Biology 9700 · AS & A Level · Infectious diseases

Infectious diseases — practice question

In 2016, the greatest number of malaria cases and malaria-related deaths occurred in sub-Saharan Africa. In many parts of sub-Saharan Africa, malaria is endemic (continually present), so the risk of infection with the Plasmodium pathogen is high. In high-risk areas, it is advised that homes are fitted with insecticide-treated nets (ITN); and that the inside surfaces of homes where Anopheles mosquitoes may rest are sprayed with insecticide. This is called indoor residual spraying (IRS).
(a)[3]

Explain how the use of ITN and IRS can help to interrupt the transmission cycle of malaria.

(b)

Fig. 2.1 shows the proportion of the population in sub-Saharan Africa at risk of malaria that is protected through the use of IRS or ITN, or both, in the years 2010 to 2016.

(b(i))[1]

State one further trend displayed in Fig. 2.1.

(b(ii))[1]

Explain why the main trend shown in Fig. 2.1 might be a concern for the World Health Organization.

(b(iii))[1]

Using Fig. 2.1, suggest a reason for the difference in trends shown for ITN only compared with IRS only.

(c)[3]

In a primary immune response, antibodies against Plasmodium are formed within one to two weeks after infection. In some people, the pathogen is removed and the concentration of antibodies in the bloodstream falls over time. A second infection by Plasmodium with the same antigens triggers a secondary response that also includes antibody production. State and explain how the antibody response after a second infection will be different from the primary immune response.

(d)[2]

In malaria, antibody production helps recovery, but in myasthenia gravis antibody production is harmful. Explain why the production of antibodies in a person with myasthenia gravis is harmful.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: Anopheles is a vector in the transmission cycle of Plasmodium

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