Communicable Diseases Flashcards
(74 cards)
what is a pathogen
a microorganism that causes disease. there are four types: bacteria, protists, fungi and viruses
What are communicable diseases, and how are they spread?
Caused by infectious organisms called pathogens (bacteria, viruses, fungi, protists).
Spread from one organism to another, often within the same species but can transfer between species.
Spread in plants via vectors like wind and insects.
In animals, mainly spread through direct contact.
What are bacteria, and how do they cause disease?
Prokaryotic cells with no nucleus or membrane-bound organelles.
They’re classified by shape
Also classified by cell wall type (Gram-positive = purple/blue under light microscope; Gram-negative = red).
Some bacteria release toxins that damage host cells.
How do Gram-positive and Gram-negative bacteria differ?
Gram-positive bacteria: Retain purple/blue stain (as it has a thick peptidoglycan wall).
Gram-negative bacteria: Appear red (thin peptidoglycan wall).
This classification affects how bacteria respond to antibiotics, as their cell wall structures differ.
what are viruses and how do they cause disease?
they are non living. they insert genetic material into host which takes over metabolic processes to produce more viruses until the host cell bursts. they mutate rapidly making them hard to treat
What are protists, and how do they cause disease?
Single-celled eukaryotic organisms with a nucleus.
Some are parasites, using hosts for life processes (e.g., malaria).
Enter host cells, digest them, and use their contents to reproduce.
Often spread by vectors like mosquitoes.
How do fungi cause disease in plants and animals?
Eukaryotic organisms, some multicellular, others unicellular (yeasts).
Reproduce via spores, spread rapidly, especially in plants.
fungi can’t photosynthesise so they digest food extracellularly. Digest host tissue, destroying cells and causing symptoms. Mainly affects plants as it impacts photosynthesis. In animals, produce toxins affecting host cells.
How do pathogens cause damage to the host?
1) Direct tissue damage:
Viruses take over cells, replicate, then burst out, destroying them.
Protists digest host cells and break them down.
Fungi digest and destroy host cells.
2) Producing toxins:
Bacteria release toxins that break down membranes, damage enzymes, or interfere with cell function.
Some fungi produce toxins affecting host cells.
what are the bacterial diseases in plants and animals
animals- tuberculosis, meningitis
plant- ring rot
what is tuberculosis
a bacterial disease which damages and destroys lung tissue and suppresses the immune system so the body is less able to fight other diseases
curable by antibiotics and preventable through vaccination
what is meningitis?
a bacterial disease the affects the protective membranes on the surface of the brain which can spread to the rest of the body causing blood poisoning and death. antibiotics could cure the disease if given early enough
what is ring rot?
infects a whole field meaning that it cannot be used to grow potatoes for at least 2 years
what are the viral diseases in plants and animals
animals- HIV/AIDS, influenza plants- tobacco mosaic virus
what is HIV/AIDS
a virus that targets t-helper cells in the immune system so people are more susceptible to other diseases. HIV is a retrovirsu with RNA as its genetic material. passed from person to person through bodily fluids. AIDS is what happens when HIV is left untreated. no cure but antiretroviral drugs slow the progress
what is influenza
a viral infection of the ciliated epithelial cells in the gas exchange system. it kills them leaving the airways open to secondary infection. there are three main strains a,b,c. strain a is the most virulent. they are classified further by proteins on their surface. the changed in the proteins are usually quite small between each strain so it might leave you with immunity unless their is a big change in the proteins. there is no cure but vulnerable people are given annual vaccinations to protect them against ever changing strains
what is tobacco mosaic virus
infects tobacco plants and other species including tomatoes, peppers and cucumbers;etc. it damages leaves, flowers and fruit, stunting growth and reducing yields which can lead to an almost total crop loss. there is no cure
what are the protists diseases in plants and animals
animals- malaria
plants- potato blight
what is malaria
a protist spread by the bite of infected mosquitoes (vector). its a parasite that has a complex life cycle with 2 hosts- the mosquitoes and people. it invades the RBCs, liver and the brain. the disease recurs making people weak and vulnerable to other infections. there are no cures but preventative measures can be taken (by controlling the vector). for example, insecticides, removing the water where they breed, mosquito nets, window screens
what is potato blight
a fungus which hyphae penetrates host cells, destroying leaves and fruit. no cure but careful management and chemical treatments can reduce infection risk
what are the fungal diseases in plants and animals
animals- ring worm, athletes foot
plants- black sigatoka
what is ring worm
different fungi infect different species. it causes grey-white, crusty, infectious circular areas of skin. its no damaging but may be itchy. antifungal creams are an effective cure
what is athletes foot
only affects humans. a form of human ring worm that grows on and digests the warm, moist skin between toes. causes cracking and scaling which is itchy and may become sore. antifungal creams are an effective cure
what is black sigatoka
a fungus which attacks and destroys the leaves. the hyphae penetrate and digest the cells, turning the leaves black. it can cause a 50% reduction in yield. fungicide can control the spread but there is no cure
What are the two types of pathogen transmission?
Direct transmission (contact, inoculation, ingestion) and Indirect transmission (fomites, droplets, vectors).
