B5 Biological Agents Flashcards
Definition of a biological agent
A micro organism, cell culture or human endoparasite, weather genetically modified, which may cause infection, allergy, toxicity or otherwise create a hazard to human health.
Definition of a micro organism
A microbiological entity, cellular or non cellular, which is capable of replication or of transferring genetic material.
Such as fungi, Protozoa, viruses and bacteria
Endoparasites are?
Parasites that are capable of infecting and living within the human body ie malaria (single celled organism that lives in the blood) or tape worm (large multicellular organism that lives in the gut
Fungi
Fungi include moulds and yeasts.
Some fungi cause infection on or inside the human body such as athletes foot.
Some fungi produce toxins (mycotoxins) that are harmful to humans.
Fungi reproduce by forming spores that are released to find a suitable environment, inhalation of a large number of these spores can cause lung disease, such as farmers lung.
Bacteria
Bacteria are simple single celled organisms, that vary wildly in shape, many have flagella (tails) to allow them to move through liquid.
Some form spores that can survive adverse conditions such as heat, cold.
Bacteria grow in virtually any environment, many bacteria do not cause disease because of the immune system and some are even beneficial.
Some bacteria cause disease such as legionella.
Viruses
Viruses are micro organisms but not strictly alive. They are self replicating molecules that invade a host cell to produce more viruses.
Viruses are smaller than fungi or bacteria
Hepatitis and aids are two types of viruses.
Viral infections are usually prevented or halted by the bodies immune system, this response takes time to come into effect so there is usually a period of illness before the bodies defences become active. Some viruses are so severe the immune system can nor respond effectively and serious disease or even death result (eg small pox).
Some viral infections are not dealt with effectively by the body and so can persist eg HIV the causative agent of AIDs
Protozoa
Protozoa are a very large diverse group of single celled organisms that have a cell nucleus and there for are different to bacteria which have no nucleus. Protozoa are often motile (able to move) and do not photosynthesise.
Many diseases are caused by Protozoa such as malaria.
Diseases caused by Protozoa can not be treated with antibiotics (only drugs) and the body does not usually self resolve ie the immune system is incapable of dealing with the infection independently.
Pathogenic
Pathogenic (disease causing) bacteria come from three main sources:
*Human = many fungal, bacterial and viral infections are passed from person to person, this can happen by transfer of bodily fluids eg viral hepatitis (needles) tuberculosis by droplets from coughing, sneezing or by physical cross contamination.
*Animal: similar mechanisms to humans ie rabies from a bite, leptospirosis from rat urine, usually in contaminated water.
A disease spread from animal to humans is referred to as zoonosis.
*Environmental: such as legionella which can come from damp soil and water courses.
Zoonosis
Diseases that can be transferred to humans from animals
Vector-borne diseases can be transferred via a bite such as a mosquito carrying malaria.
Zoonotic diseases Animal influenza
- Animal influenza - a viral disease from various animals such as birds, pigs, horses and dogs. In some cases this viral infection can transform and become passed between humans.
Zoonotic diseases- Cryptosporidiosis.
- Cryrtosporidiosis - an infectious diarrhoea disease. It is caused by a protozoan parasite and can be transmitted via contact with infected animals (mainly cattle and sheep), it can be caught by faecal matter contaminated water or salad and passed between humans due to poor personnel hygiene.
Zoonotic diseases- Psittacosis
Psittacosis (Parrot fever) - is primarily an infection of birds, it can be transmitted by inhaling in infected material or occasionally By oral infection. Persons at risk are usually poultry farmers, bird keepers, cleaners and construction workers (anywhere where birds live and shit).
Zoonotic diseases- malaria
Malaria- is caused by the protozoan parasite, the parasite is spread by night biting insects (mosquitoes).
Diseases caused by biological agents- Hepatitis
Hepatitis- there are at least five types of hepatitis (A,B,C,D & E).
A - is usually contracted by the faecal-oral route
The others are blood-borne and transmitted by contact with contaminated bodily fluids.
Hepatitis is the most common risk for medical staff and refuge disposal
Diseases caused by biological agents- HIV
HIV- human immunodeficiency virus is the virus responsible for AIDS ( acquired immune deficiency virus). HIV attacks the immune system by which the body cannot resist infections.
Diseases caused by biological agents- Legionella
Legionella is a bacteria which is responsible for two diseases legionaries disease and Pontiac fever.
Legionella is similar to pneumonia and is caused by inhalation of water vapour which has viable legionella bacteria in and is capable of reaching the alveoli.
Bacteria is widespread and can be found in water sources and soil as well as man made systems typically grows in 22 to 45C but can not survive above 60C
Requires sediment or sludge, scale and organic material.
Initial symptoms include high fever, chills, head aches and muscular pain.
Dry cough soon develops and most patients suffer difficulties with breathing.
Diseases caused by biological agents- Leptospira
Leptospira (Weils disease) - found in the kidneys of infected rats as well as other mammals such as cattle. Infection to humans is via contact with urine or water that has been urinated in.
The bacteria can enter via damaged skin or the mucus membranes of the mouth.
Flu like symptoms (head ache, fatigue! Fever) lasting about a week, it can lead to abdominal pains, jaundice and liver damage as the bacteria moves out of the blood and invades the internal organs, can be fatal if left untreated.
Diseases caused by biological agents- Norovirus
Norovirus - also known as winter vomiting bug, this is the most common cause of gastroenteritis in the UK.
The virus is highly contagious and easily spread if an infected person doesn’t wash their hands before handling food, it is possible to catch by contact with contaminated surfaces
Symptoms/ effects
Abdominal pain, vomiting and diarrhoea
Clears up after a few days
Three categories of COSHH exposure
- Deliberate intention: exposure resulting from a deliberate intention to work with a biological agent ie work with biological agents in a research lab.
- Incidental: Exposure that arises out of work activities but is incidental to it ie activities that does not involve direct work with the agent itself such as health care, refuge disposal, sewage workers.
- Does not arise out of the work activity: eg where one employee catches a respiratory infection from another, as a result of working in close proximity to each other.
The final category is not seen as work related as there is direct connection to work being carried out.
General requirements of COSHH
- Reg 6: Assessment of the Risk to health created by the work.
- Reg 7: Prevention or control of exposure.
- Reg 8: Use of the control measures.
- Reg 9: Maintenance, examination and testing of control measures.
- Reg 10: Monitoring exposure at the workplace.
- Reg 11: Health surveillance.
- Reg 12: Information, instruction and training of those exposed.
- Reg 13: Arrangements to deal with accidents, incidents and emergencies.
Properties of a biological agent
- Rapid mutation rate - characteristics change quickly making it difficult for the body to recognise and attack the agent.
- Incubation period - time delay between infection and first signs of symptoms of disease apparent.
- Infectious - A person or animal suffering from a disease is capable of spreading it to others.
- Ability to multiply rapidly- small numbers of agents that may not pose a risk of infection can multiply to a large number that are capable of overcoming the bodies defences to cause an infection.
Biological agents and RIDDOR
Biological agents can cause the following reportable incidents
- Fatality - where work related accidental exposure result in death.
- Disease - Any disease or acute illness caused by occupational exposure to a biological agent.
- Dangerous occurrence - Any event which results or could have resulted in the release or escape of a biological agent likely to cause severe human infection or illness (group 3 or 4)
Needle stick injury that could cause the above or over 7 day.
Pathogenic biological agent hazard groups
Approved list of biological agents classifies pathogenic biological agents into four categories according to their health risk by considering four characteristics
1) - Its ability to cause human disease
2) - Whether it may be a hazard to workers
3) - Likelihood that the disease might spread to the community
4) - The availability of effective prophylaxis (preventive measures such as immunisation) and treatment.
Microbiological Safety cabinet (class 1)
- open fronted where air is drawn in and filtered through a HEPA filter and discharged to atmosphere.
- cabinet protects the operator only from agents that may infect him by airborne routes.
Microbiological Safety cabinet (class 2)
Open fronted in much the same way as class 1 but air drawn down through slits in the base of the cabinet and filtered via HEPA filter and some air is returned down to form an air curtain.
Cabinet protects users and the work from external contamination
Microbiological Safety cabinet (class 3)
Totally enclosed in a leak proof cabinet where operator works using glove ports. Air is drawn in and through a HEPA filter and discharged to atmosphere.
Cabinet protects workers and work from contamination
Four criteria used to classify biological agents into hazard groups (schedule 3)
Ability or likelihood the agent will cause infection/ disease
The severity of the infection or disease that may result
How likely that infection or disease will spread to the community
Availability of vaccines or other effective treatments
