Parasites: 'You' or 'enemies' of humans?

We have been thinking for a long time, parasites that cause illness even cause people to die. However, recent experiments show the opposite: some parasites can evolve to protect "clients" from deadly diseases.

There is nothing wrong with saying the parasite is harmful to the host. They cause disease even death, so we often try to avoid parasitic infection at all costs. But some parasites - although still potentially harmful in isolated environments, actually help hosts deal with many deadly infections .

Evolution to protect host

Knowing when parasites become beneficial is very important for controlling infectious diseases. But for now we have very little knowledge about this issue.

New research by scientists published in Evolution Letters, has shown that parasites can easily develop different mechanisms to protect the host from infections. This suggests that parasites protecting hosts are quite common in nature.

The idea of "the enemy of the enemy is you" has existed for a long time in human society, and is used to describe human conflicts. However, in the natural world, this is very common, for example, harmful parasites in some conditions can become useful in other conditions.

The bacteria that live in the gut sometimes cause problems, but they also prevent the invasion of more harmful bacteria such as Salmonella enterica - the bacteria that causes food poisoning.

Similarly, some bacteria that are infected by insects are very harmful but they can provide protection against deadly infections.

Parasites are protecting us.(Photo: Shutterstock).

Parasites can also help their "owners" in many different ways , including causing more serious diseases for other species. This is one of the main reasons that gray squirrels quickly replace red squirrels on most parts of England.

Gray squirrels often carry smallpox virus from their squirrels - they kill red squirrels, but for gray squirrels, they are completely harmless. Similarly, some species of bacteria also "fought" with primitive biological weapons, by bringing the virus to 'fight' with other non-immune bacteria.

These examples show that being infected is not necessarily a bad thing and it is sometimes beneficial. But we don't know how and when parasites become useful with the host body?

Recent experiments show that less harmful bacteria that live inside worms can evolve within a few days to protect the host from lethal infections. This shows that bacteria can quickly evolve to protect "client" against other infectious diseases.

However, in nature how this evolution takes place, no one knows. And if a parasite evolves to protect the host from a more deadly disease, is the enemy now a friend?

From enemies to you

Using mathematical models, scientists discover this evolution consists of two forms of protection: resistance and endurance.

The parasites perform protection by creating resistance to the host. This will help the host reduce the likelihood of being infected by a second species, such as when bacteria in the gut prevent the invasion of other bacteria.

On the other hand, when another species transmits the disease to the host, there are parasites that create endurance for the host - this will reduce the damage of the host's disease. For example, the case of protozoa protects the butterfly butterfly larva from parasitic flies.

Scientists have discovered that both forms of host protection are evolved in a variety of conditions, even when the parasite must transform 'resources' to develop or reproduce to protect host

Gut bacteria sometimes benefit the body.(Photo: Internet).

This protection process will continue to evolve because the price to pay for this protection will be offset. The survival rate of the host is increasing and the parasite is also protected.

But there are some notable differences between the two forms of protection. For example, resistance is often beneficial to the host, but stamina can cause negative effects because it makes the host more ill. These differences indicate that it is very important to determine which protection mechanisms the parasite is using and is it really beneficial?

We can combine mathematical models with laboratory experiments on the evolution of bacteria to answer the question: how have species evolved to protect the host? Will the host evolve to protect the parasite and how can we develop a symbiotic relationship with some bacteria in the gut?

Answering these questions can help us find new ways to treat infectious diseases. In any case, the new research results of scientists have shed light on an interesting biological phenomenon that we have not known for a long time.