Infectious Diseases: Causes, Effects, and Prevention, Study notes of Biology

Download Infectious Diseases: Causes, Effects, and Prevention and more Study notes Biology in PDF only on Docsity! Module 7 Infectious Disease Causes of Infectious Diseases Inquiry question: How are diseases transmitted? Students: ● Describe a variety of infectious diseases caused by pathogens, including microorganisms, microorganisms and non-cellular pathogens, and collect primary and secondary-source data and information relating to disease transmission, including: ○ classifying different pathogens that cause disease in plants and animals ○ investigating the transmission of a disease during an epidemic ○ design and conduct a practical investigation relating to the microbial testing of water or food samples ○ investigate modes of transmission of infectious diseases, including direct contact, indirect contact and vector transmission Disease = is an abnormal condition that impairs normal body function Infectious diseases are caused by pathogens and can be transmitted from one organism to another ↪ Can be caused by microscopic & macroscopic organisms and infectious agents which: ↳ Are virulent ↳ Have a method to enter a host organism ↳ Are able to survive the internal conditions of the host’s body ↳ Have mechanisms that allow it to be transferred from an infectious host to a non-infectious host ↳ Can survive outside the host to allows for transmission to occur Pathogen = An infectious agent that is capable of causing a disease in a host 6 Types of Pathogens ↪ Pathogens can be cellular or non-cellular Bacteria - Cellular Pathogen = prokaryotes, unicellular organisms without membrane-bound organelles and a cell wall ↪ Undergo asexual reproduction via binary fission process ↪ Most are beneficial (non-pathogenic) ↪ Pathogenic bacteria can cause disease by releasing toxins or damaging host tissue ↪ Eg Tuberculosis is a bacterium transmitted by air via water droplet (sneezing) symptoms include coughing (+ coughing blood), chest pain, chills Fungi - Cellular Pathogen = eukaryote, non-photosynthetic organisms with a cell wall + uni or multicellular ↪ Fungi secrete digestive enzymes & other chemicals into the environment to break down organic matter, which can then be absorbed into the fungus. These secreted substances are responsible for causing disease ↪ Eg skin infections such as athletes foot spread by direct contact with fungus + symptoms include dry, scaly sin, peeling of foot’s skin ↪ Zoonotic = can be transferred between humans & animals eg ringworm from pets to owner Protozoans - Cellular Pathogen = diverse group of unicellular eukaryotes that causes disease in plants & animals ↪ Asexually reproduce via binary fission ↪ Heterotrophic organisms→ cannot photosynthesise to make own food ↪ The life cycle of some protozoans include multiple stages in different hosts ↪ Eg Trypanosoma brucei causes African sleeping sickness & is transmitted by the biting tsetse fly Viruses - non-cellular = non-cellular pathogens consisting of single type of nucleic acid (DNA or RNA) encased in a protein coat (capsid) ↪ Can infect all kinds of organisms & require the cells of their host for reproduction ↪ The virus attaches to a host cell which it then penetrates→ it hijacks the host's enzymes & nutrients to make its own viral proteins & nucleic acid→ these viral materials then assemble into new viruses which are released from the host cell & infect other cells Macroparasites - cellular pathogen = eukaryotic pathogen is multicellular and visible to human eye ↪ Endoparasite = lives inside the host organism’s body & obtains food ↪ Ectoparasites = live outside the host’s body (eg consuming host’s blood)→ also play role as vectors by carrying other pathogens and infecting healthy hosts ↪ Eg Tapeworm transmitted orally Prions - non-cellular = Non-cellular pathogens comprising solely of protein & no genetic material & no membrane-bound organelles or cell wall ↪ Prions cause neurodegenerative diseases in humans and other animals by promoting abnormal folding of proteins in the host’s central nervous system ↪ Eg CJD transmitted via indirect & direct contact (eg eating infected beef) Epidemics = epidemic is the sudden increase in the number of cases of a disease above what is expected in that population area Pandemic = when a disease reaches above endemic levels on a global scale & epidemics are occuring across multiple countires or continents Epidemics are the result of a change in one or more of: ↪ Virulence of the pathogen ↪ Migration of the pathogen ↪ Host exposure & susceptibility Virulence of the Pathogen = mutations can occur that increase the virulence of a disease→ new strains of disease may emerge in a population where hosts had built immunity to previous strain ↪ Eg Ebola initially contracted through consumption of bat meat & became highly virulent when crossed the species barrier, spread through bodily fluids & has a short incubation period Pathogen Migration = migration of individuals into new populations can result in an epidemic→migrating individuals bring with them a disease the new population has not been in contact with/immune to ↪ Eg Spanish Flu, highly contagious & deadly spread through air as the pathogen was breathed or coughed out of infected people→ increases through travelling Host Exposure & Susceptibility = host population may become susceptible to disease if the population’s genetics change ↪ loss of genetic variation or selection pressures can cause a population to lose genetic resistance to certain pathogens ↪ Often caused by poor sanitation & hygiene in high-density populations ↪ Eg Chlorea affects GI tract causing vomiting and diarrhoea. Origin in the Nepalese army coming to Haiti→ contaminated sewerage washed into water supply for the Haitians ● Investigate the work of Robert Koch and Louis Pasteur, to explain the causes and transmission of infectious diseases; including ○ Koch’s Postulates ○ Pasteur's experiments on microbial contamination Koch’s Postulates There are 4 postulates established by Robert Koch that can be used to verify whether a specific pathogen causes a specific infectious disease 1. The microorganism that causes the disease must be present in the tissue of the infected organism and not in a healthy organism 2. The suspected microorganism must be able to be cultivated in isolation from the infected organism 3. When a healthy organism is exposed to the microorganism they must develop symptoms of the disease 4. Samples from the second infected organism should be able to be isolated and found to be the same as the microorganism from the first infected organism Pasteur’s Experiments on Microbial Contamination Pasteur conducted a series of experiments using swan neck flasks to disprove theory of spontaneous generation ( living organisms come to life from non-living matter) - Sterile beef bone broth places in both flasks & boiled to kill microbes→ both broths sat for weeks - Flask with swan neck did not develop any microbes - Flask without did - Broth experiment proved Germ Theory Germ Theory - Germ Theory states that specific microscopic organisms are the cause of specific diseases - Proven by Pasteur’s experiments on wine→ lead to microbial fermentation theory - Pasteurisation = the process of heating that kills microorganisms in food ● Assess the causes and effects of diseases on agricultural production, including but not limited to; ○ Plant disease ○ Animal disease Agricultural diseases can significantly affect the production of agricultural products - National & international biosecurity measures are maintained to reduce the spread of infectious diseases Plant Disease = abnormal condition that harms a plant thus lowering its productivity or usefulness ↪ Plants are susceptible to many types of disease which affect the yield and quality of crops ↪ Populations of plants used in agriculture can be particularly vulnerable to disease as they often lack genetic variation Potato Blight ↪ Potatoes affected by fungal pathogen, Phytophthora infestans→ entire crop destroyed due to lack of genetic variation ↪ Transmission = produced asexually→ quicker spread of disease Panama Disease ↪ Variant of Banana, Gros Michel→ genetically identical became infected by fungal pathogen (Fusarium oxysporum) ↪ Spread from Panama to becoming a worldwide banana crisis Intensification & Change in Farming Practices = changes in farming practices can result in emergence of new disease and facilitate transmission of existing diseases ↪ Increasing global demands of livestock industry pressure increased production of meat, eggs & dairy ↪ Intensive farming means animals are stocked at higher densities which increases direct contact between animals→ increasing risk of infectious disease transmission ↪ Vaccines + antibiotics administered→ leads to antibiotic resistance + consumption & contact with infected animals can lead to spread of zoonotic diseases Mad Cow Disease = Bovine spongiform encephalopathy (BSE) is caused by an infectious prion protein, fatal neurological disease in cows - Creuxfedlt-Jakob disease disease acquired by eating products from BSE infected cattle - Transmitted as infectious prion is not denatured when cooked - Control = animal culls, banned practice feeding of mammalian protein to cattle + stricter Australian border policies Human activity influence on disease in plants & animals in agriculture All of these easy modes of transmission such as travelling from an infected country to a non-infected country, bush walking and mountain biking through affected areas, as well as importing and exporting agricultural products increases the speed of which pathogens can move around the globe and infect more people and agriculture. Loss of genetic diversity in Agriculture Artificial pollination genetic diversity as new plant species were able to be produced etc, but because the same favourable trait has often been passed on, it results in the creation of monocultures and the plants become unable to adapt and protect against diseases as their genes are too similar, it causes genetic disorders. General induced immunity = involves pattern recognition receptors that are present on the plant’s cell wall - can recognise MAMPS → when MAMPS are identified by receptors various responses triggered 1. Production of lignin to reinforce cell wall 2. Production & accumulation of proteins into the cell membrane such as protease 3. Production & secretion of antimicrobial molecules 4. Production & secretion of signalling hormones Specific induced immunity = involves the hypertensive response (HR) once the plant has recognised a specific antigen → the specific response includes resistance proteins recognising the antigen, triggering a response via signalling pathway → results in production of toxic chemicals, enzymes, which breakdown pathogens and programmed cell death in order to prevent further infection (APTOSIS) → Apoptosis is essentially programmed death of infected cells and surrounding cells of infected cell so stop the spread of pathogens, effector molecules and infection in general. Viral Pathogens & Fungal Pathogens Viral Pathogens Fungal Pathogens = Viruses lack cell membranes, cytoplasm, ribosomes and enzymes needed for protein synthesis and energy production∴ the vital envelope & capsid play an important role in enabling viruses to penetrate host cells Once virus is established in host, virus can become a localised infection and remain in a confined area of the plant or may move around in plant body→ leading to systemic infection Viruses can move through the plant by; ➝ Cell-to-cell movement via plasmodesmata ➝ Parenchyma cells (cells that make up most of the = Fungi are eukaryotic & heterotrophic organisms → Fungal pathogens can inhibit cellular processes in plants (eg photosynthesis) and the uptake of nutrients→ causing wilting, leaf & seedling chlorosis and inhibit the functioning of stomata Entering the Plant; → Some fungal pathogens infect plants through the secretion many enzymes which disrupt the plant’s physical defence mechanisms (eg cuticle & cell wall) → Other fungal species can gain entry to the plant via stomata plant’s soft tissue & mesophyll tissue - viruses able to move through symplastic pathway, between the mesophyll cells and through to vascular tissue where they continue to infiltrate the plant, causing disease) ➝ Transported in conducting channels (phloem tissue and sieve tubes) Named Australian Plant Response to Pathogen Example Plant = Eucalyptus calophylla (marri gum) Pathogen = P. cinnamomi ● P. cinnamomi is a species of water mould - water moulds are filamentous protists belong to phylum oomycota ● Cinnamomi comprises the root system causing lesions which lead to death of tree as there aren’t enough nutrients to absorb ● The parasitic mould lives in soil, attacking the roots of the plant, from which it absorbs nutrients ● Plants damaged roots leave it unable to absorb water and soil nutrients 1. Root tips of tree become infected with P. cinnamomi filaments called mycelium (large network of mycelia growing in roots means mould can access trees nutrients 2. Spore sacs release motile zoospores 3. Thick chlamydospore walls protect zoospores during long periods of dry conditions 4. Zoospores move through moist soil to infect tree roots TRANSMISSION = transmit from tree to tree - motile zoospores swim/move through moist soil to reach root tissue of host tree Through these root tips of mycelia pathogen is able to infect tree RESPONSE = ● Marri Gum is resistance to infection from P.cinnamomi→ healthy, thickened roots with increased lignin production ● LIGNIN - protects the cellulose cell wall of plant cells from damage by pathogens, including forming a physical barrier that blocks the passage of pathogens ● Presence of P.cinnamomi increases PAL production & phenolic compound production in E. calophylla ● Lignin production in E. calophylla is triggered by increased levels of PAL which increases when pathogen is present SAY: E. calophylla mounts an immediate response to the presence of P. cinnamomi by increasing production of PAL which increases lignin production to develop more lignin tissue in the roots of the tree. ● Analyse responses to the presence of pathogens by assessing the physical and chemical changes that occur in the host animals cells and tissues Human immune system is divided into 2 parts: 1. Innate or nonspecific immune system (1st & 2nd line of defence. Physical, chemical & microbial barriers) 2. Specific or adaptive immune system (3rd line) Antigens = molecules which host recognise as being foreign and initiate the adaptive immune response (eg production of antibodies to destroy antigens) and innate immune response (eg phagocytosis) - Important because they allow the body to recognise potentially harmful pathogens and mount an immune response against 1. Self-antigens = produced internally, organisms own antigen (don’t elicit immune response) 2. Non-self antigens = are external to the body & can trigger an immune response eg components produced by viral pathogens Physical Barriers (1st line of defence) Skin = large physical barrier that protects cells from pathogens in the surrounding environment→ difficult to penetrate unless wounded Mucous Membranes = a viscous slimy secretion used predominantly for protection + lubrication→ produce mucus which traps pathogens & antigens Cilia = slender hair-like structures located along the respiratory tract→ they vibrate resulting mucus (containing pathogens) being sent to throat to cough/sneeze out Acidic/Alkaline Environments = high level of acidity is able to dissolve pathogens or mucus that contains any trapped pathogens - Alkaline environments in intestines decomposes & kills pathogens Body Secretions = Urine→ acidic urine washes walls of ureter & bladder kills pathogens Lysosomes→ an enzyme that aids in the destruction of bacterial cell walls found in secretions eg saliva, nasal secretions, tears Artificially acquired ↪ Produced by vaccination ↪ Controlled antigens released into body to stimulate immune system ↪ Permanent bc of memory cells Artificial acquired ↪ Injected with antibodies from someone else ↪ Blood transfusion ↪ Antiserum Live Attenuated Vaccine = a living microbe that has been weakened in lab ↪ long lasting memory through large antibody production // not safe for immunocompromised eg measles vaccine Inactivated Vaccine = contain microbes inactivated by heat, radiation or chemicals ↪ stimulate antibody production + safe for immunocompromised // however stimulates weak immune response→ requires booster shots to maintain long-term immunity Sub-Unit Vaccine = contain only parts of microbes that have been chemically extracted or genetically engineered using recombinant DNA tech ↪ Safe for immunocompromised + easy storage // require booster shots Public Health Campaigns = media designed to promote public health awareness + reduce incidence of disease - Beneficial when dealing with outbreak of disease → informs public of cause, transmission + measures to control spread - Information in PHCs is clear, accurate + reassuring - Eg PHC on infected West Syd water supply (1998)→ PHC launched educating on parasite + causes of contamination, treatment of the water supply, bans on drinking water from all sources→ chlorine added to syd water to kill water-borne microbes - Negatives = diversity between age groups, socioeconomic backgrounds, languages → not all are exposed (eg rural)→ remain uneducated on matter & thus contribute to spread + costly for Gov - EG PHC on 5th yearly Pap Scans→ early treatment has reduced incidence of cervical cancer Use of pesticides Pesticides = chemicals used to prevent spread of infectious plant/animal diseases + to eradicate insect vectors ie mosquitoes - Pesticides may be used as spray or baits, in irrigation water - Benefit = protecting against vector-borne diseases + defends the healthy of community by sustaining their food source - Negatives = biomagnification = pesticide accumulates in the body tissue of organisms in the food chain increasing amounts of higher trophic levels + pesticide overuse promotes selection of naturally resistant strains - Overuse led to genetic resistance eg malaria was effectively reduced through pesticides but has become resistant Genetic Engineering = used to modify genetic structure of an organism using biotechnology → helps prevent spread of disease by producing - plants/animals resistant to disease - Vaccines for human/animal use - Vectors with diminished capacity to spread disease EG cows genetically engineered to produce large quantities of human antibodies to treat wide range of infectious diseases GE is being used to research + develop better disease preventatives & treatments ● Investigate and assess the effectiveness of pharmaceuticals as treatment strategies for the control of infectious disease, for example – antibiotics – antivirals Antibiotics ↳ Antibiotics are chemicals capable of destroying, or inhibiting, the growth of the bacteria that cause disease without harming host ↳ FIRST ANTIBIOTIC - Penicillin discovered in 1928 Some antibiotics - inhibits the synthesis of a bacterial cell wall→ antibiotics prevent the bacteria from fully developing their cell walls, causing the cell walls to weaken and the bacteria to die. - Bacteria with thick layer of peptidoglycan in cell wall are more susceptible to the effects of these antibiotics Some antibiotics destroy the cell membrane thus effectively destroying the bacteria Some antibiotics interfere with protein synthesis so the bacteria are unable to make essential compounds→ results in cell death ANTIBIOTIC RESISTANCE ↪ Bacteria through natural selection have evolved strains that are resistant to antibiotics due to widespread use→mutated forms of bacteria survive & then reproduce leading to population resistance to antibiotics ↪ Overuse of antibiotics for treatment of disease eg prescribing antibiotics for viral infections→ gives bacteria chance to build up populations of resistant strains ↪ Not completing full course - discontinuing when symptoms stop→ not all bacteria present in host are killed, remaining bacteria are also usually the strongest ↪ Livestock are fed antibiotics as part of their diet - this widespread use of antibiotics further promotes the formation of resistance ↪ Use of cleaning products containing antibacterial ingredients also lead to antibiotic resistance - the quantity of cleaner used is not enough to kill all of the bacteria, more resistance bacteria survive & reproduce PROBLEMS WITH ANTIBIOTICS ↪ Bacteria develop resistant strains that don’t respond to cheaper “first-line” antibiotics→ leads to effects of diseases being more severe + longer to cure, infectious period is longer …… means greater chance of passing on resistant strain ↪ Antibiotic resistance infections can lead to more serious illnesses with longer recovery periods, more frequent and longer hospitalisation and more expensive treatments ↪ “Second-line” and “third-line” antibiotics = more expensive + more toxic→ inability to afford antibiotics means disease is left untreated ஃ disease spreads STRATEGIES TO SLOW ANTIBIOTIC RESISTANCE ↪ Only use antibiotics for bacterial infection & NOT viral infections ↪ Prescribed antibiotic should target the pathogen & NOT broad spectrum ↪ Take whole course of antibiotics & NO stop when symptoms go away ↪ Only use antibiotics prescribed to you ↪ Not use cleaning products that contain antimicrobial ingredients ↪ Vaccinations - to protect against bacterial infection eg whooping cough ↪ Food safety - reduce risk of getting food borne bacterial infections by not drinking raw milk, washing your hands before food contact & cooking foods to safe temps Antivirals Antivirals can work by 1. Preventing the virus from entering the cell by binding to receptors that allow the virus to enter 2. Inhibiting enzymes that catalyse reproduction of the virus genome 3. Blocking transcription and translation of viral proteins 4. Preventing the virus from leaving the cells and so preventing the infection of other cells ● investigate and evaluate environmental management and quarantine methods used to control an epidemic or pandemic needed & surfaces and public spaces can be contaminated (not obvious) Containment strategies of indirect transmission include = - hand hygiene and infection control in hospitals eg PPE & antiseptic hand wash - Proper cleaning of surfaces - Border control at airports - Public health campaigns to educate on disease + promote vaccination when travelling Controlling Epidemics & Pandemics Controlling the spread of an epidemic & pandemic requires: - Fast identification of the disease - Local, global + regional disease alerts - Travel bands to & from regions with high prevalence - Restricted movement of animals, plants & biological products - Management of environmental factors (water supply, food sources, air quality, sanitation facilitates) - Protective behaviors (good hygiene practices + PPE) Ebola In 2014, epidemic of Ebola occured in West Africa affecting over 11 000 people CAUSE = deforestation caused fruit bats (vectors) to come in contact with humans and infect them - Ebola initially contracted through the consumption of bat meat & became highly virulent when crossed the species barriers, spread through bodily fluids & had short incubation periods - Prevalence increased due to lack of vector control ENVIRO MANAGEMENT = Can be prevented with sanitation & hygiene QUARANTINE = West Africa has a mobile population, people travelling across borders for food, work and travel. Movement of individuals lead to more becoming infected - Eg Airports screening temperature of passengers to detect possibly infected individuals so they can be further tested and isolated to stop spread to others Positives Negatives - Quick response - Limit transmissive movement of disease - Epidemic treatment - Future prevention - Treatment and prevention - Difficult to contain whole population - Indirect transmission is challenging - Lack of vector control ● interpret data relating to the incidence and prevalence of infectious disease in populations, for example: – mobility of individuals and the portion that are immune or immunised – Malaria or Dengue Fever in South East Asia PATTERNS OF INFECTIOUS DISEASE Epidemiology = the study of the patterns, causes + effects of health & disease in population → shapes preventative health care, control measures + identification of risk factors Incidence= the incidence of disease is the rate of Prevalence = the prevalence of disease measures the occurrence of new cases which indicates the risk proportion of cases in the population at a given time of people contracting the disease which indicates the spread of disease Mobility of Populations & Immunity = increase of globalisation + air travel → facilitates faster movement of people→ increasing risk of exposure to disease Malaria Cause ↪ Caused by parasitic protozoan plasmodium P. falciparum and P. vivax Transmission ↪ Main vector is the female Anopheles mosquitoes ↪ Another mode of transmission is transfusion of blood from infected persons and use of contaminated needles Host Response Cell mediated immunity ↪ Cytotoxic T cells can attack the Plasmodium during liver stages as they destroy infected liver cells ↪ Helper T cells stimulate macrophages to remove infected RBCs - macrophages kill Plasmodium ↪ Antibodies neutralise (deactivate pathogen) parasites when exposed Symptoms ↪ Fever ↪ Shivering + chills + sweating ↪ Anemia ↪ Headache + vomiting + abdominal pain ↪ Coma + death in severe cases Treatment ↪ Antimalarial drugs are used to treat malaria ↪ Combination of drugs is used to increase resistance to Plasmodium Prevention ↪ Avoidance of bites from mosquitoes ↪ Use of antimalarial drugs ↪ Spraying inside surface of walls with insecticides ↪ Long sleeve clothing and pants ↪ Use of insect repellent ↪ Mosquito nets Control ↪ Draining swamps and stagnant water ↪ Spraying breeding areas with oil eg. insecticides ↪ Biological control eg. introducing fish to eat fish larvae ↪ Genetically modifying mosquitoes so they cannot be vectors to Plasmodium Incidence ↪ Where malaria is found depends on climate factors (eg temp, humidity, rainfall). Malaria is transmitted in tropical & subtropical areas, where Anopheles mosquitoes can survive and multiply ↪ The highest incidence of malaria is in Africa South of the Sahara and in parts of Oceania eg Papua New Guinea→ because of warmer environments Statistics - 880,000 deaths per year from malaria - 70% of Southeast Asian population is at risk of malaria ● Investigate the contemporary application of aboriginal protocols in the development of particular medicines and biological materials in Australia and how recognition and protection of Indigenuous cultural and intellectual property is important for example: - Bush medicine - Smoke bush in Western Australia Many cultures have their own way of treating and managing the spread of disease. The use of traditional medicines have transcended different cultures. ↪ An understanding of the healing effects of Cinchona bark was able to treat malaria ↪ There are a number of Aboriginal protocols & traditional bush medicine that have been used ↪ Understanding of local plants has enabled the development of medicine to relieve pain & treat infectious infection ↪ Eg tea tree has been used to treat wounds, sore throats + infections→ antiseptic properties of TT scientifically proven→ used globally for fungal infections, acne ↪ Eg Emu Bush used to treat surface wounds, gargled to treat ailments→ used in modern research for its strong antibacterial properties ↪ Contemporary medicine looks at traditional remedies for novel approaches to treating diseases ↪ Indigenous medicine has potential to successfully treat diseases that we can no longer treat with antibiotics ↪ Smoke bush used by Indigenous Aus’s for healing properties→ Patented by pharma as it contained potential to destroy low concentrations of HIV→ ATSIs given 0 credit