How Do Parasites Become Resistant?

Resistance to the treatments is now widespread across microorganisms. It is then common to hear about bacteria multi-resistant to antibiotics in the news. However, even though it has smaller media coverage, resistance to treatment is also very preoccupying for parasites. As such, it is now a big fear in the medical and scientific communities that the rise of resistance to treatments among microorganisms will have catastrophic consequences in the near future. In fact, it means the many infections that are banal and easily treatable nowadays will become untreatable and maybe fatal in the near future. The situation will then be comparable to the one existing at the beginning of the 20th century before the discovery of antibiotics.

Parasites have developed many ways to counteract the effects of anti-parasitic treatments. The mechanisms of resistance are susceptible to vary depending on the parasite involved. Furthermore, the resistance may be multifactorial, meaning that it is susceptible to include many different mechanisms at the same time. Usually, it involves mutations in their genes, duplication of some genes, or acquisition of new genes from their environment in order to produce more or less of some specific proteins involved in the resistance. Finally, the mechanisms of resistance may be specific to one anti-parasitic drug or be involved in resistance to many different drugs.

One mechanism consists in modifying the surface of the parasite in order to prevent the entrance of the drug inside the parasite. On the other hand, the drug can be able to enter the parasite, but be quickly pumped outside. This situation is not optimal because the drug will still be in the parasites’ environment and susceptible to kill the parasites not able to pump the drug out. For this reason, parasites sometimes sequester the drug inside a vacuole that they keep inside themselves. Consequently, the drug is not able to reach its target and is then ineffective against the parasite.

Some parasites are also able to inactivate the drug in order to render it ineffective. Furthermore, as each drug has a specific target, modification of the target can occur in order to impair the reconnaissance of the target by the drug. An alternative pathway can also be used by the parasite in order to eliminate completely the target. Finally, the target can also be overproduced and be able to complete effectively its specific function even though some targets has been destroyed by the drug.

Another relatively new discovered mechanism used by some parasites consist in putting themselves in a sleeping mode while the drug is present in their environment in order to prevent being killed by it. When the patient stops taking the drug and all traces of it is removed completely from the body, the parasites wake up and resume the infection.

One of the biggest causes of anti-parasitic resistance is the use of suboptimal drug concentrations, which are not enough to get rid efficiently of the parasites. This situation also includes the disruption of the treatment before the end. It is mainly to avoid the development of resistance that doctors insist that we take all the prescribed medication when we are treated for an infectious disease, even if we start feeling better. The occurrence of suboptimal concentrations is common in developing countries where self-medication is widespread because of the great numbers of treatments available over-the-counter and/or on the black market.

In order to counteract the emergence of drug resistance, it is important that patients follow the indication and take the treatment fully until the end, even if they are feeling better. Furthermore, it is now recommended for some infectious diseases to take a combination of drugs rather than only one drug at the time in order to prevent the emergence of resistance to the drugs. Finally, it is now possible to test the microorganisms infecting the patient for resistance in order to prescribe right away the right drug that will be effective. This method is used to avoid changing treatments a few times in order to find an effective one and is then better for the patients.

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