Communicable Disease Noadswood Science, 2016

Tuesday, October 03, 2017 Communicable Disease To describe and give examples of communicable disease

Precise Learning Different types of disease may interact. Defects in the immune system mean that an individual is more likely to suffer from infectious diseases. Viruses living in cells can be the trigger for cancers. Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma. Students should be able to translate disease incidence information between graphical and numerical forms, construct and interpret frequency tables and diagrams, bar charts and histograms, and use a scatter diagram to identify a correlation between two variables. Students should understand the principles of sampling as applied to scientific data, including epidemiological data. Students should be able to explain how diseases caused by viruses, bacteria, protists and fungi are spread in animals and plants. Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes. It gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis. Salmonella food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions. In the UK, poultry are vaccinated against Salmonella to control the spread. Fever, abdominal cramps, vomiting and diarrhoea are caused by the bacteria and the toxins they secrete. Gonorrhoea is a sexually transmitted disease (STD) with symptoms of a thick yellow or green discharge from the vagina or penis and pain on urinating. It is caused by a bacterium and was easily treated with the antibiotic penicillin until many resistant strains appeared. Gonorrhoea is spread by sexual contact. The spread can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom. Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. It is spread in the environment by water or wind. Rose black spot can be treated by using fungicides and/or removing and destroying the affected leaves. The pathogens that cause malaria are protists. The malarial protist has a life cycle that includes the mosquito. Malaria causes recurrent episodes of fever and can be fatal. The spread of malaria is controlled by preventing the vectors, mosquitos, from breeding and by using mosquito nets to avoid being bitten. Measles is a viral disease showing symptoms of fever and a red skin rash. Measles is a serious illness that can be fatal if complications arise. For this reason most young children are vaccinated against measles. The measles virus is spread by inhalation of droplets from sneezes and coughs. HIV initially causes a flu-like illness. Unless successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells. Late stage HIV infection, or AIDS, occurs when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers. HIV is spread by sexual contact or exchange of body fluids such as blood which occurs when drug users share needles.

Pathogens Pathogens are microorganisms that enter the body and cause disease – they cause communicable (infectious) diseases which can be spread Both plants and animals can be infected by pathogens What type of pathogens are there? Bacteria Viruses Protists Fungi

Spreading Disease One easy way to defend the body against illness is by keeping it clean and hygienic as microbes can spread very quickly in unhygienic conditions The spreading of microbes is known as transmission As soon as a virus or bacterium enters the body, we are termed infected (not the same as being ill – illness results from the effects these microbes have on our body Bacteria and viruses have the ability to produce poisons known as toxins

Swab Using a Petri dish and a sterile swab kit go around the school and choose 5 places where you think bacteria might grow… Take a swab and gently apply it to the agar within the Petri dish – label where the swab came from (on the bottom of the dish)

Pathogen Spread Pathogens can be spread in many ways Water > drinking / bathing in dirty water, e.g. cholera Air > breathed in, e.g. influenza (cold) virus Direct contact > touching contaminated surfaces, e.g. athlete’s foot

Viral Diseases Measles – spread through droplets from an infected person’s sneeze or cough causing a red skin rash and a fever (can lead to pneumonia (lung infection) and encephalitis (brain infection) which can both be fatal Most people are vaccinated when young

Viral Diseases HIV – spread by sexual contact or exchanging bodily fluids such as blood causing flu-like symptoms and eventually attacking the immune system which eventually becomes badly damaged and is unable to cope against other infections (it is then known as AIDS)

Viral Diseases TMV (tobacco mosaic virus) – affects many species of plants causing mosaic patterns on the leaves and the discolouration means the plant cannot photosynthesis as well

Fungal Diseases Rose black spot – the fungus causes purple or black spots to develop on the leaves of rose plants (the leaves can then turn yellow and drop off meaning less photosynthesis occurs) It spreads in water or by the wind but can be treated using fungicides

Protist Diseases Malaria – caused by a protest with part of its life cycle taking place in mosquitos (acting as vectors) and every time a mosquito feeds on another animal malaria is spread Malaria causes repeating episodes of fever which can be fatal. Insect repellant, sleeping under mosquito nets and reducing standing water (where mosquitos breed) can reduce it

Bacterial Diseases Salmonella – causes food poisoning with infected people suffering from fever, stomach cramps, vomiting and diarrhoea (caused by the bacteria’s toxins) Salmonella can be caught by eating food that has already been contaminated with the bacteria, for example chicken that caught the disease when alive / eating food prepared in unhygienic conditions In the UK most poultry is vaccinated to control the spread of the disease

Bacterial Diseases Gonorrhoea – a sexually transmitted disease (STD) caught by sexual contact. Gonorrhea causing pain when the person urinates as well as a thick yellow/green discharge Antibiotics do treat gonorrhoea, however resistant strains are become more common so barrier contraception should be used

Practice Questions List three symptoms of Salmonella food poisoning and one way it is spread How is gonorrhoea treated? A patient in hospital has a communicable disease where they need to be put in isolation – suggest why A nurse working in a GP surgery washes her hands carefully after seeing patients – suggest how this will prevent the spread of disease

Answers List three symptoms of Salmonella food poisoning and one way it is spread – fever / stomach cramps / vomiting / diarrhoea spread by eating an animal which caught the disease when alive / unhygienic preparation of food How is gonorrhoea treated – antibiotics A patient in hospital has a communicable disease where they need to be put in isolation – suggest why – prevent the disease being passed to anyone else A nurse working in a GP surgery washes her hands carefully after seeing patients – suggest how this will prevent the spread of disease – the nurse may come into contact with pathogens for many diseases so washing hands prevents them being passed to other people