1. Unit 4 - Immunology and Public Health CfE Higher Human Biology 23. Transmission and Control of Infectious Diseases

2. Learning Intentions I can describe the transmission and control of infectious diseases. I can state that infectious diseases caused by pathogens, transmitted by direct physical contact, water, food, body fluids, inhaled air or vector organisms and controlled by quarantine, antisepsis, individual responsibility, community responsibility and vector control. Epidemiological studies of infectious diseases. I can state that classification of spread to include sporadic, endemic, epidemic, and pandemic. Control measures to include preventing transmission, drug therapy, immunisation or a combination of these. I can describe active immunisation and vaccination. I can state that active immunity can be developed by vaccination with antigens from infectious pathogens. Antigens from infectious pathogens, usually mixed with an adjuvant to enhance the immune response, include inactivated pathogen toxins, dead pathogens, parts of pathogens and weakened pathogens. I can state that The design of vaccine clinical trials including randomised, double- blind and placebo-controlled protocols. Importance of group size to reduce experimental error and statistical significance.

3. What are Pathogens? As we have seen, pathogens are agents which can cause disease. They can include many different types of organisms including: Viruses e.g. measles Bacteria e.g. cholera Fungi e.g. athletes foot Protozoa e.g. malaria Multicellular parasites e.g. hookworm

4. Viruses A virus can only survive outside a host for a very short time, however they are responsible for many diseases; -AIDS -Chicken pox -Influenza -Herpes And some cases of cancer, e.g. Cervical cancer caused by the Human papillomavirus (HPV)

5. Bacteria Bacteria are single- celled organisms and can cause diseases such as: -Cholera -Typhoid -Salmonella -Pneumonia -Tuberculosis

6. Fungus Fungi are widely used by humans but some can cause diseases like: -Thrush -Ringworm -Athlete’s Foot

7. Protozoa Protozoa are single- celled organisms which are typically mobile. They can cause: -Malaria -Sleeping sickness -Dysentery Malarial infestation by Plasmodium http://www.youtube.com/watch?v=OEDh e4MPEMc

8. Multicellular parasites Multicellular parasites include tapeworms and hookworms (pictured). They can cause -Anaemia -Diarrhoea -Low birth weight Short clip of tapeworms in situ http://www.youtube.com/watch?v=JeDD0Hde cGk

9. Pathogen Transmission These pathogens can be transmitted in many ways: -Direct physical contact -Inhaled air -Indirect physical contact

10. Pathogen transmission -Exchanging body fluids -Faecal-oral route -Vector organisms

11. Controlling Transmission Because we know how pathogens are transmitted we can interrupt it by the following; - Antisepsis – inhibiting or destroying a microorganism by sterilising everything that could carry a pathogen or prevent them reaching somewhere.

12. Controlling Transmission Quarantine – compulsory isolation of the person who is infected or has been in contact with an infected person to prevent spreading of the disease. The length of the quarantine is usually just over the length of time it usually takes for someone to display symptoms after being infected.

13. Individual responsibility Knowing what we do about transmission of pathogens there are a number of things that can be used to prevent it; -Good hygiene – washing hands, brushing teeth, showering etc. -Care in sexual health – use of condoms to prevent sexually transmitted diseases -Handling and storage of food – washing hands, keeping raw and cooked food separate and at the appropriate temperatures.

14. Community responsibility Clean water supply – our water is filtered and chlorinated to prevent growth of microorganisms… is everyone as lucky? Safe food webs – for example good manufacturing practice e.g. milk pasteurisation (heating at 72 o C for 15s to kill any microorganisms), inspection, risk analysis and traceability. Waste disposal – keeping any refuse collected regularly and recycled, buried or incinerated.

15. Community responsibility Control of vectors – Taking care to eradicate any animals which can carry diseases e.g. Bubonic plague was caused by bacteria carried by fleas on rats so being in close proximity to rats carrying those fleas put you at high risk. Malaria is caused by a protozoa carried by female mosquitoes in their saliva. How could you protect people from this animal vector? (see page 335)

16. Epidemiology of infectious diseases Epidemiology is the study of the characteristics of an infectious disease. We would look at: -The location of an initial outbreak -The pattern and speed of the spread -The geographical distribution

17. Patterns of Distribution Sporadic – occurs in scattered or isolated instances with no connection between them Endemic – recurs as a regular number of cases in a particular area Epidemic – affects an unusually high number of people in a particular area Pandemic – occurs as a series of epidemics spreading across continents or the whole world

18. What can we hope to do with this? It is essential to understand how diseases spread so that we are able to identify appropriate control measures should an outbreak occur. Think of the Swine ‘flu outbreak - http://www.bbc.co.uk/news/10483218 http://www.bbc.co.uk/news/10483218 For overview of methods used to stop the spread of infection see the following clip https://www.youtube.com/watch?v=lEzTBzh 4NQg

19. Active Immunity Naturally acquired active immunity occurs when – a person is exposed to a live pathogen, – develops the disease, – becomes immune as a result of the primary immune response e.g. immunological memory. Artificially acquired active immunity can be induced by a vaccine, a substance that contains the antigen. A vaccine stimulates a primary response against the antigen without causing symptoms of the disease. – B & T cells are produced and some persist as memory cells. Antibodies are also formed. Immunisation is the process by which a person develops immunity to a disease-causing organism.

20. Vaccines The pathogen is mixed with an adjuvant This is a chemical which increases the antigenic response, enhancing the immune system Types of vaccines include – inactivated pathogen toxins (tetanus and diphtheria), – dead pathogens (polio and hepatitis A), – parts of pathogens (HPV and hepatitis B) – weakened pathogens (measles, mumps and rubella).

21. Clinical Trials A clinical trial is a type of medical research. It aims to find new and improved ways of – preventing – diagnosing – Treating – controlling illnesses. People are involved in the trial in a controlled and carefully planned way.

22. Clinical Trials Clinical trials are designed to answer questions - about a treatment or a procedure. The main questions are usually: – Does it work? – Is it safe? – Does it cause side effects? – How does it affect quality of life? – Does it work better than existing treatments? – What is the best dose to use?

23. Clinical Trials Vaccines are subjected to clinical trials just like any other pharmaceutical medicine They must be shown to be safe and efficacious (effective when used in humans)

24. Everyone taking part in a randomised trial is put into different groups at random. Usually decided by computer. There are usually two groups in a randomised trial. Only one group has the new treatment. The other, called the control group, has the standard treatment or a placebo. The research team can then compare results from the two groups. One reason that trials are randomised is so that the research team can't choose who goes into which group based on what they know about their patients. For example, they might put people who they thought were healthier or more unwell into a particular group. This precaution helps to increase the reliability of the results. Types of Vaccine Trials Randomisation

25. Placebo Controlled Trials A placebo is a dummy treatment. E.g. a pill that looks the same as the drug being tested but just contains sugar. People can sometimes feel better when they have a placebo because they think they are having a real treatment. This is known as the 'placebo effect'. Comparing a group of people taking a new treatment with a group taking a placebo can show if the new treatment is really having an effect. A truly effective drug will show better results than the placebo.

26. Double Blind Trials In a blinded trial, you won't know whether you are getting the trial treatment, or the standard treatment or placebo. They will both look the same. Trials need to be 'blind' because just knowing that you are getting a new treatment can affect how you respond to, and make the results unreliable. Often the health professionals on the trial who give you your treatment are also 'blinded', meaning they don't know which treatment you are getting either - so they can't be influenced by what they know.

27. Experimental Error At the end of the trial, results from the two groups, which must be of a suitable size to reduce the magnitude of experimental error are compared to determine whether there are any statistically significant differences between the groups

28. Chapter23-infectious diseases and epidemiology. QuestionAnswer What is an Infectious disease?A disease that can be transmitted from one person to another by direct or indirect contact. What cause infectious diseases?Pathogens. Name some types of pathogens.Viruses(measles), bacteria,(cholera), fungi(athletes foot), protozoa(malaria), multicellular parasites(hookworm). How are infectious diseases transmitted?Physical contact, inhaled air from an infected person, indirect contact such as needles or cups, body fluids (kissing or in seminal fluids in intercourse), faecal-oral route, vector organisms(bitten by mosquito infected with malaria). What does it mean by saying transmission can be controlled by quarantine? A period of isolation for the infected person or for someone who has been in contact with an infected person for the incubation period of the disease.

29. Chapter 23-infectious diseases and epidemiology. Question.Answer. What is asepsis?Free of live micro-organisms. What is antisepsis?The inhibition or destruction of micro- organisms by carrying out procedures like sterilisation, applying antiseptics, gloves and masks. What should individuals practice to ensure good hygiene and reduce our chance of infection by a pathogen? Wash hands, shower, look after teeth, What should individuals use to protect them against STD’s like gonorrhoea and aids? condoms. What practices should individuals adopt when handling food to prevent transmission of microbes? Clean hands, separate cooked and uncooked meats, sterilise knives and work surfaces in butcher shops and abattoirs. Name the two procedures that prevent the transmission of pathogens from wild animals in drinking water. Filtration and chlorination of water.

30. Chapter 23-infectious diseases and epidemiology. Questionanswer. What do manufacturers in the UK do to prevent transmission of pathogens from milk and to keep food webs safe? Pasteurise the milk by heating it to 72 degrees for 15 seconds to kill most microorganisms including tuberculosis causing ones. They use inspection, risk analysis and traceability of food sources. What happens with our dry rubbish?Waste disposal mechanisms are in place to recycle, burn or bury it. How do we control vectors?Control of rats and their fleas that carry bubonic plague(black death) bacterium to humans. Mosquito vectors carry malaria (caused by a protozoan) and we drain stagnant water where they breed, use chemicals like insecticides and larvicides, introduce sterile male mosquitoes to reduce breeding.

31. Chapter 23-epidemiology of infectious diseases. Question.Answer. What does epidemiology of an infectious disease mean? Where the outbreak started, its pattern and speed of spread, its geographical distribution. Who does this work?Epidemiologists. They closely watch the spread of the disease and analyse it to find out what caused it and what control measures can be taken (drugs to help, immunisation, try to stop transmission from person to person and region to region. How are the patterns of infectious diseases classified? SEEP: Sporadic, endemic, epidemic, pandemic. Define sporadic.Occurs in scattered instances with no connection between them. Define endemic.Recurs as a regular number of cases in a particular area. Define epidemic.Simultaneously affects an unusually large number of people in a particular area. Define pandemic.Occurs as a series of epidemics that spread across continents or through the world.

32. Active immunisation and vaccination-page 332. Question. Answer. What is immunisation? The way in which a person develops immunity to a disease causing organism. What is active immunity? The protection a person gets from making their own antibodies against pathogens. What is naturally acquired active immunity? If a person survives infection by a pathogen and meets the pathogen again and is not affected by it then the person has acquired active immunity by natural means (primary and secondary response). What is artificially acquired immunity? Vaccination results in this. The person is deliberately given a weakened or changed form of the pathogen or its toxin to act as an antigen and start the immune response. An adjuvant is also given to promote the activity of the antigen. This starts the production of B cells and T cells and the formation of antibodies-it does not cause the disease. Some B cells and T cells stay in the body as memory cells to start the secondary response if needed. What are vaccine clinical trials? Clinical trials involves testing the drugs or vaccines on humans This can only happen when the medicines and vaccines are fully checked for safety and that they work. Clinical trials have 3 phases-see next slide. What happens before clinical trials are carried out Testing on cells and animals in the lab takes place first and then it is checked that it meets European protocol that helps keep good standards.

33. Design of phase three in the clinical trial. questionAnswer. How many groups are those who are taking part divided into? two Name the two types of groups.The test group and the control group. Which group gets the treatment?The test group. What do the control group get and what is it?A placebo that looks like the treatment but is not. Name the 3 things in the protocol used at this stage.Placebo-controlled, double-blind, randomised. What is the placebo effect?This is the effect from receiving the treatment that does not depend on the drug or vaccine-they could show improvement due to a psychological effect. The placebo allows a valid comparison to be made that takes this into account. What is a double-blind trial?Neither the subjects or the doctors know who is getting what and so this eliminates bias-the doctor could act in a different way to the patient if he knew that the patient was getting the treatment. What is randomisation?Each person is put into a group at random by a computer to further eliminate bias-a doctor might avoid putting an ill person into the treatment group without thinking. And this would…… How is experimental error further avoided?Computer ensures the groups are as similar as possible – same number of males and females, similar age groups in each group, similar weights of people in each group What happens next?The results are subjected to statistical analysis and the results from the two groups are compared to find out if the treatment works and if it does the researchers try to get a licence to make it and sell it.