Health

HEALTH AND DISEASE

*HUMAN BIOLOGY

*WHAT IS HEALTH AND DISEASE?

*What is health?

*‘The state of complete physical, mental and social well-being’

*What is disease?

* Disease is a disorder or malfunction of the mind

or body, which leads to a departure from good health.

*CAUSES OF DISEASE?

*Microorganisms-pathogens

*Bacteria, Viruses, Fungi, Protozoa

*Genetic causes

*Inherited

*Lifestyle

*Risk Factors

*What are micro-organisms?

* Micro-organisms, or microbes for short, are very small living creatures.

Bacteria (orange) on the tip of a pin. Magnification x1600 when the image is printed 10 cm high.The tip of the pin is approximately 20 µm across and the bacteria are around 5 µm long.

Most of them cannot be seen without using a microscope.

*Infection and disease

What is a pathogen?*A pathogen is a micro-organism that has the potential

to cause disease.

What is an infection?*An infection is the invasion and multiplication of

pathogenic microbes in an individual or population.

What is disease?*Disease is when the infection causes damage to the

individual’s vital functions or systems.

An infection does not always result in diseaseWHY?

* Mode of transmissionDirect contact – person to person

Example: cold soreVertical – kissing*Herpes simplex VIRUS causes cold sores.

*Initial infection occurs through direct skin contact when the secretions from another person’s cold sore, containing the virus particles, come into contact with cells of the skin around the mouth.

A couple kissing.

Cold sores on lip and mouth.

* Mode of transmission Direct contact – person to person

Example: syphilis

Vertical – sexual intercourse

*The bacterium Treponema pallidum causes syphilis.

*The bacterium enters the body through very tiny cuts on the skin or mucous membranes when there is contact with an infected person or their bodily fluids.

Interlocking gender symbols representing sexually transmitted diseases.

* Mode of transmission Direct contact – person to person

Example: gastroenteritis

Vertical – touching (faecal-oral route)

*Norwalk virus causes a type of gastroenteritis.

*Norwalk virus is found in the faeces or vomit of infected people. It is highly contagious.

*Infection occurs by having direct contact with another person who is infected and not maintaining good hygiene e.g. washing hands.

Human hand contaminated with colonies of bacteria (blue/pink patches).

* Mode of transmission Direct contact – person to person

Example: German measles

*Rubella virus causes German measles.

*When infection occurs during pregnancy the virus crosses the placenta in the blood leading to infection of the fetus.

*The virus can affect all the organs of the developing fetus.

*The risk to the baby is highest in the first 3 months – up to 85% of babies are affected if infected during this period.

Eight week old foetus attached to its placenta by the umbilical cord.

Horizontal across the placenta or via breast milk

* Mode of transmission Indirect contact – vehicle borne

Example: tuberculosis (TB)

Air/dust

* The bacterium Mycobacterium tuberculosis causes tuberculosis (TB).

* TB is spread from person to person through the air.

*When a person with active TB coughs or sneezes, droplets loaded with the infectious organism are propelled into the air.

* The moisture evaporates from these particles to leave droplet nuclei that can remain airborne for days and spread long distances.

* The Mycobacterium has a waxy coat, which protects it from drying out allowing it to survive for many months in the air and dust.

* Mode of transmission Indirect contact – vehicle borne

Example: cryptosporidiosis

* The parasitic protozoan called Cryptosporidium parvum causes a gut infection called cryptosporidiosis.

Via water

The infective stage, the oocyst, (spore) is excreted in the faeces of infected humans or animals.

It is spread by drinking contaminated water.

C. parvum has a complex life cycle, which it completes in one host, in this case the human.

* Mode of transmission Indirect contact – vector borne

Example: malaria

Internal – biological

*Malaria is a vector-borne disease caused by a single celled protozoan parasite called Plasmodium, which is transmitted by mosquitoes.

*The primary vector for malaria is the mosquito Anopheles gambiae.

*Only female mosquitoes transmit malaria when they feed on thehuman host’s blood.

A. gambiae feeding on human blood.

*Specific immune system

Antibody

*An antibody is a protein that is produced by lymphocytes (type of white blood cell) in response to the presence of a specific antigen.

*Specific antibodies bind to specific antigens and cause their destruction.

Antibody

*Vaccination

*You can become immune to a disease through vaccination.

 Immunization programmes and thedevelopment of new vaccines play an important role in protecting individuals against illness.

*Vaccination works by safely exposing individuals to a specific pathogenic microbe, artificially increasing their immunity to it. Vaccination

*What are antibiotics?

*Antibiotics are chemical compounds produced by soil fungi and bacteria.

*They are used to treat bacterial infections.

*Alexander Fleming accidentally discovered penicillin, the first antibiotic, in 1928.

*He isolated it from the mould Penicillium notatum and found it prevented the growth of bacteria.

*Penicillin was not available for commercial use until Florey and Chain purified it in 1940.

Antibiotic drugs (discs) prevent the growth of bacteria (white) demonstrated by clear zones around the discs.

*Why has antibiotic resistance occurred?

Factors leading to microbes becoming resistant to antibiotics include:

*Pressure on doctors, by patients, to prescribe antibiotics even when they are not needed.

*Patients being prescribed antibiotics without the doctor knowing the cause of the infection.

*Use of antibiotics in animals for growth promotion and prophylaxis, which allows them to enter the human food chain.

MRSA

*Genetic causes

*DNA present in cells codes for proteins

*Mutations in DNA results in production of faulty proteins

*Examples of inherited diseases

*Cystic fibrosis

*Sickle cell anaemia

*Huntingtons chorea

*Lifestyle

*CHD and some cancers caused by lifestyle

*Risk factors include

*Smoking

*Obesity

*Diet high in cholesterol

*Lack of exercise

*Diabetes and High Blood

Pressure

*Diabetes causes excess glucose to be found in urine

*High blood pressure causes proteins to be found in urine

*Examine the urine samples. Identify the substances present, diagnose possible disease, identify possible reasons for substances being present and suggest advice you would give to the patient.

*Which is the best Antibiotic?

*Examine the petri dishes provided containing a smear taken from a patient

*Which antibiotic(s) would you recommend prescribing to the patient and why?