Module 7: Infectious Diseases Flashcards
Prion
-Proteinaceous infectious particles
-Abnormally folded protein which propagates by transmitting the misfolded protein state to other cellular proteins
-Mad cow disease (bovine spongiform encephalopathy), Creutzfeldt-Jakob disease
Virus
-Single celled prokaryotic organism (no membrane bound organelles)
-Reproduce by binary fission
-Secrete toxins, invade cells and form colonies (biofilms) which disrupt cell function
HPV
Bacteria
-Single celled prokaryotic organism (no membrane bound organelles)
-Reproduce by binary fission
-Secrete toxins, invade cells and form colonies (biofilms) which disrupt cell function
Salmonella
Protozoa
-Single celled eucaryotic organism
-Heterotrophic: absorbs nutrients from hosts
-Secretes toxins, invades cells, and forms colonies to disrupt cell and tissue function
Malaria
Fungi
-Eukaryotic, heterotrophic organisms with cell walls
-Absorb nutrients from the environment by secreting digestive enzymes
-Reproduce by spreading spores that can release harmful enzymes
Tinea, thrush
Microparasite
-Ectoparasites and endoparasites
-Invade and destroys cells, creates competition for nutrients
-Tapeworm, paralysis tick
Direct transmission (person to person)
-Occurs when an infected individual touches or exchanges body fluids with another individual
-Includes kissing, sexual contact, biting and contact with oral secretions or body lesions. (Herpes, gonorrhea, HIV)
Direct transmission (droplet spread)
-The result of droplet spray caused by talking, coughing, sneezing (influenza, chickepox, measles, tubercluosis, covid)
Indirect (airborne)
-Pathogens can remains suspended in the air for many hours outside the body
-They can travel long distances and infect an individual long after the host has left the area
Indirect (contaminated objects)
Transmission occurs when a surface or object containing the pathogen is touched and the pathogen is transferred to the mouth, nose or eyes before washing the hands.
Indirect (food and drinking water)
-Several pathogens are transmitted as a result of improper treatment, handling or storage of food and water (botulism, cholera, ecoli and food poisoning)
Indirect (Animal to person contact)
Usually occurs from a scratch or bite from an infected animal or from handling of waste
Indirect (vector borne)
Usually spread by blood sucking insects, including mosquitos, fleas and ticks such as malaria and Lyme disease. 4
Epidemic
-An epidemic is defined as an outbreak of infectious disease that spreads rapidly among individuals in a defined area or population at the same time.
Pandemic
- A pandemic is the spread of a new disease across a continent or even worldwide.
ECS: Introduction to Ebola
-EVD is a Ebola Virus Disease
-Severe, often fatal diseases in humans
-Fatality rate is 50%, but ranges from 25% to 90%
-Main concerns are the spread between neighboring countries due to the possibility of it being a pandemic
ECS: Transmission and FTAT
Transmission: Fruit bats are the natural host of the Ebola virus, the virus is initially transmitted to a human from an infected animal and continues to spread through a population by direct human to human contact (through broken skin or mucous membranes)
Factors that affect transmission: Virulence of the virus strain, population density, population mobility in infected areas, host exposure and susceptibility, cultural beliefs and behavioral practices, public health infrastructure
ECS: Host response
-The Ebola virus initially inflects the cells of the dendritic cells
-This prevents an immune response against the virus
-The virus replicate on mass and infects the cells of multiple organs- cell death results, leading to the release of cytokines
-The role of cytokines are to initiate an immune response to the virus
-The volume of cytokines released results in the thinning of blood vessel walls causing them to go and leak blood
-Blood pressure drops significantly, body temperature drops, which causes the affected to go into shock and die
ECS: Symptoms
Initial symptoms: Fever, fatigue, muscle pain, headache and sore throat
-Sever symptoms: Vomiting, diarrhea, rash, impaired kidney and liver function, internal and external bleeding
ECS: Treatment
-Patients are supported with oral and intravenous fluids combined with the treatment of specific. Symptoms
-First successful vaccines developed in 2016
Koch influence (summary)
Koch developed a procedure for isolating and identifying disease causing microbes
-This method directly linked microbial growth as a causative agent in disease progression
-Microbiological origins of anthrax, cholera, tuberculosis
Koch postulates (1)
1.In all organisms suffering from disease, the microorganisms must be present in abundance
Koch postulates (2)
2.Microorganisms must be isolated from the diseased organism, and grown in pure culture
Koch postulates (3)
3.When a healthy organism is inoculated with the pure culture, it must develop the same symptoms as the original sick organisms.
Koch postulates (4)
4.Isolate and regrow the microorganism from newly infected organism. If it is identical to the microorganism cultured in step 2, it has been identified as the cause of the disease.
Pasteur experiment
-Swan-neck flask experiment demonstrated that microbes (therefore pathogens) were airborne
-Disproved spontaneous generation
-Microorganisms are responbsible for food and beverage spoilage
-Invented pasteurisation
Foot and mouth disease
-Cloven-hoofed animals including cattle, sheep, goats, and pigs.
-The clinical signs are fever followed by the appearance of vesicles (fluid-filled blisters) between the toes and on the heels, on mammary glands and especially on the lips, tongue and palate.
-It causes severe pain and distress, especially in cattle; animals may be left permanently lame and the productivity of recovered animals may be reduced.
Pathogenic adaptations facilitating entry into hosts
-Cell wall degrading enzymes
-Toxins
-Effector proteins
-Adhesion to hist cells
-Extremophiles
PA- Entry into hosts: Cell wall degrading enzymes
Break down the plant cell wall, releasing intracellular nutrients
PA- Entry into hosts: Toxins
Molecules produced by pathogens that promote infection. Toxins may damage the host tissues or disable the immune system. (Inhibiting phagocytosis)
PA- Entry into hosts: Effector Proteins
Proteins secreted into or around a host cell which suppresses host defense processes, Used by bacteria and fungi.
PA- Entry into hosts: Adhesion to host cells
Expression of adhesin molecules allows pathogens to stick in the extracellular environment, promoting their colonization of tissues and organs of hosts
PA- Entry into hosts: Extremophiles
Pathogens with the ability to survive in hostile environments, such as very high or low pH, temperature, oxygen
PA- Transmission: Reservoir sites
(living and non-living) where pathogens may lay formant for long periods of time
-Animals may act as reservoirs of human disease in zoonotic diseases
PA- Transmission: Use of vectors
Increases transmission efficiency and provides a living organism in which pathogens may continue to replicate in between human infections- for examples: ticks and Lyme disease
PA- Transmission: Bacterial capsules
A viscous substance which covers the outside of some bacterial strains- creating a protective layer over the cell wall. Capsules may protect cells from being engulfed by macrophased and improve adherence to surfaces
PA- Transmission: Viral envelopes
Composed of proteins or lipids, evelopes for a protective layer around the outside of viruses, allowing for improved longevity outside of host cells and potentially may aid in avoiding host immune system
PA- Transmission: Rapid species evolution
High rates of mutation within the genomes of pathogens, coupled with fast reproduction rates, allow pathogenic species (particularly viruses) to evolve at a rapid rate
Myrtle Rust description
Myrtle rust is a fungal infection which attacks soft, new growth such as leaves, shoot tips and young stems of plants.
-The infectoin begins as small purple spots on leaves, from which bright yellow spores form inside of bulbous pustules
-The fungus spreads by releasing spores, which are easily dispensable by wind, accounting for the high degree of transmission over a relatively short period of time.
Myrtle rust: Pre-formed defences
-Mechanical barriers such as bark, thick cell walls composed of pectin, lignin and lead cuticles
-At sites of infection, cell walls become reinforced by deposition of additional structural proteins
-Secretory cells and glands transporting defensive substances
-For eucalypts, essential oils are produced and stored in cavities that act as a chemical defense against fungal and bacterial infections
-Production of antimicrobial peptides
Myrtle rust: Incurable defences
-Innate defenses activated by recognition of non-self cells
-Non-specific immune response
-Accumulation of harmful metabolites (such as reactive oxygen species of salicylic acid) at the site of infection
-Upregulation of pathogenesis related proteins, with some antifungal activity
FLOD: Skin
-Protective layer
-Pores secrete anti-microbial fluid, inhibting surface microbial growth
-The outermost layer of the skin is constantly shed
FLOD: Mucous membranes
-Cells lining the opening of the body (respiratory tract, urinary, and reproductive systems) secrete a protective layer of mucus that traps pathogens and other foreign particles
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FLOD: Cilia
-Hair-like projections ehich line the air passages (nose and throat)
-The movement of these structures pushes pathogens away from the lungs in a wave-like motion
FLOD: Chemical barriers
Substances such as stomach acid, alkali conditions in the small intestine and enzymes in the mouth all act to destroy pathogens
-The variation of different pH conditions in the digestive tract ensures that all pathogens are neutralized
-Lysozymes dissolve cell membranes to kill pathoegns like bacteria
FLOD: Secretion
Fluids are routinely secreted from sweat glands, hair folliciles and open passages in the body
-These secretions contain cantimicrobial chemicals which destroy bacteria and fungi, as well as acting to flush out pathogens which may have settled on or in surfaces
What is the SLOD?
Apart from the pre-formed structures which block entry into the body, animals have also adapted responsive defense systems who fight off foreign organisms in the body and stop the progression of disease from pathogens.
-These are termed the ‘second line of defense’ as they are activated once a pathogen has passed through the external physical barriers
SLOD: Lymph system
-Including the lymphatic vessels, the spleen, thymus and lymph nodes
-It produces WBC responsible for enacting the immune response
-Pathogens are drained to the lymph nodes via lymph fluid, where they can be nuetralised or killed by immune cells
SLOD: Inflammation
The dilation of blood vessels and infiltration of inflammatory cells at the site of infection, causing heat, pain, redness, swelling and acute loss of function.
-When tissues are damaged they release histamines which increase the permeability of proximal blood vessels and allow WBC to travel more easily to the site
-The purpose of inflammation is to clear out necrotic cells from the area and iniative tissue repair by stimulating the flow of blood to the area
-By heating the area, pathogens are subjected to higher temps- deactivating them
SLOD: Phagocytosis brief (role)
-Specialized WBCs, microphages and neutrophils are able to change their shape to engulf pathogens or cellular debris
-Once pathogens are enclosed within the immune cells, they can be broken down my enzymes
SLOD: Phagocytosis detail and process
1.Phagocytic receptors on the surface of WBCs bind to microbes
2.Bound materials are internalized, forming phagosomes
3.The phagosome fuses with lysosomes in the cell, forming phagolysosomes
4.The microbes inside phagolysosomes are killed by acidification, antimicrobial proteases and enzymes, reactive oxygen and nitrogen species and antimicrobial proteins
SLOD: Apoptosis
-Macrophages and lymphocytes may surround a pathogen and undergo programmed cell death APOPTOSIS). This results in the formation of a cyst which blocks pathogen movement and nay nutrient supply, causing it to die.
What is the innate immune system?
-Provides nonspecific protection against pathogens by responding in a generic matter to all foreign invaders
-The innate response is iniated immediately following exposure to a pathogen, or within a few hours (rapid response rate)
-No memory
What is the adaptive immune system?
-Highly specific, providing specialized protection against pathogens which enter the body
-Needs time to develop upon primary exposure to a pathogen (not as rapid)
-It has immunological memory, which means response upon secondary exposure and thereafter is stronger and faster
B cells overview
-Produces antibodies responsible for antibody mediated immunity
-Once activated by pathogenic antigens, B cells undergo mitosis and differentiate into two types
-Plasma B cells and Memory B cells
Plasma and memory B cells
-Plasma cells (immediete protection): secrete antibodies of the same antigen specificity as the selected parent B cell
-Memory B cells (persistent protection): circulate through the body initiating stronger, more rapid responses upon secondary antigen detection
T cells overview
Responsible for cell mediated immunity
-There are a number of T cells (HCRM-Happy Cats Ride Motorcycles)
Helper T cells
Assist other WBC such as B cells in their immunological processes. Once selected by antigen, helper Ts rapidly divide and secrete cytokines which help to coordinate the immune response
Cytotoxic killer T cells
These T cells release cytotoxins such as perforin and granzymes that kill target cells by triggering apoptosis. Essentially, they send singla so the infected cell, forcing it to kill itself and any pathogens inside of it.
Regulatory suppressor T cells
Control cell-mediated immunity by suppressing the activity of other T cells once the immune reaction has achieved its purpose. They stop the killer T cells from killing everything
Memory T cells
Provide immunological memory by remaining in circulation after infection- quicker more effective immune response upon re infection.
What are antibodies?
-Antibodies (immunoglobulins) are proteins naturally produced by B cells in response to antigens. They therefore play a critical role in the immune systems defense against infection and disease.
Structure of antibodies
-Each antibody consists of four polypeptides: two heavy chains and two light chains forming a Y shaped molecule.
-Heavy chain and lower end of the chain are conserved in all antibodies
-Variable regions of the light chain are identical antigen binding sites and attach to identical antigens.
What are antigen and antibody interactions?
-Antigens are molecular markers present on the surface of all cells
-Each cell type exhibits a certain antigen (all have slightly diff shapes) by which they are recognized.
-The body is able to recognize foreign pathogens as non self by their antigens
-Antibodies bind specifically to antigens, allowing for a number of immune responses
Antibody function
1.Neutralisation: antibodies binding to pathogens or toxins to block their effect on host cells. Once immobilized, toxins and pathogens may be degraded, either by macrophages or killer T cells
2.Opsonisation: The binding of antibodies to antigens improves the efficiency of phagocytosis
3.Complement system: by binding to pathogens present in the blood stream, antibodies activate lysis and ingestion of infections.
What is clonal selection?
-The process by which the adaptive immune system gains its specificity against pathogens
-it occurs in both T and B cells- rapid evolution of our immune system
Steps of clonal selection
1.Variation: our body has a pool of variable immune cells. These naïve cells will circulate the body until they encounter an antigen
2.Selection pressure: by binding to a specific immune cell receptor and the antigen selects that cell
3.Reproduction: the selected cell rapidly divides, producing lots of copies of the cell which produces antibodies best suited to the antigen. These cells differentiate into the different cells of the immune response (plasma and memory etc)
Limiting local disease spread
Immunization to create herd immunity within populations
-Personal hygiene practices including washing and drying hands regularly, covering coughs and sneezes, and cleaning surfaces regularly
-Safe health practices including limiting STDS using contraceptives and staying home if ill.
-Provision of public health information to improve knowledge
Limiting regional disease spread
-Water supply, sanitation facilities, food, Climate: Distribution and population size of disease vectors are heavily affected by climate (MOSQUITOS IN HUMID CLIMATES)
-Flooding, improving swift ID, continued surveillance collection, analysis, interpretation of health data
-Rapid Recog: Disease awareness and reporting from the community
-Efficient prognosis of microbial cause
Limiting global disease spread
-Communication between countries with global health organizations is essential
-WHO member states are required to report within 24 hours any disease or event that may constitute a health emergency
-Implementation of quarantine measures that involves things such as travel bans from disease ridden countries
-Monitoring movement of potentially effected individuals
MOPDC: Hygiene practices
Washing hands, cleaning wounds and undertaking responsible food preparation all minimize the likelihood of micro-organisms entering the body
MOPDC: Quarantine
Isolation of an individual for a set period of time in order to prevent the spread of disease. This allows for the infectious disease period to elapse or for symptoms to develop. Quarantine may be used for foods, plants, and animals. BY physically detaining diseased individuals, it allows for other individuals in the community to be protected.
MOPDC: Vaccination
Introduced attenuated pathogenic particles into the body can trigger a small-scale immune response
-Allows for specific antibodies to be produced against certain diseases, allowing for a stronger, more rapid response under second exposure
-This reduces the likelihood of infection from pathogens such as viruses
-HPV program in Australia- fall in viruses and cervical abnormalities
MOPDC: PH Campaigns
-Focus on management and prevention and aim to raise awareness and spread understanding about causes and impacts of disease. This may lead to healthier choices in the community and ending the spread of disease
-For eg, ACON provides AIDSHIV information and support to at risk groups
-Test more, treat early, stay safe
MOPDC: Pesticides
-Chemical or biological agents which control pests, including herbicides, insecticides and antimicrobials
-Stopping vectors of disease such as mosquitos
MOPDC: Genetic Engineering
Creating malaria resistant mosquitos using CRISPR
-Removing host factor gene which encodes a protein that helps the malaria parasite survive in the gut of the mosquito and develop for transmission
-By deleting the gene from mosquitos, they become resistant to malaria and the chain of transmission amongst humans is broken
Antivirals
A class of antimicrobial used to treat viral infections but inhibiting the development of the pathogen inside the host cell.
-They can’t destroy viruses but only inhibit the development of the pathogen (REPLICATE)
-In order to inhibit development, antivirals may target a number of different stages in the virus life cycle
Effectiveness of antivirals
Antivirals can be designed to target specific viral pathogens. • They can significantly improve the health outcomes and life expectancy of infected individuals. (HIV AIDS)
-Viruses uses the host cells machinery to reproduce. Drugs used to target a virus therefore often cause harm to the host cell. • The problem is further complicated by the very high mutation rates of viruses
Antibiotics
A class of antimicrobials used to treat bacterial infections. This may be achieved either by killing the infective bacteria or inhibiting its growth
- Interference with cell membrane permeability, interference with nucleic acid synthesis, interference with protein synthesis, interference with cell wall synthesis.
Effectiveness of antibiotics
Due to different cell structures, e.g. cell wall, bacteria are more easily targeted than viruses.
-Antibiotics only work on bacterial infections.
Misuse and overuse have led to multiple examples of antibiotic resistance
What is incidence and prevalence?
The frequency of new cases of a disease over a specified period of time
The proportion of a particular population affected by a disease
Whats herd immunity?
-When an estimated 95% of a population is vaccinated (herd immunity) against a disease there is less of the disease in the community, which makes it harder for the disease to spread.
-This is essential to protect individuals who cannot be vaccinated for medical reasons or babies who are too young to yet receive vaccinations.
Modern prediction of disease
DNA profiling: we have discussed in Module 6 allow us to see the short tandem repeats responsible for a particular disease
DNA sequencing allows us to see the specific nucleotide sequence in a gene that may be responsible for particular disase
Bush medicine
Term used to dscribe the skills and practices used to maintain health, based on Indigenous beliefs and experiences
-Doesn’t just refer to native flora and fauna but preventative and diagnostic techniques and the treatment of mental illness
(TEA TREE ON WOUNDS)
Smoke bush case study
Contains the active that can destroy the HIV virus in low concentrations medicinal treatments.
-At the time of issuing the license, the WA government had not acknowledged or included the Aboriginal people of WA in any royalties or compensation agreements.
Evaluating dengue and cholera changes
-As a result, specific preventive and control measures can be taken to avoid infection.
-In addition with the etiology known, predictive modelling can be used to determine possible outbreaks.
-For example, for both malaria and cholera specific vaccines have been developed for each disease.
-In addition, preventative measures and treatments for both diseases are known.
-Timely detection of malaria and cholera cases is essential to limiting the severity of outbreaks.
- For both diseases, predictive modelling using satellite imagery and global climate patterns is now used to track the diseases and predict possible outbreaks.
