Mod 4: Communicable diseases Flashcards
Vectors
Vectors carry pathogens from one organism to another, eg water and insects
Two ways that bacteria can be classified
Two ways that bacteria can be classified:
-By their basic shapes - rod shaped (bacilli), spherical (cocci), comma shaped (vibrios), spiralled (spirilla) and corkscrew (spirochaetes)
-By their cell walls - two main types that react differently with Gram staining
Gram staining cell walls of bacteria
Gram staining cell walls of bacteria:
-Gram positive bacteria look purple-blue under the light microscope eg MRSA
-Gram negative bacteria appear red - eg E.coli
Why is identifiying cell walls of bacteria with gram staining useful?
Gram staining is useful because the type of cell wall affects how bacteria react to different antibiotics
What are antibiotics?
Antiobiotics = a compound that kills or inhibits the growth of bacteria
Features of viruses
Viruses:
-About 0.02-0.3 micrometers in diameter (50 times smaller than average bacterium)
-Invade living cells where genetic material of virus takes over the biochemistry of the host to cell to make more viruses
-Reproduce rapidly
-Evolve by developing adaptations to the host
-Considered by scientists to be the ultimate parasites
Viruses that attack bacteria
Viruses that attack bacteria are called bacteriophages :
-They take over the bacterial cells and use them to replicate, destroying the bacteria at the same time
-Now used to identify and treat some disease, and are important in scientific research
Protoctist/Protista features
Protoctist/Protista features:
-Small percentage act as pathogens
-Protists which cause disease are parasitic (they use people or animals as their host organism)
-Pathogenic protists may need a vector to transfer them to their hosts eg malaria or may enter body directly through polluted water eg giardia
Fungi features
Fungi:
-Eukaryotic organisms often multicellular (Excluding yeast)
-Cannot photosynthesis
-Digest their food extracellularly before absorbing nutrients
-Many are saprophytes (feed on decaying matter) but some are parasitic (feed on living plants and animals) -> these are the pathogenic fungi that cause communicable diseases
-When fungi reproduce they produce millions of tiny spores that spread huge distances meaning they spread fast
Ways that viruses damage the host tissue directly
Ways that viruses damage the host tissue directly:
-Viruses - take over the cell metabolism - viral genetic material gets into the host cell and is inserted into the host DNA - virus then uses host cell to make new viruses which then burst out the cell, destroying it and then spread to infect other cells
Ways that protoctista damage the host tissue directly
Ways that protoctista damage the host tissue directly:
-Take over cells and break them open as the new generation emerge, but htey do not take over the genetic material of the cell - they simply digest and use the cell contents as they reproduce - malaria is an example of this
How fungi damages host tissue directly
How fungi damages host tissue directly:
-Fungi digest living cells and destroy them -> this combined with the response of the body to the damage caused by the fungus gives the symptoms of disease
Producing toxins which damage host tissues
-Most bacteria produce toxins that poison or damage the host cells in some way, causing disease -> some bacterial toxins damage the host cells by breaking down the cell membranes, some damage or inactivate enzymes and some interfere with the host cell genetic material so that the cells cannot divide
-Some fungi produce toxins which affect host cells and cause disease
Process of a virus destroying a bacterial cell (bacteriophage)
Process of a virus destroying a bacterial cell (bacteriophage) :
1). Attachment of virus to host cell
2). Insertion of viral nucleic acid
3). Replication of viral nucleic acid
4). Synthesis of viral protein
5). Assembly of virus particles
6). Lysis of host cells
Bacterial shapes
Bacterial shapes (which they can be classified by):
Their basic shapes - rod shaped (bacilli), spherical (cocci), comma shaped (vibrios), spiralled (spirilla) and corkscrew (spirochaetes)
Ring rot in plants cause
Ring rot in plants:
-Bacterial disease of potatoes, tomatoes and aubergines caused by the Gram positive bacterium (clavibacter michiganensis)
Effect of ring rot in plants
Effect of ring rot in plants:
-Damages leaves, tubers and fruit - can destroy up to 80% of the crop and there is no cure
-Once bacterial ring rot infects a field it cannot be used to grow potatoes again for at least two years
Cause of tobacco mosaic virus (TMV) in plants
Cause of tobacco mosaic virus in plants (TMV):
-Virus that infects tobacco plants and 150 other plant species
Effect of TMV on plants
Effect of TMV on plants:
-Damages leaves, flowers and fruit, stunting growth and reducing yields, and can lead to an almost total crop loss
-Resistant crop strains available but there is no cure
What causes potato blight ?
Cause of potato blight in plants:
-Caused by fungus-like protoctist oomycete (phytopathora infestans)
Effect of potato blight on plants
Effect of potato blight on plants:
-The hyphae penetrates host cells, destroying leaves, tubers and fruit causing lots of crop damage
-No cure, but resistant strains, careful management and chemical treatments can reduce infection risk
What is black sigatoka caused by?
Black sigatoka is caused by the fungus mycospharella fijiensis, which attacks and destroys the leaves
-Disease that affects bananas
Black sigatoka effect on banana plants
Effect of black sigatoka on banana plants:
-Hyphae penetrates and digests cells, turning the leaves lack
-If plants are infected, it can cause a 50% reduction in yield
-Resistant strains are being developed - good husbandry and fingicise treatment can control spread of disease but there is no cure
What is husbandry in agriculture?
Husbandry = the cultivation and production of edible crops or of animals for food
What is tubercolosis (TB) caused by?
TB is a bacterial disease of humans, cows, pigs, badgers and deers commonly caused by mycobacterium tuberculosis and M.bovis
Effect of tubercolosis (TB)
TB effect:
-Damages and destroys lung tissue and suppresses the immune system, so the body is less able to fight off other diseases
-People with HIV/AIDS are much more likely to develop TB
-TB is curable by antibiotics and preventable by improving living standards and vaccination
What is bacterial meningitis caused by?
Bacterial meningitis - a bacterial infection (commonly streptococcus pneumoniae or neisseria menigitidis) on the meninges of the brain, which can spread into the rest of the body causing septicaemia (blood poisioning) + rapid death
What are the meninges of the brain?
The meninges of the brain are protective membranes on the surface of the brain
Effect of bacterial meningitis
Bacterial meningitis effect:
-Mainly effects young children and teens
-Blotchy red/purple rash that does not dissapear when a glass is pressed against it
-Up to 25% of people who recover have some permanent damage
-Antibiotics cure the disease if early, and vaccines can protec against some forms of bacterial meningitis
What is HIV/AIDS caused by? (acquired immunodeficiency syndrome)
-Caused by HIV (human immunodeficiency virus) - targets T cells in immune system - gradually destroys immune system to people are more prone to secondary infections
-Virus is passed on in bodily fluids, most commonly through unprotected sex, shared needs, contaminated blood products and from mothers to babies during pregnancy, birth or breast feeding
Process of HIV infection
HIV:
-Retrovirus with RNA as its genetic material
-Contains enzyme reverse transcriptase, which transcribes the RNA to a single strand of DNA to produce a single strand of DNA in the host cell
-This DNA interacts with the genetic material of the hose cell
Effect of HIV/AIDS
HIV/AIDS effect:
-Weakens the immune system
-No vaccine or cure, but treated with anti-retrovrial drugs
Cause of influenza/flu
Cause of influenza:
-Viral infection (orthomyxoviridae spp.) of the ciliated epithelial cells in the gas exchange system - kills them and leaves the airways open to secondary infection
-Three main strains (A, B and C)
-Flu viruses mutate regularly
-Major changes in surface antigens heralds a flu epidemic/pandemic as no antibodies available
Effect of influenza/flu
Influenza effect:
-Can be fatal, young children, old people and people with chronic illness are most vulnerable -> mostly from the secondary infections
Strain A of influenza
Strain A viruses - most virulent - classified further by proteins on their surfaces eg A (H1N1) and A (H3N3)
Cause of malaria
Cause of malaria:
-Caused by the protoctista plasmodium and spread by bites of infected anopheles mosquitoes
-Plasmodium parasites has complex life cycle - two hosts - mosquito and people
-Female mosquito takes two blood meals to provide her with proteins before laying her eggs - which is when plasmodium is passed onto people, which invades rbc, livers and brain
Effect of malaria
Effect of malaria:
-Diseases recurs, making people weak and vulnerable to other infections
-No vaccine against malaria and limited cures, but can be prevented by controlling the vectors
-> eg insectidies to destroy the mosquitos, mosquito nets, window and door screens, long sleeved clothing, etc
What is ring worm caused by in mammals?
Ring worm is a fungal disease affecting mammals inclugin cattle,d ogs, cats and humans
-Different fungi infect different species
-In cattle -> trichophyton verrucosum
Effect of ring worm in mammals?
Ring worm effect:
-Causes grey-white, crusty, infectiours, circular areas of skin
-Itchy but not damaging
-Treated with antifungal creams
What is athlete’s foot caused by?
Athlete’s foot is caused by a human fungal disease caused by tinia pedia
