Module 4 Flashcards
What is a communicable disease?
illnesses resulting from the infection, presence and growth of pathogens in an individual host
What is a pathogen?
a disease causing organism which takes nutrition, energy and protection from and damages its host. (parasite)
What type of cell is bacteria? How are they classified?
prokaryotes classified by shape- rod (bacilli), spherical (cocci), comma shaped (vibrios), spiralled (spirilla) and corkscrew (spirochaetes)
By cell walls- 2 main types have different structures that react differently to gram staining Gram positive- look purple/ blue and Gram negative look red. The cell wall affects how they react to antibiotics
What is the chain of infection?
infective agent (pathogen)- bacteria, virus, protoctists, fungi
source of infection- the reservoir is the location of the microorganism which must meet needs of pathogen to grow and survive
mode of transmission- direct (skin to skin, bodily fluids) or indirect (pathogen transferee to intermediate that’s not infected but transfers pathogen to host (airborne droplets, insects)
susceptibility of host- young, elderly and those with underlying health conditions often have weaker immune systems
Are viruses living?
What structure do they have?
How do they replicate?
How do they evolve?
What are bacteriophages?
non living and very small
Have DNA/RNA surrounded by a protein
they invade living cells and their genetic material takes over the biochemistry of the host to make more viruses
They evolve my adapting to their host
They can even attack bacteria, using them to replicate and killing them at the same time
What type of cell are protocista? How do they infect?
Eukaryote parasitic using people/ animals as host
What type of cell are fungi?
what is their cell wall made of?
How do they absorb nutrients?
what type of fungi are pathogenic?
How do they affects plants?
How do they spread?
Eukaryote
cell wall of chitin
Can photosynthesise so digest food extracellularly before absorbing nutrients- saprophytic feeders. parasitic ones are as they live off organic matter
stop them photosynthesising as they affect the leaves
when they reproduce they produce millions of tiny spores
Bacterial animal disease
- Name of pathogen
- method of transmission
- symptoms/ method
- Tuberculosis
- mycobacterium tuberculosis
- Direct- droplets through air
- Lung tissue destroyed, immune system suppressed, coughing, fever, fatigue
- Bacterial meningitus
- Neisseria meningitidis, haemophilis influenzae
- direct- droplets though air and exchange of fluids In meninges (tissue surrounding brain to prevent entry of bacteria) of brain but can spread causing blood poisoning and death. Blotchy red rash that doesn’t disappear when a glass is pressed against it shows blood poisoning. Nausea, vomiting, fever, headache, muscle pain
Virus animal disease
- Name of pathogen
- method of transmission
- symptoms/ method
HIV/AIDS
- Human immunodeficiency virus (HIV)
- Direct- contact with bodily fluids, mother to child in breast milk
- Targets T cells in immune system and contains enzyme reverse transcriptase which transcribes RNA to a single strand of DNA in the host cell. HIV is a retrovirus as the process is opposite to usual.
- Flue like illness, fatigue, join and muscle pain
Influenza
- Influenza A, B and C
- Direct- droplets in air
- Sudden fever, body ache, fatigue, dry cough, kills cilia allowing airways to be infected
Protoctist animal disease
- Name of pathogen
- method of transmission
- symptoms/ method
- Malaria
- Plasmodium falciparum
- indirect- female anopheles mosquito.
- reproduce in mosquito then invade red blood cell then liver
- High temperature, headache, vomit, muscle pain, diarrhea
Fungus animal disease
- Name of pathogen
- method of transmission
- symptoms/ method
Cattle ringworm
- Trichophyton verrucosum
- Direct- contact with infected cattle
- grey white areas of skin with ashy circular areas. may be itchy
Athletes foot
- Epidermophyton floccosum, trichopyton rubrum, T. Mentagrophytes
- direct- contact with towels used by infetced people.
- Grows on and digests warm moist skin between toes causing cracking and scaling- itchy and sore
Bacterial plant disease
- Name of disease
- host plant
- names of pathogen
- Method of transmission
- Symptoms
- Ring Rot
- Potato, tomato
- clavibacter, michiganensis
- Direct contact with infected tubers, cultivation spreads it as bacteria remain of machinery damages leaves, tubers and fruit. Infects vascular tissue and blocks them so no water can enter leaves. Once a field is infected can’t grow potatoes for 2 years
Viral plant disease
- Name of disease
- host plant
- names of pathogen
- Method of transmission
- Symptoms
- mosaic
- Tobacco Tobaco mosaic virus (TMV)
- direct- contact with leaves of infected plants
- indirect- via aphids as vectors
- damages leaves, flowers and fruit, stunting growth. Yellow mosaic pattern on leaves. spreads though plasmodesmata and phloem
Fungus plant disease
- Name of disease
- host plant
- names of pathogen
- Method of transmission
- Symptoms
Black sigatoka
- bananas
- mycosphaerella fijiensis
- direct- spores are dispersed through air and spores germinate and grow into leaf through stomata. they are also present in soil
- indirect- fungus on infected plant releases spores and an insect eating the plant picks up the spores and transmits to other plants when it feeds
- yellow spots and black streaks. Hyphae penetrate and digest cells so leaves go black as can’t photosynthesise
Protocist plant disease
- Name of disease
- host plant
- names of pathogen
- Method of transmission
- Symptoms
- late blight
- potato, tomatoes
- phytophthora infestans
- direct- swimming zoospores and aerial spores
- hyphae penetrate host cells and destroy leaves, tubers and fruit.
- Blue/ grey spots, shrivel and go brown
disease transmission
why is it not always successful?
the transfer of pathogens from an infected host to an uninfected one
large numbers of pathogen produced to reach chances of reaching a host
infective stages are small to avoid wasting energy
Direct transmission:
CONTACT: between individuals TMV, RINGROT, RINGWORM kissing or bodily fluid contact HIV, microorganisms from faeces transmitted to hands
SPORES: BLACK SIGATOKA, LATE BLIGHT. Insects carry spores so could be indirect
INGESTION: contaminated food and drink, mouth to hands
ANIMAL BITES/ PUNCTURE WOUNDS (inoculation)
Indirect transmission:
VECTORS:
- wind carries spores
- water allow spores to swim in surface film of water on leaves
- animals carry pathogens and spores from one plant to another when they feed
- humans transmit pathogens and spores by hands, clothing, farming, transporting plants around the world
MALARIA, TMV
DROPLETS: of saliva and mucus in the air when you cough, sneeze and talk contain pathogens and can be inhaled by others
TB, MENINGITIS, FLU
FOMITES: inanimate objects transfer pathogens like door handle and towel
ATHLETES FOOT
WATER maybe soil
Factors affecting direct transmission animals and plants:
Animals/ human: close proximity like schools, hospitals and cramped housing- poverty
Plant: High density monocultures of crop plants
Factors affecting indirect transmission animals and plants:
climate and weather- damp and warm is good for vectors, especially mosquitos. Aphids and mosquitos need 20*c and over. Climate change worsens this as increased rain and wind increases spread, animals vectors are spread to new areas, but drier conditions in some areas could reduce spread there
Factors that affect transmission of human diseases
- poor nutrition
- compromised immune system
- poor waste disposal creates breeding sites for vectors
- culture and infrastructure- medical practices socioeconomic- lack of trained HC workers
- warning when outbreak
- poor sanitation and sewage
- housing contaminated water
- travel and migration bring diseases to populations with no natural resistance or immunity behaviour
- sexually transmitted diseases can be lowered depending on number of partners
Preventing spread of plant diseases:
leave space between plants
rotate crops (bacteria/spores die if no host)
strict hygiene- wash hands, boots machinery control insect vectors ?????
plant crops less susceptible to disease
plenty of minerals so healthier plants with more tolerance to infection
retrovirus
a virus like HIV with single stranded RNA as its genetic material, not DNA. when the retrovirus invades a host cell it uses its enzyme reverse transcriptase to make DNA from RNA template. Other RNA viruses like influenza don’t use their RNA as a template for making DNA
what is a vector:
an organism that transfers a pathogen from an infected host to an uninfected host and is not harmed by the pathogen itself


