COVID-19 and intestinal parasites: risk or additional protection?

Parasitic infections of the intestines are usually caused by two types of organisms:

  • Protozoa. These single-celled organisms can live and multiply inside your body. Infections caused by protozoa include giardiasis, an infection you can get from drinking water infected with Giardia protozoa.
  • Helminths. These multicellular organisms, commonly called worms, can live inside or outside your body.

On 3 1/2 billion people in the world are affected by intestinal parasites. People living in developing countries are disproportionately affected.

A recent study found that intestinal parasites can reduce the severity of coronavirus disease 19 (COVID-19). However, other studies have shown that parasitic infections can prevent the immune system from responding effectively to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19.

For scientists, this topic of debate is complex and difficult to study. Much more research is needed to determine how intestinal parasites may affect a person’s immune response to SARS-CoV-2 infection.

In this article, we review what we currently know about how intestinal parasites affect the immune system, SARS-CoV-2 infections, and COVID-19 vaccines. Keep reading to learn more.

When we talk about the effect of intestinal parasites on the human immune system, we often talk about helminths or parasitic worms.

Helminths consist of several cells and are rather large. In fact, they can often be seen with the naked eye. Here are some examples of helminths that can infect humans:

Potential benefits

Simply put, it has been observed that helminths can dampen specific parts of the immune response. Obviously, this is beneficial for the parasite, as it means the immune system is less likely to attack and kill it.

However, it may also have a beneficial effect on humans. This dampened immune response can help protect a person against things like allergies, autoimmune diseases, and certain inflammatory diseases.

In fact, a decrease in helminth infections has been proposed as a contributing factor to the increase in allergic and inflammatory diseases in developed countries. This is called the “hygiene hypothesis”.

Potential disadvantages

Despite the potential immune benefits of helminths, there are also some big downsides. Helminths can cause serious damage to the human host. As they grow, they can cause blockages in internal organs such as the intestines or bile ducts.

A 2017 study also found that helminth infection can increase the risk of cancer.

In addition to causing serious diseases themselves, helminths can aggravate certain infectious diseases. And they can decrease the effectiveness of vaccines.

In severe cases of COVID-19, high levels of inflammation may be present in the body. This is called “cytokine storm” and can lead to serious complications such as acute respiratory distress syndrome (ARDS).

Could the moderating effects of intestinal parasites on the immune system help protect against these high levels of inflammation?

Although there is some evidence that intestinal parasites may be associated with reduced severity of COVID-19, there is also evidence that intestinal parasites may impair the immune system’s ability to ward off SARS-CoV infection. -2. At the end of the line : more research still needs to be done.

Research showing that parasites can reduce the severity of COVID-19

A study 2021 was conducted in Ethiopia from July 2020 to March 2021. A total of 751 people with laboratory confirmed COVID-19 were included in the study.

Of 751 people, 284 (37 4/5 percent) also had a parasitic infection. Regarding the severity of COVID-19, only 10 3/5% of people with severe COVID-19 had a parasitic infection. Moreover, none of these people died from COVID-19.

The researchers suggest that the higher prevalence of intestinal parasites in developing regions of the world, particularly in Africa, may contribute to the lower prevalence and severity of COVID-19 in these regions.

However, the study has some limitations, including:

  • a small number of participants
  • potential bias

Conflicting views and research

A 2022 letter expresses skepticism of the above findings. In it, the authors express concerns about potential study bias, as participants were first tested for SARS-CoV-2 before being tested for intestinal parasites.

Additionally, a 2020 review notes that parasitic infections, particularly with helminths, have already been shown to increase the severity of other infectious conditions, such as HIV, tuberculosis and malaria.

As such, the reviewer notes that it is possible that a parasitic infection could potentially prevent the immune system from responding effectively to COVID-19. It can actually increase the severity of the disease in some cases.

Vaccination is the most effective way to protect against serious illness and death from COVID-19. However, to be effective, vaccines must initiate an immune response. Could the immune effects of intestinal parasites affect this?

There is in fact evidence that parasitic infections can decrease the effectiveness of vaccines. However, no research has specifically evaluated the effect of parasites on COVID-19 vaccines.

Research studies show parasites lead to poorer vaccine outcomes

A 2020 review of studies sought to dig deeper into the topic of parasites and vaccines. A total of 50 articles were analyzed. The researchers note that several parasite- and vaccine-related factors can affect vaccination, such as:

  • specific type and stage of parasite infection
  • the time of infection, for example whether it is acute or chronic
  • type of vaccine and mode of administration
  • type of immune response the vaccine aims to generate

After the analysis was completed, it was found that having a parasitic infection at the time of receiving a vaccine resulted in a poorer vaccine outcome. Chronic helminth infections are more likely to negatively affect the effectiveness of vaccination.

You may have a few more questions about intestinal parasites. Let’s answer some of them now.

How do you catch intestinal parasites?

Often the eggs of an intestinal parasite pass in a person’s stool. You can catch an intestinal parasite if you ingest these eggs.

This can happen by coming into contact with fecal particles in the environment, especially soil, and then touching your mouth without washing your hands first. Consumption of contaminated food and water can also spread these parasites.

Certain types of intestinal parasites, such as Strongyloides species, are transmitted through the soil. In this case, contact with contaminated soil allows the larvae of this parasite to burrow into your skin and travel to your intestines.

What are the symptoms of an intestinal parasitic infection?

The exact symptoms of an intestinal parasite infection can vary depending on the specific parasite. Some people may not even have any significant symptoms. When symptoms are present, some to watch out for include:

What happens if an intestinal parasitic infection is not treated?

If you suspect you have an intestinal parasitic infection, it is important to see a doctor for diagnosis and treatment. When an intestinal parasitic infection is left untreated, it can lead to complications such as:

Does an intestinal parasitic co-infection affect the treatment of COVID-19?

At this time, the effect a parasitic infection may have on COVID-19 treatments is unclear. Research on the interaction between intestinal parasites and COVID-19 is still in its infancy.

Intestinal parasites can dampen certain aspects of the immune response to avoid being attacked by the immune system. This effect can protect against certain diseases but can also aggravate others.

There is evidence that intestinal parasites can reduce the severity of COVID-19. However, these data come from a single study and further research on this topic needs to be done.

If left untreated, intestinal parasitic infections can lead to complications. See a doctor if you have symptoms such as severe abdominal pain, diarrhea, or nausea and vomiting. They can help you find out what may be causing your symptoms.

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