chapter 10

• Physical processes that influence glaciated upland landscapes include: erosion, transport, deposition, weathering and mass movement
• Some physical processes continue to operate on relict (old) glaciated upland landscapes that we see in the UK
• Disease caused by a pathogen
• Cause harm to health of host
• Can be passed from one organism to another i.e. communicable/transmissible
• Pathogens = Parasitic disease-causing microorganisms
• Can be prokaryote/eukaryotes
• E.g. bacteria, virus, protoctists, fungi
• Gain entry to host
• Colonise host tissue
• Damage host’s tissues
• Resist host defences
• No membrane-bound organelles
• No nucleus, DNA lies free in cytoplasm in the nucleoid region
• Plasma membrane, cytoplasm, peptidoglycan cell wall, 70S ribosomes, circular DNA, DNA is naked
• Cholera:

  • Causative organism: Vibrio cholerae – a bacterium
  • Transmission: Faecal-oral route, food-borne, water-borne
  • Symptoms and Effects: Severe diarrhoea, dehydration, weakness, fatigue, low blood pressure, weight loss, vomiting
  • Treatment: Oral rehydration therapy with oral rehydration solution (ORS)
  • Prevention: Proper sewage treatment, chlorinate water, drink bottled water
  • Global Distribution: Endemic in developing countries like West and East Africa, Afghanistan, Latin America, parts of Asia
• Malaria:

  • Causative organism: Plasmodium – a protoctist (eukaryote), parasite
  • Vector/Transmission: Female Anopheles mosquitoes, blood transfusions, unsterile needles, placenta from mother
  • Symptoms: Fever, anaemia, nausea, headaches, muscle pain, shivering, sweating, enlarged spleen
  • Treatment: Anti-malarial drugs like quinine, chloroquine, artemisin
  • Prevention: No vaccine, use prophylactic drugs, reduce mosquitoes, prevention of bites
  • Global Distribution: Endemic in tropical and sub-tropical areas due to survival and breeding of Anopheles mosquito
• HIV/AIDS:

  • Causative organism: Human immunodeficiency virus (HIV) – a virus
  • Life cycle: Viral RNA and reverse transcriptase enter T helper lymphocytes, viral DNA incorporated into host DNA, viral proteins assembled into new viruses
  • Transmission: Direct exchange of body fluids, blood transmission, mother to baby transmission
  • Symptoms and Effects: Slow infection, destruction of helper T cells, body unable to defend against infection
  • Prevention: Through safe sex practices, avoiding sharing needles, antiretroviral therapy
  • Global Distribution: Worldwide pandemic
• Antibiotics e.g. Penicillin
• Why antibiotics don't work on viruses?


  viruses don't have peptidoglycan cell walls, have protein coat
• Antibiotic Resistance:

  • Cause: Overuse/misuse of antibiotics
  • Consequence: Ineffective treatment, increased healthcare costs, higher mortality rates
  • Prevention: Proper antibiotic use, infection prevention and control measures
• Symptoms of HIV infection:

  • Flu-like symptoms and then symptomless (since virus can stay dormant for years)
  • Opportunistic infections can occur as a result of a compromised immune system
  • Collection of opportunistic diseases associated with immunodeficiency caused by HIV = AIDS
• Opportunistic infections associated with HIV/AIDS:

  • Oral thrush
  • Pneumonia
  • Cancers like Kaposi's sarcoma
  • Neurogenerative diseases like dementia
  • Tuberculosis (TB)
  • Malaria
  • Malnutrition
  • Weight loss
  • Diarrhoea
  • Fever
  • Sweating
• Treatment for AIDS:

  • No cure for AIDS
  • Drug therapy can only slow down the onset of AIDS
  • Zidovudine binds to viral enzyme reverse transcriptase and inhibits it
  • Drugs can target viral protease and inhibit it as well
  • Combination therapy must follow a strict pattern and timing of medication
  • If not followed properly, patients may develop strains of HIV resistant to drugs
• Prevention of HIV/AIDS:

  • No vaccine
  • Use of condoms, femidoms, and dental dams
  • HIV testing promoted in high-risk groups
  • Contact tracing where the person with HIV traces people he/she has put at risk of infection and that person to provide a HIV test
  • Discourage needle sharing
  • Donated blood is screened for HIV and heat-treated to kill viruses
  • Control mother-to-child transmission using drugs
  • HIV+ women of high-income countries should avoid breastfeeding to reduce transmission
• • HIV+ women of low/middle income countries advised to breastfeed because milk provides protection against other diseases and lack of clean water outweigh the risk of transmitting HIV
• Global Distribution of HIV/AIDS:

  • Pandemic in the whole world
  • Especially high numbers/high prevalence in Africa
• Tuberculosis (TB) Causative organism:

  • Mycobacterium tuberculosis, M. bovis - bacteria
  • M. tuberculosis causes TB in humans
  • M. bovis causes TB in cows, humans, and other mammals
• Transmission of Tuberculosis:

  • Mycobacterium tuberculosis is transmitted by aerosol infection
  • Pathogen is in airborne droplets
  • Infected person coughs/sneezes
  • Uninfected person breathes in droplets
  • Mycobacterium bovis is transmitted from infected cows/cattle
  • Eat undercooked contaminated meat
  • Drink unpasteurised milk containing bacteria
• Symptoms and Effects of Tuberculosis:

  • Site of primary infection = lungs
  • Secondary infections in lymph nodes, bones, and gut
  • Slow infection - many infections are controlled by the immune system and people don't suffer symptoms, cannot pass on the disease
  • Bacteria may be activated after many years when the immune system is weakened by other infections (e.g. HIV)
  • The incubation period is a few weeks to a few years
• Diagnosis of Tuberculosis:

  • X-ray
  • Microscopical examination of sputum (mucus and pus) for bacteria
• Treatment of Tuberculosis:

  • Long treatment time because bacteria is slow-growing and not very responsive to drugs
  • Combination therapy using multiple antibiotics such as streptomycin, isoniazid, rifampicin to prevent drug-resistance
  • DOTS (direct observation treatment, short course) makes sure patients take medicine regularly and reduce spread of drug resistance
• Prevention of Tuberculosis:

  • Bacillus Calmette-Guérin (BCG) vaccine
  • Derived from M. bovis
  • Isolate patients which are in infectious stages
  • Contact tracing and TB screening for early detection to prevent spread
  • Cattle tested for TB
  • Pasteurise milk
• Global Distribution of Tuberculosis:

  • Endemic all over the world
  • Especially high rates in cities due to high migration rate
  • And in overcrowded areas where there is poverty
  • Also where HIV/AIDS is prevalent
• Correlation between global distributions of AIDS and TB:

  • Countries where many people have AIDS also have a high death rate from TB
  • Many people who have AIDS die of TB
  • TB is an opportunistic infection
  • People who are HIV+ are more susceptible to TB
  • Dormant TB more likely to become active if person is HIV+
• Antibiotics:

  • Antibiotics are drugs used to kill/inhibit growth of bacteria without harming the infected organism
  • Bacteriocidal antibiotics kill bacteria
  • Bacteriostatic antibiotics inhibit bacterial growth
  • Prevent spread of bacteria within the body
  • Have no effect on viruses
• How antibiotics work:

  • Inhibit bacterial cell wall synthesis
  • Inhibit activity of specific membrane protein/glycoprotein to block binding to cells
  • Block specific enzyme action
  • Inhibit protein synthesis and nucleic acid synthesis targeting enzymes that bacteria have, but humans don't
• Why antibiotics do not affect viruses:

  • Viruses do not have peptidoglycan cell wall, have a protein coat
  • Viruses do not have their own metabolism, rely on host cells
  • Viruses have no cell structure/very few organelles, making few sites for antibiotics to act on
  • Viruses live inside host cells, out of reach of antibiotics
  • Antivirals exist to target viral glycoproteins on the viral envelope and inhibit specific viral enzymes
• Antibiotic Resistance:

  • Caused by spontaneous/random mutation in bacteria
  • Mutation causes a change in protein/production of new protein that cannot be targeted by antibiotics
  • Natural selection enables resistance genes to spread
  • Resistant bacteria survive and reproduce, spreading antibiotic resistance gene to the next generation and other bacteria
• Antibiotic Resistance:

  • Antibiotic-resistant genes are usually found in plasmids
  • Bacteria can spread antibiotic resistance genes using vertical transmission (pass plasmids down to daughter cells by binary fission) and horizontal transmission (pass plasmids to other bacteria by conjugation)