the leading causes of disease and death in the world. It is estimated that there are 300 to 500 million new cases every year, with 1.5 to 2.7 million deaths worldwide.

Malaria occurs extensively in tropical and subtropical regions.

Method of Infection

Malaria is spread through the bite of an infected female mosquito.

Malaria is caused by an infection of the red blood cells with a tiny organism or parasite called protozoa. There are four important species of the malaria protozoa (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae) and each has a slightly different effect.

These organisms are carried from person to person by the Anopheles mosquito. When it bites an infected person, the mosquito sucks up blood containing the parasite, which may then be passed on to the mosquito’s next victim.

Signs and Symptoms

The infected person may have feverish attacks, inuenza-like symptoms, tiredness, diarrhoea or a whole range of other symptoms.

The main symptom of malaria is a fever that occurs in regular episodes, with sweating and shivers (known as rigors), and exhaustion (because of anaemia). In some cases, it can affect the brain or kidneys.

About 90 per cent of travellers who contract malaria do not become ill until after they return home. Only about 12 per cent of these will become seriously ill.

On average, symptoms develop 10 days to four weeks after being bitten, but symptoms can appear up to a year later.

Malaria should always be suspected if these symptoms occur within the rst year of return from an infected area, and a test should be carried out to exclude the possibility of malaria as soon as possible.

The most severe form of the disease is cerebral malaria, which is fatal in up to six per cent of adults, mainly because it’s not diagnosed until it’s too late.

(34)

Workers at Risk

Malaria occurs where the Anopheles mosquito breeds, predominantly in rural tropical areas. From a Western perspective, it’s a threat to people travelling to malarial regions in Africa, the Middle East, Asia and Central America.

To put this into context, every year about 2,000 people return to the UK with malaria, and approximately 12 people a year die as a consequence of the disease.

Malaria is a major killer in many countries where resources for prevention, proper diagnosis and drug treatments are lacking. If diagnosed promptly, it can be easily treated but the symptoms can be vague.

Precautionary Measures

By far the most important step is to avoid being bitten by mosquitoes by: ▪ Using effective insect repellent;

▪ Wearing long sleeves and full-length trousers; and

▪ Staying in accommodation with screen doors and closing windows

It is important to take the recommended antimalarial drugs. Generally speaking, these are taken from one week before travel until one month after return, but this can vary depending on the type of drug and the country visited.

Even when taken exactly as advised, antimalarial drugs are not 100 per cent effective, so other preventive measures listed above should still be followed.

A major problem is the steady increase in malaria’s resistance to drugs used in both prevention and treatment. Prescribed antimalarial drugs should be taken in accordance with medical advice with the course of treatment being completed even if there are no symptoms being shown.

(35)

Snake Bites

A snake bite often results in puncture wounds inicted by the animal’s fangs and sometimes results in the injection of venom. The majority of snake species are non-venomous and typically kill their prey with constriction rather than venom. Venomous snakes can be found on every continent except Antarctica. Snakes often bite their prey as a method of hunting, but also for defensive purposes against predators.

Since the physical appearance of snakes may differ, there is often no practical way to identify a species and professional medical attention should be sought.

Method of Infection

Infection is usually by a snake bite or the direct injection of venom from a snake into the bloodstream of the patient.

Signs and Symptoms

The outcome of snake bites depends on numerous factors, including the species of snake, the area of the body bitten, the amount of venom injected, and the health conditions of the victim. Feelings of terror and panic are common after a snake bite and can produce a characteristic s et of symptoms mediated by the autonomic nervous system, such as a racing heart and nausea. Bites from non-venomous snakes can also cause injury, often due to lacerations caused by the snake’s teeth, or from a resulting infection. A bite may also trigger an anaphylactic reaction, which is potentially fatal.

First aid recommendations for bites depend on the snakes inhabiting the region, as effective treatments for bites inicted by some species can be ineffective for others.

The number of fatalities attributed to snake bites varies greatly by geographical area. Although deaths are relatively rare in Australia, Europe and North America, the morbidity and mortality associated with snake bites is a serious public health problem in many regions of the world, particularly in rural areas lacking medical facilities. Further, while South Asia, Southeast Asia, and sub-Saharan Africa report the highest number of bites, there is also a high incidence in South America and other equatorial and subtropical regions.

Workers at Risk

All workers where snakes are prevalent are at risk, such as grassy areas, dry sandy areas, wetlands, depending on the type of snake.

1026 Int Diploma IB5 v2

Element IB5:

Element IB5:

Biological Agents

Contents

Contents

Types and Properties of Biological Agents

Types and Properties of Biological Agents

Assessment and Control of Risk

Assessment and Control of Risk

References

Types and Properties of

Biological Agents

Fungi

Bacteria

Viruses

Protozoa

Sources of Biological Agents

Human Sources

Fungi

Bacteria

Viruses

Animal Sources

Fungi

Bacteria

Viruses

Environmental Sources

Fungi

Bacteria

E. Coli

Salmonella

Tetanus

Staphylococcus

Streptococcus Pneumoniae

Mycobacterium Tuberculosis

Viruses

Special Properties of Biological Agents

Cross Contamination

Rapid Multiplication

Rapid Mutation

Incubation Period

Infectious

Assessment and Control of Risk

Intentional Work and Opportunistic

Infection

Diseases Caused by Biological Agents

Zoonoses

Psittacosis (Ornithosis, Parrot Fever)

Method of Infection

Signs and Symptoms

Workers at Risk

Precautionary Measures

Leptospirosis (Weil’s Disease)

Method of Infection

Signs and Symptoms

Workers at Risk

Precautionary Measures

Cryptosporidiosis

Method of Infection

Signs and Symptoms

Workers at Risk

Precautionary Measures

Farmer’s Lung

Method of Infection

Signs and Symptoms

Workers at Risk

Precautionary Measures

Precautionary Measures

Hepatitis

Hepatitis

Method of Infection

Method of Infection

Signs and Symptoms

Signs and Symptoms

Precautionary Measures

Precautionary Measures

Human Immuno Deciency Virus (HIV) /

Human Immuno Deciency Virus (HIV) /

Acq

Acq