Why Do Parasites Not Kill Their Hosts Immediately?

By Antonia Čirjak on June 2 2020 in Did You Know

  • Parasites come in contact with practically every species on this planet, which makes them so dangerous when it comes to the transmission of dangerous and deadly pathogens.
  • Many parasites have been successfully cooperating with their hosts for thousands of years, like the ones we have inside our intestines.
  • Malaria is a deadly parasitic disease spread by mosquitoes.

From a biological perspective, there is nothing wrong with parasitism as a lifestyle. Yet, there are so many negative connotations associated with this term. Parasites, because they depend on another organism to stay alive, sometimes cause harm to the host organism. However, there is more about this deadly relationship than its possible outcome aims to suggest.

Welcome To Parasit-Ville!

You might be surprised that parasitism is a frequent choice of lifestyle for nearly half of all the animal and plant species that exist on this planet. This means that, at some point in their lives, close to 50% of those species end up in a parasitic relationship. Interdependence is one thing, and everyone is in one way or another connected to the environment they inhabit, but this type of symbiosis commonly does not last too long. However, some of them last for a lifetime, and human bodies are a popular place to visit among the parasitic community. There are more than 340 different species of parasites inside our bodies, and most of them are in our intestinal system. 

Although things can sometimes go south in the parasitic relationship you are not even aware of, those parasites have no intention of killing us. From an evolutionary perspective, that would be just plain stupid from them to do. They are with us until the very end, and (pardon for the dark twist to this tale) beyond. Some types of parasitic fungi continue to feed on their hosts even after the body dies. Remember, in the cycle of life, everything is recycled as far as it can go, and fungi are a prime example of this type of post-mortem feeding habits.  

Back to the title at hand, why do some parasites not kill the host immediately, or they delay the process as much as possible?

Parasites As A Defensive Mechanism

Believe it or not, some of them protect us more than they do harm. For example, the parasitic bacteria that live inside our gut prevent more serious enemies from entering our system. Salmonella Enterica is one of those dangerous bacteria that we get from food poisoning, and the parasites that are already inside us sometimes fight that and help us defeat the disease. In a parasitic relationship, the parasites are many, but the host is only one, so it is the most important thing to protect. There can be only one! Or a few hundred, but who is counting anymore? 

However, this is just a rare occurrence we can brag about when they ask us if we can keep a steady relationship. Parasites are a problem for all species on this planet, and generally, everyone tries to avoid coming in contact with them. It is harder said than done, though, as all the different parasitic tapeworms, barnacles, fleas, and bacteria do serious damage to the host organism. Malaria is a parasitic type of disease, and it kills hundreds of thousands of people every year. Although we evolved together with different parasites, most of them are dangerous and live up to such a bad name. 

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