5.4 - Bacterial & Protist Diseases

Chlamydia

• Chlamydia is caused by a bacterium (Chlamydia trachomatis).
• It's a sexually transmitted disease - passed on during sexual intercourse.
• It often causes no symptoms, so it can go untreated. Left untreated, it can lead to infertility.

Treatment and prevention

• Treatment - Antibiotics.
• Prevention - Using a condom during sex reduces its spread.

Tuberculosis (TB)

• Cause - The bacterium Mycobacterium tuberculosis.
• How it spreads - Through the air, when an infected person coughs.
• Symptoms - Coughing and damage to the lungs.

Infected people can reduce the spread of TB by:

• Avoiding crowded places
• Practising good hygiene
• Sleeping alone
• Keeping their homes well ventilated

A BCG vaccine is also used to help prevent infection.

TB is treated with a long course of antibiotics.

Stomach ulcers (Helicobacter)

• Stomach ulcers can be caused by the bacterium Helicobacter pylori.
• It's taken in by mouth - for example, by swallowing contaminated food or water.

Symptoms

• Stomach pain
• Nausea
• Vomiting

Reducing its spread

• Clean water supplies
• Hygienic living conditions

Cholera

• Cholera is caused by a bacterium (Vibrio cholerae).
• Spread - Through drinking water contaminated with the diarrhoea of infected people.
• Main symptom - Severe diarrhoea.
• Prevention - Making sure people have access to clean, safe water supplies reduces its spread.

Malaria

• Malaria is caused by a protist called Plasmodium - a single-celled parasite.
• It's spread from host to host by mosquitoes acting as vectors (organisms that carry a pathogen from one host to another without getting the disease themselves).

How malaria is spread

1. A mosquito feeds on the blood of an infected animal and picks up the protist.
2. When it next bites, it injects the protist into the blood of a new host.

Effects on the body

• Inside the body, the protist destroys red blood cells.
• In serious cases it also damages the liver.
• This causes recurrent episodes of fever, and malaria can be fatal.

Reducing the spread

• Stopping the mosquitoes breeding.
• Killing them with insecticides.
• Stopping them biting people, using mosquito nets and insect repellent.