What is it
Giardiasis is an infection with the protozoa Giardia lamblia (also known as Giardia intestinalis and Giardia duodenalis). The infection typically occurs in the upper part of the small intestine (known as the duodenum).
Giardia can infect people as well as other mammals. People typically become infected by ingesting water or food contaminated with feces from an infected person or animal which contain the infective cysts (a cyst is sort of like an egg). Once these infective cysts enter a person’s duodenum, they “hatch” so to speak and the live organism, known as a trophozoite, emerges. It is this trophozoite that causes symptoms and that also produces more cysts that can be passed in the stool and potentially infect others. Although both trophozoites and cysts are passed in the stool, it is only the cysts that are infective. If you hit the thumbnail image below, it’ll open a window with a diagram of the life-cycle of this critter.
The live organism typically does not live for very long once outside of the body, and even if live ones are ingested, they will be killed by stomach acid. Although contaminated food and water is the most common way infective cysts get ingested, it can also occur through close person-to-person contact via poor hygiene, changing babies diapers, particular sexual practices that involve fecal exposure (I’ll avoid a detailed description here folks…Use your imagination), etc. About half of people who become infected will not exhibit much if any symptoms. They can be carriers and unwittingly infect others.
Although trophozoites can’t live long outside the body, under proper cool, moist conditions, the cysts can remain infective for weeks or months.
Although anyone can potentially become infected, outbreaks are commonly seen in children’s daycare centers, mental institutions, and in individual households. Community water supplies can become contaminated and there have been some fairly large outbreaks in Australia and Norway in recent years..
Giardiasis is more common in folks traveling outside the U.S., campers and hikers who drink from ponds and streams, male homosexuals, and people with impaired immune systems. People who swim or bathe or drink from beaver ponds are particularly at risk and thus this infection is sometimes referred to as “Beaver Fever.”
Of interest, giardia was first observed under a microscope in 1681 by Antonie Philips van Leeuwenhoek while looking at his own diarrhea. Giardia was named for Professor Alfred Giard, a Frenchman, in 1915
What are the Symptoms and Signs?
As mentioned, a lot of folks never really show many signs of infection, but simply become carriers and/or eventually their body manages to fight the infection off.
Giardia infection mostly causes inflammation and damage to the small intestinal lining.
The most common signs include diarrhea, weight loss and weakness. The typical incubation period for infection is 1-3 weeks. Symptoms may come on suddenly or gradually. The acute phase usually only lasts for a few days to a few weeks, though people may continue to pass cysts for quite some time. In some people, it may become a chronic infection lasting for years.
The diarrhea can range from mild to severe. The diarrhea may become very watery and greasy and have a very foul smell. There is typically no blood or pus. The diarrhea may also be intermittent, coming and going, with normal stools or even constipation between bouts of diarrhea.
Less frequently, patients may experience nausea and vomiting, abdominal pain and cramps, increased belching (with a sulfur-like smell which is sometimes described as so foul tasting that it causes vomiting), gas-passing, stomach growling, and abdominal distension (bloat). Young children and infants may have less than normal growth and development. Some folks may also have specific nutritional deficiencies due to poor absorption. Also, some people will develop a loss of interest in food altogether.
Also, there seems to be a rare association between giardiasis and joint, eye, and skin problems, but we aren’t sure exactly why that occurs.
How is it diagnosed?
Typically, it is diagnosed by looking for evidence of the infection in a stool sample. When I was in practice as a veterinarian, I used to see this infection quite a bit in small animals, but it could be quite tough to diagnose. It basically involved examining a stool sample under a microscope and looking for the cysts and trophozoites. They can be very tough to spot. The trophozoites typically will die rather quickly making them harder to find as they quit moving. Also, patients (both human and animal) will often have a great amount of variability in the amount of cysts and trophozoites being passed in the stool. Often a person may have symptoms for a week or more before ever passing any. It is not at all unusual for diagnosis to require obtaining multiple stool samples.
There are also other tests available including what are known as Antigen Assays. Without going into too much technical mumbo-jumbo, these are basically chemistry tests that detect the presence of the organism in the stool. There are also some other diagnostic procedures that involve various methods of collecting samples and biopsies directly from the duodenum.
There is typically no value in using x-rays to make this diagnosis. Blood cell counts are typically unremarkable. There are some tests for antibodies in the blood that are of questionable clinical value.
How is it treated?
I used to typically treat this in animals with a medicine called Metronidazole (it’s brand name is Flagyl), and this medicine is frequently used in humans as well. It is not specifically approved for this use in humans by the FDA, but is frequently used in what’s known as an “Off-Label” fashion. Depending on the research study you look at, this medicine may have a fairly high rate of failure in treatment of giardiasis. For what it’s worth, I had a great deal of success in using it in veterinary patients. I have so far, not diagnosed a case of giardiasis in a human, but if I did, this would probably be the medicine I’d reach for first.
Like any medication, this one can have side effects. The one of most concern in most folks is what’s known as a disulfarim-like reaction. Basically, this means that if you take this medicine and drink any alcohol (even a little itsy-bitsy-bit) it can make you absolutely miserably sick. I’ve even heard of cases where patients got sick while on this medicine from simply having alcohol in their skin from underarm deodorant. So, if you are ever prescribed this medicine (for Giardia, or anything else) AVOID ALCOHOL.
A medicine in the same pharmaceutical class as Metronidazole has become available relatively recently in the U.S. It is called Tinidazole. I have no personal experience with this medication, but reports I’ve read seem to indicate a higher rate of treatment success than with Metronidazole.
Other medicines that are sometimes used include Furazolidone, Quinacrine, Albendazole and Paromomycin. I have never personally used any of these medications to treat giardiasis.
What’s the prognosis?
Fortunately, treatment is typically successful and leaves no long term problems. Left untreated, giardiasis can rarely turn into a chronic infection and has been known to lead to chronic nutritional malabsorption that can contribute to death from other causes.
How can it be prevented?
The easiest and most obvious answer is to avoid ingesting the infective cysts.
This is best accomplished through strict hygiene. Obviously, people caring for children, changing diapers, etc., must practice good hand-washing habits and proper diaper disposal. People engaging in the aforementioned unusual sexual practices should perhaps do a little cost/benefit analysis and maybe consider other ways to express their feelings for one another.
If traveling in areas without reliably clean water supplies such as in the wilderness or in less developed countries, water should either be boiled for at least a minute or filtered with a filter that has a pore size of 1 micrometer or less (That’s really small folks…for the cheapskates, I’m sorry but a coffee filter just won’t cut it.). Such filters can be obtained relatively cheaply from camping and hiking suppliers. You can also try chemical disinfection with chlorine or iodine, but this may not be as reliable due to variables such as water pH, temperature, and cloudiness.
Don’t eat food that might be contaminated with feces either. Wash and or peel all fruits and vegetable before eating. It should go without saying that you need to use safe uncontaminated water to do this. Also, avoid eating raw uncooked food if traveling in areas where the local water supply is likely to not be adequately protected from contamination such as undeveloped countries, etc.
It can be killed with ozone and with chlorine, but the concentrations of chlorine normally used to sanitize community water systems is actually too low to effectively kill cysts. If you get your water from a well, it can be tested for Giardia, but this requires passing a very large amount (thousands of gallons) of water through special filters and can be quite expensive. Therefore such testing is usually not done unless there is already a suspicion of such contamination.
