Communicable Diseases PDF

# Communicable Diseases ## Pathogens: - include viruses, bacteria, protists & fungi - are microorganisms that can cause infectious disease - infect plants and animals, spreading through - either direct physical contact, by water, or by air ## Viruses: - Very small - move into cells, infect a h...

# Communicable Diseases ## Pathogens: - include viruses, bacteria, protists & fungi - are microorganisms that can cause infectious disease - infect plants and animals, spreading through - either direct physical contact, by water, or by air ## Viruses: - Very small - move into cells, infect a host cell or cells and replicate themselves within the cell, 1000 times - replicate their DNA and protein coats which are then made into new virus particles - Leads to cell bursting/damage and releases all copies into bloodstream - Damage/destruction of cells make a hosting person feel ill ## Bacteria: - small - multiply very quickly through dividing process called Binary Fission - produce Toxins - damage cells and act as poisons ## Protists: - some are parasitic - use humans & animals as host - live on and inside - causing damage ## Fungi: - either single celled or body made of thread like structures (hyphae) - produce spores - spread to other organisms ## Ways that pathogens are SPREAD: - **Direct Contact:** - touching - kissing, direct skin to skin - **By water:** drinking or contact with dirty water - **By air:** - pathogens can be carried in the air and breathed in - common example is DROPLET infection - when sneezing, coughing, or talking, let out pathogens in droplets - can be breathed in ## Reducing damage caused by diseases - **Improving hygiene:** - hand washing, using tissues when sneezing, using disinfectants - **Reducing contact with infected individuals** - **Vaccinations:** injecting a small amount of harmless pathogen into the human body - so they become immune - can't pass it on # Viral Diseases - Dangerous - enter all types of cells & yet to develop medicines to cure ## Measles: - **Symptoms:** - Fever & red skin rash - lead to lung infection, blindness, and brain infection - **How it's Spread:** droplet infection (when sneezing, coughing, or talking, let out pathogens in droplets which can be breathed in) - **How it's prevented:** vaccinations for young children ## HIV: - **Symptoms:** - Initially flu like symptoms - then virus attacks immune system and leads to AIDS - **How it's spread:** sexual contact or exchange of bodily fluids (eg blood) - **How it's prevented:** - The spread: - using condoms, not sharing needles - mothers with HIV bottle feeding needles to their children instead of breastfeeding - Development: use of antiretroviral drugs - stop virus replicating in the body ## Tobacco mosaic virus: - **symptoms:** discolouration of leaves - affected part can't photosynthesize - **How it's spread:** contact between diseased plants & healthy plants, insects act as vectors (living things that carry disease) - **How it's prevented:** good hygiene & pest control # Bacterial Diseases ## Salmonella: - **Symptoms:** fever, abdominal cramps, vomiting & diarrhoea - **Spread:** by contaminated food ## Gonorrhoea: - **Symptoms:** thick yellow discharge from vagina or penis - pain when urinating - **Spread:** by sexual contact # Fungal Diseases ## Athlete's Foot: - **symptoms:** scaly, itchy rash often between toes - **Spread:** by direct contact with others or contact with contaminated surface ## Rose Black Spot: - **Symptoms:** dark purple or black spots on leaves - **Effect:** reduces photosynthesis - reduces plant growth - **Prevention:** by removing affected leaves - **Cause:** caused by spores carried by the wind. # Protists Diseases ## Malaria: - **Symptoms:** severe fever, where protists burst at blood cells - **Cause:** caused by mosquitos (vectors - carry diseases) - **Prevention:** kill mosquitos & use mosquito nets # Human Defence Systems - Works to prevent pathogens entering the body ## Skin: - Physical Barrier ## Nose: - has nasal hairs & mucus - prevent particles from entering lungs ## Hydrochloric Acid in Stomach: - produces HA acid - kills any pathogens ## Immune System - White Blood Cells: ### Phagocytosis: - changes shape to surround the bacteria - then bacteria is engulfed and then digested by enzymes inside the phagocyte ### Producing antibodies: - each pathogen has antigens on the surface - with a complementary antibody that can attach to and the antibody attach and prevent bacteria from functioning. - the attached antibodies signal to phagocytes that a pathogen should be engulfed. ### Making antitoxins: - some WBCs (lymphocytes) produce chemicals called antitoxins that bind to toxins and reduce effects / neutralize them ## KEY WORDS - **Antitoxins:** chemicals that neutralize effects of Toxins - **Toxins:** poisonous chemicals that cause body harm - **Antibodies:** attach to antigens on a specific pathogen & cause pathogens to clump together. - **Antigens:** markers on the surface of cells that identify a # Vaccination - **Vaccines expose immunity system to weakened pathogens, allowing immunity without causing disease.** - **Herd immunity occurs when enough individuals are vaccinated, limiting the spread of disease.** - **Vaccinated individuals rarely cause severe reactions, making benefits outweigh risks.** - **Some may not provide full immunity or cause mild side effects.** # Antibiotics, Antivirals, Antifungals ## Antibiotics: - Specifically target bacteria - aiding immune system by damaging bacteria and preventing bacterial function ## Antivirals: - Target viruses affecting their replication - Reduce effect of communicable diseases ## Antifungals: - Treat infections caused by fungi, target fungi by killing fungi or prevent its growth. - Antifungals help reduce symptoms of communicable diseases & prevent speed of infection. # Drug Testing - **New drugs needs to be tested before doctors prescribe them for:** - **Safety:** - Drugs may be toxic and may have side effects. - **Effectiveness:** - Check how effective they are against the disease. - **Dosage:** - Check the optimum quantity required to treat the disease. - Too high a dose may be toxic/harmful. ## Stages of Drug Testing: - **Preclinical drug trials:** - The drugs are tested using computer models and skin cells grown using human stem cells in the laboratory. This allows the efficacy and possible side effects to be tested. Many substances fail this first test of a preclinical drug trial because they damage cells or do not seem to work. - **Animal testing:** - Drugs that pass the first stage are tested on animals. In the UK, new medicines have to undergo these tests. But it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side effects. - **Human clinical trials:** - Drugs that have passed animal tests are used in human clinical trials. They are tested on healthy volunteers to check that they are safe. The substances are then tested on people with the illness to ensure that they are safe and that they work. Low doses of the drug are used initially, and if this is safe the dosage increases until the optimum dosage is identified. # Monoclonal Antibody production - **Antigen is injected into a mouse.** - **Mouse naturally produces lymphocytes - produce antibodies specific to the antigen.** - **Spleen cells which produce lymphocytes are removed - operation** - **Lymphocytes are fused with tumor cells (which divide very easily unlike lymphocytes). Fused lymphocytes are called Hybridomas.** - **Hybridomas undergo cell division, creating more clones capable of producing identical MONOCLONAL ANTIBODIES.** # Uses of Monoclonal Antibodies: ## Pregnancy Tests: - As urine passes through the reaction zone, HCG hormone binds to the mobile HCG antibody in the reaction zone. - Passing up the stick, HCG binds to the immobilized HCG antibodies in the results zone. - The rest of antibodies which don't attach to HCG hormone bind to antibodies in the control zone. - **Monoclonal antibodies are used to measure levels of hormones in the blood.** - **Pregnant women produce HCG (hormone).** # How monoclonal antibodies are produced: 1. Scientists obtain mice lymphocytes (a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific antibody. 2. They are combined with tumor cells (do not make antibodies but divide rapidly), to form a cell called a hybridoma. 3. The hybridoma can divide to produce clones of itself, which all produce the same antibody. 4. The antibodies are collected and purified.