Giardiasis: Issues for Pregnancy and Breastfeeding

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Giardiasis is a parasitic infection in the gastrointestinal tract caused by a protozoan parasite. This is an organism consisting of a single cell called Giardia, usually a particular species of Giardia called Giardia lamblia, which also is called Giardia duodenalis or Giardia intestinalis. Giardiasis develops in approximately 2 percent of adults in developed countries. It is the most common parasitic disease in the United States that strikes humans. In developing countries, almost 33 percent of people suffer from giardiasis at some point in life. Risk factors that put pregnant women at risk are traveling in a country where giardiasis is common, caring for children, being in contact with someone who has had giardiasis, contact with animals that are infected, such as a dog or cat (even though they typically are infected with a different species of Giardia than usually infects humans), and drinking water that is contaminated with Giardia parasites or Giardia eggs. Often, the infected water is untreated water from lakes or rivers that people drink while hiking or camping.   

If you develop giardiasis, symptoms will include diarrhea, characterized by loose, bad-smelling, greasy stools. Other symptoms that you may experience include flatulence (gas), cramps in your belly, nausea, bloating, fatigue, anorexia (lack of appetite), and loss of weight. All of this can dehydrate you as well. A giardiasis infection can be acute, consisting of symptoms that begin 7 – 14 days after you become infected and lasts roughly 7 to 14 days. On the other hand, you can have chronic giardiasis; this means that the condition persists several months after the infection and the symptoms come and go.

As for diagnosis of giardiasis infection, this involves a clinical pathologist using a microscope to examine a sample of your stool after your doctor orders an “O and P” (ova and parasites) for a stool sample that you need to provide. If the clinical pathologist, or other examiner, finds mature parasites cells and eggs of Giardia, that is enough to make the diagnosis. Tests that use antibodies to reveal Giardia also are conducted in some cases. When analyses of repeated stool samples come out negative but still there is a strong suspicion that you have giardiasis, the next step is to get a sample from the duodenum, the first part of the small intestine, because this is where the concentration of the parasites would be highest in an infected person. The sample can be obtained through a non-invasive technique called the “strong test”, in which you swallow a gelatin capsule that is attached to a string. The capsule end of the string moved through the stomach and into the duodenum as the gelatin dissolves. The string is then pulled out through the mouth, along with contents from the duodenum that have attached to the string. These contents can be examined for Giardia cells and eggs. Also there is a more complicated procedure called endoscopy that can be performed to obtain better duodenal samples, if the simpler tests come out negative.

Although this parasitic infection does not harm the baby directly, if you do become dehydrated, this can reduce the volume of amniotic fluid, slowing fetal growth, and possibly triggering premature labor and delivery. Fortunately, however, there are medications for treating giardiasis. The main drug given is metronidazole, which can be taken during the second and third trimesters, if needed. However, metronidazole must be avoided during the first trimester, since it can harm the embryo and early fetus. On the other hand, a medication called paromomycin is both effective against Giardia and safe throughout the entire pregnancy, because it is not absorbed through the gastrointestinal tract. Since it does not enter the mother’s blood, it also does not get into breast milk, so it is also safe if you are nursing. There have been reports of strains of Giardia resistant to metronidazole and paromomycin. The drugs quinacrine and furazolidone are effective against such strains, but quinacrine and furazolidone are not available in the United States. If you are pregnant with only mild giardiasis symptoms, you may not need any medication. In addition to medication, management of fluids and electrolytes (by fluid and appropriate chemicals intravenously) is a very important component of treatment. You need to drink fluids and, in some cases, intravenous fluids may be needed.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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