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A pathogen is a biological agent that causes diseases. Two examples of pathogens are bacteria and viruses.
Shape and size
Proteins and nucleic acid determine the shape and size of a virus. They come in different shapes such as helical, polyhedral, enveloped and complex
There are so many species of bacteria and they all come in 3 different shapes. Some bacteria cocci (shaped like balls)
Some are borrelia (helical or spiral)
Some are Bacilli (rod or stick shaped)
Fungi also come in different shapes and sizes. They are single cells and also come in enormous chain cells that can stretch for miles.
Protozoa come in different shapes and sizes. There is an amoeba which changes its shape to paramecium that has a fixed shape and structure.
Have a genetic information molecule and protein layer that protect information molecules. The core has nucleic acids which make up the genetic information in the form of RNA and DNA. The capsid surrounds and protects the nucleic acid.
They are single microscopic organisms. They have cells which are smaller than animal and plant cells
The body of fungi consists of branching and colourless threads called hyphae. All the fungus will contain a number of thus hyphae linked to make up a tangled web called mycelium.
They are microscopic unicellular eukaryotes that consist of a complex internal structure and also carries out complex activities
They reproduce through the lytic cycle. Here they are joined to the host cell and fill the cell with its cucleic acid.
Some viruses do not multiply as quick and these are viruses such as HIV and herpes and this is because the nucleic acid in the chromosome is not active. Once it separates from the genetic material of the host cell it starts to multiply.
Bacteria reproduces by a form known as binary fission. Bacteria contains DNA which is copied and divided. Bacteria can divide every 20-30 minutes
Fungi can reproduce without sex and the single-yelled yeast reproduce asexually by budding.
Asexual reproduction of protozoans takes place when the cell separates in half by binary fission. Protozoans which are parasites multiply inside the host whilst other protozoans reproduce sexually
The transmission and development of infection
Cholera is a disease caused by a bacteria known as vibro cholerae. This bacteria cause watery diarrhoea which can lead to dehydration and can potentially cause death. An affected person can look out for symptoms such as vomiting, thirst, low blood pressure, dry mucous membranes and a rapid heart rate. These symptoms must not be ignored and the required immediate attention and one need to be highly hydrated.
To avoid cholera, people require the right sanitation, clean uncontaminated food and a clean water supply. A toxin known as choleragen is released in the small intestine after bacteria has passed through the stomach. Choleragen interrupts the epithelium functions to allow salts and water to leave the body which cause diarrhoea leading to dehydration.
To stay protected and avoid contraction cholera, boiling water before drinking and cooking is advised. Using chemically disinfected water is also recommended. Water can be disinfected by boiling and filtering it whilst adding drops of bleach or iodine tablet.
Raw food such as unwashed fruits and vegetables, unpasteurised milk products , uncooked fish, meat are also culprits when it comes to causing cholera. Hands should always be washed before and after any activities especially when handling food and using the toilet.
Athletes foot is caused by fungi belonging to a group known as dermatophytes. This fungi requires warmth, moist environments and feeds on keratin which are dead cells found in hair nails and skin. It does not normally affect people who are barefooted because of the conditions it requires. Fungal infection is normally and mainly affects the feet.
Dermatophytes enter the skin through tears and cuts where they begin to infect the cells. Tinea pedis is also a fungal infection which is the most known and most contagious. It can be passed on through skin-to-skin or non-direct contact. Anyone can be infected with this fungal infection through any place where the fungus is present.
Signs to looks out for if one suspects that they may have athletes foot are; scaling and flaking of skin which is accompanied with itching. Scratching can cause inflammation, swelling and pain. Blisters can also appear in affected areas.
To prevents athletes foot, regular washing and drying of feet using a separate towel is recommended. Avoiding using towels that would have been used by someone else can also - fungal powder can also be used to powder the feet.elp to minimise risks of transmitting the fungi.
Malaria is an infectious disease caused by parasitic protozoans. It is spread by mosquitoes bites. There are five parasites and the on e know to cause malaria is known as plasmodium. 90% of malaria deaths are in Africa. (www.who.int)
It is spread by a female mosquito called anopheles which normally moves and bites at night. After biting, the parasite is then passed into the blood stream and to the liver where it reproduces and destroys the cells. Anopheles mosquitoes breed in water and prefer to bite humans more than animals. They tend to favour seasonal conditions during and after rainy weather.
Vector control can reduce the transmission of malaria. To reduce the risks of infection, mosquito nets can be used which can reduce mosquito bites. Stagnant waters should be avoided and also using insecticides can control the mosquitoes. When one is travelling to places where there is a high risk of infection, medication known as sulfadoxin and pyirimethamin are recommended. Anti malarial medicines can minimise and prevent the risks of contracting malaria.
Influenza is a viral infection that targets the respiratory system such as the nose, throat and lungs. Symptoms of the flu are dry cough, nasal congestion, sweats and chills, headache and fever.
It is very contagious and can easily be spread by inhaling infected droplets in the air. These droplets are created when an infected person coughs or sneezes and this is when they are passed on to nearby people. It can also be spread by touching. If someone touches a surface with flu virus on it and then touch their nose, eyes or mouth, this can then pass on the virus.
The World Health Organisation (WHO) recommend flu-vaccination which can prevent an individual from being infected with the virus especially for people with low immune systems, the elderly, sick people, children as well as vulnerable people such as health workers. Good personal health and hygiene such as washing hands before and after activities is important. Putting hands over the mouth and nose whilst coughing and sneezing is good practice as well as washing hands after doing this. Staying away whilst infected with the virus can also avoid cross contamination.
Cross infection is the spread of infection from one organism to the next. The main culprits of the organisms are bacteria and viruses. Cross infection occur amongst patients and hospital equipment. These infections can be threatening to one' health and can cause serious illnesses such as pneumonia and meningitis alongside other diseases. Diarrhoea is also very common and can easily be passed if poor hygiene is being practised.
The main causes of cross-infection are bacteria from sneezing, coughing, virus through human contact, unclean environment and using unsterilized medical equipment.
Workers play an important role in minimising and preventing the risk of cross infection. Hand hygiene is one of the most important activity that one could do to avoid and reduce the spread of infection. A correct technique needs to be followed when washing hands and it is believed that very few people follow this. Soap and warm water need to be used when washing hands or an alcohol gel can also be used as a substitute. Hands need to be decontaminated before and after contact with a patient, after using the toilet and also before and after handling food. Whilst working in the health industry hand preparations are also to be followed to minimise the risks of infection. These include, covering cuts with appropriate dressings, artificial nails must not be warn, nails should be kept short and without polish.
Personal protective equipment should be used on patients if they need to and also the healthcare worker. This equipment includes gloves, aprons, goggles, masks and visors.
Disposal of chemicals, waste and sharps should be followed and done correctly. Policies on waste disposal showed be written and displayed where all stuff can see and read it. All waste should have colour coded bags, for example; red bags should be used for soiled linen and clothing; yellow bags should be used for clinical waste. Sharps should be disposed of in a sharps box or whichever method is in the hospital's policy.
How the body defends itself against pathogens which cause infectious diseases
T and B cells are defence cells that are moulded to different germs. When germs attack the body, T and B cells recognise and respond to this attack. They multiply in order to fight the infection and also they keep in mind whom the attacker was and make the body immune to it if there is going to be another attack. Infections occur when a pathogen attacks the body cells and reproduces. When the body has been attacked, this will lead to an immune response. A quick effective response will eliminate the infection. Some infections can be so severe that they will lead to diseases and these diseases mainly occur when the immune system is weak or when the virulence of the pathogen is high.
The specific immune response is made up of cells in the blood and other parts of the body. Immune tissues trap pathogens and there is a place where the cells can work together. In the immune system, the organs and tissues involved are the thymus, bone marrow, lymph nose, spleen, appendix, tonsils and Peyey's patches.
Non-specific barriers of the body are physical and chemical barriers that deter distant agents from penetrating the outer layer of the body. These barriers consist of the skin, mucous membrane, hairs and alia, gastric juice, vaginal secretions as well as urine tears, sweat, saliva and cerum. In the respiratory system there is the nasal opening covered by mucous membranes that trap dust and other airborne particles. The mucous membranes prevent these particles from reaching the lungs.The skin is a very important layer. It has dead hard cells that allow the surface to be acidic. When sweat leaves the body, salt is left on the skin. These conditions deter microorganisms from growing on the skin.
Tears get rid of fragments from the eyes. Vaginal secretions are also acidic and put off the growth of pathogens. In the eyes, mouth and nasal openings there is an enzyme called lysozyme that breaks down bacteria cell walls. Lysozyme is also in blood, sweat and some tissue fluids. The blood also contains elements that protect the body from organisms that cause diseases. There are white blood cells that kill invading bacteria and viruses as well as infected cells. Blood plasma clots the blood when there has been an injury, preventing invaders such as pathogens. Proteins in the blood take part in a cascade of molecular events that cause inflammation and release of molecules that stimulate phagocytic cells.
Inflammatory response is also a nonspecific defence mechanism that prevents infections from spreading though it can lead to tissue damage or death in serious cases as it involves swelling, high temperature and pain.
Organisms are kept under control by the host's defence which lessens chances of them causing diseases. Normal flora microorganisms compete with disease-causing organisms to protect the body.
Specific mechanisms are there for when the nonspecific mechanisms fail to protect the body. The specific defences allow the body to aim particular pathogens and pathogen-infected cells for destruction. Specific mechanisms rely on specialised white blood cells known as lymphocytes and contain T cells produced from lymphocytes that mature in the thymus gland and B cells from lymphocytes that mature in the bone marrow.
There are two specific immune responses which are cell-mediated response and the antibody-mediated response. T cells in the cell-mediated response are responsible for tearing down infected body cells by viruses or cancerous cells. Antibody-mediated response have both T and B cells and they destruct invading pathogens as well as get rid of toxins.
Cell-mediated and antibody-mediated responses are instigated after a type of phagocytic cell, a macrophage and engulf a pathogen. Macrophages digest pathogens and display antigens from the surface area of the pathogen. Antigens are molecules like proteins that bring out an immune response.
The cell-mediated response is triggered when lymphokines released from T cells stimulate other cells to take part in the immune response. Antibody-mediated response is triggered when lymphokines activate particular B cells to produce antibodies. Antibodies are tied to antigens on the surface of the pathogens and signal attack by phagocytic cells.
When a hoist comes across an antigen that activates a specific immune response the memory lymphocytes identify it and start to grow , divide and produce high levels of lymphokines and antibodies. This response is very quick because of the memory cells present. This quick response is also an explanation as to why hosts are immune to developing many diseases the second time round. This quick response does not give a pathogen enough time to reproduce to levels that arise in disease before the host's body destroys it.
Immunity is the physical, chemical and cellular defence against antigens. Immunity is classed as natural, acquired passive and active.
Natural immunity also known as innate is the state of being able to resist illnesses. Natural immunity is present from birth as one inherits it from parents unlike acquired immunity and remains throughout birth. It protects the body from contracting diseases.
It protects the body from pathogens present on other members of the same species. Acquired immunity is one which an individual develops during their lifetime. It can either be short lived or lifelong and it can result due to vaccinations or it can be passed down from a mother before the baby is born. It can also result after a disease has attacked the body and the most common one being chicken pox.
Like passive immunity, active immunity protects and fights the body against pathogens and is produced due to contact with these pathogens and antigens. Active immunity is classed natural or acquired and the immune response is not immediate as it can take days or weeks to develop but it is long lasting. During its response it produces antibodies.
Passive immunity is almost opposite to active immunity although they both protect the body against pathogens. It is transferred from one human to another human by injection and it is a very effective protection but it disappears with time, usually a few weeks or months. This immunity produces a quick response.
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