Question

Question 1

1. Give the full scientific name of one of the protist species that causes malaria. (1 mark)
2. Briefly explain how the complexity of the malaria life cycle influences the host’s immune response.
3. Name one diagnostic test appropriate for use in the diagnosis of a current malaria infection and explain how it works.
4. State two strategies to prevent malaria.

Question 2

1. New variants of influenza can be generated by processes known as antigenic drift and antigenic shift. Distinguish between these two processes.
2. How might antigenic drift affect the design of a vaccination programme for influenza?
3. RT-PCR can be used to identify an influenza infection. State one other diagnostic test for influenza and describe how it can be used to determine the subtype of influenza.

Question 3

Read the following three statements and then answer the question below.

• In 2019, the UK lost its ‘measles-free’ status.
• The basic reproduction number for measles (R0) is given as between 12 and 18, in different studies.
• The immunisation rate in the UK for measles dipped to a low point in 2003 to 80% coverage and since then has risen to 91% in 2019.

Explain, using calculations, the causal link between these three statements and briefly discuss whether there is any prospect of the UK regaining its ‘measles-free’ status in the next 5 years.

Question 4

Cholera is an acute diarrhoeal disease endemic in some areas but prone to resurgences in pandemics.

1. What is the primary cause of death in cases of cholera?
2. What is the normal habitat of Vibrio cholerae? (1 mark) Describe one way in which people can become infected (1 mark) and one step that an individual could take to minimise that risk of infection (1 mark)
3. A stockpile of oral cholera vaccine is maintained by the WHO for use in humanitarian crises and outbreaks. From your knowledge of the biology of cholera infection, and referring to aspects of the appropriate immune response, explain why oral vaccines are used.
4. A freak weather event on a large tropical island destroys housing and leads to the local population being rehoused in a cramped refugee camp, where a cholera epidemic soon occurs. Apart from distributing oral cholera vaccine, what additional public health measures should be taken in the refugee camp to limit further infection and/or deaths from cholera?

Question 5

1. Your friend is suffering from a fever and respiratory symptoms. She visits her GP and requests antibiotics. Explain why antibiotics may not be appropriate for her infection.
2. Describe the effects of the overuse of antibiotics on the bacterial population in humans.
3. In order to distinguish between viral and bacterial infections some GPs now use a rapid point-of-care (POC) test for levels of C-reactive protein (CRP). Explain the role of CRP in the immune response and its relevance to use in this test.
4. In a hospital setting, treatment with antibiotics is a risk factor for infection with Clostridium difficile. Explain why Clostridium difficile is commonly acquired in hospitals.

Question 6

1. The cytokine IFNγ is produced by Th1 cells. Outline three different functions of IFNγ in inflammation and/or the immune response.
2. Name one cytokine that is produced specifically by Th2 cells and state what effect it has on its target cell(s).
3. What advantage is there for the host in having two distinct patterns of immune response, controlled by Th1 and Th2 cells?

Answer 1

1

a) Malaria is caused by the protozoan parasite Plasmodium

b)Plasmodium, the parasite responsible for malaria, impairs the ability of key cells of the immune system to trigger an efficient immune response.They express lower levels of membrane molecules that stimulate other cells of the immune system, and their cytokine production is lower than that of normal dendritic cells. Hosts can mount a level of protective immunity, which can occur following initial infection and render the host shielded against subsequent disease. Individuals who are repeatedly exposed to malaria develop antibodies against the sporozoite, liver-stage, blood-stage, and/or sexual-stage malaria antigens.

c) The gold standard for the diagnosis of malaria involves microscopy with visualization of Giemsa-stained parasites in a blood sample. Species determination is made based on morphological characteristics of the four species of human malaria parasites and the infected red blood cells.

d)There are two main prevention methods: Protective bed nets treated with long-lasting insecticides prevent bites from malaria-infected mosquitoes and kill them. Nets should be available for free or at low prices thanks to high subsidies

2.

a) Antigenic drift involves the accumulation of a series of minor genetic mutations. Antigenic shift involves “mixing” of genes from influenza viruses from different species. Pigs, birds, and humans.

b) Most flu shots are designed to target an influenza virus' HA surface proteins/antigens. The nasal spray flu vaccine (LAIV) targets both the HA and NA of an influenza virus.When antigenic drift occurs, the body's immune system may not recognize and prevent sickness caused by the newer influenza viruses.

c) Nucleic acid tests use a "probe" which is a long strand with a short strand stuck to it. The long primer strand has a corresponding (complementary) sequence to a "target" strand from the disease organism being detected.

4.

a)

Cholera is an infectious disease that causes severe watery diarrhea, which can lead to dehydration and even death if untreated. It is caused by eating food or drinking water contaminated with a bacterium called Vibrio cholerae.

b) The vibrio cholera may also live in the environment in brackish rivers and coastal waters. A person can get cholera by drinking water or eating food contaminated with the cholera bacterium. Individual restrict himself by consuming market food which is not produced in hygenic environment.

c) Oral Cholera Vaccine (OCV) can play an important role in outbreak prevention and control, and in long term control of cholera. HO established the Global Oral Cholera Vaccine (OCV) stockpile and received long term support from Gavi, the Vaccine Alliance for use of OCV in epidemic and endemic settings. Since then the targeted use of the vaccine in endemic, epidemic and humanitarian settings has increased dramatically under the guidance from the Global Task Force on Cholera Control .