Communicable Diseases and Pathogens

Communicable Diseases and Pathogens

• Communicable diseases are infectious and can spread between animals and plants.
• Pathogens are the microorganisms that cause infectious diseases.
• Pathogens include bacteria, viruses, fungi, and protists.

Bacterial Pathogens

• Bacterial pathogens can reproduce rapidly within the body.
• They may produce toxins that cause damage to tissue.

Viral Pathogens

• Viral pathogens infect body cells where they reproduce.
• This process of viral reproduction inside cells causes damage.

Human Defense Systems (Non-Specific)

• Non-specific defense systems protect against all microorganisms.
• Hair and mucus in the nose trap microbes.
• Stomach acid (hydrochloric acid) kills microbes present on food.
• Skin acts as a physical barrier to prevent microbe entry unless damaged.

Defense in the Lungs

• The trachea (windpipe) and bronchi contain cilia (tiny hairs) and mucus.
• Cilia trap microbes and move them out of the body.

White Blood Cells

• White blood cells defend against pathogens inside the body.
• Phagocytosis: white blood cells engulf and digest pathogens, destroying them.
• Antibody Production: white blood cells produce antibodies that attach to antigens on a microbe's surface, helping to kill the pathogen.
• Antitoxin Production: white blood cells produce antitoxins to counteract toxins produced by bacterial pathogens.

Vaccination

• A vaccine contains dead, weakened, or inactive pathogens.
• Injection of a vaccine stimulates white blood cells to produce antibodies against the pathogen.
• Memory cells remain in the body, enabling a rapid antibody response upon reinfection.

Salmonella Food Poisoning

• Pathogen: bacterium (Salmonella)
• Spread: eating infected food
• Symptoms: fever, abdominal cramps, vomiting, diarrhea (due to bacterial toxins)
• Prevention: vaccinating poultry, washing hands, disinfecting surfaces

Gonorrhea

• Pathogen: bacterium
• Spread: sexual contact
• Symptoms: discharge from vagina or penis, pain during urination
• Treatment: antibiotics
• Prevention: barrier methods like condoms

Measles

• Pathogen: virus
• Spread: inhaling droplets from sneezes or coughs
• Symptoms: fever and red skin rash
• Complications: can be fatal
• Prevention: vaccination

HIV

• Pathogen: virus
• Spread: sexual contact, exchange of body fluids (e.g., sharing needles)
• Symptoms: flu-like illness initially, later attacking immune system/white blood cells, potentially leading to AIDS
• Treatment: controlled by anti-retroviral drugs
• Prevention: condoms, avoiding needle sharing

Tobacco Mosaic Virus

• Pathogen: virus
• Spread: contact between plants
• Symptoms: mosaic pattern discoloration on leaves, less photosynthesis, reduced growth
• Treatment: remove and destroy infected plants

Rose Black Spot

• Pathogen: fungus
• Spread: wind or water
• Symptoms: purple or black spots on leaves, leaves turn yellow and drop, less photosynthesis, reduced growth
• Treatment: remove/destroy plants, fungicides

Malaria

• Pathogen: protist
• Spread: mosquitoes (vectors)
• Symptoms: recurring fever, can be fatal
• Prevention: prevent mosquito breeding, mosquito nets

Antibiotics

• Antibiotics cure bacterial diseases by killing bacterial pathogens.
• Specific antibiotics work with specific bacteria, and some bacteria are antibiotic resistant.
• Antibiotics are ineffective against viruses.

Painkillers

• Antibiotics are ineffective against viruses.
• Painkillers treat symptoms of illness, but do not kill pathogens.

Drug discovery

• Traditionally, new drugs were founded from plants and microbes.
• Digitalis (a heart drug) comes from foxgloves.
• Aspirin (a painkiller) comes from willow trees.
• Penicillin (an antibiotic) comes from penicillium mold.

Drug testing

• Drugs are tested for toxicity, efficacy, and dosage.
• Chemicals are made, or extracted from plants for possible drugs to treat a targeted disease.
• These go through pre-clinical trials, and are tested on cells or tissues.
• Clinical trials are done on healthy volunteers to monitor side effects.
• Optimum drug dosage is tested.

Double Blind Trials

• Double blind trials are performed to test efficacy.
• Some volunteers are given a placebo treatment that does not contain the drug.
• Peer reviews follow clinical trials to prevent false claims and bias.

Monoclonal Antibodies (Triple Science Only)

• Monoclonal antibodies are produced from a single clone of cells.
• Specific to one protein antigen.
• Protein antigens are injected into mice.
• The mouse lymphocytes produce the antibody for the antigen.
• The antibody is then merged with a tumour cell to replicate indefinitely.

Uses for Monoclonal Antibodies

• Pregnancy test diagnosis- antibodies are fixed to the test strip, if pregnancy hormone is present in urine, the antibody will detect it and cause a colour change.
• Laboratories can use them to detect pathogens.
• They can be used in research to identify certain cells.

Treatment of Disease with Monoclonal Antibodies

• Monoclonal antibodies can have drugs attached to them.
• They can attach to cancer cells and deliver the drug to destroy those cells.
• Healthy cells are unharmed

Plant Diseases (Triple Science Only)

• Plant diseases are detectable through malformed stems, stunted growth and decay.
• Can be identified through gardening manuals or websites.

Plant Disease (Higher Tier)

• Plant diseases can be identified by taking infected plants to a lab.
• Test kits can be used that include monoclonal antibodies.

Plant Deficiencies (Higher Tier)

• Iron or nitrate deficiencies lead to stunted growth because nitrates are needed for amino acid production and protein for growth.
• Magnesium deficiency leads to chlorosis because magnesium ions are needed to make chlorophyll, and less chlorophyll means less photosynthesis.
• Plant responses protect from microorganisms.

Plant Defence

• Physical defense such as layers of dead cells around stems that fall off.
• Waxy cuticles protect stems from microorganism invasion.
• Thorns/Hairs deter animals from climbing or eating plants.
• Curled leaves droop.
• Mimicry is used for deceptive protection to trick animals into staying away.