Disease is any condition that adversely affects the function of any part of a living thing. Health is the wellbeing of the organism. All our body functions, which are under the control of our genes, work together to maintain health. Difficulties in determining health and disease: Disease can cover a wide range of conditions including minor conditions, such as a cut finger or an ant bite, as well as the more obvious diseases like cancers. Health varies on a daily basis and is not just the absence of disease. Health varies with age and the susceptibility to disease.
It is a state of physical, mental and social wellbeing. The difficulties of defining the terms health and disease include that: * it is possible for a person to be healthy and have a disease at the same time * The terms are used in general conversation and have different meaning to the scientific definition. * For example: pregnancy affects “normal functioning” of the body BUT IS NOT considered a disease. * The terminology again, is subjective and biased to how the individual perceives themselves to be healthy or not Infectious and non-infectious disease:
* Non-infectious diseases can’t be passed from one person to another. Instead, these types of disease are caused by factors such as environment, genetics and lifestyle. Non-infectious diseases are not caused by specific organisms and are studied and cared for more in developed countries, where many infectious diseases are under control. Examples of inherited non-infectious conditions include cystic fibrosis and Down syndrome, and examples of conditions caused by environmental or lifestyle factors include heart disease and skin cancer.
Ways of prevent of non-infectious diseases can be for example cutting down on exposure to cigarette smoke and the sun’s rays as these will prevent certain types of cancers and eating healthier which can prevent diabetes. * Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the diseases can be spread, directly or indirectly, from one person to another. Zoonotic diseases are infectious diseases of animals that can cause disease when transmitted to humans.
Infectious diseases can be transmitted from the air, contact with infected people like kissing, consuming infected water or foods, sexually and from blood for example mosquitoes passing on malaria to a person. Many infectious diseases are bigger problems in underdeveloped countries, where there is less control of sanitation, fewer vaccinations and other problems that contribute to higher levels of infectious disease. Examples of infectious diseases include colds, flu, herpes, measles and aids. Pathogens: A pathogen is any organism that can produce a disease.
Pathogens range from viruses so small that thousands will fit side by side in one millimetre to tapeworms that can be several metres long. They are all infectious. Transmission of pathogens occurs through many different routes, including airborne, direct or indirect contact, sexual contact, through blood, breast milk, or other body fluids. Pathogens may live outside the body, such as the fungus that causes ringworm, inside particular organs, such as parasitic worms in the intestine, in tissues or inside cells. Prions: A Prion is an infectious agent that is composed primarily of protein.
To date, all such agents that have been discovered propagate by transmitting a miss-folded protein state; the protein itself does not self-replicate and the process is dependent on the presence of the polypeptide in the host organism. Prion’s cause neurodegenerative disease by aggregating extracellular within the central nervous system to form plaques known as amyloid, which disrupt the normal tissue structure. This disruption is characterized by “holes” in the tissue with resultant spongy architecture due to the vacuole formation in the neurons.
While the incubation period for Prion diseases is generally quite long, once symptoms appear the disease progresses rapidly, leading to brain damage and death. Prions, like viruses, are not actually alive, although both can reproduce by hijacking the functions of living cells. Example of Prion diseases include Bovine spongiform (mad cow disease) encephalopathy and Creutzfeldt-Jakob disease. Viruses: Viruses are tiny organisms that may lead to mild to severe illnesses in humans, animals and plants. This may include flu or a cold to something more life threatening like HIV/AIDS.
A virus is not a living thing as it can’t reproduce outside its host. The virus particle or the virions attack the cell and take over its machinery to carry out their own life processes of multiplication and growth. An infected cell will produce viral particles instead of its usual products. Viruses Consist of DNA or RNA enclosed in protein, live inside living cells. They are so small that they cannot be seen with a light microscope. Bacteria: Bacteria do not contain a nucleus. If bacteria form a parasitic association with other organisms, they are classed as pathogens.
Pathogenic bacteria are a major cause of human death and disease and cause infections such as tetanus, typhoid fever, diphtheria, syphilis, cholera, food borne illness, leprosy and tuberculosis. Protozoan: Protozoa are a diverse unicellular group of organisms. Some kinds of protozoa act as a parasite in humans; they cause diseases like malaria, Amoebiasis and Chagas disease. Fungi: Fungi are living creatures; some fungi can cause serious diseases in humans, several of which may be fatal if untreated. These include aspergilloses, candidoses and mycetomas.
Other fungi can attack eyes, nails, hair, and especially skin, the so-called dermatophytic and keratinophilic fungi, and cause local infections such as ringworm and athlete’s foot. Fungal spores are also a cause of allergies, and fungi from different taxonomic groups can evoke allergic reactions fungi is also used as a drug to kill bacteria and fungi infections for example penicillin. Macro-parasites: Macro-parasites are parasites that are large enough to be seen by the naked eye; examples of macro-parasites include ticks, mites and flatworms. Malaria Malaria is a disease caused by a protozoan of the genus Plasmodium.
It has a complicated life cycle requiring a mosquito of the Anopheles genus to carry the Plasmodium to its host. The disease is common in tropical areas where the Anopheles mosquito lives. The female mosquito requires a blood meal to complete the reproduction cycle of the mosquito. During the blood meal the Plasmodium (sporozoites) are transferred from the mosquito salivary glands into the blood system of the host. The sporozoites travel to the liver via the blood system and enter cells in the liver. After 12 days a new form of the protozoan called merozoites are released and these enter blood cells. At the same time toxins are released.
This causes the sweats and fever that are associated with the disease. Some of the merozoites develop into gametocytes and may be sucked up by another mosquito in another blood meal. In the gut of the female mosquito the gametocytes become gametes and are fertilised. This forms sporozoites which will travel to the salivary glands of the female mosquito and await the next blood meal to enter another host. The disease was known from the start of recorded history but it took many researchers to uncover the complicated life cycle above. Sir Ronald Ross (1857 – 1932) was a British medical officer working in India.
For thousands of years, people had been puzzled about the way in which malaria spread but they knew that malaria was common in areas close to swampy land. In the late 1800s, people were beginning to wonder if mosquitoes could spread malaria. Ross collected mosquitoes and painstakingly dissected them under a microscope. He discovered the micro-organism that was known to cause malaria, inside the bodies of Anopheles mosquitoes. This led to the realisation that insects could carry pathogens, that is, they can be vectors of disease. Date| Development| 18 BC| The disease malaria was described by the Romans.
Malaria was thought to come from swamps so the name means ‘bad air’. | 1820| Quinine used to prevent the disease, and was very effective but had bad side effects. | 1880| Charles Laveran a French army doctor observed the malarial parasite. | 1886| Golgi observed asexual reproduction in the protozoan Plasmodiumand identified two species. | 1897| Ronald Ross discovered that Plasmodium was the protozoan that caused the disease malaria. | 1988| Giovanni Grassi named the Anopheles mosquito as the carrier of the malarial parasite| 1940| Chloroquinine the first synthetic anti-malarial drug was use|
HIV| Cause| The Human immunodeficiency virus | Transmission| HIV can be transmitted from an infected person to another through: * Blood (including menstrual blood) * Semen * Vaginal secretions * Breast milkActivities That Allow HIV Transmission * Unprotected sexual contact * Direct blood contact, including injection drug needles, blood transfusions, accidents in health care settings or certain blood products * Mother to baby (before or during birth, or through breast milk)| Host response| Antibodies to HIV are formed but these neither clear the infection nor are protective.
| Major symptoms| Early stage: * No early symptoms – some people notice no early infection symptoms * Sore throat * Body rash * Flu-like symptoms * Fever * Headache * Tiredness * Enlarged lymph nodes Late stage: * persistent tiredness * night sweats * weight loss * persistent diarrhoea * blurred vision * white spots on the tongue or mouth * dry cough * shortness of breath * fever of above 37C (100F) that lasts a number of weeks * swollen glands that last for more than three months| Treatment| There’s no cure for HIV/AIDS, but a variety of drugs can be used in combination to control the virus.
Each of the classes of anti-HIV drugs blocks the virus in different ways. It’s best to combine at least three drugs from two different classes to avoid creating strains of HIV that are immune to single drugs. The classes of anti-HIV drugs include:Non-nucleoside reverse transcriptase inhibitors (NNRTIs). NNRTIs disable a protein needed by HIV to make copies of itself. Examples include efavirenz (Sustiva), etravirine (Intelence) and nevirapine (Viramune). Nucleoside reverse transcriptase inhibitors (NRTIs). NRTIs are faulty versions of building blocks that HIV needs to make copies of itself.
Examples include Abacavir (Ziagen), and the combination drugs emtricitabine and tenofovir (Truvada), and lamivudine and zidovudine (Combivir). Protease inhibitors (PIs). PIs disable protease, another protein that HIV needs to make copies of itself. Examples include atazanavir (Reyataz), darunavir (Prezista), fosamprenavir (Lexiva) and ritonavir (Norvir). Entry or fusion inhibitors. These drugs block HIV’s entry into CD4 cells. Examples include enfuvirtide (Fuzeon) and maraviroc (Selzentry). Integrase inhibitors.
Raltegravir (Isentress) works by disabling integrase, a protein that HIV uses to insert its genetic material into CD4 cells. | Prevention| * Use a new condom every time you have sex. * Use a clean needle. * If you’re pregnant, get medical care right away. If you’re HIV-positive, you may pass the infection to your baby. But if you receive treatment during pregnancy, you can cut your baby’s risk by as much as two-thirds. * Tell your sexual partners if you have HIV. * Use the drug trudava which helps to prevent the virus, but a condom should still be used during sex.
| control| To control HIV it is important to inform people about the ways it can be transmitted and how to eliminate the risk of getting it, also all blood donors have to be tested for HIV and all myths to be dispelled. | Epidemiology: lung cancer as an example Epidemiology is the study of the patterns, causes, and effects of health and disease conditions in defined populations. It is the cornerstone of public health, and informs policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive medicine.
To be valid the study must be focused on a large group of people rather than a few individuals and relate a certain population that can be identified. Through doing so it allows for trends and causative factors to be observed. The study must also have unequal exposure to the thing that is suspected to cause the disease for example studying if cigarettes create a higher risk of lung cancer, the population should consist of people who smoke and people who don’t. Also other considerations like age, sex, ethnic and group and occupation must also be noted. Epidemiology has three main aims: * To describe disease patterns in human populations.
* To identify the causes of diseases (also known as aetiology). * To provide data essential for the management, evaluation and planning of services for the prevention, control and treatment of disease Epidemiologic studies determine whether people exposed to a certain risk factor (e. g. , cigarette smoking) are significantly more likely than those not exposed to develop a certain health outcome (e. g. , lung cancer)—in other words, is there a strong relationship between the exposure and the illness. Analysis is accomplished through statistical manipulation of data regarding the health problem under investigation.
* Descriptive: First type of study when investigating the cause of a disease. In relation to smoking causing cancer they looked at age, sex, exposure. * Analytical: Used to collect more data, which is then statistically analysed to develop hypotheses as to the likely cause(s) of the disease. Two indicators include: Morbidity (number of cases of the diseases) and mortality (% of the population that dies from the disease). * Case control studies: Compare people with the disease (case) to people without the disease (control) and looking for different exposure to the possible causes of the disease.
* Cohort studies: Involves studying two or more similar groups who are free of the disease. * Intervention: Used to test the effectiveness of a treatment, or the effectiveness of a public health campaign to change the behaviour of the population as a whole in order to decrease the incidence of the disease. Inherited disease Cystic fibrosis: Inherited diseases are genetically transmitted and are caused by errors in genetic information. Cystic fibrosis (CF) is a chronic disease that affects organs such as the liver, lungs, pancreas, and intestines.
Cystic fibrosis is caused by a mutation in a gene called the cystic fibrosis transmembrane conductance regulator (CFTR), which serves an important function in creating sweat, mucus, and digestive juices. Only one copy of this gene is needed to prevent cystic fibrosis, and most people have two copies. However, if a person lacks at least one unaltered version of this gene that can produce a CFTR protein, cystic fibrosis will result. Cystic fibrosis is a hereditary disease in that one can only get it if his or her parents both are carriers.
A child must inherit two copies of the defective gene in order to have CF. A child with two parents who are carriers of the defective gene has a 25% chance of having cystic fibrosis and being a carrier of two defective copies of the gene, a 25% chance of not being affected nor a carrier of a defective copy of the gene, and a 50% chance of not being affected by CF but carrying one defective copy of the gene. Symptoms: * Recurrent and severe chest infections. * Malabsorption of nutrients and failure to thrive. * Passing by large, foul-smelling motions. * Excessive salt in sweat. * Infertility.
There is no treatment but giving supplements to their diet to counter the effect of insufficient digestion and absorption of nutrients and daily physiotherapy breathing exercises to prevent the excessive build up of mucous in the lungs, helps to control the disease. Nutritional deficiencies (Scurvy) Nutritional deficiencies are caused by diets lacking the proper balance and amounts of nutrients. Scurvy is a disease caused by a diet that lacks vitamin C (ascorbic acid). This may be due to ignorance, famine, anorexia, restrictive diets (due to allergies, food fads, etc. ), or difficulty orally ingesting foods.
Patients develop anaemia, debility, exhaustion, edema (swelling) in some parts of the body, and sometimes ulceration of the gums and loss of teeth. Initial symptoms: * Pain and tenderness in the legs. * Swelling of the long bones. * Swollen, purplish and spongy gums. Advanced symptoms: * Gangrene. * Re-opening of old wounds. * Spontaneous haemorrhaging. Treatment: Simply involves the inclusion of adequate amounts of Vitamin C in the diet. In order to prevent the occurrence of scurvy, adequate amounts of Vitamin C should be included in the daily diet. Environmental diseases (Mesothelioma).
Environmental diseases are those caused by lifestyle or exposure to chemicals. Mesothelioma, more precisely known as malignant mesothelioma is a rare cancer of the mesothelial cells, most commonly those in the lining that covers the lungs. Mesothelioma is caused by exposure to asbestos and patients don’t get any symptoms until 20 to 30 years after exposure. There is no cure and treatment can only slow down the progression of the disease. Symptoms: * Shortness of breath caused by tumour squashing the lungs. * Chest pain. * Weight loss, loss of appetite, fatigue, fevers and anaemia. Smoking and lung cancer:
Smoking can causes lung cancer as tobacco smoke contains 70 different cancer causing substances. When you inhale smoke, these chemicals enter your lungs and spread around the rest of the body. Scientists have shown that these chemicals can damage DNA and change important genes. These causes cancer by making cells grow and multiply out of control. Lung cancer isn’t just caused from smoking it can also be hereditary, from second hand smoking, HPV infection, exposure to substances (chromium, tar, arsenic, and nickel) and the second most likely cause of smoking radon gas. Statistics for smoking causing lung cancer:
Between 80 and 90% of lung cancers are due to smoking, yet 10% of men and 20% of women who develop the disease have never smoked. On the other side of the equation, many people who smoke do not develop lung cancer. An earlier Canadian study quoted the lifetime risk for male smokers at 17. 2% (11. 6% in women) versus only 1. 3% in male non-smokers (1. 4% in female non-smokers). In a 2006 European study, the risk of developing lung cancer was: * 0. 2% for men who never smoked (0. 4% for women) * 5. 5% for male former smokers (2. 6% in women) * 15. 9% for current male smokers (9. 5% for women)
* 24. 4% for male “heavy smokers” defined as smoking more than 5 cigarettes per day (18. 5% for women) Skin cancer (melanoma) | Occurrence| Australia has the highest incidence of melanoma in the world and melanoma is often referred to as Australia’s national cancer. * Melanoma makes up only 2. 3% of all skin cancers but is responsible for 75% of skin cancer deaths. * Melanoma is the third most common form of cancer in Australian men and women (10% of all cancers) * 1 in 17 Australians will be diagnosed with melanoma before age 85 * Melanoma is more commonly diagnosed in men than women.
The risk of being diagnosed with melanoma by age 85 is 1 in 14 for men compared to 1 in 23 for women. | Symptoms| Main symptom is Unusual moles To help identify characteristics of unusual moles that may indicate melanomas or other skin cancers, think of the letters A-B-C-D-E:A is for asymmetrical shape. Look for moles with irregular shapes, such as two very different-looking halves. B is for irregular border. Look for moles with irregular, notched or scalloped borders — characteristics of melanomas. C is for changes in colour.
Look for growths that have many colours or an uneven distribution of colour. D is for diameter. Look for new growth in a mole larger than 1/4 inch (about 6 millimetres). E is for evolving. Look for changes over time, such as a mole that grows in size or that changes colour or shape. Moles may also evolve to develop new signs and symptoms, such as new itchiness or bleeding. Other suspicious changes in a mole may include: * Scaliness * Itching * Spreading of pigment from the mole into the surrounding skin * Oozing or bleedingCancerous (malignant) moles vary greatly in appearance.
Some may show all of the changes listed above, while others may have only one or two unusual characteristics. | Cause| Like other cancers, melanomas are composed of cells which multiply without the normal control of the body’s regulating systems. It has not yet been possible to completely identify how melanoma develops however a significant link between exposure to sunlight and the development of melanoma has been established. People living in climates with high levels of ultraviolet light have an increased risk of melanoma. Indoor tanning beds increase the risk of melanomas as they produce high levels of UV light.
Melanoma could also be hereditary as test can now be done to see if people are at higher risk of getting melanomas. | Treatment/management| Surgery is the best option during the early stage of the melanoma as it can get rid of it before it spreads to certain organs and places which are hard to treat. Drugs or other substances can be used to target and destroy melanoma cells and leave normal cells. Radiation therapy. Immunotherapy is a type of systemic therapy useful in the treatment of melanoma at high risk for recurrence and for metastatic disease.
Chemotherapy is a type of therapy in which a medication is given to treat melanoma. The goal of chemotherapy is to destroy melanoma cells throughout the body. | Bibliography: * C Parker E Neville, Lung cancer 8: Management of malignant mesothelioma, Thorax scientific journals 2003 volume 58 issue 9, http://thorax. bmj. com/content/58/9/809. full * Epidemiology [on-line] 2011, http://www. health. qld. gov. au/epidemiology/, 2/9/2011 * Glenda CHIDRAWI MARGARET ROBSON with Stephanie HOLLIS, Biology In Focus, The McGraw-Hill companies, First published in 2008.
* HSC online Search for better health: 2. Infectious and non-infectious diseases [On-line] 2013, http://hsc. csu. edu. au/biology/core/better_health/9_4_2/942net. html * Melanoma [online] 2013, http://www. cancer. org. au/about-cancer/types-of-cancer/skin-cancer/melanoma. html, 19/3/2013 * Mesothelioma [ON-LINE] 2013, http://www. betterhealth. vic. gov. au/bhcv2/bhcarticles. nsf/pages/Mesothelioma, 23/07/2013 * Pathogen information [On-line] 2011, http://www. epa. gov/enviro/html/icr/pathogens. html, 28/10/2011