Communicable Diseases

• What are the 4 types of pathogen?


  bacteria, viruses, protists, fungi
• What are bacteria and how do they cause disease?


  Single-celled living organisms that are important for our environment and body. They cause diseases by dividing rapidly by going through binary fission. They may produce toxins that affect your body or directly damage your cells.
• What are viruses and how do they cause disease?


  They are even smaller than bacteria and have a regular shape. They cause diseases in every type of living organism by taking over the cells of your body . They live and reproduce inside the cells, damaging and destroying them
• What did Ignaz Semmelweis do?


  Showed that handwashing decreased the incidence of childbed fever. Doctors would go straight from working on dead bodies to delivering babies. Also another doctor died with similar symptoms to childbed fever after working on a dead body with a cut
• What did Louis Pasteur do?


  Showed that microorganisms cause disease and developed vaccines against diseases
• What did Joseph Lister do?


  Started to use antiseptic chemicals to destroy pathogens before they caused infection in operating theatres
• What are the symptoms of measles?


  Fever and a red skin rash. Can cause blindess, brain damage and can be fatal.
• How are measles spread?


  The inhalation of droplets from sneezes and coughs
• What is the treatment for measles?


  There is no treatment so the infected need to be isolated. Children also get vaccinated at a young age
• What are the symptoms of HIV/AIDS?


  Mild flu like symptoms at first. HIV attacks the immune cells and after the mild illness it remains hidden until the immune system becomes so damaged it can't deal with infections or certain cancers. By this point, the patient has AIDS
• How is HIV spread?


  Sexual contact, or exchange of body fluids such as blood when drug users share needles. Can also be passed from mother to child in breast milk
• What is the cure for HIV/how can it be prevented?


  No cure and no vaccine. Can be prevented by using condoms, not sharing needles, screening blood used for transfusions and HIV-positive mothers bottle-feeding.
• What can prevent the development of AIDS?


  Antiretroviral drugs can give HIV-positive people an almost normal life.
• What is tobacco mosaic virus?


  Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes.
• What are the symptoms of tobacco mosaic virus?


  A distinctive 'mosaic' pattern of discolouration on the leaves. This affects the growth because the affected areas don't photosynthesise.
• How is tobacco mosaic virus spread?


  Contact between infected and healthy plants. Insects may act as vectors which transfer the virus between different plants. Virus can remain infectious in soil for 50 years
• What is the cure for tobacco mosaic virus?


  No treatment. Farmers now grow TMV-resistant strains of many crop plants.
• What is salmonella?


  A type of bacteria found in raw meat, poultry and eggs. If they enter the body via food poisoning, they can affect natural gut bacteria.
• What are the symptoms of salmonella?

  Fever, abdominal cramps, vomiting and diarrhoea. In young and old people it can be fatal because of dehydration.
• What is gonorrhea?


  STD
• How is gonorrhoea spread?


  Unprotected sexual contact with an infected person.
• What are the symptoms of gonorrhoea?


  Early symptoms include yellow/green discharge from genitals and painful urination, although it may be symptomless. Long term and untreated can cause pelvic pain and infertility.
• What is the cure for gonorrhoea?


  Antibiotics. Also reduction of sexual partners and protection
• Do plants get bacterial diseases?


  A few but these are usually found in tropical and sub-tropical regions.
• Can humans get fungal infections?


  Few fungal diseases affect people e.g., athlete's foot, infections from damaged heart valves and these can be treated with drugs but deep-seated infections are hard.
• What are symptoms of rose black spot?


  Purple or black spots develop on leaves which turn yellow and drop early. This weakens the plants as it reduces the area of leaves for photosynthesis.
• How is rose black spot spread?


  Through water and the wind
• How is rose black spot treated?


  Fungicides and/or removing and destroying affected leaves.
• What are protists?


  Single celled eukaryotes that are rare but cause serious damage to the infected. Diseases caused by protists usually involve a vector.
• What is malaria?

  Malaria is a disease caused by protist pathogens that are parasites
• How do humans get malaria from mosquitoes?


  The protists reproduce sexually in the mosquito. The female mosquito needs 2 meals of human blood before she can lay her eggs. This is when the protists pass into the human body. They affect the liver and damage red blood cells
• What are symptoms of malaria?


  Recurrent fevers and shaking when the protists burst out of the red blood cells and can lead to death
• How to control the spread of malaria?


  Using insecticides

  Using mosquito nets

  Removing standing water to not allow the vectors to breed

  Travellers taking antimalarial drugs
• How is skin a human defence response? (3)

  1) Acts as a barrier between pathogens and when you get a cut the platelets set up a chain reaction to form a clot which dries into a scab

  2) Skin produces antimicrobial secretions repelling pathogens

  3) Healthy skin is covered with microorganisms
• What are the defences of the respiratory and digestive systems? (3)


  1) Mucus and hairs trap particles in the air that may contain pathogens

  2) The trachea and bronchi are covered in cilli that waft up to the back of the throat

  3) The stomach produces acid and this destroys microorganisms
• What are the internal defences of the immune system? (3)


  1) Phagocytosis

  2) Some white blood cells produce antibodies and these target specific bacteria/viruses and destroy them.

  3) Some white blood cells produce antitoxins and these counteract the toxins released by pathogens
• What are aphids?


  They bite into the phloem of the plant and drink glucose from it. They attack in large numbers depriving the plants in the required products for photosynthesis

  - less glucose

  - less respiration

  - less amino acids made

  - less protein

  - less cellulose
• What are symptoms of diseased plants? (7)


  1) stunted growth

  2) spots on leaves

  3) areas of decay

  4) growths

  5) malformed stems and leaves

  6) discoloration

  7) presence of visible pests
• What are the physical plant defences? (4)


  1) Cell wall

  2) Tough waxy cuticle

  3) Bark on trees and a layer of dead cells

  4) Leaf fall
• What are the chemical plant defences?


  Antibacterial chemicals