Communicable Diseases

• Pathogens are microorganisms that cause infectious disease
• Pathogens may be viruses, bacteria, protists or fungi
• Pathogens can infect plants or animals and can be spread by direct contact, by water or by air
• Bacteria and viruses may reproduce rapidly inside the body
• Bacteria may produce poisons (toxins) that damage tissues and make us feel ill
• Viruses live and reproduce inside cells, causing cell damage
• Protists are single celled eukaryotes
• Some protists are parasites which live on or inside other organisms and cause damage
• Parasites are often transferred to other organisms by a vector which does not get the disease itself
• Some fungi have hyphae which can grow and penetrate human skin and the surface of plants causing diseases
• Hyphae can produce spores which can be spread to other plants and animals
• Some pathogens can be transmitted by drinking or bathing in dirty water
• Some airborne pathogens can be transmitted by small droplets that are carried in the air
• Some pathogens can be transmitted by touching contaminated surfaces
• 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 so 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 and if not successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells
• Late stage HIV infection (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
• HIV is a virus
• Measles is a virus
• Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes
• Tobacco mosaic virus gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis
• Tobacco mosaic virus is a virus
• Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early which in turn affects the growth of the plant as photosynthesis is reduced
• Rose black spot 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
• Rose black spot is a fungus
• 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 salmonella and the toxins they secrete
• Salmonella is a bacteria
• 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
• Gonorrhoea 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 of gonorrhoea can be controlled by treatment with antibiotics or the use of a barrier method of contraception such as a condom
• The pathogens that cause malaria are protists
• Gonorrhoea is caused by bacteria
• The malarial protist has a life cycle that includes the mosquito (vector)