Chapter 10: Infectious disease Flashcards
Define the term “infectious disease”
A disease caused by a pathogen which
can be transmitted.
Define the term “non-infectious disease”. Give two
examples.
A disease that cannot be transmitted by
direct contact between individuals, e.g.
sickle cell anaemia or lung cancer.
State the binomial name and pathogen type for
cholera.
● Vibrio cholerae
● Bacterium
State the binomial names and pathogen type for
malaria.
● Plasmodium ovale ● Plasmodium falciparum ● Plasmodium malariae ● Plasmodium vivax ● Protoctist
State the binomial names and pathogen type for
tuberculosis.
● Mycobacterium tuberculosis
● Mycobacterium bovis
● Bacterium
State the pathogen type for HIV/AIDS
Virus
What does HIV stand for?
Human immunodeficiency virus
What does AIDS stand for?
Acquired immunodeficiency syndrome
What causes HIV/AIDS?
- HIV virus is transmitted by direct contact with blood, semen, rectal
fluids, vaginal fluids and breast milk - Attachment proteins bind to complementary CD4 receptor on TH cells
- HIV particles replicate inside TH cells, killing or damaging them
- AIDS develops when there are too few TH cells for the immune system
to function
How is HIV/AIDS treated?
Taking a combination of antiretroviral drugs
prevents HIV replication. Post exposure
prophylaxis (PEP) can prevent infection after
exposure.
What causes tuberculosis (TB)?
- Transmitted by droplet infection (inhalation)
- Trigger inflammatory response by infecting phagocytes in lungs
- Infected phagocytes are sealed in waxy-coated tubercles so
bacteria remain dormant. Primary TB has no symptoms - If another factor weakens immune system, bacteria become
active. Secondary TB destroys lung tissue
Outline the symptoms and primary treatment of TB.
Patients take a combination of antibiotics
for several months.
How is cholera transmitted?
● Fecal/oral transmission.
● Ingesting contaminated food or water
How is cholera treated?
● Rehydration (fluid and electrolytes)
● Antibiotics
Why may the incidence and prevalence of
communicable diseases change over time?
● Development of vaccines
● Development of treatments, e.g. antibiotics
● Random mutations cause antigen variability in
pathogens. Memory cells no longer complementary
● Random mutations result in treatment-resistant strains
How can the spread of HIV be prevented?
● Take PEP
● Multi-drug treatment (HIV difficult to control due to high antigen variability)
● Use clean needles
● Screen blood donations to ensure they are not HIV positive (ethically
important not to outsource cheap blood e.g. from prison donations)
● Education
● Use of condoms
How can the spread of TB be prevented?
● Combination of drugs and vaccinations (expensive)
● Cover mouth & nose when coughing/ sneezing
● Quarantine (socially isolating)
● Improved sanitation
How can the transmission of cholera be prevented?
● Education on water sanitation i.e. don’t drink
untreated water
● Education on contamination of water supply
e.g. sewage
Outline the mode of transmission and infection of the
Plasmodium spp. parasite.
● Female mosquito acts as vector when it transfers
saliva to another organism during feeding
● Parasite reproduces asexually in red blood cells
in liver, causing lysis
How is endemic malaria controlled?
● Preventing mosquito bites - mosquito nets, insect repellent
● Controlling mosquito numbers - pesticides, chemical
treatment of standing water and sewage, introduction of
predators for mosquitoes
● Drug treatment
Consider the biological, social and economic factors
of preventing infectious disease.
● Diseases generally spread faster in densely populated and poorly sanitized areas
● Countries with healthcare systems and good education often have less disease. People educated
on how to prevent the spread of disease and can access treatments and vaccines
● Social stigma - some countries may see diseases (e.g. HIV) as socially stigmatising. People may
avoid seeking treatment for risk of social fallout
● Patronage of developed countries - vaccination programmes from developed nations considered
suspicious. Programmes used in the past to sample DNA without the consent of indigenous people
Describe and explain the global patterns of malaria,
TB and HIV/AIDS.
● Malaria - generally in tropical countries (warm temperatures required for survival of
plasmodium). Such countries tend to lack education and healthcare. Malaria is uncontrolled
and there is a lack of or no education regarding prevention methods.
● TB - common in developing countries where people live in cramped, poorly sanitised
conditions (proximity essential for TB transmission). Treatment and education in prevention
are rare.
● HIV/AIDS - common in developing nations. Lack of access to education in prevention. Lack of
access to healthcare means many people go undiagnosed and untreated.
How does penicillin act as an antibiotic? Name its
type and mode of action.
Penicillin inhibits the synthesis of the peptidoglycan wall in
bacteria, preventing new cell walls forming. The cell bursts.
This class of antibiotic is bactericidal. They work by preventing cell wall synthesis or disrupting protein synthesis
Why do antibiotics have no effect on viruses?
Antibiotics work by targeting machinery
found in bacteria (prokaryotic cells). Viruses
do not have this machinery ∴ antibiotics
have no effect on viruses.
Why is it important antibiotics do not affect
eukaryotes?
Humans (host) are eukaryotic. If
antibiotics affected eukaryotic cells they
could potentially kill the recipient.
How does antibiotic resistance occur?
● Spontaneous mutation of bacterial plasmids can occur which may lead to
improved tolerance to an antibiotic. These cells are able to survive long
enough to divide, increasing the prevalence of the mutation and making the
population more resistant to a particular antibiotic.
● Resistance can be spread ‘horizontally’ – the movement of genetic material
between unicellular and/or multicellular organisms (conjugation) other than
by the ‘vertical’ transmission of DNA from parent to offspring via reproduction.
How can we mitigate bacterial resistance?
● Complete the course of antibiotics to ensure the bacterial infection is eliminated
● Do not overuse antibiotics
● Do not use antibiotics in animal feed
● Reduce contamination in hospitals
● Aseptic techniques in hospitals
● Isolation of infected patients
● Emphasis on hygiene
● Reduce use of antibacterial hand gel – removes non-pathogenic bacteria, allowing
pathogenic bacteria to survive.
