Named Disease Case Studies: AQA Required Examples

Named Disease Case Studies: AQA Required Examples

Gonorrhoea — Bacterial STI

• Pathogen: Neisseria gonorrhoeae — a bacterium
• Symptoms: Thick yellow or green discharge from the penis or vagina; pain or burning when urinating. Important: many people have no symptoms at all (asymptomatic), which makes it easy to spread unknowingly.
• Transmission: Spread by unprotected sexual contact. The bacteria pass directly between mucous membranes (e.g., vagina, urethra, throat, rectum). It is not spread by casual contact such as touching or sharing toilet seats.
• Treatment: Treated with antibiotics. However, antibiotic-resistant strains are increasingly common — some strains are now resistant to several types of antibiotic, making treatment more difficult. This makes gonorrhoea an important example of the antibiotic resistance problem.
• Prevention: Using barrier methods (condoms) during sexual contact; regular sexual health screening so infections are detected and treated before spreading further.

Exam link: AQA often asks about gonorrhoea in the context of antibiotic resistance. Be ready to explain why resistance is developing and why this is a global health concern.

Chalara Ash Dieback — Fungal Plant Disease

• Pathogen: Hymenoscyphus fraxineus (previously called Chalara fraxinea) — a fungus
• Host: Ash trees (Fraxinus species) across the UK and Europe
• Symptoms: Leaf loss (leaves wilt and die); crown dieback (upper branches die back progressively); dark lesions (wounds) on the bark, particularly near the base of the tree. Affected trees gradually lose their ability to photosynthesise and transport water and nutrients.
• Spread: Wind carries the tiny fungal spores across distances. Movement of infected nursery stock (young ash trees bought and planted across the UK) spread the disease rapidly before it was identified.
• Impact: Threatens over 80 million ash trees in the UK. Ash is one of the most common woodland trees, so its loss has major ecological consequences — affecting thousands of species that depend on ash trees for habitat or food. There are also significant economic costs (timber industry, landscape management).
• Treatment and control: There is no effective treatment — affected trees cannot be cured and usually die. Control measures focus on felling infected trees, restricting the movement of ash tree nursery stock, and monitoring woodlands to slow the spread. Research into resistant ash tree varieties is ongoing.

Exam link: Chalara ash dieback illustrates how fungal plant diseases spread via spores and how human activity (moving nursery stock) can accelerate the spread of pathogens.