communicable diseases

what does a vector do?

carry pathogens from one organism to another

what are the two main ways bacteria can be classified

1) cell wall

2) shape

what is meant by the term health?

Health is a state of physical, mental and social well-being, not just an absence of disease.

name the features of tuberculosis

• caused by bacteria (Mycobacterium tuberculosis)

• spread by droplets from the coughs or sneezes of an infected individual

  symptoms and causes:

• most commonly effects the lungs

• damages and destroys lung tissue and supresses the immune system

• symptoms include a persistent cough, weight loss, high temperature, tiredness/ fatigue, loss of apetite and breathlessness

  treatments and prevention:

• curable with antibiotics

• preventable by improving living standards and vaccination

what is a communicable disease

• caused by a pathogen

• transported from one organism to another

• vectors carry pathogens from one organism to another

what are the 4 types of pathogens?

• bacteria

• fungi

• virus

• protoctista

describe the features of bacteria

• prokaryotes (no membrane bound organelles)

• reproduce rapidly via binary fission

• can be classified into two categories based on there shape and cell wall

• they cause disease by producing toxins which damage the host cells or they release waste products into the host cell.

• minority of bacteria are pathogens

how is gram staining useful in sorting bacteria?

• used to sort bacteria into one of two groups

• Gram-positive bacteria retain the stain and will appear

  blue / purple under a microscope.

• Gram-negative bacteria have thinner cell walls and

  therefore the dye is washed away by the alcohol which they are then stained with safranin dye which they will then appear red.

explain the features of a virus

• non living

• Short sections of genetic material (RNA or DNA) surrounded

  by a protein capsid and a membrane.

• Infect cells by inserting its own genetic material into that of

  a host cell.

  ○ The infected host cell will then replicate the virus (rapidly).

  ○ The host cell will eventually burst, releasing new viruses

  to infect surrounding healthy cells.

• Viruses can affect all types of organisms, including bacteria –

  viruses that infect bacteria are called bacteriophages.

can a virus reproduce outside of a host cell

no

how does a virus reproduce?

1. Virus attaches to host cell.

2. Viral genetic material (RNA or DNA)

is inserted into the host cell.

3. Viral genetic material is replicated.

4. Protein coded for by viral genetic

material is synthesised.

5. Assembly of new virus.

6. Lysis of host cell releases new

viruses.

name the features of protoctista

• eukaryotic cell

• exist as both single and multi celled organisms

• majority of protoctista are not pathogens

• protists that do cause disease are parasitic

• Often protoctista require a vector to transfer the

  disease. For example, Malaria is caused by a protoctista

  that is transferred by a mosquito.

• Cause disease by entering host cells and feeding on their contents, e.g. Malaria digests haemoglobin in erythrocytes.

name the features of a fungi

• eukaryotic cell

• exist as both single and multicellular organisms

• some are saprophytes (they live on dead or decaying matter)

• Mostly affect plants, digesting surrounding tissue, causing decay and ultimately killing the plant.

• Produce many millions of spores that rapidly infect other organisms.

name the features of bacterial meningitis

• Meningitis is more commonly caused by a virus, but can be caused by bacteria (such as Streptococcus pneumonia or Neisseria meningitidis).

• Many ways it can be transmitted, including vertical transmission and droplet transmission, because it is caused by multiple pathogens.

• Inflammation of the protective membranes that surround the brain and spinal cord, known as the meninges.

  symptoms:

• Can spread to the rest of the body causing sepsis, which can cause death within hours.

• Symptoms include headaches, fevers and a stiff neck.

• Permanent disabilities (such as brain damage, hearing loss, and

  learning disabilities) can result from the infection.

  treatment and prevention:

• Can be treated using antibiotics and can be prevented by vaccinations and foetal testing.

name the features of HIV

• Caused by a virus

• HIV can be transmitted by sexual contact,

  sharing needles and by vertical transmission

  treatment and prevention:

• HIV can be prevented by using condoms and not sharing needles.

• Currently no cure or vaccine, but treatment can be used to control HIV.

  symptoms:

• HIV attacks the immune system and can cause AIDS (acquired immunodeficiency syndrome) if left untreated.

• Flu-like symptoms, including a fever, rash,

  muscle aches and fatigue for example.

features of malaria

• Caused by a protoctista (Plasmodium).

• Spread by a vector – specifically by the

  female Anopheles mosquitos.

  symptoms:

• Symptoms include a fever, headaches,

  vomiting, muscle pain and diarrhoea.

  treatment and prevention:

• There is currently no vaccine and limited

  cures so preventative methods against the vector are used, e.g. mosquito nets, insect repellents, window and door screens, and can be very effective.-

• Anti-malarials are available for short-term

  protection – 90% effective (NHS).

features of influenza

• caused by a virus

• Flu affects mammals, including humans

  and pigs, and birds, including chickens.

• Three main strains: A, B and C, and they

  are further classified by the proteins

  present on their surfaces.

• Affects the ciliated epithelial cells in the

  gas exchange system.

  symptoms:

• Increases susceptibility to other

  infections.

  treatments:

• Vaccines available to prevent infection.

what are the different types of direct transmission?

○ Direct Physical Contact

○ Droplet Transmission

○ Sexual Transmission

○ Vertical Transmission

○ Faecal-Oral Transmission

define direct transmision

The spread of a pathogen from a host to a new host, without an intermediary.

name an example of an indirect transmision

touching a contaminated surface

define droplet transmission (also referred to as inhalation)

An infection transmitted from one individual to another by droplets of saliva and mucus expelled from the upper respiratory tract through talking, sneezing or coughing.

define sexual transmission

Transfer of blood, pre-ejaculate, semen or vaginal fluids from one host to another can result in infection.

define vertical transmission (also referred to as non-sexual transmission)

Transmission from mother to fetus during pregnancy, during childbirth or after exposure to female bodily fluids (e.g. blood, vaginal fluid or breast milk).

define faecal-oral transmission (also known as ingestion)

Water that has been contaminated with human faeces containing the bacteria is drunk, or food that has been exposed to the contaminated water is consumed.

what social factors affect transmission of communicable diseases?

• Overcrowded Living/Working

Conditions

• Poor Nutrition

• Compromised Immune System

• Poor Disposal of Waste

• Climate Change

• Traditional Medical Practises

• Lack of Healthcare

Professionals

• Poor/Crowded Infrastructure

• Culture

define indirect transmission

The passage of a pathogen from a host to a new host, via an intermediary, e.g. a vector.

define a fomite infection

A fomite refers to inanimate objects that can carry and spread

pathogens, such as bedding, socks or cosmetics.

name the features of ring worm

• caused by fungus

• These fungi are dermatophytes – they require keratin in order to grow.

• Affects mammals, including humans, cattle, dogs and cats

• Transmission is by direct contact and indirect contact with infected surfaces and soil.

  symptoms:

• Symptoms include red or grey/white crusty, itchy, infectious, circular areas of skin anywhere on the body.

  treatment and prevention:

• Anti fungal creams are an effective cure.

• Can be prevented by keeping skin dry and clean, not walking bare foot in public spaces, changing socks and underwear daily and good hygiene.

name the features of athletes foot

• caused by fungus

• transmitted by indirect and direct contact

• A form of human ringworm that digests keratin in our skin and grows – the warm, moist environment between toes provide a perfect environment for the fungus to survive and grow.

  symptoms:

• Symptoms include cracking and scaling, which is itchy and can

  become sore.

  treatment and prevention:

• Anti fungal creams are an effective cure

• Can be prevented by drying feet well after showering, changing socks regularly and allowing your feet time to ‘breathe’ without shoes or socks.

describe the function of t helper cells

● T-helper cells bind to antigens presented by antigen-

presenting cells.

● In response, they release interleukins that attract

phagocytes and activate B cells and T-killer cells.

how do t killer cells destroy pathogens?

T-killer cells are stimulated by interleukins released by T-helper cells.

• Receptor on T-killer cell binds to antigens on a pathogen or an infected cell.

• In response, T-killer cells produce and release perforin, which makes holes in the membrane of the pathogen/infected cell.

• Holes in the membrane of the infected cell/pathogen make it freely permeable (substances can move in and out with no control) and allow enzymes that cause apoptosis to enter, causing the pathogen to burst / shrivel and die.