Giardia Infection

OVERVIEW OF Giardia Infection :

Disease overview:

It is an infection that takes place in the small intestine and it is caused by microscopic parasite called Giardia lamblia. Giardiasis spreads through contact with infected people. The giardiasis can be transmitted from by ingestion of contaminated foods or drinking contaminated water. Pet dogs and cats also frequently contract giardia.


G. lamblia are found in human faeces. These parasite also thrive in contaminated food, water and soil and also they can survive outside the host for longer period of time. Accidentally consuming these parasite might leads to an infection.

The most common way to get giardiasis is to drink water that contain G. lamblia. Contaminated water can be in swimming pools, spas, and bodies of water, such as lakes. Sources of contamination include animal feces, diapers, and agricultural runoff.

Contracting giardiasis from food is less common because heat kills the parasites. Poor hygiene when handling food or eating produce rinsed in contaminated water can allow the parasite to spread.

Giardiasis also spreads through personal contact. For example, unprotected anal sex can pass the infection from one person to another.

Changing a child’s diaper or picking up the parasite while working in a day care center are also common ways to become infected. Children are at high risk for giardiasis because they’re likely to encounter feces when wearing diapers or potty training.

The following includes the risk factor:


The infection is more common among children than in adults. Children are more likely to get the disease as they come in contact with the faeces especially if they wear diapers, toilet training or spend time in a child care center. People who is with small children are also at higher risk of developing the disease.

People without access to safe drinking water:

Giardia infection is present in the areas where adequate sanitation is not present. The person is at higher risk when he/she travels to distant places. The risk is greatest in rural od wilderness areas.

People having anal sex:

 People who have anal sex or oral-anal sex without using a condom or other protection are at increased risk of giardia infection, as well as sexually transmitted infections.


Giardia infection is almost never fatal in industrialized countries. But it can cause lingering symptoms and serious complications, especially in infants and children. The most common complications include:

  • Dehydration. Often a result of severe diarrhea, dehydration occurs when the body doesn't have enough water to carry out its normal functions.
  • Failure to thrive. Chronic diarrhea from giardia infection can lead to malnutrition and harm children's physical and mental development.
  • Lactose intolerance. Many people with giardia infection develop lactose intolerance — the inability to properly digest milk sugar. The problem may persist long after the infection has cleared.


The life cycle of giardia consists of two from that is the cyst form and trophozoite form. The most infectious form is cyst form and once if it gets entered into the host cells, it might gets transferred into the trophozoite form. As the trophozoites continue along the gastrointestinal tract they gets revert back to their  cyst form which is excreted with the faecal matter. Ingestion of only a few of these cyst is needed to generate infection in another host cells.

Infection with Giardia results in decreased expression of brush border enzymes , the shape of the microvillus gets altered , increased intestinal permeability and the programmed cell death of small intestinal epithelial cells occurs. Both trophozoites and cyst are contained within the gastrointestinal tract and they do not invade beyond it. The attachement of trophozoites to the small intestine causes dysfunction of the microvilli and also distrupts the enzyme that break down dissacharides sugar in the intestinte. The group of microorganisms that grows in the intestine may get enlarge in size and due to this further symptoms arises. The alteration of the villi leads to an inability of nutrients and water absorption from the intestine, resulting in diarrhoea which is one of the main symptoms.

The species Giardia intestinalis uses enzymes that break down the protein to attack the villi of the brush border and appears to increase crypt cell proliferation and crypt length of crypt cells existing on the sides of the villi.

In the immunological level, the activated host T- lymphocytes attack those endothelial cells that have been injured in order to remove the cell. This occurs after the damage to the proteins that connects brush border endothelial cells to one another. The result is increase in intestinal permeability. 

There arises programmed cell death by Giardia intestinalis which further damages the intestinal barrier and increases permeability. There is significant upregulation of programmed cell death cascade by the parasite and furthermore also simultaneously downregulation of the anti apoptotic proteins Bcl-2 and upregulation of the proapoptotic protein Bax. Giardia protects its own growth by reducing the formation of the nitric oxide gas by consuming all local arginine which is the amino acid necessary to make the nitric oxide. Arginine starvation is known to be cause of programmed cell death and the local removal is strong apoptotic agent.


Giardiasis spreads through contact with infected people. The giardiasis can be transmitted from by ingestion of contaminated foods or drinking contaminated water. Pet dogs and cats also frequently contract giardia.




diarrhoea or greasy stools

loss of appetite


bloating and abdominal cramps

weight loss

excessive gas


abdominal pain


Stool culture:

Isolation of the organisms and susceptibility profile. The organisms are viewed under microscope and they are investigated.


The endoscope reveals any abnormalities or inflammation occurring in the small intestine due to an infection

Endoscopic biopsy:

In this type of biopsy, the physician uses an endoscope an hollow tube . light emitting structure to down the stomach and tissues are obtained.


The best treatment is with Nitroimidazole, Metronidazole, tinidazole , ornidazole, albendazole

First line therapies: Metronidazole, tinidazole and nitazoxanide.

The following drugs certain type of efficiency: Quinacrine, Bacitracin, Zinc, Paromycin and Mepacrin.

The paromycin is the drug of choice during the pregnancy times since the paromycin absorption in the small intestine is less and hence foetus exposure is reduced.


The vaccination are under developing. They are targeting recombinant proteins DNA vaccine , variant specific proteins, cyst wall proteins and giadins, enzymes.

At present one commercially available vaccine exists called GiardiaVax. But this vaccine is used only for veterinary purposes.


If the person immune system is good then the disease automatically subsides without any treatment.

If the immune system of the person is weaker then he might catches the chronic infection

And sometimes lactose intolerance and other complications might occurs in children



Avoid the foods which is contaminated

Boil drinking water before use

Cook the foods properly

Wash the hands properly before taking meals

Clean and sanitize the surfaces properly

Wash the toys used by the kids properly

Have safer sexual practices

Minimize the contact with the ponds and lakes.


Medicines used in the Treatment :