All About Giardiasis

Share Button

Recently, I wrote about a relatively unusual medical issue for developed countries: parasitic worms. Problems related to poor hygiene and sanitation, chronic issues in many countries, cause parasites to reach epidemic status.

There are other types of parasites, however, that are more common in local water sources than worms, and they can have dire consequences. One of these is Giardia, a family of parasites that is found in just about every region on Earth. The most common species to affect North America is Giardia lamblia, sometimes called Giardia intestinalis.

A parasite feeds off another organism to survive, and Giardia prefers mammals, including humans. Giardia is a hardy bug, though, and can live for long periods of time in moist soil or water. Infection, known as “giardiasis”, occurs as a result of ingestion of food or water contaminated with feces. Once a person or animal becomes infected with Giardia, it inhabits the intestines and is passed in excrement.

The most common cause of giardia transmission occurs from person to person. Poorly prepared food, unsterile water, and improper bathroom hygiene accounts for the majority of cases. Despite this, the clearest streams in the Colorado backcountry may be contaminated by Giardia, causing it to be an issue for wilderness hikers who don’t pay strict attention to water disinfection and frequent hand-washing.

Mothers and child care workers who fail to adhere to strict hand washing while changing diapers of infected babies are also at risk.


The symptoms of Giardia don’t often appear immediately. They can begin as early as 2 days after infection. As an intestinal infection, you can expect to see significant watery diarrhea interspersed with soft, greasy stools. Other symptoms include:

  • bloating
  • excessive gas
  • abdominal cramps
  • upset stomach
  • nausea
  • weight loss
  • fatigue

You might not consider the above all that severe, but in many cases, the symptoms last for weeks and may lead to severe dehydration, a common cause of otherwise-avoidable deaths in earlier times, and a serious issue today anywhere advanced care isn’t available. Children are especially prone to malnutrition and, if chronic, may experience stunted growth and development.


Severe symptoms can be treated with hydration and antibiotics like Metronidazole (aquarium equivalent: Fish-Zole) or anti-worm drugs (also known as “anti-helminthics”) like Albendazole.

Many less severe giardia infections may resolve without treatment after a few weeks. It’s thought, however, that some people may develop a “carrier” relationship with giardia; symptoms become less noticeable with time, but the carrier can transmit the infection to others (even sexually through oral-fecal routes).


There is no medication or vaccine that will prevent Giardia infection. There are, however, a number of precautions that will minimize your risk of infection:

  • Wash your hands. Hand washing after going to the bathroom, changing diapers, and before/after the preparation of food. Use alcohol-based sanitizers if soap and water aren’t available.
  • Disinfect questionable water. Avoid drinking untreated water from lakes, rivers, creeks, and springs unless you filter it with products like the Lifestraw, Mini-Sawyer, or Berkey.  Alternatively, bring water to an active boil for 1-5 minutes first. Add 1 minute for every 1000 feet of elevation (water boils at lower temperatures higher up). It should be noted Giardia is relatively resistant to bleach, a commonly-used water disinfectant.
  • Travel concerns: Use bottled water wherever water is of dubious quality, even for brushing teeth. Avoid putting ice made from local water in drinks. When swimming, keep your mouth closed.
  • Wash food before you eat it. Wash raw fruits  and vegetables before adding them to your meals.
  • Practice safe sex. Sexual intercourse, especially anal sex, can transmit Giardia. Avoid this method or use a barrier like a condom.

The smallest organisms can cause major medical issues in good times or bad. Pay careful attention to sanitation and hygiene, and you’ll keep it together at home, on that wilderness hike, or abroad.

Joe Alton, MD


(Thanks to Dr. Pam Hendrix for suggesting this topic for an article)

Find out more about giardiasis and many other survival-related medical issues in our brand new 700 page Third Edition of
The Survival Medicine Handbook: The Essential Guide for when Medical Help is Not on the Way, available at Amazon or on this website.

Hey, don’t forget to check out our entire line of quality medical kits and individual supplies at Also, our Book Excellence Award-winning 700-page SURVIVAL MEDICINE HANDBOOK: THE ESSENTIAL GUIDE FOR WHEN HELP IS NOT ON THE WAY is now available in black and white on Amazon and in color and color spiral-bound versions at

Share Button
Print Friendly, PDF & Email
The Future of Fish Antibiotics in Survival?
Parasitic Worms