10. Infectious Diseases Flashcards
What are infectious diseases?
Diseases that are caused by pathogens
What is the pathogen that causes cholera?
Vibrio cholerae
(Bacterium)
What is the pathogen that causes malaria?
(Protoctist)
Four species of Plasmodium:
Plasmodium falciparum
Plasmodium malariae
Plasmodium ovale
Plasmodium vivax
What is the pathogen that causes HIV/AIDS?
Human immunodeficiency virus
(Virus)
What is the pathogen that causes TB?
Mycobacterium tuberculosis
Mycobacterium bovis
(Bacterium)
How do infected cholera patients spread their bacterium?
They carry out large numbers of bacteria in their faeces so if these contaminate the water supply or if infected people handle food or cooking utensils without washing their hands then bacteria are transmitted to uninfected people
Define the word disease
An illness or disorder of the body or mind that leads to poor health.
What is the treatment for cholera?
People are given oral rehydration therapy by a solution of salts and glucose.
People who can’t drink are given this solution intravenously
How effective is the treatment for cholera?
Glucose is effective because it is absorbed into the blood and this is linked to the uptake of sodium and potassium ions
What is a disease vector?
An organism which carries a pathogen from one person to another or from an animal to a human.
How does Malaria spread?
May be transmitted during blood transfusion
When unsterile needles are re-used
The plasmodium can also pass across the placenta from mother to fetus
Why does female Anopheles mosquito feed instead of the male?
Female Anopheles mosquitoes feed on human blood to obtain the protein they need to develop their eggs.
What are the two drugs used to treat malaria?
Quinine and chloroquine- prophylactic drugs taken before and after visiting a place where malaria is prevalent.
What is chloroquine and how does it work?
It can be used as a prophylactic drug, stopping an infection occurring if a person is bitten by an infected mosquito. Chloroquine inhibits protein synthesis and prevents the parasite spreading within the body.
As a result of drug resistance strains, what is the best treatment for malaria currently?
Artemisinin based combination therapy (ACT)
What are the three main ways to control malaria?
- Reduce the number of mosquitoes
- Avoid being bitten by mosquitoes
- Use prophylactic drugs to prevent Plasmodium infecting people.
What is the most effective method to control malaria?
To kill the insect vector and break the transmission cycle. Mosquitoes lay their eggs in water and the larvae hatch and develop in water but breath by coming up to the surface so oil can be spread over the surfaces of water to make it impossible for mosquito larvae and pupae to breathe.
Name the 2 biological control measures that can be used for malaria
- Stocking ponds, irrigation and drainage ditches with fish which feed on mosquito larvae
- Spraying a preparation containing the bacterium Bacillus thuringiensis which kills mosquito larvae but is not toxic to other forms of life.
The best protection against malaria is to avoid being bitten, how can people do this?
People are advised to sleep beneath mosquito nets and use insect repellents.
Insecticides must also be sprayed inside the house
What three factors may lead to improvements in the control of malaria?
- The use of modern techniques in gene sequencing and drug design
- Development of vaccines targeted against different stages of the parasites life cycle
- A renewed will to remove burden if malaria from the poorest parts of the world allied to the generous donations from wealthy individuals and foundations
How does the HIV virus affect the human body?
It infects and destroys the body’s immune system so that their numbers gradually decrease. When T helper lymphocytes are low the body is unable to defend itself against infection, so allowing a range of pathogens to cause variety of opportunistic diseases.
What is an opportunistic infection?
An infection caused by pathogens that take advantage of a host with a weakened immune system, as may happen with an HIV infection
How is HIV spread?
Spread by intimate human contact
Transmission is only possible by direct exchange of body fluids
Name 4 ways HIV can be spread?
- Sexual intercourse
- Blood donation
- Sharing of needles by intravenous drug users
- From mother to child across the placenta.
What has been successful over the years in terms of treating HIV?
Drug therapy can slow down the onset of AIDS so that an HIV+ person can have a normal life expectancy.
The drugs are similar to DNA nucleotides.
Stops the replication of the viral genetic material and leads to an increase in some of the body’s lymphocytes
What makes HIV hard to control?
The virus’s long latent stage means that it can be transmitted by people who are HIV+ but who show no symptoms and do not know they are infected.
Why is the body not able to recognize the virus?
The virus changes its surface proteins which makes it hard for the body’s immune system to recognize it, this also makes developing a vaccine very difficult
Name ways to prevent the spread of HIV?
-People can be educated about the spread of the infection and encouraged to change their behavior so as to protect themselves and others.
-Condoms, femidoms and dental dams are effective protection during intercourse as they form a barrier between body fluids.
What is contact tracing and why is it important?
It is an important part of controlling the spread of HIV.
If a person who is diagnosed as HIV+ is willing and able to identify the people he or she has put at risk of infection by sexual intercourse or sharing needles then these people will be offered an HIV test.
What is the first opportunistic infection to strike HIV+ people?
TB.
The HIV infection may reactivate dormant infections of M. Tuberculosis which may have been present from childhood of if you’re uninfected making them susceptible to infection.
How does TB spread?
It is spread when infected people with the active form of the illness cough or sneeze and the bacteria are carried in the air in tiny droplets of liquid. The transmission cycle ends when uninfected people inhale the droplets.
Who is typically most vulnerable to TB?
It spreads most rapidly among people living in overcrowded conditions.
People who sleep close together in large numbers
The homeless
People who live in poor substandard housing
Those with low immunity because of malnutrition or being HIV+
What happens if TB is not treated or if the patient stops treatment before the bacteria are completely eliminated?
The bacteria spread throughout the body, increasing the likelihood that mutations will arise as the bacteria survive for a long time and multiply.
How can the spread of M. Bovis from Cattle be controlled?
TB bacteria are killed when milk is pasteurized
Cattle are routinely tested for TB and any found to be infected are destroyed.
What is an antibiotic?
A drug that kills or stops the growth of bacteria without harming the cells of the infected organism
How do antibiotics work?
They interfere with some aspect of growth or metabolism of the target bacterium:
1. Synthesis of bacterial cell walls
2. Activity of proteins in the cell surface membrane
3. Enzyme action
4. DNA synthesis
5. Protein synthesis
How does Penicillin work?
Bacterial cell have walls made of peptidoglycan which is held together by cross links that form between them. So penicillin prevents the synthesis of the cross links between the peptidoglycan polymers in the cell walls of bacteria by inhibiting the enzymes that build these cross-links
Explain how the enzymes secreted in the bacterial cells progressively damages itself.
A growing bacterial cell secretes enzymes called autolysons which make little holes in its cell wall and these holes allow the wall to stretch so that new peptidoglycan chains can link together. However, penicillin prevents the peptidoglycan chains from linking but the autolysons keep making new holes. The cell wall therefore becomes progressively weaker. The bacterial also live in watery environments and take up water by osmosis. When they are weakened the cell walls cannot withstand the target pressure exerted on them and the cell bursts
Why does penicillin have no effect on M. Tuberculosis?
Because the cell wall of this bacterium is not very permeable and because the bacterium has a gene that codes for an enzyme that catalyzes the breakdown of penicillin
How can we reduce the number of circumstances in which bacteria develop resistance to antibiotics?
- Using antibiotics only when appropriate and necessary
- Reducing the number of countries in which antibiotics are sold without a doctor’s prescription
- Making sure that patients complete their course of medication
- Making sure patients do not keep unused antibiotics for self medication in the future
- Avoiding using antibiotics in farming to prevent rather than cure infections
How can we reduce the number of circumstances in which bacteria develop resistance to antibiotics?
- Using antibiotics only when appropriate and necessary
- Reducing the number of countries in which antibiotics are sold without a doctor’s prescription
- Making sure that patients complete their course of medication
- Making sure patients do not keep unused antibiotics for self medication in the future
- Avoiding using antibiotics in farming to prevent rather than cure infections
- Reducing the use of wide spectrum antibiotics and using antibiotics specific to the infection.
Why is malaria very difficult to control?
- No vaccine as plasmodium is eukaryotic and antigens differ in the different life stages.
- Drug resistance in Plasmodium
- Insecticide resistance in Plasmodium
- Infected individuals not identified
What factors led to the successful eradication of smallpox
- It did not mutate
- Same vaccine was used for whole program
- Vaccine gave strong immune response
