Illness Types, Causes and Prevention
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Published: Tue, 22 May 2018
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Consuming food or water contaminated with the bacterium Vibrio cholerae, causes acute diarrhoea and vomiting resulting in dehydration. Vibrio cholerae is usually found in impure water supplies (unsanitary disposal of excrement) and is spread to humans by drinking this contaminated water e.g. vegetables irrigated by fresh sewage, raw or uncooked fish/seafood taken from sewage, polluted water municipal water supplies. This pathogen colonizes and multiplies in the human small intestine causing diarrhoea which passes back into the water supply and the cycle continues.
The bacterium Vibrio cholerae is sensitive to acids in the stomach and digestive tract which are normally killed by the stomach but the toxin infects the intestinal cells and the sodium and chloride are altered by the increase of cyclic AMP levels. When cholera toxin (Ctx) which is a protein complex secreted by Vibrio cholerae, enters the infected intestine from the bacteria, it binds to the intestinal cells known as enterocytes, triggering endocytosis of the toxin. The Ctx consists of 5 B sub-units and 1 Active sub-unit.
To prevent and control spread of Cholera frequent proper washing, water should be boiled or disinfected for drinking, brushing teeth, washing cutlery, vegetables and fruit as well as food preparation equipment and containers. Don’t eat food or drink from unknown sources. Don’t eat raw meat , fish or seafood caught in tropical reefs or open water.
Athletes foot/ Tinea Pedis
Common fungul infection-harmless bacteria and fungi live naturally on your skin. When organisms multiply the skin becomes infected by a fungi called dermatophytes which live in and feed off dead skin tissue (not living ones). Its contagious and usually a scaly red rash begins between the toes. Fungus thrives in damp, warm , moist conditions e.g. showers, locker room floors and around swimming pools. Dermatophytes enters the skin through cuts and tears. They produce in the way of spores and can live a few years on surfaces. It is transmitted through direct contact or non-direct contact. Tinea Pedis produces asexual spores called conidia. When the dead skins cells slough off conidia is carried along. This infection can be very sore, itchy, scaly and sometimes flaking, blisters and cracked skin can occur and if untreated can spread to the groin and other parts of the body. To Prevent Athletes foot Dry feet properly with separate towel and don’t share your towel if infected put in the wash once used. Wear 100% cotton socks and change twice daily or more whenever damp. Avoid synthetic shoes, use anti-fungal powder or cream on your feet and anti-fungal powder in your shoes.
Tropical disease spread by infected female Anopheles mosquitoes. Caused by a parasite known as plasmodium. Malaria is not spread from person to person. Once bitten sporozites enters the blood stream and travels to the liver where they multiply into merozoite which infects the liver and then returns to the bloodstream, invading the red blood cells. The parasite grows and multiplies in the RBC Regular intervals (48hrs-78hrs) the infected RBC burst, releasing more parasites into the blood stream which causes the human to have bouts of chills, fever and sweating each time.
Malaria is spread by female mosquito biting an infected person, ingests the gametocytes. In the mosquitoes gut the infected human blood cells burst releasing the gametocytes to develop further into mature sex called gametes. Male and female gametes fuse forming diploid zygotes-develop into actively moving ookinets that bury into the mosquitoes gut wall forming oocysts, thus growing and dividing into sporozites. Oocytes burst releasing sporozites which travel and invade the mosquitoes salivary glands then having a human blood meal and the cycle of human infection starts all over again.
To prevent them from biting a mosquito net with no damage to it is to be used in High risk Malaria areas to prevent mosquitoes from biting and use of repellent and to keep very clean as Mosquitoes are attracted to sweat.
Virus infects respiratory system.
Three types of flu viruses A, B and C. Spread through air by sneezes, coughs or touching infected area then touching mouth or nose.
Influenza virus binds through hemagglutinin onto sialic acid sugars on surface of epithelial cells (nose, throat, lungs). Hemagglutinin is separated by protease then the cell imports the virus by endocytosis. Viral RNA (vRNA) molecule accessory proteins are released into the cytoplasm. The vRNA enters cytoplasm and translates or stays in nucleus. Newly formed viral proteins pass through golgi apparatus to cell surface or transport back into nucleus binding vRNA to form new viral genomes. Plasma membrane engulfs the virus and an endocytic vesicle is formed.
Virus is delivered to endosomal cell compartment (mildly acidic Ph conditions in endosomal lumen) and fusion of viral membrane occurs with membrane of endosome. vRNA is delivered to the nucleus. Synthesis of mRNA and vRNA are multiplied. Synthesis of viral protein in endoplasmic reticulum and cell cytosol result in budding and assembly of new viruses. Virus finally exits host cell.
To prevent spread of influenza wash hands and dispose of tissue. Cover mouth with tissue when coughing and sneezing. Avoid touching eyes,nose and mouth. Stay away from or take care when in contact with infected people. It is an ever changing virus and a new vaccine is offered frequently.
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To prevent cross-infection, best practise is a having hand hygiene routine, keeping hands clean and removing microorganisms:
- Before and after the procedure of a patient or body substance exposure.
- After body fluid exposure risk
- Before a clean or asceptic procedure.
- After touching their surroundings.
Wear protective clothing.
Wash hands thoroughly with soap for at least 15 seconds after removal of gloves, dry hands thoroughly with single-use towels disposed in pedal bin. Use alcohol-based hand rubs consisting of at least 60% – 80% v/v ethanol or similar. Use regularly even after hand-washing.
Aprons or gowns should be worn for single procedures, appropriately disposed of in area of use in allocated bins.
Where blood is splashed/sprayed wear gown, protective eyewear and gloves wearing only once. Asceptic technique used to sterilise sharps, equipment and surface barriers. Clean routinely.
When handling used/soiled linen wear gloves and gown, keep away from your body and put in laundry bin.
All ward beds should be cleaned weekly the ward domestic. Colour coded tagging system to be used to ensure no bed or trolley is ever missed.
When coughing or sneezing use your hand or tissue to cover, dispose immediately in waste bin and wash hands.
Better infection control of C.difficile and MRSA by controlled use of anti-biotics which can prevent further spread of resistance. Good hand hygiene by staff, visitors and patients prevents spreading
Assess patients on admission and isolate if necessary in private room and toilet facilities for infected patients.
Disposable gloves and gowns for staff and visitors.
Thorough cleaning with chlorine bleach
Avoid unnecessary use of anti-biotics but if necessary use the one with a narrow spectrum and shortest time possible. If very serious one must close off infected wards.
Regular deep cleaning and Vaporized hydrogen peroxide is advised in the use of decontamination of these infectious illnesses as well as general cleaning in the hospital to stop infections spreading.
Floors, toilets, beds surrounding areas should all be regularly kept clean and dry. Planned extensive deep cleaning and decontamination is needed for cleaning entire wards.
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The outer layer of skin, the epidermis, usually provides the first barrier to pathogens unless it is damaged by a cut, burn or insect bite.
Another physical barrier would be mucus membranes such as lining of the mouth, nose and eyelids which have mucus membranes that secrete mucus to fight against microorganisms. For example the tears in the eyes contain an enzyme called lysozyme that attacks bacteria and and protects the eye from infection i.e. sty or conjunctivitis.
In the airways microorganisms get stuck to the mucus along the passageways which is either blown out or coughed up which is aided by cilia that line the airways. The cilia aids the mucus up the airways, away from the lungs.
In the digestive tract, stomach acid, pancreatic enzymes, intestinal secretion and bile are other effective barriers. Peristalsis (stomach contractions) and the normal removal of cells lining the intestine will help eradicate harmful microorganisms.
In the Bladder it is protected by the urethra so when the bladder empties, it flushes out any bacteria that reaches it.
Blood also helps defend the body from harmful bacteria which will increase the white blood cells also known as leukocytes (monocytes and neutrophils) to engulf and destroy harmful or invading microorganisms. This increase can occur within a few hours because the white blood cells are made in the one marrow are then released.
Mast cells are found in most of the bodies tissue which usually come into close contact with the outside environment,the skin,airways and intestines. They are perfectly placed so they can detect early pathogens. Once they are activated these mast cells release a variety of soluble factors. Once stimulated they undergo degranulation, mediators are present within the cytoplasmic granules containing inflammation, including histamine. If you get a cut on your hand blood vessels dilate, the endothelial cells make adhesion molecules to the surface and are recognised by the immune cells which bind to the adhesion molecules and stick to the blood vessel wall then the leukocytes enter the tissue surrounding the vessel. The immune cell-chemoattractants cause the immune cells to exit the blood vessel and move to the site of injury signalling molecules of histamine which is capable of dilating blood vessels, increasing blood vessel permeability, and causing immune cells to exit the bloodstream and enter the damaged tissue.
During infection, Neutrophils, the most common of cells (80%), are the first to increase by numbers. They move about in contact with the endothelium of the blood vessels where they engulf the bacteria. Once taken up the bacteria is digested by lysosomes. The neutrophils then squeeze through the cells lining the capillaries and move to the tissues. The blood will carry the white blood cells to where the infection is because they are attracted to the chemicals that are released by the microorganisms. Neutrophils survive only for a few days. Macrophages are developed from the other white blood cells called monocytes which make up 6% of the white blood cells. They are made in the bone marrow and after circulating in the body for a day or two they also squeeze through the cells lining the capillaries and migrate into the tissues where they become macrophages.
Macrophages are relatively large cells and travel in the blood as monocytes, where they wander around collecting either microorganisms or other foreign bodies. There are plenty in the lungs, kidneys, lymph nodes and spleen. Neutrophils are the first cells to arrive at the infection but the macrophages which are longer lived take over at any major site.
If it is an allergic reaction or a parasitic infection the white blood cell eosinophils will help target this infection but only if it is not bacterial.
Sometimes the immune system overreacts to harmless foreign bodies and can have a very sensitive response such as an allergy which is an excessive immune response (hypersensitivity). Can be induced by plenty of harmless foreign bodies e.g. cat fur, bee/wasp stings, certain drugs, grass or pollen. They are then reacted by a type of antibody called IgE which bind to the mast cells. Then this causes the mast cells to produce potent chemical substances such as histamine which are responsible for the unpleasant symptoms.
Histamine cause the dilations of the capillaries , itching, flushes of the skin and constriction of the bronchi and can also cause the organs and tissues to swell due to capillaries being permeable and then increasing tissue fluid. One way of treating this reaction is by counter-reacting the histamine by giving an antihistamine.
Lymphocytes are unspecialised cells in the bone marrow. Some pass to the the thymas and to the lymph nodes. T-lymphocytes (T cells) are from the ethymas and the others cells are called B-lymphocytes (B cells)
B cells multiply rapidly and are stimulated by the presence of an antigen, some produce antibodies, while some become memory cells. The antibodies pass into the blood plasma and lymph and combine at the receptor sites with the antigen making it harmless in other words a humoral response which deals with foreign material.
When a human cell becomes infected by a harmful microorganism, these cells are recognised by the Killer T cell hence it will destroy the infected cell by direct contact and releasing a chemical which perforates the cell membrane.
Free movement of killer t cells that deal with foreign matter is known as cell-mediated response which can also help identify and act against cancer cells and bring about the rejection of transplanted tissue.
There is also the Helper T cells that assist other cells in the immune system. They don’t destroy or kill pathogens directly but they detect foreign antigens on the surfaces of the virus then send responses to the killer t cells, b cells and the macrophages to go into action.
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Higher Human Biology second edition James Torrence
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