Infectious Diseases

Infectious diseases• Pathogen

Organism which causes disease e.g. bacterium, virus, protocista (one celled organism)

• TransmissionTransfer of pathogen from one organism to another –

may involve a vector

• World wide importance Countries and numbers

• Prevention and control Need to understand pathogen and its

transmissionAttitude of individuals, local government,

pharmaceutical companies and the world health organisation

Malaria

Name of pathogenTransmission

Worldwide importancePrevention and control

Malaria – the life cycle of the pathogen Plasmodium

Malaria

Name of pathogen - Plasmodium species (one eukaryote cell = Protocista)

Transmission – vector needed; female Anopheles mosquito infected blood drunk; then pathogen passed to an uninfected person in saliva

Worldwide importance – tropics e.g. China, India, South America, West Indies

Prevention and control – prevent completion of mosquito life cycle; vaccination difficult as many antigens;treatment affected by drug resistance; sickle cell allele gives protection

Can you explain these words?How are they involved in recovering

from infectious diseases?

• Antibodies

• Antibiotics

• Resistance to antibiotics

Antibiotics (p215-6)Antibiotic - a chemical produced by one

microorganism which is able to destroy or inhibit the growth of another microorganism

Resistance - due to mutation so new allele of gene produced. The antibiotic no longer affects the micororganism.

Key words which may confuse you

antigen

antibody

antibiotic

resistance

What does each word mean?How are the words connected?

Infectious diseases• Pathogen

Organism which causes disease e.g. bacterium, virus, protocista (one celled organism)

• TransmissionTransfer of pathogen from one organism to another – may involve a vector

• World wide importance Countries and numbers

• Prevention and control Need to understand pathogen and its

transmission

AIDS

True or false?

How much do you know about AIDS?

Kaposi’s sarcoma in an AIDS patient

AIDS orphans in Lesotho, southern Africa

The pathogen – HIV

AIDS – Acquired Immune Deficiency Syndrome

• Pathogen – HIV = human immunodeficiency virus

• Transmission – in body fluids e.g. blood, semen, vaginal fluid, across placenta, breast milk

• Worldwide importance – pandemic

• Symptoms – diseases which immune system cannot deal with because the T helper lymphocytes do not function

• Prevention and control – education, screening, human genome project?

Could the human genome project help to eradicate diseases like malaria and

AIDS?

• Identify people immune to the disease• Isolate the relevant gene• Then either identify the protein antigen

and use it to develop a vaccine • Or give gene therapy to people at risk

e.g. sickle cell allele gives resistance to malaria

e.g. some people seem to be immune to the effects of HIV page 151

Work on Antibiotics1) Antibiotic - a chemical which is able to kill or inhibit the growth

of bacteria or fungi

2) Practical – culture your bacteria E. coli or Micrococcus luteus on an agar plate and compare with a plate with antibiotic discs added. Draw and explain the results of the antibiotic sensitivity test.

3) Distinguish between each pair of terms and include examples• bacteriostatic or bacteriocidal antibiotics

• broad spectrum or narrow spectrum antibiotics

• susceptible or resistant strains of bacteria

4) Page 216 – answer SAQ 15.14 about antibiotic sensitivity

5) Why must we be careful about how antibiotics are used?

TB – Tuberculosis – key words

Mycobacterium. bovis/tuberculosis

coughing poor housing

cows milk badgers

HIV and AIDS human migration

mutations in bacteriamalnutrition

TB - Tuberculosis

Pathogen = Mycobacterium tuberculosis or M. bovis (both are

bacteria)

Transmission – in airbourne droplets or unpasteurised milk

TB was thought to be eradicated due to vaccination, better diet and improved housing.

So why has there been an epidemic recently in some countries?

Answer – see p 213 e.g. bacteria resistant to antibiotics;

the AIDS pandemic; poor housing; inadequate

vaccination;immigration; TB bacteria in badgers and

cows

Questions on HIV and AIDS1) What do the letters HIV and AIDS mean?2) Why is AIDS called an epidemic and

pandemic?3) Why was the epidemic in USA and

Europe initially among homosexual men?4) Why are haemophiliacs no longer at risk

from HIV infection?5) Give details of HIV and AIDS symptoms6) What social and economic effects does

AIDS have in developing and developed countries?

7) How can HIV transmission be controlled? Do you think that AIDS be eliminated?

8) Exam question – June 2004 - 6