Explanation:

- Plague is caused by the bacterium *Yersinia pestis*. It is not caused by a parasite.

- Pneumonia is an infection of the lungs that can be caused by bacteria, viruses, or fungi, but not by parasites.

- Goitre is a condition characterized by the enlargement of the thyroid gland, often due to iodine deficiency, not related to parasites.

- Malaria is an infectious disease caused by Plasmodium parasites, transmitted through the bite of infected Anopheles mosquitoes.