Health And Diseases

Health and Disease Personal health To maintain the state of good health individuals can concentrate on following steps: -

Diet : inadequate or unbalanced diet may result in Nutritional deficiency diseases and person will be more susceptible to other diseases.

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Personal hygiene : washing hands after going to toilet washing hands before handling food washing body and changing clothes

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Domestic hygiene :

keeping cooking pots clean keeping flies out of the house

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Clean food and water : wash vegetables and fruits well When cooking heat in to high temperature to kill bacteria and tapeworm -

Not smoking : smoking causes lung cancers, bronchitis, emphysema, atherosclerosis and heart attacks Exercise

Community Health Steps taken by the community to maintain and improve standard of health Clean drinking water Efficient methods of sewage disposal Education about diseases Types of diseases Infectious diseases : can spread from one person to another Brought about by pathogens such as bacteria, viruses, fungi and protoctists Deficiency disease : lack of food, vitamins or minerals Anaemia – lack of iron Goitre – lack of iodine Kwashiorkor – lack of protein Night blindness – lack of vit C Scurvy – lack of vit C Rickets – lack of vit D and calcium

Inherited disorders : cause genetically Haemophilia – blood takes a longer time to clot

Sickle cell anaemia – shape of the red blood cells change

Cystic fibrosis

Auto-immune disease : cancer – cells reproduce at abnormal rate Mental disorders : cause due to failure in the normal pattern of growth or disturbance in the production of hormones Depression

Routes of entry The ways that disease causing organisms are spread and access to human tissues : inhalation of mucous droplets containing pathogens through natural openings such as mouth, nose (droplet infections) -

Contaminated food and water that is consumed Pathogens already in food. Eg : tapeworm in pork or beef Pathogens fall on already prepared food. Through houseflies. Unsterilized water -

Sexual contact Venereal diseases : spread only through sexual contact (homosexual or heterosexual) STD (sexually transmitted diseases) : causative organisms are spread by contact during

sexual intercourse eg: Gonorrhoea, Syphilis, AIDS -

Contact Contagious diseases Fungal spores touching skin (skin to skin or skin and clothes) Eg: tetanus causing bacteria can get into the body when contact with broken skin

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Vectors piercing skin Insects feed by biting through the skin of mammals and sucking blood. Insects secrete saliva into the wound with anticoagulant to prevent blood from clotting and that saliva might have pathogens which injected into the blood stream of the host Eg : mosquito, lice

Disease Disturbance to the healthy state usually brought about by a disturbance of homeostasis

Pathogen Disease causing organisms Eg : bacteria, viruses, fungi Protoctists (single celled organisms such as plasmodium-causing malaria and amoeba-causing amoebic dysentery) Vector Disease (disease causing pathogen) carrying organism Transmits the disease without suffering from it Eg : mosquito malaria Housefly

typhoid, cholera

lice typhus water snail

Bilharzia

Transmission How the disease is spread from one to another Eg: droplet infections Contaminated food and water Sexually contact Incubation Period Time interval between entry of the pathogen and the time taken to show signs and symptoms. Symptoms – What the patient complains of ( eg headache, dizziness) Signs – What the doctor sees (eg rashes, enlarged tonsils, fever) Infective Period Period in which the patient is infective to others (the patient is still shedding the pathogen to others).

Notifiable disease A disease of worldwide importance where the WHO must be informed of every case in order to control its spread. Eg : cholera AIDS SARS Bird flu Endemic disease Disease that is prevalent (common) at all times, but the number of sufferers is

low (eg Malaria in Sri Lanka) Epidemic disease Sudden outbreak of a disease in a localised area where the number of sufferers is high (eg Cholera outbreak in Colombo in 1999) Passive immunity Immunity a person is born with (acquired via placenta and lactation) Active Immunity Immunity brought about by infection and vaccines which results in the formation of memory cells. Immunisation Vaccination of a dead or weakened pathogen This ‘tricks’ the immune system to produce -antibodies -memory cells This is a form of active immunity Usually gives lasting protection against disease. Antibiotic Used against bacterial infections Eg : Penicillin from Penicillium fungi Prophylaxis – Prevention Pathogenesis – Course of the disease within the body Syndrome – Collection of different diseases

Body’s defense mechanisms 1. -

The skin physical barrier dead outer layer, cells contain keratin/cornified cells waterproof impenetrable to microbes secrete sebum; has antiseptic properties-kills bacteria

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mucous membranes especially in mouth, vagina, nose epithelium of trachea produces mucus traps bacteria cilia beat and move mucus to throat

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stomach has enzymes and acids (pH =2.0)

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Tear glands secrete tears have anti-bacterial properties

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Blood clotting heal wound prevent entry of pathogens through open skin

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Phagocytes engulf bacteria

7. Antibody and Antitoxin production

The course of an infectious disease Enemy : pathogen Army : WBC Victory depends on : relative number of the pathogen compared to the number of WBC Why it is difficult to control the pathogens inside the body (problem for the army) : microorganisms breed very rapidly / metabolism is very rapid blood is the ideal medium for pathogens to thrive and multiply (due to ideal temperature and plenty of food) pathogen enters the body incubation period pathogen multiplies in number while pathogen multiply, they produce toxins, poisons and waste products onset of signs and symptoms of disease. Eg :fever meanwhile, phagocytes try to fight against pathogens. So increase cell lysis and cell debris may make symptom worst

pathogen gains access to blood circulation and numbers increase further; lymphocytes start to look for correct antibody the correct lymphocyte clones itself as an attempt to increase its numbers to that of the enemy the clone produces antibody antibody clumps and kills pathogen antitoxins neutralize any toxins symptoms begin to subside antibody level become very high symptoms completely subside; recovery phase; restoration of health memory cells and antibodies remain to give lasting immunity against that pathogen memory cells allow future antibody production to occur sooner, faster and in greater quantity Questions Q1) 2006 May There are several ways in which the body prevents microorganisms gaining entry to the cells. a) Describe the role of each of the following in preventing the entry of microorganisms into the body. (i) the skin (4) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… (ii) the lining of the airways (5) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… b) (i) Describe how microorganisms that do succeed in gaining entry to the body are then able to produce signs and symptoms of disease. (3) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………

(ii) How does the immune system respond to an invasion of the body by pathogens? (8) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………… total 20 marks Q2) Some microorganisms cause disease in human and usually the person recovers naturally from the disease. i) Describe the stages in the course of a non-lethal bacterial disease and explain what is occurring in the body at each stage. (from the time of entry of the pathogen until normal health is restored) (15) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………… ii) Explain why, having recovered from a bacterial disease, a person is unlikely to suffer from the same disease on a future occasion. (5) ……………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………… total 20 marks

Bacterial Diseases Bacteria

Prokaryotic organisms No true nucleus/ genetic materials are not organized into chromosomes and into nucleus. Have circular DNA-plasmids No membrane bound organelles such as mitochondria, ER, Golgi Cell wall is made out of murein May have flagella for movement Reproduce by Binary fission

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Nutrition : phototrophic : use light energy to synthesis organic matter from inorganic compounds Saprophytic : obtain food from dead or decaying organic matter Mutualism : close relationship between living organisms and both get benefit eg : Rhizobium, nitrogen fixing bacteria living in the root nodules of legume plants E.coli, in the gut of human, contributes for vit B Cellulose digesting bacteria live in gut of ruminants Parasites : parasites that cause diseases are pathogens

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Advantages :

soluble

1. as decomposers – digest dead organic matter into

substances for green plants to use so prevent water pollution

inorganic decompose sewage,

2. involved in nutrient cycles – eg : nitrogen cycle Nitrification - Nitrosomonas Denitrification Nitrogen fixation – Rhizobium

cattle food)

3. use by humans in food production eg : vinegar yoghurt cheese single cell protein (used as 4. use in industry eg : biogas (methane production) producing antibiotics –

streptomycin 5. use in biotechnology eg : producing Insulin (hormone) -

Disadvantages :

1.

causing diseases eg : cholera, tetanus, tuberculosis, typhoid, diphtheria, gonorrhoea

2.

spoil food

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Culturing bacteria

sterilised the (by heating until it glows The sterilise loop is red) inoculating loop dipped into a source of microbes eg : spoiled food

Kills microbes or spores already present on the loop microbes are streaked onto sterile sealed with tape fresh agar medium with source and date incubate in an oven provide nutrient and water for microbes to placed upside down grow (to prevent any condensation falling back onto agar)

marked

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Testing antibiotics To compare the effect of antibiotics : Culture of bacteria grow on an agar plate Discs of filter paper, each soaked in one antibiotic Place on the agar plate (same distance between each) Seal agar plates Incubate Examine the diameter of the clear zone (no bacterial growth) Largest clear zone : best antibiotic

TYPHOID caused by : Transmission : Patients suffering from the disease pass the bacteria in (method of spread) their faeces and vomit. i) washed into rivers and wells – spread by unsterilised water ii) Vectors such as houseflies and cockroaches transfer bacteria on their body from source to clean food and water. iii) Food-handlers not practicing good personal hygiene eg : not cutting nails not washing hands after use of toilets

Signs and Symptoms Pathology (cause of disease)

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Fever, diarrhea, vomiting and abdominal pain :

bacteria enter intestine

Multiply on intestinal wall (mucosa) producing many toxins these toxins irritate cells causing i. increase peristalsis ii. increase secretions (in an attempt to flush out

bacteria and toxins)

severe diarrhea leads to dehydration if uncorrected, dehydration leads to drastic fall in blood volume and pressure which may be fatal. Treatment : i) antibiotic therapy to kill bacteria ii) Rehydration (to correct fluid balance) IV saline or in early stages ORF (same osmotic potential of blood so helps restore fluid balance) Prevention : i) Boil water for a period of 10 minutes Chlorinating well Washing vegetables in chlorinated water Cook food thoroughly ii) Hygienic disposal of faeces Efficient sewage treatment Sewage should not be used as fertilization iii) In kitchen ; keep all garbage bins covered throw all scraps of food all prepared food should be covered kitchen surfaces and utensils need to be washed and disinfected regularly food handlers should wear gloves separate knives and boards for meat and vegetables washing hands after use of toilet PHI paying regular visits to restaurants and hotels Control measures : Educate the public Isolation of patients during epidemics (notifiable disease) Travelers going to typhoid zones should take the TAB vaccine (which offers mild protection) Government must fund proper hygienic disposal of faeces

People in close contact with the patient should take the TAB vaccine or a dose of the prescribed antibiotic to prevent the disease.

Cholera

Caused by : Motile bacteria, have flagellum Transmission : contaminated food and water Symptoms : severe, uncontrollable diarrhea Dry skin, nausea, vomiting, tiredness, rapid pulse Pathology : after incubation period of two to six days diarrhea begins Bacteria produce toxins that irritate intestinal wall leading to a severe increases peristalsis Danger is due to death by dehydration Treatment : - Management of the patient using ‘rehydration’ methods Eg : IV saline - Treatment with antibiotics to kill bacteria - Isolation of patient to prevent spread - Incineration/burn of all utensils and linen used by patients Prevention : same as for Typhoid Control measures : - Isolation of patient - Inoculate people in an infected area - Outbreaks of cholera should be notified to WHO - Restriction on travel from infected areas

Tuberculosis (TB) Caused by : Transmission : droplet infection spread through the air, when people who have the disease

cough, sneeze or spit. Symptoms : - persistent cough - appetite loss - loss of weight - coughed out blood-tinged sputum (blood contain mucus like) Bovine TB by mycobacterium bovis that live in cow’s udder. Drinking unsterilised milk will be the cause. Pathology : Bacteria settle in alveoli and bronchioles Multiply forming colonies that form ‘tubercles’ in lungs Tubercles increase in number, eroding healthy lung tissue and may even rupture the lung (lung collapse) To compensate the body produces large amount of sputum in order to flush out the bacteria (phlegm cough) Diagnosis : Throat swab and planting of mucus – TB test on mucous Mass chest x-ray Treatment : Problems have arisen due to resistance (by the bacteria) to the prescribed antibiotic. For every TB patient WHO should be informed Isolate patient and give them a well balanced diet Prevention : 1. Immunisation programme : BCG vaccine (given at birth) 2. If there is an epidermic : Tuberculin test is carried out to check if the community has enough antibodies. (inject a drop of dead bacteria under the skin and look for reaction) Mass chest x-ray Prevent overcrowding Public buildings and hospitals should be well ventilated 3. Bovine TB : Pasterisation of milk Testing of cattle milk Antibiotic theraphy

Diphtheria Caused by : Corynebacterium diphtheriae Immobile, curved rod shape bacteria Diphtheria is an upper respiratory tract illness. The tonsils are areas of lymphoid tissue on either side of the throat. Like other organs of the lymphatic system, the tonsils act as part of the immune system to help protect against infection. In particular, they are believed to be involved in helping fight off upper respiratory tract infections. Symptoms : sore throat low fever Difficulty in breathing Adherent membrane on tonsils Transmission : droplet infection Pathology : 1 ) Bacteria reproduce rapidly on the fauces (is the posterior part of the mouth, which leads into the pharynx) of the throat, releasing a grey exudate that is thick and sticky. This exudates coats the faucess and spreads rapidly so that it may block the airways Needs to be remove surgically 2) Diphtheria bacteria produce a powerful toxin that paralyses the heart. Treatment : - removal of exudates - anti-biotic therapy (to prevent transmission) - anti-toxic injection into muscle immediately Prevention : 1) immunization programme “Triple” vaccine (DTP) – Diphtheria, Tetanus, Pertussis (whooping cough) The vaccine consists of a series of five shots, typically administered in the arm or thigh, and is given to children at ages: 2, 4, 6, 18 months and 4-6 years. Adults at 10 years intervals. 2) Prevent overcrowding isolation of patient informing WHO

Gonorrhoea Sexual transmitted disease Caused by : Bacteria (Neisseria gonorrhoeae) Transmission : sexual contact(skin of genitalia touching) Due to mixing of sexual secretions Symptoms

: male –green/yellow discharge Difficulty in urination Female – usually asymptomatic (no symptoms) Late stage may be difficult to urinate

Pathology : In male When the penis comes in contact with the bacterium in the urethral opening. Bacteria multiply causing inflammation and discomfort. As the bacteria multiply the infection spreads up The urethra causing swelling and strictures (narrowing) Long term effect – infertility

intercourse.

In female Vagina and urethra get infected, but it rarely causes discomfort But bacteria multiply and spread easily during sexual

Diagnose : sexual secretions or swab genitals Treatment : antibiotic therapy(oral) Antibiotic creams applied Complete abstinence from sex Prevention : use of condoms Early recognition of signs and symptoms Educate the public Once patient is diagnosed you need to carry out contact tracing Abstinence until cured Treat patients and all his/her sexual partnars

Class test (2002 January) a) Typhoid is caused by Salmonella typhi. The symptoms include a severe fever, diarrhea and vomiting and if not treated typhoid can lead to death. i) Explain why a higher fever, diarrhea and vomiting may lead to death if the person does not have treatment. (5) ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………………………………………………. ii) List four precautions that can be taken to prevent typhoid being transmitted from one person to another. For each precaution, explain how it prevents the transmission of typhoid. (8) ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………… iii) Some people carry Salmonella typhi in their body but show no symptoms of the disease. Why could it be especially dangerous if such a person worked in a hotel kitchen. (3) ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………. b) Some species of Salmonella cause food poisoning. Describe and explain two precautions which should be taken during the preparation of food to ensure that the food is safe to eat. (4) ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………………. .................................................................................. ......................................................................... ……………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………………………………………………………………

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Viral Diseases Virus Structure :

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no cytoplasm no cell membrane no nucleus no cellular organization at all Protein coat around a DNA or RNA strand Out side a host cell no living characteristics Within host cell show reproduction only Obligatory parasite – need a host cell to survive Disease transmission – by water eg: polio By droplet: flu By vector: yellow fever Antibiotics are not effective for viral diseases

Reproduction of viruses

Influenza (flu) Caused by : many different viruses (RNA viruses) Transmission : droplet infection (through saliva, nasal secretions)

Symptoms : fever, sore throat, runny nose, headache, Sign : swollen lymph nodes in neck Treatment : no drugs against viruses Treat symptoms Runny nose – piriton Fever – Panadol Prevention : - prevent overcrowding - building should be well ventilated - disposable tissue should be discarded You can not develop lasting immunity for influenza because many viruses cause it. In humans, influenza's effects are much more severe and last longer than those of the common cold. Recovery takes about one to two weeks. Influenza, however, can be deadly, especially for the weak, old or chronically ill. The flu can worsen chronic health problems. People with emphysema, chronic bronchitis or asthma may experience shortness of breath while they have the flu, and influenza may cause worsening of coronary heart disease or congestive heart failure. Smoking is another risk factor associated with more serious disease and increased mortality from influenza

AIDS (Acquired Immuno-Deficiency Syndrome) Caused by : HIV (Human immuno-deficiency virus) RNA virus

Syndrome is a collection of diseases Transmission : 1) Sexual secretions – virus may be present in semen or vaginal fluids Unprotected sex with homosexual or heterosexual It has to involve the mixing of semen with vaginal secretions Usually following cell abrasion/scrap

(friction of penis with vagina often causes slight scrap that allow virus to penetrate) 2) Blood – blood transfusions Through open wounds Heroin addicts sharing same needle Haemophiliacs who require frequent blood Health workers 3) Via placenta and breast feeding – from mother to developing fetus Pathology : Host cell – T Lymphocyte HIV – RNA virus The virus binds to receptors on T lymphocytes. Viral RNA is then injected into the cell and copied to DNA by the enzyme “Reverse Transcriptase”. The viral DNA or VDNA enter the lymphocyte nucleus and become attached onto human DNA as a permanent part. As the lymphocyte divide so does the VDNA and the spread is rapid.

The VDNA can stay dormant for up to 6 years. When replication occurs, the VDNA shuts down the effector T and helper T cells. So these cells can not produce lymphokines nor can they help B lymphocytes to produce antibodies. This erases all immunity to previous diseases and the body immunity system is severely damaged. Virus penetrates T cell Injects its RNA Reverse Transcriptase RNA converted to DNA in host cell Viral DNA penetrates host nucleus Viral DNA fuses with human DNA When the T lymphocytes are affected, the immune system is destroyed and previous memory cells and antibodies are all wiped out. So a patient with AIDS has no effective immune system and may even die of a simple cold. Signs and Symptoms : - The typical picture of AIDS is a collection of rare diseases that are usually not seen together. Eg : A rare form of skin cancer (Kaposi’s sarcoma) Severe diarrhea all at the same time Severe blood poisoning - First a flu then months or years of good health. Micro organisms infect the body causing repeated minor infections Eg : fungal attacks of skin Weight loss Diarrhea pneumonia

(Extra : The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi's sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss.) Traetment : Drugs that inhibit the enzyme Reverse Transcriptase can help reduce the spread of the virus. Eg : Zidovudin Symptomatic treatment Treat the symptoms as and when they occur and try to manage the patient Treatment of secondary infections with antibiotics Prevention : -

stick to one sexual partner use of condoms use disposable needles government should distribute free needles/ syringes to drug addicts Efective screening of donated blood All medical workers shoul wear rubber gloves Sex education at school and awareness Contact tracing (notifiable disease) Those at risk shoul be given immuno-enhansing drugs

Poliomyelitis Extra : Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecaloral route. The term derives from the Greek polio meaning "grey myelon”, referring to the "spinal cord", and -itis, which denotes inflammation. Although around 90%

of polio infections cause no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream.[3] In fewer than 1% of cases the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and paralysis. Different types of paralysis may occur, depending on the nerves involved. Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. Bulbar polio leads to weakness of muscles innervated by cranial nerves. Bulbospinal polio is a combination of bulbar and spinal paralysis

Caused by : RNA virus Transmission : - droplet infection - contaminated food or water - houseflies

Signs and symptoms : ‘flu’ like symptoms for 3 to 4 days Then paralysis Pathology : biphasic disease Phase 1 : - virus infects lymphnodes of the throat or intestine - It rapidly multiplies and enters the blood stream - This causes fever and flu symptoms followed by 48 hour of wellbeing - during this time the virus leaves the blood and invades the cerebral spinal fluid of CNS Phase 2 : -Virus attacks the grey matter of the spinal cord mainly in the region where the motor neurones (cell bodies of motor neurone) - killing motor neurones cause paralysis Treatment : - No drugs to treat polio - physiotherapy - crutches - iron lung (An iron lung is a large machine that enables a person to breathe when normal muscle control has been lost or the work of breathing exceeds the person's ability. It is a form of medical ventilator. Properly, it is called a negative pressure ventilator.) Prevention : Polio vaccine (oral) (immunisation) – shedule 2,4,6,18 months 4.5 years Proper sewage disposal Prevent overcrowding Ventilation Purification of water Control of house flies

Fungal Diseases Fungi Structure

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Eukaryotic organism consist of multicellular filaments called hyphae hyphae forms mycellium cell wall is made out of chitin some fungi are single celled organisms eg : yeast cell eg : moulds (moulds on bread- Rhizopus, mould on dung – mucor) mushrooms yeast

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Reproduction : Asexual reproduction – by spores produce from sporangium Sexual reproduction

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Nutrition : Saprophytic – depent on dead organic matter Hyphae of fungi secrete enzyme on to dead matter and absord soluble molecules Parasitic

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Importance of fungi :

Helpful 1. Decay fungi (decomposers) – release nutrient for green plants from dead organic matter 2. Yeast – respire anaerobically

Use Co2 for bakers (yeast act on sugar in dough, making it rise)

Use alcohol for brewers and wine-makers Gasohol is ethanol brewed from sugar cane 3. Produce antibiotics – eg : Penicillium produces Penicillin 4. As Food Natural – mushrooms Certain yeasts, grown in fermenter vessels containing solution of ammonium and other salts which is bubbled through with natural gas, are harvested to give “single cell protein (SCP)” , very cheaply to feed cattle for more growth Harmful 1. Decay fungi – spoil food 2. Plant diseases – eg : potato blight 3. Dry rot – destroy house timber 4. animal diseases – eg : athlete’s foot

Athlete’s Foot Parasitic fungal infection of the epidermis of the human foot It is typically caused by a mold (but in some cases a yeast) that grows on the surface of the skin and then into the living skin tissue itself, causing the infection. It usually occurs between the toes, but in severely lasting cases may appear as an extensive "moccasin" pattern on the bottom and sides of the foot. More commonly affects males than females. Caused by : Tricophyton (mould fungus) Transmission : foot needs to make contact with fungal spores Eg : swimming pool walkways, sharing socks or towels, gym floors Symptoms : itchiness between toes White patches (like a rash) on skin Treatment : use of anti-fungal cream Keep feet dry Prevention : wear well ventilated shoes Keep feet dry and clean Make sure people wear slippers when walking on swimming pool pathway Dry gym floor and disinfect it regularly

Class test (Jan 2005) a) describe how the fungus causing athletes foot obtain its food. (6) ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………………………………………… b) describe how athlete’s foot is passsed from one another. (4) ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… …………………………………… c) describe measures that can be taken to prevent spread of athlete’s foot. (4) ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ……………………………………

d) Describe how spread of schistosomiasis differ from athlete’s foot. (6) ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………………………………………………………

Thrush Caused by : candida albicans (yeast like fungus) Transmission : infants – white thrush on tongue (milk rash) Adults – genital area mainly in women - By contaminated nursery equipmant only in babies because they donot have a stable immune system yet. - Transmission to vagina due to weak personal hygene. Fungi usually live harmlessly in the region of vagina and are prevented from spreading by bacteria. Excessive intake of antibiotics kill bacteria allowing the fungus to grow – thrush - sexual intercourse with an infected partner. Males are asymptomatic but they may transmit the disease. - Soiled underwear and towels Symptoms : mambrane

vagina – itchiness and a thick white discharge Mouth – small white flakes coats the tongue and mucous

Treatment : vagina – use of antifungal creams Vaginal pessary to traet cervix Mouth – glycerene to clean away fungus Prevention : adult – boil and sterilise underwear Keep genital region dry Treat sexual partner Do not overuse antibiotics Practice good personal hygene **** Thrush is common in women as the moisture and pH of vagina favour the growth of fungus. Infants – boil and sterilise all nursery eqipment thoroughly

Paracitic Diseases Typhus Caused by : lice (vector) Transmission : spread by lice bitting scalp to suck blood and droppings enter wound Treatment : anti lice shampoo and specific combs to comb out eggs Prevention : do not share combs, brushes, towels No sex until cured Regular checks in school Regular washing of bed linnen and clothing Worm infections Schistosomiasis (Bilharzia) Caused by : blood fluke called ‘schistosoma’

Schistosoma is a parasytic flat worm called a blood fluke because it lives in the blood vessels of the intestine wall or the urinary bladder wall. The eggs are layed in smaller blood vessels and the egg use their spines to vibrate and drill a hole through the gut wall. Therefore the eggs leak into the intestine where they are expelled along with the faeces. Within the human, the larvae enter through the lymph vessels. It first infects the liver where the larvae develop into the adult worms. The adult worms then enter the circulation and live in brances mainly of the hepatic portal vein. Symptoms : blood stained stool or urine Constant tiredness and sleepiness Fever and abdominal pain Treatment : worm treatment like vermox Prevention and control :

locate source of infection and inform people in that area not to use it for drinking, washing and swimming boil / chlorinate water thoroughly do not use toilets that drain into rivers use biological methods to kill water snails use molluscicides (chemicals) to kill snails build bridges over canals dryout canals that are not being used provide water proof foot wear like boots for chilren to use use copper salts to kill snails (cheaper) educate people to stay out of infected water

Ascariasis and Amoebic Dysentry Ascariasis Cause by

Amoebic Dysentry (BIO)

transmission

pathogenesis

Round worm called Ascaris

Consumption of contaminated food and water -

Consumed eggs hatch into larvae Larvae enter blood stream Travel to lung where they enter alveoli crawl up the branchial tree to the throat swallowed again and enters oesophagus; finally the intestine adult worm lives in small intestine Unicellular organism (similar to amoeba)

Consumption of contaminated food and water - Amoeba reproduce in intestine - produce toxins that causes severe colic pain and diarrhoea

Prevention and control (for both) : wash hands before preparing food make sure kitchen utensils and surfaces are clean store food ina fridge instead of keeping it outside. Prepared food kept covered remove all refuse from kitchen proper disposal of sewage and faeces during an out break, salads and raw vegetables must be washed in chlorinated water food taken out from fridgeshould be consumed immediately make sure all food is consumed before expiry date

Malaria Caused by : Plasmodium vivax (unicellular organism) Spread by : female Anopheline mosaquito (vector) Life cycle of plasmodium

Transmission : Mosquito’s adaptations : - pairs of peircing stylets (to pierce skin) - proboscis to suck blood - antennae to detect food source - light body and quick reflexs to escape When a mosquito bites a malaria victim, it suckes up the blood containing the paracyte. The paracyte then lives in the salivary glands of the mosquito where it undergoes developmental changes and matures When the mosquito bites its next victim, it pierces the skin using its stylets and first secretes a drop of saliva. The saliva contains an anti- coagulent that prevents clotting so that the mosquito can suck up a liquid meal. That drop of saliva would contain the parasite and mosquito allows it to gain direct access to the blood circulation. Pathogenesis :

- parasyte first infects the liver where it lives for upto 10 days - then they re-enter the blood, where they infect the red blood cells - development takes place within RBC’s, causing RBC’s to burst, releasing parasites and toxins - the bursting of RBC’s give rise to very high fever - the fever takes place approximately every 48 hours

Complications of malaria : liver damage anemia cerebral malaria (one species of parasite plasmodium falciparum infects CSF and brain) fever, vomiting, headache the persist due to dehydration and build up of toxins Treatment : anti malaria drugs - chloroquin primaguin

Prevention : Life cycle of mosquito

Hatching of eggs after 2/3 days

Siphon – breathing tube Interuption of life cycle of mosquito (biological method) -

spray oil to cover water bodies (larvae can not breath) drain/dry up water bodies intraduce fish that will break surface of water intraduce predator fish that will feed on larvae eg : thilapia intraduce bacteria that feed on larvae release sterile male mosquitos to prevent mating prevent stagnation of water

physical/barrier method -

use mesh on windows use mosquito nets wear long sleeved shirts and trousers close doors/windows at dusk and dawn

chemical methods Use DDT/ insecticides on adult mosquito Insect repellant Mosquito coils, oils, tablets