health can be defined as your physical, mental and social welbeing.
If you are in good health, you are:
- free from disease
- able to carry out all the normal physical and mental tasks expected in society
- well fed, with a balanced diet
- usually happy, positive outlook
- suitably housed with proper sanitation
- well intergrated in society
disease can be defined as a departure from good health.
- a disease is a malfunction of the body or mind which causes symptoms
- these symptoms may be physical, mental or social
- diseases can be grouped according to their causes
- diseases caused bu living organisms are called infectious diseases
- the symptoms of these are usually physical but may effect mental or social health
a parasite is an organism that lives on/in another living thing (its host), causing harm to it's host.
- cause harm by taking nutrition from the host
- may live all or part of their life in/on the host
- parasites that live on the host are called external parasites e.g headlice
- parasites that live in the host are internal parasites e.g. tapeworms
- parasites may live unoticed on the host, which benefits the parasite so that the host doesnt try to remove it
- parasites may cause damage which allows other organisms to invade the host and cause a secondary disease.
A pathogen is an organism that causes disease.
- human body is an ideal habitat for micro-organisms
- pathogens live by taking nutrients from the host and they cause damage in the process
- damage can be considerable
transmission of malaria
- Malari is caused by plasmodium; plasmodium falciparum is the most widespread.
- Malari is spread by vector (an organism that carries a disease-causing organism from one host to another).
- the female anopheles mosquito carries the plasmodium from person to person when it withdraws their blood.
- the paracites live in the red blood cells of the human host and feed on the haemoglobin.
- the malarial parasite can also be transmitted by careless and unhygienic medical practices, unscreened blood transfusions, use of unsterile needles and it can also be passed through the placenta into a unborn child.
transmission of malaria (2)
the parasites are transmitted by the following cycle:
- if the host already has malaria, the mosquito will **** the parasite gametes into its stomach
- the gametes fuse and the zygotes develop in the mosquitos stomach
- infective stages are formed aand these move to the mosquitos salivary glands
- the saliva contains the infective stage of the parasite
- in the human host, the infective stages enter the liver, where they multiply before passing into the blood again.
- in the blood they enter red blood cells, where the gametes are produced.
transmission of HIV/AIDS
HIV/AIDS is caused by the Human Immunodeficiency Virus. The virus may enter the body but remain inactive (known as being HIV positive). When active the virus destroys T helper cells in the immune system, that usually help prevent infection. if destroyed resistance to infection is reduced.
HIV can be transmitted by:
- exchange of body fluids - like blood to blood contact
- unprotected sex
- unscreened blood transfusions
- unsterile surgical equipment
- sharing needles
- across the placenta in pregnancy
- from mum to baby during breast feeding
transmission of tuberculosis
TB is caused by 2 species of bacterium: Mycobacterium tuberculosis and M.Bovis. TB is usually found in the lungs and it is transmitted by droplet infection.
- the tiny droplets of liquid are released when an infected person coughs, sneezes, laughs or talks.
- you can become infected when you inhale these droplets-luckily it isnt that easy to contract
- usually takes close contact with an infected person over a prolonged period of time to contract the disease.
- conditions that help the spread of TB are: over crowding-many people sleeping and living in one house together, poor ventilation, poor health- especially if a person has HIV/AIDS they are more likely to catch T, poor diet, homelessness, living or working with people who have migrated from areas where TB is common.