PrepperMed 101: Giardia, The Most Common Water-Borne Infection

We talk a lot here at 3BY about water purification. Really though, are you likely to get cholera if you drink from a creek during a bug-out? Or diptheria, or typhoid, or a bunch of disease you mostly only find in history books? Nope, unless hygiene’s been bad in the area for a long time. Giardia infection, however, is so danged common that even here in nice tame mid-Missouri, I know some kids who came down with it after swimming in our local lake. (Just a touch of irony that their mom is a parisitologist.)

What’s Giardia?

Giardia lamblia is a protistan. That makes it a single-celled organism, similar in size to one of your cells. This protistan lives in the intestines of mammals. Many of the microbes that live in our guts are harmless, but this one provokes diarrhea, gassiness, and other gut malfunctions.

It not only reproduces itself in the gut, but can form cysts. Cysts are basically the hibernating form, much tougher than the active microbe but not able to do anything until it goes active again. Giardia cysts are shed in feces, and when swallowed by a different mammal they can go active once they reach the lower gut.

 

How does one get Giardia?

Drinking water with Giardia cysts is the usual way to get the infection. As I mentioned above, some people have gotten it by swimming in infected waters; but they were very small people and may not have been careful to not drink the water.

The insidious part of it is that it takes very little fecal contamination of water to make it infective. It can be a clear mountain stream, melting off a glacier just half a mile away, but if an infected marmot or raccoon or person pooped by the streamside last week, drinking the water may earn you a Giardia infection.

Giardia occurs in most states too, as the map below shows. Nor is it limited to the United States; Giardia infection is one of the most common parasitic infections worldwide.

In the cyst form, it persists somewhere from months to days, depending on temperature, etc. It lasts better in cool, moist conditions. (5)

How does one *not* get Giardia?

Consistently purifying drinking water is a great protection from Giardia. Yes, there have been cases from more casual contact such as my colleague’s kids, but they are far more rare.

The good news is that being a protist, Giardia is pretty big. Any filter of reasonable quality will remove it. All the other standard water purification methods such as boiling and various chemical treatments do it too. That’s no accident: Giardia is so widespread and common that you could hardly call something a general water purification method if it didn’t catch Giardia.

There’s info on water purification all over 3BY, but here’s a good starting point: https://beansbulletsbandagesandyou.com/2018/07/08/choosing-water-purification-method/

How do you know if someone’s got Giardia?

If a person develops yellow, bad-smelling diarrhea that is frothy (with bubbles) but without blood or mucus probably has Giardia. The diarrhea may be a constant thing or may come and go. The person’s likely to be bloated and gassy too, and the gas will smell and taste like sulfur. (1) Weight loss and lethargy show up after a while, to no one’s surprise.

Here’s where I don’t put in a photo for clarification. You’re welcome.

The most reliably occurring symptoms are abdominal pain and cramping (usually without fever). Since that’s true of most gut disorders, it’s not terribly helpful for diagnosis.

Sometimes people or other animals will have and spread Giardia without showing any symptoms themselves, as well. Their immune systems are controlling it well enough to keep them functioning, but not to eliminate the parasite. Such cases are relevant because of their ability to spread the disease, and because they can develop symptoms at a later time when something else interferes with their immune systems or their gut function.

Fecal smears looking for cysts are effective and pretty easy (if I remember correctly from back in the dark ages when I did this). However, most preppers won’t have the means on hand; and due to fluxes in microbe populations and such, any given smear from an infected organism is only about 70% likely to show positive though, so persistence might be required.

What can you do about it if someone’s got Giardia?

I’m not a physician, so rather than give you medical advice I’ll just pass along information from one of my favorite sources, David Werner’s Where There Is No Doctor. (1)

He suggest metronidazole (trade name Flagyl). If it’s a recent infection, it’s given 3 times a day for 5 days. People over 8 yrs old get 250 mg (1 tablet) per dose; children 3-7 half that; younger children 1/4 of a tablet per dose. It’s not suitable for pregnant women, especially in the first trimester, and breastfeeding women on high doses shouldn’t give their babies their milk for 24 hrs after a dose. 

Giardia infections that have lasted six months or longer should be treated with doses three times as big for 10 days; and quinacrine too, says Dr. Werner. 

Quinacrine (brand name Atabrine) is another option, but not as good because it can cause headaches and vomiting. It’s given as 3 100 mg doses (1 tablet each) per day for a week. Half the dose size for children under 10. If it’s being used for the long-standing infection with the metronidazole, use the same dose but give it for 2-3 weeks.

If you don’t have these … well, the person’s immune system sometimes wins without chemical help against Giardia. Good nutrition will help. (2)

Pets get Giardia too

Many kinds of mammals get Giardia; both suffering symptoms and spreading the microbes. Dogs and cats are at higher risk than people … ever try to stop a dog from taking a lick at a stray puddle when he’s thirsty? Their fondness for sniffing butts doesn’t help, either. Cattle and other food animals also have problems with it, and it can spread very well in their shared water sources. (3)

Symptoms in dogs are very like those in people. Treatment with metronidazole is used for dogs as well as people, and fenbendazole is used in dogs too. (4) Dosage wasn’t specified (you’re supposed to get your vet to do that, which is a great idea when feasible) … if it were my dog, I’d use a dose proportionate to body size, using 250 mg metronidazole per 150 lb patient as the guide.

References

1) Werner, D. 2011. Where There Is No Doctor: A village health care handbook. Hesperian Health Guides, Berkely, CA. Available for download from https://theboatgalley.com/where-there-is-no-doctor-free-download/

2) Ventura, L. L. A., Oliveira, D. R., Viana, J. C., Santos, J. F. G., Caliari, M. V., & Gomes, M. A. (2013). Impact of protein malnutrition on histological parameters of experimentally infected animals with giardia lamblia. Experimental Parasitology, 133(4), 391.

3) Ehsan, M. A., Akter, M., Ahammed, M., Ali, M. A., Ahmed, M. U., Leveck, B., & Claerebout, E. (2017). prevalence and clinical importance of cryptosporidium and giardia in human and animals. Bangladesh Journal of Veterinary Medicine, 14(2), 109. 

4) Ward, E. (n.d.) Giardia in dogs. VCA Animal Hospitals. https://vcahospitals.com/know-your-pet/giardia-in-dogs

5) CDC. 2015. Giardia & Pets. https://www.cdc.gov/parasites/giardia/prevention-control-pets.html