By: Pooja Sharma

In a breakthrough discovery, scientists found out that Giardia – one of the most common cause of gastric diseases mimics the human cell functions in the gut and feed off them. A team of scientists at the University of East Anglia (UEA) has been investigating the secret behind sickening success of Giardia. Science world has been confused with this secret for over 300 years now. Despite the fact that Giardiasis is so widespread, scientists did not know what the pathogen does to a host’s intestine. The confusion mainly garnered attention because symptoms of the infection could vary greatly from severe nausea, dehydration, diarrhea to nothing at all.

The paper was published on 29th of January in the journal Gigascience. Researchers from the Norwich Medical School at the University of East Anglia in England finally lay bare an answer and it certainly looks a lot like microscopic espionage. Giardia parasites release proteins that are able to look and act just like certain human cells. This helps the parasite to stealthily cleave open the intestinal cells and leave them open – a process that exposes the host’s GI tract to bacterial feeding frenzy. Study author Kevin Tyler, senior lecturer at Norwich Medical School was actually surprised by how simple the mechanism was.


Tyler and his colleagues analyzed several Giardia specimens with the help of a mass spectrometer in order to identify the parasite’s protein composition. With the help of roughly 1600 proteins that the researchers saw, 2 of the families made a cut through all the layers of the protective mucus in the human gut.


The first family of proteins that was revealed to have cut through are called proteases. These proteins play an important role in helping the human body to digest the other proteins. When they interact with a cell, they will tend to eat through the cell lining and cause damage. So, they are probably part of the story.

The second family of proteins that was revealed after the experiment was more surprising. There was a large group of proteins that looked more like human protein we call tenascins. These are some of the structural and functional mimics that have evolved in the parasite independently to do some of the same things that our proteins do.

Tenascins play a role in the cellular remodeling crew in the human body. They are a part of human body’s extracellular matrix that is present between the cells to help them bind together and make tissues. When your body needs the cells to remodel the tissue and move around, you need proteins that can unstick them and that’s what tenascins help in: unsticking the cells.

When combined with proteases, these look alike proteins of tenascins can help in making a very powerful one-two punch in the host’s intestinal cells. With the help of protease, these parasites are able to pull the cells of the intestines apart to get what the scientists are calling ‘ready-made meals’ for the parasite. So, they have essentially used these human proteins to keep the flow of nutrients open.

Giardiasis: Is your biome to blame?

Once Giardia enters the body, it colonizes the gut. Any cells that it slices open easily becomes vulnerable to an unpredictable swarm of naturally occurring gut bacteria. This is also known as your microbiome. This swarm will also want to feed on your sugars, lipids and amino acids that are seeping between the cells. Tyler and his team hypothesized during the experiment that this bacterial buffet and not the Giardia itself can lead to the most severe symptoms that are caused by the pathogen.

Tyler also mentioned at the end of the experiment that the majority of the damage from the Giardia infection probably comes from the accompanying bacteria that are included in the environment. They increasingly starts to proliferate on the foodstuffs that are released between the cellular junctions. All the people have a different kind of bacteria in their guts for example some individuals might have more bacteria that can lead to an inflammatory infection while others might have an immune system that can react in more of an inflammatory way. The reason why some people will experience much severe symptoms when they are infected by Giardia.

The researchers at UEA hope that this deeper understanding of the Giardia is able to lead us to more effective treatments. Not only will it help in treatment but would also provide methods for differentiating the most dangerous Giardia strains from the innocuous ones. The studies has also opened gates for research into other common parasites that could be exploiting the same infection strategies as that of the protein mimicker Giardia. The scientists in the experiment most certainly believe that there are other pathogens that might use the same mechanism and Giardia is only the first one they noticed.


Giardia infection affects the intestine and can cause severe diarrhea, abdominal cramps and nausea. The pathogen that causes Giardia is found worldwide especially in the areas of poor sanitation and unsafe water. It is one of the most common waterborne diseases in the US. The parasite is found in streams, lakes and sometimes swimming pools, wells and municipal supplies as well. The infection can spread through food or person to person contact.

The incubation period is around 7-10 days but in some cases the infected person might not show any symptoms and they keep spreading it to others. The treatment of Giardia involves antibiotic medication. Many people get better within a few days but some might suffer from long term intestinal problems.