Theory question 103
Microorganisms and Health(a) Complete the table below:
Disease | Causative organism | Vector | Control
Cholera | | |
| Trypanosome | |
| | Female Anopheles mosquito |
Ringworm | | None |
(b) Explain briefly the biological basis of preserving foods using each of the following methods: (i) salting; (ii) irradiation; (iii) smoking.
Show the model answer
(a) Cholera – causative organism: Vibrio cholerae (bacterium); vector: none (spread by contaminated water/food, houseflies can carry it); control: boil or treat drinking water, good sanitation, wash hands, cover food, vaccination.
Sleeping sickness (trypanosomiasis) – Trypanosoma; vector: tsetse fly; control: clear bushes where tsetse flies breed, use insecticides and traps, treat patients.
Malaria – Plasmodium; vector: female Anopheles mosquito; control: sleep under treated nets, clear stagnant water and bushes, spray insecticides, take antimalarial drugs.
Ringworm – a fungus (e.g. Tinea/Trichophyton); vector: none (spread by contact and shared items); control: personal hygiene, avoid sharing combs, towels and clothes, antifungal creams.
(b)(i) Salting: salt draws water out of the food and out of microorganisms by osmosis; without water, bacteria and fungi cannot grow, so the food does not rot.
(ii) Irradiation: exposing food to radiation (e.g. gamma rays) kills microorganisms and insects in it, and slows ripening or sprouting.
(iii) Smoking: heat dries the food (removes water) and the chemicals in smoke kill or stop the growth of microorganisms.
In the table fill each blank cell; give the scientific name of each organism.