6.2 non-bacterial pathogens Flashcards
what are pathogens?
-organisms which cause disease, usually microorganisms
causative agents
-Infectious diseases are often first classified by the pathogen that causes them
e.g malaria or influenza caused by a virus
3 modes of transmission
1.Anthroponoses
2.Zoonoses
3.Sapronoses
Anthroponoses
-diseases transmissible from human to human
Zoonoses
-diseases transmissible from living animals to humans
Sapronoses
-human diseases transmissible from abiotic environment e.g. cholera from water
types of transmission- direct
-direct physical contact
-exchange of bodily fluids
-direct contact with animals or animal waste
types of transmission- indirect
-transmission through intermediates known as vectors
-airborne; aerosols, droplets
-vehicle borne; surfaces, objects
-food and waterborne
mode of infection of flu
-infects cilliated epithilial cells of the respiratory system
-viral RNA reaches nucleus of host cell and produces new virus particles
-cell lyses, releasing more viruses and dying in the process
-reaction of body to the lysis causes symptoms of disease
components of influenza virus
-nucleoprotein (RNA)
-lipid envelope
-capsid
-hemagglutinin
-neuraminidase (sialidase)
how is influenza spread?
-droplets from coughs and sneezing
-direct contact with infected person
-contact with contaminated surfaces and infected animal waste
Virus entry
-some viruses, such as those that infect bacterial cells (bacteriophages) inject only their DNA in host cell
-others such as those that infect animal cells, can be wholly engulfed (endocytosis) or have their lipid envelope fuse with the cell membrane
structure of fungi
-normally single celled
-cell walls made of chitin and glycans
-they do not photosynthesise
-many fungi grow as hyphae
-spores used for reproduction
pathogenic fungus
some fungi can be;
-poisonous
-cause allergies
-cause parasitic diseases
how can fungi impact human existence?
-cause fungal plant disease which has a major impact on food security
what does stem rust fungus do
-produces orange spores which infect the wheat plant
-carried by wind to other plants where they land, germinate and cause new infection
-extracts nutrients and causes plant tissue to erupt
-clonal, asexual production
the word ‘protist’
-means the very first
-may have been the first eukaryotes to evolve on earth
why are protists difficult to characterise?
-massive diversity
-unicellular or multi
-asexual and sexual
-many organelles, chromosonal DNA with proteins
-free living or live symbiotically
which mosquitos can spread malaria?
-pregnant females only
prevelence of malaria
-one of worlds biggest killers
-kills nearly 800000 people per year
-child dies every 45 seconds
-children most at risk as they have not developed natural immunity
why do only females transmit malaria?
-require additional protein from blood to develop their eggs
protist life cycle
-some reproduce asexually through binary fission
-some carry out meiosis and reproduce sexually
-some use vectors as a part of their life cycle
malaria life cycle (summary)
-involves extracellular and intracellular forms
-includes sexual reproduction in mosquitos
-includes asexual reproduction in liver cells and red blood cells of humans
3 key stages of malaria life cycle
1.Exo-erythrocytic cycle (Human liver stages)
2.Erythrocytic cycle (Red blood cell stages)
3.Sporogonic Cycle (Mosquito stages)
what actually causes malaria
-pathogen- plasmodium
sporogonic stage
-mosquito bites human and secretes saliver into blood stream to prevent coagulation
-disease transferred in form of sporozoites (capable of causing infection)
exo erythrocitic stage
-malaria found in the liver and attack liver cells
-reproduce asexually
-cell lysis, burst out in to blood
erythrocitic stage
-malaria burts in to blood in form of merozoites
-they invade the red blood cells
-red blood cell lysis releasing malaria and toxins which cause fever attacks
what are endemic diseases
-Diseases which are constantly present in a country or area or a certain time of year
-Malaria, chickenpox and the common cold are examples of endemic diseases.
living with endemic disease
-requires robust policy response
-response typically not intense for things such as influenza
history of malaria treatment
-In 1920, 2 french chemists isolated the chemical quinine
- In late 1800s and early 1900s that protozoa was identified as the pathogen causing malaria and its lifecycle was deduced
why is malaria still a global challenge?
-increases resistance to antimalarial drugs and insecticides
-Widespread poverty and inadequate availability of good healthcare systems in malaria endemic countries.
-Increased global air travel and migration, this might have helped the spread.
-New breeding sites for mosquitoes due to environment changes caused by humans
why is control more effective than treatment
-complexity of malaria life cycle makes it hard to treat
methods of prevention and treatment
-insecticide treated nets
-indoor residual spraying
-breeding site reduction
-biological control
-sudden death
intermittent preventative treatment
-IPT is a dose of the drug sulfadoxine pyrimethamine recommended to vulnerable populations (pregnant women and infants) in areas where transmission is high.
-IPT is now integrated into malaria control programmes and is a national policy for pregnant woman across sub-Saharan African countries.
antimalarial drugs
-Artemisinin-based combination therapies (ACTs) are the standard treatment.
-act rapidly on parasites in the blood and are able to destroy gametocytes
-different combinations prescribed depending on severity and presence of resistance in the area
