mod 7 infectious diseases

disease

any disturbance of structure or function of the body of an organism/adversely affects the function of an organism

• associated with characteristic structural changes and symptoms

health

a state of physical, mental and social wellbeing and not merely the absence of disease or infirmity.

pathogen

parasitic disease causing agent. transmittable by air, water, food

infectious disease

disturbance of function or structure of the body caused by the invasion of the body by a pathogen. transmissable from individuals via direct or indirect contact

cellular pathogens

microorganisms and macroorganisms that invade host cells.

non-cellular pathogens

prions and viruses which invade host cells

communicable disease

disease that can be transmitted by a pathogen from one organism to another

non-infectious disease

an abnormality in structure or function caused by environmental factors, nutrition or an inherited mutation that cannot be transmitted between individuals.

prions

non-living pathogenic agents that induce abnormal folding of specific normal cellular proteins (___ proteins) found abundantly in the brain.

• <15nm in in diameter

• creutzfeld jakob disease

spongiform disease

disease caused by ____ resulting in the abnormal folding of the __ proteins causing brain damage and the characteristic signs and symptoms of the disease

• transmissable spongiform encephalopathics

• brain becomes full of holes like a sponge

• mad cow disease, Creutzfeld Jakob disease

• transmission by ingesting infected tissue or inherited mutation

virus

a non living non-cellular organism that contains DNA, Rna and a protective coat. it can only replicate inside a host cell. less than 500nm. its not.visible with a light microscope

• hep b, AIDS, smallpox

• outer coat and inner core of nucleic acid

• it penetrates the host cell and inserts its DNA, RNA and replicates

viroids

smaller and simpler than viruses, lack a protein coat, single strand of RNA, only known to be pathogens of plants

bacteria

prokaryotic organism 0.5-5μm in size. they reproduce asexually, are commensalistic and sometimes parasites. pathogenic versions produce toxins that cause symptoms. visible with light microscope

• DNA in form of plasmid.

• Some have flagella, spores or a capsule.

• they are classified according to shape

• streptococcus pneumoniae, MYCOBACTERIUM TUBERCULOSIS, escherichia coli, bacillus anthrax

protozoa

unicellular eukaryote with a complex life cycle. 50-150μm

• malaria, giardasis

fungi

eukaryotic mostly multicelllular, 3-10μm with a cell wall of chitin. reproduction by spores, either heterothallic (sexual) or homothallic (asexual). it excretes enzymes to digest substrate.

• yeast (thrush), trichophyton (ringworm + athletes foot)

endoparasites

pathogenic organisms that live inside the host’s body. they can invade vital organs, gut, tissues, bloodstream

• roundworms (transmitted by faeces in soil. 1.7bil infected), tapeworms

ectoparasites

pathogenic organisms that live on the outside of the body, usually sucking blood.

• invertebrates and their bites can cause intense irritation and transmit pathogens such as bacteria typhus.

• mosquitoes, ticks, flies, leeches, mites, lice

direct contact

transmission of a pathogen via contact between an infected and non-infected organism

• touching, sexual contact, body secretions (HIV, measles)

• ringworm

• droplet spread (influenza, tuberculosis)

• person- person

indirect contact

transmission of a pathogen via contact with an infected surface or material that harbours a reservoir outside the host itself.

• airborne (water vapour, gases) (cold virus, measles)

• water (not purified, non-proper sewage)

• food (careless handling, storage) (escherichia coli)

• vectors

• nonsterile utensils

airborne transmission

transmission of a pathogen through the air containing gases, water vapour. infected individuals cough, sneeze.

endemic

a disease that exists permanently in a particular region or population

• eg malaria in africa

non-infectious disease

disease caused by factors other than a pathogen. non-transmissable

macroparasite

eukaryotic, multicellular organism thats parasitic and visible with the naked eye

epidemic

an outbreak of an infectious disease that spreads rapidly among individuals in a defined area or population at the same time

pandemic

spread of a new disease across a continent or even worldwide

• tuberculosis, covid, hiv

louis pasteur

invented pasteurisation as a result of wine factories.

• discovered disease was called by microscopic organisms and proposed the germ theory

• straight and swan-necked flask

• disproved spontaneous generation and belief in miasma

• anthrax. in cows

• attenuated vaccines

• fermentation caused by living organisms

robert koch

invented postulates to prove that a particular organism causes disease

• worked on anthrax disease

  • obtained infected matter from sheep

  • isolated bacterium and examining under a microscope

  • all infected organisms had the microbes

• conclusively showed organisms were the cause of anthrax

• demonstrated a link between a particular organism and particular disease

koch’s postulates

guidelines to prove a microorganism causes disease

1. the microorganism must be present in all infected organisms

2. microorganism is isolated from the host and grown in a pure culture

3. healthy organism is injected with the microorganism and develops the same symptoms

4. the microorganism is isolated again and is the same as the original microorganism

keratin

a protein found in the epidermis cells that helps bind the cellular matrix to make the skin impenetrable to pathogens

epidermis

top layer of the skin. a thin layer with keratin

dermis

the middle layer of the skin. contains sweat and sebaceous glands to create an acidic environment for microbes

hypodermis

lowest layer of skin containing blood and lymph vessels

endemic

a consistently present disease within a region

host factors

factors that contribute to disease development as a result of the host’s susceptibility to the disease.

• access to pathogen

• concurrent health state (nutrition etc.

• climate

pathogen factors

factors that contribute to disease development as a result of the pathogen’s availability including its ability to transfer between hosts, virulence factors and establishment in host tissues

environmental factors

factors that contribute to the development of disease as a result of the envrionmental conditions of organisms. e.g. overcrowding in farms lead to a build up of wastes which are favourable environments for pathogen resevoirs.

increased mobility of human populations

factor contributing to the risk of infectious disease. travellers, imported livestock and shoes all carry disease. pathogens can form resevoirs in food, soil and seeds

rise of intensive industrial type agriculture

factor contributing to the risk of infectious disease is this due to increased populations, there has been a change in the style of agriculture and lockstock production. intensive feedlots mean higher stocking densitities and easier transmission of pathogens.

changing patterns of land use

factor contributing to the risk of infectious disease as a result of land use. deforestation and irrigation may change the distribution of insects

climate change

factor contributing to the risk of infectious disease relating to the weather. it changes the distribution and abundance of insect vectors. rainfall patterns also change which may favour pathogen resevoirs. availability of nutrients change thus changing animal response to pathogens.

antimicrobial resistance

factor contributing to the risk of infectious disease relating to antibiotic resistance. overuse or offlabel use quickens microbe’s resistance to antimicrobials. these antimicrobials are used among high density populations since theyre more exposed to others + waste.

abscission

dropping of an infected fruit/leaf

reservoir

the habitat in which the agent normally lives, grows, and multiplies

lymphocyte

an immune cell WBC made in bonemarrow. two primary ones. one makes antibodies and the other regulates immune responses by helping to kill infected cells and orchestrating the activity of other immune cells.

t lymphocytes

WBC that attacks invader cells by transforming into cytotoxic t cells and seeks infected cells, binding to them and destroying them. responsibile for the cell mediated response

primary immune response

when the adaptive immune system is first exposed to a pathogen and the b and t lymphocytes respond. This initial response leads to the production of antibodies and memory cells, allowing for a faster response on subsequent exposures.

secondary immune response

when the adaptive immune system is exposed to a pathogen after the initial response where the b and t lymphocytes respond far quicker and in more abundance than initially

cell-mediated response

the immune response coordinated by T lymphocytes that targets and destroys infected cells for infections within the body cells

humoural response

when pathogens infect bodily fluid. the b lymphocytes are responsible for producing antibodies that target these pathogens, while T lymphocytes facilitate the destruction of infected cells.

antibodies

protein molecules with a specific molecular structure that helps them to recognise and bind to specific pathogens.

plasma cells

matured b lymphocyte which releases antibodies after receiving instruction from immature b cells

cytokines

chemical messengers released by helper t cells that promote the development and differentiation of T and B lymphocytes.

apoptosis

the process of programmed cell death that occurs in multicellular organisms, which helps to maintain health by removing damaged or unnecessary cells.

helper t cells

release chemicals that acitiate the cloning of cytotoxic cells

cytotoxic cells

a type of T cell that directly kills infected cells by recognizing specific antigens.

memory t cells

remain in the body to respond to future infections by the same antigens

suppressor t cells

suppress the immune response when infection has been defeated

phagocytes

specialised white blood cells which engulf a foreign particle and destroy it

phagocytosis

the process by which wbc change shape to engulf a foreign particle and destroy it.

neutrophils

the first wbc to find an infection which squeeze between endothelial cells and fight acute infections.

monocytes

wbc that circulates in the blood until attracted to inflamed tissue used to fight chronic infections where they undergo transformation into macrophages and dendritic cells. when damage occurs, TLRs recognise foreign material and then differentiate and remove microbes.

toll like receptors

receptors responsible for the recognition of foreign particles

dendritic cells

antigen presenting cells. the bridge between adaptive and innate immune systems.

macrophage

differentiated monocytes which engulf and kill microbes.

the complement system

around 20 proteins that assist other defence systems in destroying extracellular pathogens

• stimulate phagocyte activity

• form a coat around antibody-pathogen complexes to signal phagocytosis

pyrexia

fever: hypothalamus emits pyrogens. the heating up of body tissue to kill or limit growth of pathogens and enhance WBC activity

innate immunity

non-specific immune response present at birth involving both physical and chemical barriers as well as cellular responses

physical barriers

• skin

• mucous

• epithelial tissues

• cilia

• peristalsis

• sphincters

• granuloma formation

• vomiting + diarrhoea

• urination

• wound healing

chemical

first line of defence

non specific physical and chemical barriers that attack any pathogen. part of innate immunity

second line of defence

non specific attack of pathogens activated before pathogens damage the body

• inflammation

• phagocytosis

• fever

• cell death

lymphatic system

as blood circulates around the body, plasma moves out of capillaries and becomes part of the tissue fluid. this is the one-way drainage system back to the heart.

lymph nodes

structures in the lymphatic system that filter pathogens out of plasma before returning it to the heart. can swell, change in shape, size + texture are indicative of disease

microbiome

collective of all the microbes that live on the human body. live off the nutrients and conditions on the body in a mutualistic way. in return, they inhabit and occupy space where pathogens could live and grow.

candidiasis

thrush: a funal infection in the vagina as candida albicans is part of the natural microbiome on the female genital tract. an abundance of C. albicans = thrush as a result of a change in the microbiome

epithelial tissues

tissues line all the major internal cavities

proliferation

the division + maturation of cells

mucus membranes

an epithelial tissue that lines internal cavities. has cell junctions to increase cohesion and block pathogen entry

mucus

slippery substance secreted to protect the linings of the body by trapping foreign substances

green = wbc activity

peristalsis

the involuntary moving of food by the smooth wall of the small intestine to move food to the anus. stasis = bacteria growth

sphincters

circular muscle that maintains constriction of orifices and relaxes as required by normal physiological function

granuloma formations

when an infection cant be controlled, surrounding cells die to isolate the infection, forming a capsule of dead cells

vomiting and diarrhoea

______ is triggered by the brain to expel harmful substances. ___ rapidly removes pathogens from the digestive system

urination

when the bladder is infected, the body flushes out infection through frequent small urinations

wound healing

when barriers expose tissue to pathogens requires healing. bleeding if blood vessels are damaged

haemostasis

stops bleeding to maintain blood pressure

inflammation

part of the second line of defence: a non-specific response where pyrokines trigger the heating of tissue.

1. pain (mediators)

2. heat (increased blood flow)

3. redness (increased microcirculation)

4. swelling (fluid leakage from capillaries)

5. loss of function (pain/swelling)