Component 3A - Disease Flashcards
How does the human body act as a host?
Many organisms live in or on the human body in symbiotic and parasitic relationships. Help us defend against disease or cause disease
What is cholera caused by and what is its current status?
Gram-negative bacteria and it is endemic in parts of the world
How does cholera affect a person?
Its toxins affect the gut lining causing watery diarrhoea leading to severe dehydration and frequently death.
How is cholera transmitted?
Humans act as reservoirs or carriers and contaminate water supplies in which the organism is transmitted, although it only multiplies in the human host.
Control method for cholera
Cholera prevention is by the treatment of water, good hygiene and the provision of clean drinking water.
Vaccine (killed organism or possibly genetically engineered) may provide temporary protection.
What is the treatment for cholera?
1) Antibiotic treatment of water
2) Rehydration - giving patients electrolytes orally
What is tuberculosis caused by and what is its status?
A bacterial disease that is again on the increase, partly due to the link with the HIV epidemic (immune system in those with HIV-AIDS is less efficient)
How is tuberculosis transmitted?
It can be spread rapidly in overcrowded conditions and is transmitted in airborne droplets when infected people cough and sneeze.
What parts of the body are effected by TB and what are the symptoms of the disease?
The most common form of TB attacks the lungs and neck lymph nodes. Symptoms include coughing, chest pain and coughing up blood.
How is TB prevented?
By a BCG vaccination programme for children
What does the treatment of TB involve?
Treatment involves a long course of antibiotics.
What is smallpox caused by and what is its fatality rate?
It is caused by the virus Variola major and can have a 30 to 60% fatality rate
How is smallpox transmitted?
Inhaled or transmitted in saliva or from other bodies if there is close contact with an infected person
What part of the body is affected by smallpox?
It causes a rash, fluid-filled blisters and survivors suffer scars from these as well as blindness and limb deformities
How was smallpox treated?
- Infected people are given fluids, drugs to control fever and antibiotics to control bacterial infection
- The smallpox vaccine
Why was the smallpox vaccine very successful?
Because it was based on the virus’ lack of antigenic mutation (changes to avoid immune response) and highly immunogenic nature of its antigens (produces a very large immune response)
There was no animal reservoir and people were keen to be immunised because of the devastating effects of the disease.
What is different about humans involvement with smallpox than other diseases?
Smallpox is the only organism that humans have intentionally made extinct (outside specialist laboratories).
What is influenza caused by?
It is caused by a virus of which there are three main sub-groups. Within each sub-group there are many different antigenic types.
(Describing ‘flu A in these flashcards)
What part of the body does influenza effect and what are the symptoms?
It infects cells lining the upper respiratory tract causing sore throat, coughing and fever.
How is influenza transmitted?
Sufferers spread the disease by droplet infection (aerosol transmission from coughs and sneezes)
How is the risk of getting influenza reduced?
1) Quarantine
2) Hygiene e.g discarding tissues
3) Annual vaccination programmes are available but due to the number of types, together with the emergence of new types, they are not always effective.
-Influenza’s mode of spread is difficult to control.
How are antibiotics involved with influenza?
Antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection
How can pandemics occur as a result of Influenza?
When a new strain of ‘flu appears with new protein on the virus’ surface the human immune system cannot provide adequate protection.
How can viruses be pathogenic?
1) Cell lysis when they escape from cells to infect other cells/ organisms
2) Production of toxic substances
3) Cell transformation where they can trigger cells to
become cancerous
4) Suppress the immune system (e.g. HIV)
How do viruses make more virus particles?
They use a cells metabolic pathway
What is malaria caused by and what is its status?
Malaria is caused by Plasmodium spp., a protoctistan parasite, endemic in some sub-tropical regions.
The disease is caused mainly by two species within which are many antigenic types.
How is malaria transmitted?
Female mosquitoes, feeding on blood taken, act as vectors to transmit the parasite to new victims.
How does the parasite infect the host?
The organism initially invades liver cells and then multiplies in red blood cells which burst, releasing more parasites
What is a symptom of malaria?
severe bouts of fever
What is used to prevent transmission of malaria?
1) Prevent biting by use of nets
2) Clothing
3) Insect repellent
How can mosquito larvae or adults be killed?
1) They are aquatic so eaten by introduced fish
2) Drainage of breeding sites
3) Spraying of oil on the water surface.
4) The adults are killed with insecticides, with bacterial infections or by sterilisation.
Control method for malaria
Drug treatment is available but mainly to reduce the chances of infection.
Treatment of malaria and their problems
1) Plasmodium is affected by drugs when outside the cells in the blood but these have limited effectiveness and have side effects; resistance is an increasing problem.
Problems with developing a vaccine for malaria?
1) Antibodies also are only effective against the parasite when outside body cells so limiting the target stages for a vaccine
2) Malarial parasite mutates and there are different antigenic types
