Biology 9700 · AS & A Level · Infectious diseases

Infectious diseases — practice question

Tuberculosis (TB) is an infectious illness caused by a bacterium. For most people, the lungs are the only organs affected. In most instances, TB passes from an infected person to someone uninfected through $\textit{Mycobacterium tuberculosis}$. A different species of bacterium is responsible for TB being passed from cattle, such as dairy cows, to humans.
(a)[1]

Name the species of bacterium that causes TB to be transmitted from dairy cows to humans.

(b)[1]

In some regions, cattle cannot be tested or treated for TB on a regular basis. In these places, milk and dairy products from infected dairy cattle may enter the human food chain. Outline a control measure that can be used to protect people who consume milk and dairy products from these infected cattle.

(c)[2]

Cattle are not usually affected by $\textit{M. tuberculosis}$, although the pathogen can cause disease in other animals. A small number of cases of TB being transmitted from people to animals have been reported. Explain the most likely way that TB is transmitted from an infected person to an animal.

(d)[2]

In most people, the immune system's response to infection of lung tissue by $\textit{M. tuberculosis}$ can prevent the bacterium spreading to other organs in the body. The bacterium is kept in the lungs in a dormant state. This is known as latent TB. Outline the treatment used to kill $\textit{M. tuberculosis}$ in latent TB infections.

(e)[3]

$\textit{M. tuberculosis}$ can spread in the blood and lymph to other organs in the body. In very rare cases, a condition known as mycotic aneurysm can result from infection of the arterial wall, especially in elastic arteries. Damage caused by the pathogen can lead to rupture (bursting) of the artery. With reference to the structure of the wall of elastic arteries, suggest how damage caused by $\textit{M. tuberculosis}$ infection can result in the rupture of the artery. You may draw a diagram if you wish.

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