IGCSE human biology-- chap: disease....by T@NV!R


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IGCSE human biology-- chap: disease....by T@NV!R

  1. 1. Human biology Disease Microbes are of two types: • Pathogenic -- can cause disease in human • Non-pathogenic – does not cause disease in human e.g. E.coli Types of pathogenic disease in human: Jul. 22nd • Bacterial – e.g. salmonella typhi causes typhoid 2012 • Viral – e.g. HIV causes AIDS • Fungal – e.g. tinea causes athletes foot Types of disease: • Animal vectors • Air borne –through droplet infection • Water borne • Direct contact • Sexually transmitted • Food borne STD [sexually transmitted disease] • AIDS • Syphilis • Gonorrhea Immunity --- it is the ability of the body to resist infection • Natural active immunity --- it is a kind of immunity acquired when an individual is able to make its own antibody against the pathogen. The entry of which is natural. • Natural passive immunity --- it is a type of immunity acquired where the naturally occurring antibodies made against the pathogens are taken in form an outside source. The antibodies are not self made • Artificial passive immunity --- specific antibodies are directly injected into a person acquired form a different source. Provide immunity temporarily. The antibodies which are injected are called serum • Vaccine -- A vaccine is an immune biological substance which contains the live or dead form of the pathogen, which when injected provide lifelong immunity • Incubation period --- the period between becoming infected by germs and the appearance of the symptoms of disease • Vaccination – the process of injecting a person with a harmless [weakened or dead] form of a virus to stimulate the immune system to produce cells and proteins that will destroy that type of virus • Carrier – it is an individual which harbours the germs without showing signs and symptoms of the disease and unknown to discharge the multiplying germs through faeces and expiration. • Case – it is an individual suffering from a disease and showing signs and symptoms • Vector – a vector is an individual which is known the causative without itself getting infected.• Endemic disease – a disease which is always present in an area• Pendemic disease – a large –scale outbreak of disease which spreads from country to country
  2. 2. Human biology Disease• Epidemic disease -- a sudden outbreak of disease which spreads quickly through the population of an area Viral diseases • What are the diseases caused by viruses? Influenza [flu],Jul. 22 AIDS, hepatitis, west Nile, measles, herpes, shingles, chicken pox, nd colds, 2012 monkey pox, polio, small pox, Ebola & some cancers [Epstein barr] • Common cold [influenza-‘flu] Causative agent – influenza virus [affects upper respiratory tract] The virus changes it s composition very rapidly by mutation. Thus it becomes resistant to medicines or vaccines. So successful vaccination against common cold is not easy Mode of transmission --- By air droplet infection: when a person suffering from common cold sneezes, coughs or even breaths they spread out a fine spray of pathogens. These pathogens enter into healthy person through the nose during breathing in and out and thus infect the person Treatment --- symptomatic treatment Influenza being a viral disease has got no curative treatment since the virus changes their genetic composition by mutation very rapidly. So no successful vaccine is available Prevention --- • An infected person should cover the mouth while talking, sneezing and coughing with a handkerchief • Avoid close contact with an infected person • Do not use personal belongings of an infected person • Avoid gathering and overcrowded and poorly ventilated places • Treatment of the infected person helps eliminating the source of infection • Health education • Improvement of socio economic condition • AIDS [acquired immune deficiency syndrome] Causative agent -- HIV [retrovirus] {human immune deficiency virus} – weakens the immune system Mode of transmission – It is transmitted through body fluid by: • Through sexual intercourse with multiple sexual partners and amongst homosexuals • Through blood transfusions • Through cuts and mucus membrane • Placental transmission from the mother to the baby
  3. 3. Human biology Disease• During surgical operation with infected instrumentsTreatment --- symptomaticPrevention ---• Avoid multipleJul. 22nd sexual partners• Use sterilize surgical instruments 2012• Screen blood before transfusions• Avoid pregnancy if the person is sex worker• Use condom during sexual intercourse• Identify cases and isolate them• Use sterilize syringe [needle]• Avoid using same needles for different persons in hospitals and among drug abusers• Burn all the personal belongings of the infected person after death• Provide health education • PoliomyelitisCausative agent --- polio virus [it affects children between the age group of 0-5]General information:• This disease is becoming less common due to wide spread use of prophylactic immunization by oral vaccines.• The polio virus attack the spinal cord, brain stem & cortex [CNS]• The polio virus eats up the nerve cells• Unfortunately, the nerve cells cannot regenerate / recover. So the damage done is permanent• Polio vaccine is a live attenuated- vaccineIncubation period – from seven to fourteen daysMode of transmission --- • By droplet infection • Oro-faecal route – through contaminated finger, water, milk, food, fliesSymptoms –The virus enters through the respiratory tract, i.e. though the nasopharynx. Ai the onset, there is a mild headache andpyrexia. This is followed by neck stiffness and meningeal irritation. Paralysis may occur later.Treatment --- • In the early stages bed rest is required • Paralysis is the greatest at the end of the 1 st week of the major disease • Gradual recovery may take place for several months but any muscle showing no sign of recovery by the end of the month will not regain useful function • Death may occur due to respiratory paralysisPrevention – By oral vaccination between the age of 3 to 6 months and after one yearOral vaccine --- small pox
  4. 4. Human biology Disease Bacterial diseases • Diseases caused by bacteria: Cholera, tuberculosis [TB], Lyme disease, pertussus, salmonella, staph infections, streep throat, Jul. 22nd leprosy, tetanus, diphtheria, E. coli, flesh eating [necrotizing fasciitis] & rickets • Cholera 2012 Causative agent --- bacteria [vibrio cholerae] Mode of transmission – [water and food borne disease] Untreated sewage reaching a water source and the water consumed without proper treatment / chlorination Infected shell fishes or algae from water contaminated with untreated sewage Houseflies that sit on untreated sewage as well as food for humans and transmit bacteria into food Careless attendance of patients, contaminate themselves and spread the disease • Incubation period: 2-6 daysSign and symptoms – • Diarrhoea and vomiting • Fever muscle cramps weakness and even death if not rehydratedTreatment – • ORS [oral rehydration saline]: to replace water and electrolytes lost during diarrhoea • Antibiotic: e.g. tetracycline to kill bacteria. Drugs like-Chloren phenicol and sulphur diazolePrevention of spread – • Prevent excess houseflies [since houseflies sit on sewage as well as human food] by: • Killing them with insecticides • Keeping the food covered / inside fridge • Hygiene disposal of faeces since patients pass bacteria in faeces • Supply of clean and safe drinking water since bacteria is transmitted in water • Isolation of the patient • Tuberculosis [TB] Causative agent – Mycobacterium tuberculosis [they break down lung tissue] This bacterium is of 3 types: • Human type – causes pulmonary tuberculosis in lungs • Bovine type – cause TB in cattle • Atypical type – seen mostly in children • A carrier is more dangerous than a case • Carrier is an infected person showing no signs & symptoms • A carrier ca discharge the germs through the fingers, nails, and faeces to make them get infected unknowingly Mode of transmission –
  5. 5. Human biology Disease• By air borne droplet infection• When an infected person sneezes, sputum,, coughs, or even breaths, he spreads a fine spray of pathogens• The pathogens enter into the air and takes up a layer of moisture producing droplets• When a healthy personnd Jul. 22 encounters these droplets through the nasal root is infected• Sputum from an 2012or sputum causative [positive] pulmonary TB patient to the primary source of infection. open• Milk form infected cattle and its products are the source of infectionSymptoms ---Persistent cough, breathlessness, fever, weight loss, generalized weaknessTreatment ---• Patient must be hospitalized because side effects in most cases are quite severe• Combinations of antibodies are given for six to nine months with enough vitamins & iron supplements• Common drugs are: Streptomycin, INH [isoniazide], and Rifanpicin Q: WHY A COMBINATION OF DRUGS ARE NECESSARY?The TB bacteria like influenza virus can mutate to alter its structure or metabolism which makes an antibiotic lesseffective or sometimes useless against the bacteriaMutation makes the bacteria resistant against an antibioticThis means that new antibiotics are to be used in a combination therapy to ensure effective treatmentPrevention –• Inject BCG vaccine to all new born• Pasteurized cattle milk before drinking• This makes the TB bacteria unable to adjust to the frequent fluctuations of temperature making them die• Avoid overcrowded places• Avoid poorly ventilated areas / housing• Maintain personal hygiene• Promote health education• Improvement of socio economic condition Added information –• TB is most common in amongst people who have a poor lifestyle quality• Suffering from some levels of poverty• They have poor / weak immune system which makes more vulnerable to develop TB • Typhoid [bacterial disease]Causative agent --- salmonella typhiMode of transmission --- by drinking water contaminated with human faeces, or by flies transferring the bacteriumform the faeces to foodIncubation period --- about 2 weeks
  6. 6. Human biology Disease Symptoms ---A high fever, headaches, a cough, and a general feeling of being unwellThis disease develops over nd following weeks, when the patient suffers stomach cramps, constipation, or the Jul. 22diarrhoea, vomiting and delirium [mental confusion] 2012Diarrhoea leads to several dehydrationTreatment ---Vaccines against typhoid are available, and antibiotics such as penicillin are effective against the bacteria. Oralrehydration therapies are effective against the bacteria. Oral rehydration therapy is effective. In counteracting theeffects of dehydration caused by diarrhoea.Prevention ---Good sanitation and hygiene is essential.It only spreads in places where human faeces or urine come in contact with the food or drinking waterQ: How are viruses treated?• Vaccines which prevent the host from contracting the virus• Antiviral drugs which treat the virus once contracted• Viral diseases can be very difficult to treat because the viruses have no metabolism of their own. Hence antibiotics have no effect on them Q: How are bacteria transmitted? • Direct contact with an infected person • Contaminated food or water [salmonella, E. coli] • Dirty objects [tetanus] • Infected animals [rabies]Q: How are bacteria harmful?Terrorism, disease, tooth decay, food spoilageQ: How are bacteria helpful?Antibiotics, nitrogen fixing, food, tanning leather, breaking down waste products, digestionTreatment for bacterial infections ---Antibiotics : a chemical substance that stops the growth of some micro-organisms such as bacteria within thebody Or, they are compounds that block the growth and reproduction of bacteriaSterilization : [heat] making something completely free of germs; or making an organism incapable ofreproduction Or, it is a way of destroying all bacteria by subjecting them to great heatPathogens : they are disease causing agentsQ: What are the 2 general ways that bacteria cause diseases?
  7. 7. Human biology Disease • Some damage the tissues of the infected organism directly by breaking them for food • Others release toxins that harm the body After infection, a pathogen must do three things to produce a disease: Attachment, entry [penetration], colonization Jul. 22nd HOST – an organism2012 another organism lives and gets nourishment and protection in which Food borne infections including salmonella can spread in 2 ways: • By not cooking food thoroughly E.g. raw eggs, newly laid eggs may be contaminated • By contaminating cooked meat form handling raw meat first• Air borne infections are spread when an infected person coughs, sneezes, talks or breaths, as the pathogens are passed into the air in small droplets, saliva, mucus and water• Insect bites can transmit pathogens through the saliva of the insectAfter a person has been infected with a disease, there is an incubation period.SIGN SYMpTOMA sign of a disease is visible to other people. It can be A symptom is not usually visible to other people. It isseen heard or measured what the patient experiencing as a result of the disease, such as pain, chills, dizziness or nauseaFUNGAl DISEASES ---Athletes foot ThrushCausative agent: tinea like ringworm Causative agent: Candida albicansSymptoms – Symptoms:Forms white patches over the skin which are Red inflammatory patches over the skin or moistgenerally circular mucus membrane e.g. mouth, vaginaMay sometimes irritate • Athletes foot and thrush are most common in individuals who are known to go through a major surgery and taking a long term antibiotic course • Thrush is more common in hospitals • Thrush spreads through the infected bed sheets, pillow covers of the hospitals Mode of transmission ---Through skin to skin contact e.g. 1. Sharing of foot wears & undergarments [socks, under wears, stockings, towels]2. In public places e.g. gyms [gymnasium], foot mats [public toilets, food bath, sports changing room]General information: fungi grows best in moist damp conditions3. through infected pets4. Sex workers [prostitutes]Treatment ---Anti – fungal ointments, tablets/ drugsPrevention --- • Avoid using personal belongings of infected individuals [undergarments]
  8. 8. Human biology Disease • Avoid going to public places which is overcrowded • Identify cases • Treat infected pets Jul. 22nd • Avoid multiple sex partners 2012 Amoebic Dysentery [protozoan disease]Causative agent: Amoeba (Entamoeba histolytica) – normally live harmlessly in the human intestine feeding onfood particles or bacteriaMode of transmission: 1. Water Borne DiseaseDrinking or washing fruits &salads water contaminated by untreated sewage. 2. Houseflies & cockroaches the transmit cyst of amoeba to foodSign & symptoms: 1. Diarrhoea & vomiting 2.Ulceration & bleeding of the intestine 3. It can lead to kidney failure & death due to dehydrationTreatment: ORS [oral rehydration saline] to replace the water & electrolyte lost due to diarrhoea & vomiting.Drugs like metronialozole followed by iodoquinol.Prevention or spread: 1. Supply of clean & safe drinking water 2. Hygienic disposal of faeces 3. Proper sewage treatment 4. Prevent houseflies & cockroaches reaching food by keeping food covered or in the refrigerator.Q: How can dehydration lead to kidney failure? • Dehydration is the result of a loss of excessive salt & water • Dehydration leads to decrease of blood volume • The kidney purifies blood & to do so requires high pressure • Impure blood enters into the kidney via renal artery at a low pressure leads to the failure of kidney. Bilharzia (parasitic disease) Schistosoma causes bilharziasis. It is a parasite flatworm. Life-cycle: The adult Schistosoma lives in the hepatic portal vein or blood vessels leading to the bladder. The male is larger than the female so the male carries the female on it. Eggs are laid in the blood vessel. The eggs have a spiny covering. As the eggs mature it vibrates &penetrates the wall of the blood vessel & enters the blood stream. They are excreted out of the body along with the urine & faeces. The eggs are released in fresh water. The egg hatches producing the miracicluim larvae which cannot survive if they do not enter a snail & are released. If the cerceriac larvae have to survive it has to enter a human body with 1 to 2 days. They can enter the human body by: 1. If untreated water is swallowed.
  9. 9. Human biology Disease 2. It can also penetrate the skin of the ankle by enzyme reaction. The larvae first enters the lymphatic system & then into the venous system & eventually into the circulation. It takes about 23 days for the larvae to become an adult. The adult then establishes it on the blood vessels. Treatment: Give anti-bioticnddrugs Jul. 22 1. Nilodin 2.Miracil-D 2012 Prevention / Control-• Mapping an area for the sources of water with which people comes in contact. If snails are found they should bechecked for containing schistosoma larvae.• Water should be chlorinated, filtered & boiled before drinking• Walking barefooted into the water should be avoided and children should be given proper health education.• Fresh water should be avoided from coming in contact with untreated water• Prevent growth of weeds on which snails feed. Malaria [protozoan disease/ parasitic disease]Causative agent: plasmodium [a protozoa]—single celled organismPlasmodium has 2 hosts—Primary host: female anopheles mosquitoSecondary host: human The 4 species of plasmodium which are responsible for causing malaria are—Plasmodium vivax: causes tertian malariaPlasmodium falciparum: causes malignant malariaPlasmodium malariae: causes quantum feverPlasmodium ovale: it is very rare and little is known about itMode of transmission: female anopheles mosquito transmits plasmodium in her saliva when she sucks blood fromhumansSymptoms: alternating cold sweats and fever, vomiting, joint pains and anemia Adult insect Egg Pupa Larvae How we can control the spread of malaria? We can control the spread of malaria by controlling the vectors of plasmodium. Female anopheles mosquito is the vector of transporting malaria from one host to another. The vectors can be controlled by the following ways:
  10. 10. Human biology DiseaseMethod purpose• Spraying oil on stagnant water Oil floats on water and prevents the larvae and egg form respiring since air and swampy grounds cuts air coming in contact [the oil cuts the oxygen supply into the water]• Spraying insecticides like DDT It blocks the trachea of the mosquito causing suffocation. It kills the mosquito Jul. 22nd [ drawback: the mosquito can easily mutate to change its genetic composition 2012 to become resistant to an insecticide]• Removing stagnant water / Stops the breeding of mosquito increasing the speed of slow Mosquitoes lay egg in stagnant water. Why? water The eggs of mosquito are very fragile so they easily break and flow away in flowing water. So to avoid this, mosquitoes lay their eggs in stagnant water.• Keep the surroundings clean Mosquito cannot take shelter [loses habitat] [clearing the bushes]• Avoid littering• Use mosquito nets while going Mosquito can’t penetrate through the nets and bite to cause malaria to sleep• Take anti-malarial drugs when visiting to places where malaria A epidemic• Use mosquito repellence Keeps away / repels the mosquito• Cover or conceal doors and Prevents mosquito from entering the house cover the windows with net Two cells which are attacked by the malaria parasite:Liver cell& the red blood cellsWhat is plasmodium?It is a protozoa which lives on the blood stream of humans.How is the disease malaria transmitted form one person to another?A female anopheles mosquito bites an infected person by piercing the mouth piece into the person’s skinThe mosquito secretes saliva to prevent blood clotting and ensure continuous sucking of bloodAs a result, the mosquito harbours the disease insideThe malarial parasites spreads anywhere between 2 weeks and several months in the person’s liver before the nextstage in the life cycle infects RBCThen well known symptoms appear altering cold sweats and feverSymptoms: mild headache, shivering fever, sweating fever, general body aching, high temperatureTreatment: antimalarial drugsWhat are the three harmful effects of female anopheles mosquito? • It sucks blood • It spreads malaria
  11. 11. Human biology Disease • It irritates human Q: Mosquitoes have a high reproductive rate. Why? • Adult mosquitos have a very short life span of only seven days • They haveJul. 22nd eggs to ensure the continuation of their generation to lay lot of 2012 Gonorrhoea [bacterial disease]It is a sexually transmitted diseaseCausative agent: Neisseria gonorrheaMode of transmission:It is transmitted by sexual contact onlyLess than 50% of female is suffering from the disease which does not show any symptomThey harbour the bacteria in the vagina as the vaginal secretion contains itIt is transmitted to a healthy male during sexual intercourse.The disease affects the urinary and the genital system Treatment: isolate the patient and hospitalize if necessary. There is no immunity to gonorrhoea Give antibiotics like; penicillin, tetracycline, Ampicillin Prevention of spread: • Avoid infected person • Use condom during intercourse • Avoid multiple partners • Maintain a healthy sexual life • Identify cases and provide treatment • Health education • Improvement of socio economic condition • Maintenance of personal hygiene Symptom:• The 1st symptoms in men are pain and a discharge of pus from the urethra. In women, there may be similar symptoms or no symptoms at all• In men, the disease leads to the blockage of the urethra and to sterility• A woman can pass the disease to her child during her child birth.• The bacteria in the vagina invade the baby’ eyes and cause blindness. Syphilis [bacterial disease] It is a sexually transmitted disease Causative agent: Treponema pallidum Incubation period: 1 week to 3 months
  12. 12. Human biology Disease Symptoms: in the 1st stage of the disease, a lump or ulcer appears on the penis or vulva, 1 week to 3 months after being infected. The ulcer usually heals without any treatment after about 6 weeks. By this time bacteria have entered the body and may affect any tissue or organ. There may be a skin rash, a high temperature and swollen lymph nodes. But the symptoms are variable and the infected person may appear in good health for Jul. 22nd many years. 2012 Added information: if the disease is not treated in the early stages, the bacteria will in time cause inflammation almost anywhere in the body. They can do permanent damage to the blood vessels, heart or brain leading paralysis or insanity. In pregnant woman, the bacteria can get across the placenta and infect the fetus. Treatment: penicillin will cure syphilis. But unless it is used in the early stages of the disease, the bacteria may do permanent damage. pREvENTING FOODS FROM BECOMING CONTAMINATED --- House files: house flies must be prevented from carrying pathogens to food. There are 4 main ways to do this— • Keep all unwrapped food in fly-proof containers such as refrigerators or larders. • Enclose all food waste in fly proof dustbins so that the flies cannot pick up the bacteria. • Never leave human faeces were flies can reach them [if faeces cannot be flushed into the sewage system, they must be buried] • Destroy houseflies, wherever possible, in the places where they breed, such as rubbish tips and manure heaps. Processing: • Cooking destroys any bacteria present in food • Refrigeration and freezing slow down or prevent bacterial reproduction • Dehydration, pickling, canning and irradiation are methods of preserving food • These processes destroy the bacteria which might cause disease. They also stop the food from going bad. Describe the ways in which the body prevents bacteria from entering the bloodstream Skin• The dead confined later of the skin is very hard and tough which resists bacterial invasion• Bacteria cannot enter into the body through the skin• The skin also reduces the chances of mechanical injury into the body• The skin has sebaceous glands which secretes sebum. Sebum keeps the skin supple & waterproof. And it is mildly antiseptic Inhalation• The walls of the trachea contains cilia and mucus• Cilia by its to and fro motion distributes the mucus around the trachea• The mucus traps the dust and germs of the inhaled air• The lining of the nasal cavity also has ciliated cells and film of moisture which also traps the dust and germs of the air inhaled by the nose.
  13. 13. Human biology DiseaseStomachThe germs which enter the stomach through the food source is killed by the concentrated hydrochloric acid secreted by thewalls of the stomachEyes Jul. 22ndThe eyes secrete tears which keep the conjunctiva moist, wash it clean 2012The tears are antiseptic in nature which prevents bacterial invasion How some organisms enter into the body? • Nose: [dry air borne spores or microbes in droplets of moisture]Common cold, influenza, pneumonia, tuberculosis, scarlet fever, whooping cough, chicken pox, measles, poliomyelitis, smallpox, anthrax, leprosy, typhoid fever • Mouth: [organisms in food, and water or on the fingers]Dysentery, food poisoning, parasitic worms, cholera, tuberculosis, typhoid fever, poliomyelitis • Insect bites:Malaria [female anopheles mosquito], sleeping sickness [tsetse fly], yellow fever [aedes mosquito], bubonic plague [fleas],Secondary infection of bites by bacteria and viruses • Skin: [damaged or undamaged]Tetanus [through cut], rabies [bite of infected dogs and other animals], small pox [direct contact with infected skin],ringworm and athlete’s foot [fungal infections], some nematode worms [ore through skin] • Reproductive:Venereal diseases [syphilis and gonorrhoea]Diseases are often caused by organisms which live as parasites. A parasite is an organism which obtains its food from theliving body of another organism called their host; but not all parasites harm their host. Most humans, for example, have aparasitic bacterium, ESCHERISCHIA COLI, living harmlessly in their intestines. Parasites which harm their hosts are said topathogenic, or pathogensHow pathogens cause disease?Once inside the body, some pathogens release poisonous chemicals called toxins. Most toxins are proteins and are bi-products of the parasite’s metabolism. They produce disease symptoms in the host like high temperature, headache, andvomiting.Symptoms do not appear immediately a pathogen enters a host. There is an interval called the incubation period beforesymptoms appear, during which germs multiply rapidly or larger parasites develop to full size.Some parasites, including nematode worms and insects, bore through host tissues causing wounds which may then becomeinfected by bacteria and viruses. This is called secondary infection.
  14. 14. Human biology Disease Salmonella food poisoningOutline: One of the commonest causes of food poisoning is the toxin produces by the bacteria salmonella typhimurium S,Enteritidis or some varieties of Escherichia coli.These bacteria live in the 22nd Jul. intestines of cattle, pigs’ chickens and ducks without causing disease symptoms.Humans however, may develop food poisoning if they drink milk or meats or eggs which are contaminated with salmonella 2012bacteria from the alimentary canal of an infected animal.Intensive methods of animal rearing may contribute to a spread of infection unless care is taken to reduce the exposure ofanimals to infected faeces.Causative agent: salmonella typhimurium S. enteritidis or some verities of Escherichia coli [E.coli]Mode of transmission: infection is most likely if untreated milk is drunk [contaminated milk], meat is not properlycooked, or cooked meat is contaminated with bacteria transferred from raw meat.Symptoms: diarrhoea, vomiting and abdominal painIncubation period: 12 to 24 hours after eating the contaminated foodTreatment: although the symptoms are unpleasant, the disease is not serious and does not need treatment with drugs.Elderly people and very young children however may be made very ill by food poisoning.Prevention: the salmonella bacteria are killed when meat is cooked or milk is pasteurized. Or to more accurate—to avoidthe disease, all milk should be pasteurized and meat should be thoroughly cooked. People such as shop assistants and cooksshould not handle cooked food at the same time as they handle raw meat. If they must do so, they should wash their handsthoroughly between the 2 activities. IGCSE SpECIFICATION -disease Students should know what the main effects of the diseases mentioned in this section are but a detailed knowledge of symptoms is not required. Students will be assessed on their ability to: a) The general course of a disease. (i) Recall the methods of infection, incubation, signs and symptoms. (ii) Understand the difference between endemic and epidemic diseases. b) Diseases caused by pathogenic microorganisms. (i) Viruses: recall a brief description of their structure and reproduction. Recall methods of transmission, treatment and prevention of spread of influenza, poliomyelitis and AIDS (Human Immuno-deficiency Virus — HIV). (ii) Bacteria: recall a brief description of their structure, nutrition and reproduction. (iii) Bacteria as pathogens: recall methods of transmission, treatment and prevention of spread of typhoid, tuberculosis and gonorrhoea. (iv) Fungi: recall methods of transmission, treatment and prevention of spread of thrush and athlete’s foot.
  15. 15. Human biology Diseasec) Diseases caused by other parasites.(i) The parasite schistosoma: recall its nutrition and life cycle.Recall the worldwide effects of the disease schistosomiasis (Bilharzia.), including Jul. 22ndmethods of preventing its spread.(ii) Understand the relationships between: mosquito and malarial parasite; housefly and 2012typhoid bacillus.d) Explain the role of these vectors in transmitting causative agents of disease and thetreatment and prevention of spread of the disease and its vector.e) Defence(i) Immunity: understand that it can be natural and artificial, both active and passive, withreference to diseases.(ii) Vaccines: explain what a vaccine is and how it works.(iii) Understand the antibody/antigen reaction.(iv) Recall the sources and role of antibiotics.