The term agent can be used in different ways. In this opportunity, we are interested in staying with its meaning as that which has the capacity to act or produce something. Pathogen, on the other hand, is an adjective that qualifies what causes a disease (a variation of the state of health).
It is interesting to know the etymological origin of the two words that give meaning to the term that concerns us now:
-Agent derives from Latin, specifically from “agentis”, which can be translated as “he who takes action”. It is the fruit of the sum of two different elements: the verb “agere”, which is equivalent to “act”, and the suffix “-nte”, which is used to determine the one who performs the action.
-Patogen, on the other hand, has Greek roots and means “that produces disease.” This word is made up of two clear parts: the noun “pathos”, which is synonymous with “disease”, and “geno”, which is equivalent to “produce” or “generate”.
According to Digopaul, the notion of pathogen refers to an element that can cause an organic disease or disorder in a host. It should be noted that the organism that carries or houses another organism is called a host.
Therefore, the pathogen stays in a host and causes some kind of damage. A virus, bacteria, or fungus can act as pathogens through different infectious mechanisms. The hosts can be humans, animals, or plants.
Protozoan Toxoplasma gondii, for example, is a pathogen that can stay in a cat and cause toxoplasmosis, a disease that is spread to people. In this case, the cat becomes a host for the pathogen Toxoplasma gondii and causes the contagious disease called toxoplasmosis. Once the cat acquires toxoplasmosis, it can defecate and transmit the parasite to people.
Another example of a pathogen is Corynebacterium diphtheriae, a bacillus-type bacterium that is found in humans and causes diphtheria. This disease causes the development of false membranes in the throat, nose and skin, causing pain, increased temperature and injuries of different kinds. There is a vaccine that prevents diphtheria infection.
That without forgetting another example such as the bacterium Clostridium tetani, which is what is considered responsible for tetanus. Its way of acting is to “enter” the body through a wound and then, once inside, release a toxin.
In the same way, we cannot ignore that nematodes are also considered to be pathogens. In your case, they are responsible for causing different diseases in what are plants.
These are small worm-shaped, they feed, as a rule, delving into what are the roots of the aforementioned plants and once there “devour” what is the cellular content. To counteract them, there are currently numerous insecticides and similar chemicals, which are in charge of preventing these living beings from ending up dying or suffering serious damage due to these pathogens.