Module 7 - Infectious diseases Flashcards
what is a pathogen?
Pathogens are organsims or biogenic molecules which cause infection. They are often specified to their host e.g. Prions, Viruses, Bacteria, Protozoans, Fungi, Macroparasites
What is the difference between signs and symptoms
SIGNS = the measurable factors e.g. temperature, blood pressure
SYMPTOMS = factos reported by a patient e.g. pain, fatigue, nausea
Prions
Prions are non-living proteins whcih cause brain disease in mammals. They are abnormally folded proteins (which are already present) in the brain and spinal cord. They are transmitted through direct contact or consumption. Prion disease cause neurons in the brain to pocess vacuoles, resulting in holes thorughout the brain tissue. Symptoms include: loss of motor control, dementia, wasting and eventual death. Example of prion caused diseases include:
– Jakobs Disease (creutzefeldt) → impact humans and is inherited
– Mad Cow disease (encephalopathy) → imapcts cattle
Viruses
Viruses are non-living or acellular infectious agents composed of genetic material. Viruses are parasites and are completely dependent on a host, often having a harmful impact on an infected organism. Examples of virus diseases include:
– (HUMAN) Covid-19 (Coronavirus) → transmitted from person-to-person via the inhalation of aerosols or via direct contact
– (PLANT) Tobacco Mosaic Virus → transmitted through cuts or wounds and direct contact with other plants or soils
Bacteria
Bacteria are single-celled prokaryotic cells that cause disease through the production of toxic compounds (exotoxins), and through the release of substances when destroyed (endotoxins). Examples of Bacteria include:
– (HUMAN) Tuberculosis (Mycobacterium Tuberculosis) → spread via droplets from coughing, sneezing, and speaking. The bacteria can remain dormant within a host for decades
– (PLANT) Black rot (Xanthomonas Campestris) → spread via wounds or cuts in leaves, producing polysaccharides (carbohydrates) which block the xylem vessels, preventing the transportation of water throughout the plant
Prtozoans
Protozoans are single-celled eukaryotic organisms which reproduce via the process of binary fission, the majority of protozoans are motile (meaning they can move). Example of diseases caused by protozoans include:
– (HUMAN) Malaria (Plasmodium) → spread through the bites of infected mosquitos (vector)
– (PLANT) Cryptosporidiosis → transmitted via the swallowing of fecal contaminated water (often pools) and from uncooked meat.
Fungi
Fungi can be unicellular (yeast) or multicellular (mold), they are commonly eukaryotic non-photosynthetic organisms which live on dead plant/animal material. They can reproduce asexually or sexually and cause approximately 300 diseases in humans.Examples of fungi caused diseases include:
– (HUMAN) Tinea (Tinea Pedis) → transmitted via direct skin contact or contaminated surfaces
– (PLANT) Grey mold disease (Botrytis Cinerea) → transmitted via windblown spores which germinate and infect plants by secreting organic acids which degenerate the cell wall.
Macroparasites
Macroparasites are visible multicellular eukaryotic organisms which vary in size. They tend to take long periods of time to develop and either directly or indirectly cause disease.
Endoparasites → live inside the body. Examples include: tapeworms → transmitted via contaminated food or water, feeding on their host’s tissue, fluids and ingested food
Ectoparasites → live outside the body. Examples include: ticks fleas → commonly feed on the host’s blood and inject toxins whilst feeding, causing inflammation, allergic reactions etc.
Example of a macroparasite include:
– (HUMAN) Asian Tapeworm (Taenia Asiatica) → transmitted from the consumption of undercooked meat containing larvae and orally via poor hand washing
What is the chain of transmission?
- Host → susceptible to th disease
- Pathogen → capable of causing the disease
- Mode → of transmission
Direct Contact
Direct contact is the physical contact between host and a non-infected individual e..g touching, sexual contact, kissing, contact with nasal or oral regions, biting, contact with bodily fluids (blood, saliva). Two variations include:
1. Vertical transmission → parent and offspring, parental (during pregnancy) and Perinatal (after birth) e.g. via breast milk
2. Horizontal transmission → between people who aren’t parent and child
Diseases cause by direct contact include: HIV/AIDS, Herpes, HPV, Glandular fever, syphilis, rubella, ringworm, impetigo
Indirect Contact
Indirect contact is an infection picked up from an external reservoir from a diseased host. (fomite = a surface of an object which carries infection). This includes airborne diseases, touching infected surfaces, contaminated food and water, surgical or tattoo equipment which hasn’t been sterilised. Diseases cause by indirect contact include: measles, E.coli, toxoplasmosis, influenza
Vector
Vector transmission is an organism typically a biting insect or tick that transmits a disease or parasite from one animal or plant to another during a blood meal. This includes
– Arthropods → insects, ticks, aphids
– Mammals → pigs transit pork tapeworms
– Birds → transmit psittacosis
Diseases caused by vector transmission include Malaria, Dengue fever, Canine and Feline heartworm, Zika virus.
List 3 ‘good’ microbes (food)
Dairy foods → yoghurt and sour cream results from fermentation by microorganisms in milk and the product of milk. BACTERIA = streptococcus and lactobacillus
Bread → results from microbial action of yeast. UNICELLULAR FUNGUS = saccharomyces cerevisiae
Soy Sauce → produced by soybeans, wheat, salt, water and fermentation agents. FUNGUS = Aspergillus Oryzae
Microbes in water (‘the bad’)
Water acts as a reservoir, supporting the growth of pathogens (mainly protozoan and some viruses). Most microbes in water are harmful and are usually responsible for causing diarrhoea, vomiting and complications such as kidney failure and even death → this is why it is important to test and treat our water through: filtration, disinfection, florindation
What happens when microbes reproduce?
Microbes grow and cluster together when conditions are suitable → moisture, nutrients, warmth. They begin to form colonies which are visible to the naked eye and can be distinguished through size, shape, surface profile and colour. BACTERIAL COLONIES = small, shinny and colour, FUNGAL COLONIES = fluffy and large