Disease Flashcards
How is the body a host?
Many organisms live in or on the human body in a symbiotic or parasitic relationships. These may help to defend us against disease aka beneficial (commensal and mutualistic) or harmful and cause disease (pathogenic).
Define pathogenic.
Denotes an organism that cause damage to a host.
Define infectious
Relating to a disease that can be passed from one organism to another.
Define carrier
An individual who has the microorganism that causes a disease and can pass it on, but has no symptoms of the disease itself
What is a disease reservoir?
A long term host of a pathogen that cause an infectious disease
Define endemic
When a disease is always found at low levels in a certain area
Define epidemic
The rapid spread of an infectious disease to a large number of people in a population
Define pandemic
An epidemic of infectious disease that has spread through populations on multiple continents.
Define vaccine
A treatment that provides active, acquired immunity to a disease
Define antibiotic
A substance produced by microorganisms that affects the growth of other microorganisms
Define antibiotic resistance
When a microorganism which should be affected by an antibiotic, is no longer susceptible to it
Define antigenic types
Organisms with the same or very similar antigens on their cell surface,
Usually sub groups or strains of a microbial species which can be used to trace infections. They are normally identified by using antibodies from serum.
Define vector
A living organism that transmits a disease from one organism to another
Define toxin
A poisonous substance produced by microorganisms that damages their host
Describe mutualistic bacteria that can become harmful.
E. coli is good in the large intestine for synthesising vitamin K but in the small intestine it can cause disease
Mites in hair follicles on eyelashes eat dead cells but can cause inflammation if they build up
Entamoeba grazes on dead cells of our gums but when it builds up it causes gingivitis
Describe characteristics and treatment of cholera.
Gram negative Vibrio Cholerae. Can only reproduce inside the human host.
Source: contaminated water and food, faecal/oral transmission - people become carriers and act as reservoirs for the disease
Tissues affected: a toxin it produces affects the chloride channel proteins in the small intestine causing watery diarrhoea, because water and ions aren’t absorbed, leading to severe dehydration and a fall in BP
Prevention and treatment: proper sanitation, vaccine, antibiotics and fluid and electrolytes.
Describe characteristics and treatment of Tuberculosis.
bacterium Mycobacterium Tuberculosis
Source: airborne droplet transmission
Tissues affected: lungs and neck and lymph nodes - symptoms include coughing up blood and chest pain. People lose their appetite and develop a fever.
Treatment: BCG vaccination of children to prevent disease, antibiotics as treatment
Describe characteristics and treatment of Smallpox, Variola Major
Source: droplet transmission and bodily fluids
Tissues affected: skin then multiple organs, causing a rash then blisters
Treatment: vaccination - it is now eradicated due to its low rate of anti genetic variation and mutation, and the highly immunogenic nature of its component antigens. It also lacked an animal reservoir.
Describe characteristics and treatment of influenza.
There are three subgroups, A, B and C. It’s RNA has 8 single strands instead of one. The phospholipid envelope around the virion has two antigens - haemagglutinin (H - enters) and neuraminidase (N - leaving).
Transmission: droplet transmission, contaminated surfaces
Tissues affected: upper respiratory tract - sore throat, cough, fever
Treatment: quarantine and hygiene. Antiviral drugs and vaccination but due to the number of different emerging types of the virus the vaccination had a limited effect.
What are the 2 origins of the antigenic types of influenza?
- Antigenic drift - no RNA proofreading enzymes so following each round of replication on average every new virion has a new mutation. This produces a gradual change in surface proteins
- Antigenic shift - influenza A has 16 types of H and 9 times of N. If one cell is infected by viruses with different H as N combinations they can recombine and make new virus types.
Describe the characteristics and treatment of malaria.
Caused by plasmodium.
Source: female mosquitos carrying plasmodium
Tissues affected: invades liver cells and then multiplied in red blood cells which then burst, releasing more parasites and causing sever bouts of fever
Treatment: nets, clothing, insect repellent, killing aquatic mosquito larvae with fish, draining breeding sites or spraying oil on the surface insecticides, bacterial infections, sterilisation, drugs and vaccines have limited effectiveness.
Describe the transmission of malaria.
When a mosquito takes blood from an infected person it takes in the sexually reproducing stage of plasmodium called gametocytes. They produce zygotes, which develop into an infective stage, called sporozoites. These migrate from the mosquitos gut to salivary glands. Then the sporozoites are injected into the human during a blood meal and travel to the liver and reproduce asexually into merozoites. These are released into the blood and infect red blood cells where they do more reproduction. The red blood cell bursts releasing more merozoites which infect more red blood cells. Some merozoites become gametocytes.
What is the pathogenicity of virus’s?
The way in which they cause diseases and is related to the way viruses produce more virus particles using the cells own metabolic pathways.
What are the diseases mentioned?
Bacterial infections - cholera and TB
Viral infections - influenza and smallpox
Protoctistan infection - malaria
