If we take a closer look at these two statements, they go hand in hand. For example, pathogens are disease-causing organisms that are structurally diverse – these include bacteria, protozoa, fungi and viruses that are not considered living and on the other hand living insects that obtain nutrients at the expense of the host.
Examples of parasites include bacteria, protozoa and fungi. But not all parasites are harmful to their host – for example – Bacteroides thetaiotaomicron lives in the human gut, and provides no known benefits or harm (note the opportunistic pathogens) All pathogens are. However, not all germs cause disease.
What is Pathogen?
Once infected, the microorganisms that cause the disease can be said to be the bacteria. It is important to note that any pathogen is transmitted after infection by another organism, which is usually harmful in nature, and only then can the pathogen in question be said to be a virus.
What is Parasite?
A microorganism that infects other organisms and obtains nutrients etc. from a host that may or may not reduce the fitness of the host may be called a parasite Similar to a pathogen, a parasite must be attached to live within or near another organism.
However, this infection may or may not lead to reduced survival and fitness of the host organism. This, as mentioned earlier, distinguishes pathogens from bacteria in a very early way.
Difference between Pathogen and Parasite?
| Pathogen | Parasite |
| Pathogens usually kill their host through diseases. | Most parasites do not kill their host but do cause some damage. |
| Pathogens typically do not require a host to complete its life cycle. | Parasites will have to depend on their host to complete their life cycle. |
| Pathogenicity is the ability of an organism to infect another organism (host). | Parasitism can be considered as a kind of interaction between two species, where one species is benefitted, and the other is harmed. |
