3.3 Bacterial, fungal and protist diseases

Four diseases to know

Salmonella (bacteria)

• Spread: in food, for example undercooked chicken or eggs, or food prepared in unhygienic conditions.
• Symptoms: fever, abdominal cramps, vomiting and diarrhoea, caused by the toxins the bacteria release.
• Control: in the UK, poultry are vaccinated against Salmonella. Cooking food thoroughly and good kitchen hygiene, such as washing hands and keeping raw meat separate, also stop it spreading.

Gonorrhoea (bacteria)

• Spread: by sexual contact.
• Symptoms: a thick yellow or green discharge from the vagina or penis, and pain when urinating.
• Control: it used to be treated with the antibiotic penicillin, but many strains are now resistant to it, so other antibiotics are used. Using a condom and tracing and treating sexual partners stop the spread.

Rose black spot (fungus)

• Spread: spores are carried in the environment by water and wind.
• Symptoms: purple or black spots on the leaves, which often turn yellow and drop early.
• Fewer healthy leaves mean less photosynthesis, so the plant grows less well.
• Control: spraying with fungicides, and removing and destroying the affected leaves.

Malaria (protist)

• The malaria protist has a life cycle that includes mosquitoes, which are vectors.
• Symptoms: recurrent (repeated) episodes of fever. Malaria can be fatal.
• Control: stop the vectors breeding, for example by draining standing water and using insecticides, and use mosquito nets to avoid being bitten.