Pathogens are organisms organisms: living entities-ie animals, plants or microorganisms. that cause disease. They include microorganisms such as bacteria, viruses, fungi and protozoa.ood contaminated with protozoa can cause infections such as amoebic dysentery, of which severe diarrhoea is a symptom. Some protozoa are parasites. These organisms live on, or inside, another organism and cause it harm. Malaria is a disease caused by protozoa that live in the blood.
In most cases, erectile dysfunction is caused by something physical. Common causes include: 1  Heart disease. 2  Clogged blood vessels (atherosclerosis). 3  High cholesterol. 4  High blood pressure. 5  Diabetes.
1 Psychological conditions, such as stress, anxiety or depression. 2  Drug and alcohol use, especially if you're a long-term drug user or heavy drinker. 3  Prolonged bicycling, which can compress nerves and affect blood flow to the penis, may lead to temporary or permanent erectile dysfunction. 4  Causes.