Module 4- Disease Flashcards
Define communicable disease
Diseases that can be passed between animal and plant individuals
What are communicable diseases caused by?
Harmful microorganisms- pathogens
What do pathogenic microorganisms include?
Bacteria, viruses, protoctista, fungi
Describe direct transmission
-Physical contact is made between an infected animal or plant spreading the pathogen between individuals
-can take place through bodily fluids such as saliva or blood
-inoculation through a break in the skin
-ingestion-taking in contaminated foods or drinks
Describe indirect transmission
-pathogens are not spread through physical contact but instead by animal vectors, sir or waterborne transmission (cough droplets or fungal spores), fomites which are objects in which the pathogen sheds (door handle, human movements (footwear or clothing)
Risk factors for disease are …
-a weak immune system makes it harder to fight off disease e.g babies, elderly those with chronic underlying conditions
-living in crowded conditions are more likely to spread pathogens e.g in hospitals, prisons or homes less shelters
-having poor access to healthcare could mean disease are not treated early enough and their progression is more serious
Describe TB, its treatments, how its spread
-infectious disease of the lungs caused by bacteria
-without treatment it can be fatal
-can be treated using antibiotics or vaccinations such as the BCG vaccine are available for some strains of TB
-is spread when infected droplets from the lungs are coughed into the air and breathed in by others
-transmission can be prevented by using tissues when coughing/sneezing and having a good handwashing practice
Describe bacterial meningitus, its treatment, causes
-Results in the inflammation of the membranes surrounding the brain and spinal cord
-without treatment it can result in sepsis and death
-can be caused by many different pathogenic bacteria
-treatment is antibiotics
-transmission is via direct contact
-vaccinations are available to help prevent infection and spread of disease
-mainly affects very young children and teenagers between 15-19
-about 10% infected will die
Describe ring rot, causes, effects and treatment
-bacterial disease affecting potatoes and tomatoes in cool regions of northern and Eastern Europe
-devastating effects on agriculture
-in tomatoes it is sometimes known as birdseye
-transmission is through planting infected material and indirect contact with contaminated equipment
-control can be improved by rigorous cleaning of agricultural equipment
-some insect vectors can also spread the bacteria causing ring rot
Describe HIV/AIDS, treatment, causes
-can’t be treated with antibiotics as the virus uses the cells of the host for replication
-human immunodeficiency virus attacks CD-4 cells of the human immune system so that infections become increasingly more difficult to fight (targets T helper cells)
-without treatment HIV sufferers may develop acquired immunodeficiency syndrome (AIDS) which is a life threatening condition
-antiretroviral drugs are used to prevent the multiplication of the virus inside the body
-there’s no cure
-transmission of HIV is via direct contact with infected bodily fluids e.g blood and semen
-no vaccine currently available
-prevention relies on promoting awareness of risks, using condoms during sex, not sharing needles, identifying infection early
Describe influenza, treatments, causes
-Viral disease caused by different strains of virus which vary in symptom severity but can cause serious outbreaks of flu each year
-caused by influenza viruses which mutate frequently, giving rise to strains that are difficult for the immune system to recognise and produce vaccinations against. Kills ciliates epithelial cells in the gas exchange system
-this means that viruses that previously only infected animals can jump species barrier to humans becoming zoonotic
-can be spread through both direct and indirect contact
-in humans good hygiene and hand washing practices can stop the spread of flu
-in agriculture restricting the movement of farm animals can prevent transmission from wild animals outside
-treatment is with antiviral drugs
-annual vaccination programmes are carried out for humans most at risk of contact with strains judged to most likely cause outbreak in the year
-every so often there is a major change in the surface of antigens and this causes a flu epidemic as there are no antibodies available
Describe tobacco mosaic virus, treatment, causes
-viral disease affecting tobacco plants and tomatoes
-tobacco mosaic disease is caused by TMV
-first virus to be discovered
-can survive 50 years in infected material, making treatment for disease difficult
-there is currently no known fully effective chemical control
-transmission happens directly between infected plants as well as indirectly through contaminated soil, equipment and people
-the virus can contaminate seed coats, also leading to infection of the developing plant
-control of tmv is through removing and burning infected plants as well material and discarding infected soil
-through washing and bleaching equipment helps reduce cross contamination
-inoculating young plants with less serious strains helps prevent infection later on
Describe malaria, treatment, causes
-disease caused by protoctista
-results in cyclical symptoms of fever, chills and death if untreated
-parasite can use birds, bats and other animals as hosts
-is caused by several species of the plasmodium genus
-the parasite grows and multiplies in erythrocytes causing them to burst every 2-3 days, releasing plasmodium in the bloodstream
-is treated using antimalrial medication such as doxycycline and mefloquine
-a preventative course of this medication should be taken before travel to high risk regions- this can reduce the risk of malaria by up to 90%
-different anti malarial meds can be used to treat disease if the preventative course doesn’t work
-is transmitted by insect vectors specifically the female anopheles mosquito when they bite you
-most common in Africa, Asia and South Americas because the climate is suitably warm for the mosquito to live in and the probability of biting an infected person is higher
-removing the insect vectors is 100% effective in preventing transmission however this isn’t always practical on a large scale
-sleeping under mosquito nets, applying insect repellent and covering exposed skin help reduce the risk of being bitten in the first place
-the disease recurs making people weak and vulnerable to other infections
Describe late blight, treatment, causes
-disease caused by protoctista that affects potatoes and tomatoes
-is what caused the Irish Potato Famine in 1845
-the protoctista causes spores to develop on leaves of infected plants and germ tubes to grow through the leaf epidermis
-wounds, eyes and lenticels on tubers also allow infection
-fungicides are most commonly used although resistance to some fungicides has developed
-individual plants are unlikely to survive once they are infected, some dying within a week
-spores can be airborne or waterborne infecting soil and plants
-spores can encyst if the conditions are too cold and develop only when temperatures are above 15 degrees C
-developing blight resistant cultivars helps to reduce susceptibility of plants to the pathogen and control its spread
-forecasting when weather conditions may promote transmission means that fungicides can be sprayed at optimum times
Describe black Sigatoka, treatment, causes
-fungal disease affecting the leaves of banana plants attacking and destroying them
-can cause yield losses of over 50%
-caused by the black Sigatoka fungus
-is spread through both direct and indirect contact
-transmission is more likely in conditions of high humidity and rainfall
-infective spores are airborne while infective conidia are waterborne
-hyphae penetrate and digest the cells turning the leaves black
-removal of affected leaves acts as a control as well as maintaining a space between plants and adequate drainage
Describe ring worm, treatments, causes
-fungal infection that is most commonly used although in cattle but can affect all mammals and is zoonotic
-treatment is with at least 2 applications of anti fungal cream 3-5 days apart
-the crust of the skin must be removed to allow the cream to reach the fungus
-the crust then must be burnt to prevent transmission by indirect contact
-direct contact with infected skin areas is usually how it spreads but can also be transmitted indirectly because the fungus produces spores that can be viable for many years in dry environments
-regularly cleaning/disinfecting animal housing, avoid high stocking densities of animals, ensuring animal housing is dry, allowing animals to have regular exposure to sunlight prevents it
-is not damaging but is unsightly and itchy
Describe athletes foot, treatments, causes
Fungal infection affecting the feet mainly in between toes but any part of the body can be faceted if infected skin is scratched and the fungus is transferred
-caused by a form of human ringworm
-treatment is with anti fungal creams, sprays, powders and anti fungal medication
-transmission is usually indirect contact with contaminated objects
-warm humid environments promote growth and spread of the fungus so transmission often occurs I. Shows, swimming pools, sharing fomites such as socks and towels
-direct contact with the infected skin can also transmit the fungus so transmission
-prevention- keep feet clean/dry, wear footwear in high risk areas, avoid sharing potential fomites with others
What does basal resistance react to?
The presence of a microbe or pathogen associated molecular patterns (PAMP or MAMPs) such as flagellins and chitins found in pathogens
What does MAMP receptors do?
-they recognise the molecular patterns and begin a cascade of responses
-causing the plant to up regulate the expression of genes producing chemicals resulting in an oxidative burst
What is an oxidative burst?
-big release of chemicals such as nitric acids, oxygen species, hydrogen peroxide and salicylic acid
-functions to strengthen cell wall linkages and signals to other cells the presence of a pathogen threat
What happens during the basal resistance response?
Callose is deposited between the plant cell membrane and cell wall around where the pathogen infects. Callose helps strengthen the cell wall and make it more difficult for pathogen to enter adjacent cells.
the stomata close in order to prevent the entry of pathogens
Describe the hypersensitive response
-can be triggered by the presence of bacteria, viruses, fungi or nematodes
-the response causes localised cell suicide (apoptosis) at the site of infection, which cuts off the nutrient and water supply to the pathogen
-triggering the HR response resulting in systematic acquired resistance to broad ranges of pathogens for a length of time. However, SAR can be artificially stimulated by spraying plants with plant activators
Describe the hypersensitive response in plants
-can be triggered by the presence of bacteria, viruses, fungi or nematodes
-the response causes localised cell suicide (apoptosis) at the site of infection, which cuts off the nutrient and water supply to the pathogen
-triggering the HR response resulting in systematic acquired resistance to broad ranges of pathogens for a length of time. However, SAR can be artificially stimulated by spraying plants with plant activators
What are the primary non specific defences for animals
The skin, mucous membranes, blood clotting, inflammation, fevers, phagocytes
Describe the skin as a non specific primary response defence
-covers the body and prevents the entry of pathogens
-has healthy microorganisms that outcompete pathogens for space on the body surface
-the waterproof covering makes it hard for pathogens to penetrate without a wound being present
-the skin also produces sebum which inhibits the growth of pathogens
Describe the mucous membranes and role in defence
-line many of the body tracts
-they secrete a sticky mucus that traps microorganisms and contains lysosomes which destroy bacterial and fungal cell walls
-also contains pathogens which remove remaining pathogens
-irritation of the mucous membranes causes expulsive reflexes such as coughing and sneezing which forces the mucous (containing the pathogen) out of the body
Describe blood clotting role in defence
-when you cut yourself the skin is breached and pathogens can enter the body
-the blood clots rapidly to seal the wound
-when platelets come into contact with collagen in the skin or the wall off the damaged blood vessel they adhere and begin secreting several substances
-thromboplastin is an enzyme that triggers a cascade of reactions resulting in the formation of a blood clot
-serotonin makes the smooth muscle in the walls of the blood vessel contract so they narrow and reduce the supply of blood to the area
-epidermal cells beneath the scab start to grow ,sealing the wound permanently, while damaged blood vessels regrow
-collagen fibres are deposited to give the new tissue strength
-the blood clotting cascade is where once the clot forms blood can’t leave and pathogens can’t enter
Describe inflammation response in primary non specific defences
-is a localised response to pathogens resulting in inflammation at the site of the wound
-characterised by pain, redness, heat or swelling of tissue
-most cells are activated in damaged tissue and release chemicals called histamines and cytokines
-histamines make the blood vessels dilate allowing more blood to enter the tissue, causing localised heat and redness. This raised temperature helps prevent pathogens reproducing
-histamines make blood vessel walls more leaky so blood plasma is forced out, once forced out of the blood it is known as tissue fluid which causes swelling and pain
-cytokines attract white blood cells (phagocytes) to the site which then dispose of the pathogen by phagocytosis
