A pathogen is a microorganism or another factor that can cause disease.

It is important to note that not all pathogens are microorganisms - for example, viruses are not classified as living organisms but they can still cause disease.

A vector is a living organism that transmits a pathogen from an infected organism to another organism.

1. Bacteria
2. Viruses
3. Fungi
4. Protoctists

Bacteria usually cause damage by producing toxins.

The pathogen responsible for cholera is the bacterium Vibrio cholerae.

It is transmitted via contaminated water and food handled by infected individuals.

Cholera can be prevented and controlled by provision of clean water and vaccination programmes.

The pathogen that causes malaria are the protoctist species Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae.

The pathogens are transmitted via blood through female Anopheles mosquitoes, blood transfusions or from mother to fetus.

The pathogen responsible for causing HIV/AIDs is human immunodeficiency virus (HIV).

It is transmitted through the exchange of bodily fluids (during sexual intercourse, blood transfusions or sharing of needles) or from mother to fetus.

1. Screening blood donations
2. Treating HIV-positive pregnant women
3. Barrier methods of contraception
4. Education programmes

The pathogen that causes tuberculosis is Mycobacterium tuberculosis or Mycobacterium bovis.

It is transmitted by inhaling airborne droplets containing the bacteria, or through contaminated meat and milk.

1. Contact tracing
2. Vaccination
3. Testing cattle
4. Milk pasteurisation

1. Reducing mosquito numbers using insecticides
2. Using mosquito nets and repellents
3. Prophylactic drugs to prevent infection of fetuses

Mosquitoes are considered vectors because they transmit the pathogen (a protist) that causes the disease malaria.