Giardiasis

What is Giardiasis?

Giardiasis is an infection in your intestines caused by a tiny organism called Giardia duodenalis. This is particularly common in areas where access to clean water and sanitation are limited. Symptoms often include passing gas and having watery diarrhea. The tiny organism, known as a protozoan, which causes this infection, is the most common intestinal parasite found in the United States and the most frequent protozoan intestinal parasite around the world. The infection is more common in children than adults.

People who travel internationally, enjoy outdoor activities, and daycare workers in the United States are most at risk for this disease. Although some people might not show symptoms, others can experience severe symptoms that can lead to dehydration and weight loss. Thankfully, treatment with specific medications, namely nitroimidazole or medicines that kill parasitic worms, can be very effective and often results in rapid recovery.

The protozoan Giardia duodenalis can lead to a harmless state called colonization, wherein the organism lives in our digestive tract without causing a disease, or can cause diarrhea ranging from a sudden, short-term condition to a long-term persistent illness. Research has found this organism in up to 80% of water from lakes, ponds, and streams, and in about 15% of filtered water samples. In developing countries, this parasite commonly causes chronic, long-term diarrhea and hampers growth in children. People with weakened immune systems, individuals who travel to regions where the infection is widespread, and certain men who have sex with men are at high risk and often show symptoms.

What Causes Giardiasis?

Giardiasis is a disease caused by a microscopic parasite called “G duodenalis.” This parasite, also known by other names such as G lamblia and G intestinalis, is spread by infected animals. These animals pass the parasite’s eggs, called cysts, into freshwater sources like rivers and lakes. These cysts can survive and remain infectious for weeks or even months.

The parasite has seven different varieties or “assemblages,” labeled A through F. However, only A and B have been found to cause infections in humans.

People often get infected by drinking water contaminated with these cysts. Direct contact with an infected person, for instance, through poor hand hygiene, can also transmit the disease. Daycare centers have become significant sources of giardiasis infections because of insufficient handwashing practices, particularly when changing diapers.

Once ingested, these cysts break open, releasing active forms of the parasite called “trophozoites” within our intestine. Trophozoites are pear-shaped and move around using whip-like structures called flagella. They also have two nuclei, or control centers.

Risk Factors and Frequency for Giardiasis

Giardiasis is the most common type of intestinal parasite infection worldwide. It affects around 2% of adults and 8% of children in developed countries, whereas in developing countries, it affects 33% of people. This disease is found both in temperate and tropical regions, showing varied rates of prevalence from 4% to 42%. In developed countries, typically, it ranges from 2% to 5%. It’s a leading cause of diarrheal outbreaks among children in developing countries, with 15% to 20% of children under 10 years infected.

In the United States, an estimated 1.2 million people have giardiasis. However, many do not know they have it, as they may not show any symptoms. According to the Centers for Disease Control and Prevention, there were 15,223 reported cases in 2012. The most affected group included children aged 0 to 4 years, with the majority of cases from the northwestern US. The disease is most common during late summer and early fall, which is when outdoor water activities increase.

• Giardiasis is transmitted mainly by eating or drinking contaminated food or water.
• The infection can also be spread from person to person.
• Animal-to-person transmission is less common.
• An infected individual could release 1 million to 1 billion infectious forms of the protozoa (cysts) into the environment every day, though as few as 10 cysts could cause infection.
• People without symptoms can carry the disease and spread it to others.
• In the United States, high-risk groups include international travelers, outdoor enthusiasts, childcare workers, some men who have sex with men, and professionals dealing with human waste.

Signs and Symptoms of Giardiasis

Giardiasis is an infection where nearly half of the people infected do not show any symptoms. Those who do experience symptoms typically start to feel them 1 to 2 weeks after getting infected. Usual symptoms may include:

• Stomach pain
• Nausea
• Frequent passing of gas
• Large amount of watery and smelly feces

Kids with this infection may feel stomach pain with little diarrhea. Because of the frequent loose stools, people with giardiasis might get dehydrated. Some folks may also have a fever. In rare situations, the infection can cause skin lesions and joint pain. Usually, these symptoms go away on their own within a month. However, if the infection becomes chronic, it might lead to weight loss or even vitamin deficiency.

The seriousness of the symptoms can depend on the strength of the parasite, the amount of it, and how the body’s immune system responds. Most people with giardiasis have diarrhea. Some individuals also experience tummy cramps, frequent passing of gas, and a bloated feeling. Chronic giardiasis might lead to continuous diarrhea, weight loss, nausea, fatigue, and loss of appetite. Some people may also experience a decrease in lactase, an enzyme that digests lactose, after the infection.

Manifestations outside the intestinal tract are rare but do occur, such as allergic reactions and diseases affecting the bile ducts. These symptoms are likely due to the activation of the body’s immune system.

Healthcare professionals are advised by the CDC to consider giardiasis as a possible cause of diarrhea persisting for more than 3 days. They should ask patients about any possible risk factors, such as recent travel abroad or to wilderness areas, exposure to unsanitary water, working in a daycare setting, and certain sexual practices. Women who can have children should also be checked for pregnancy, as this can affect treatment options.

When doing a physical check-up, doctors usually don’t find anything unusual. However, mild dehydration is commonly spotted. Fever is rare, but possible. On touch, there might be slight tenderness. Doctors might also hear abnormal sounds in the abdomen, and they may also check for any skin abnormalities such as hives. Additionally, a rectal examination should reveal normal stools. In severe cases, signs of dehydration or wasting (undue weight loss) might be observed.

Testing for Giardiasis

Traditionally, doctors diagnosed giardiasis, a type of parasitic infection, by identifying Giardia organisms in stool samples. Nowadays, more advanced techniques like nucleic acid amplification techniques (NAATs), which identify the genetic material of the parasite, are widely used. Stool antigen tests, which find proteins produced by the parasite, are also available. These tests are especially useful in situations where many people are at risk of infection, such as during an outbreak or in daycare centers. However, they should not replace traditional stool tests. These advanced tests are typically faster, more sensitive, and more specific than traditional microscopy. Detecting Giardia through traditional stool tests can be challenging as the parasites are not always present. The success rate of these tests can be improved by collecting 3 stool samples on different days.

PCR (Polymerase Chain Reaction) techniques are another way to identify Giardia in stool samples. They are so sensitive that they can find even very small amounts of the parasite. PCR may also help test water supplies for the presence of the parasite. Real-time PCR is effective in detecting both mild and symptom-free infections.

As standard laboratory tests for eggs and parasites may not routinely include Giardia testing, the CDC advises healthcare providers to specifically ask for Giardia testing when sending stool samples. Additionally, even if advanced tests are obtained, traditional stool tests should be performed when diagnosing giardiasis because other parasitic diseases could be causing the symptoms.

When it comes to routine laboratory tests, like complete blood count and electrolyte levels, the results are usually normal in cases of giardiasis. Finding an increased number of a specific type of white blood cell called eosinophils is infrequent.

If a patient is suspected to have giardiasis but the diagnosis is not confirmed after the stool microscopy and the antigen test, an procedure called an esophagogastroduodenoscopy (EGD) could be considered. This is also helpful for patients who continue to have difficulties absorbing nutrients despite treatment. A biopsy collected during an EGD can provide a visual picture of what’s happening in the body, such as if the surface has become flattened with mild white blood cell infiltration and the presence of Giardia organisms.

Treatment Options for Giardiasis

If you have giardiasis, a disease caused by a microscopic parasite, you’ll feel very sick but shouldn’t be overly worried. In many cases, you can regain your strength by drinking lots of fluids. However, if the disease is severe, you might require fluids to be given through your veins.

The most common treatment for giardiasis is antibiotic therapy and the preferred choice is a drug called metronidazole. However, it’s important to remember that this drug might not work for everyone, especially for those who won’t or can’t take the medicine as directed. There has also been an increase in the number of cases where the infection doesn’t respond to this type of treatment, especially in people who have traveled to India and other Asian countries. To find the best treatment plan for such cases is still a point of research.

A method called Real-time PCR can help to verify if the treatment is working. Research has shown that this test usually turns negative about a week following treatment if the therapy has been successful.

Metronidazole does have some side effects. For instance, pregnant women, in particular, during their first trimester, should be especially careful as this drug could lead to risks of congenital discrepancies like cleft lip in the baby. Therefore, metronidazole should only be given to expecting mothers if the potential benefits outweigh these risks. All patients taking this drug should avoid consuming alcohol as it can cause unpleasant side effects such as red or flushed face, headaches, and feeling nauseous.

This antibiotic is safe for children; if your child has Giardia and is showing severe symptoms like diarrhea, or is failing to gain weight due to the disease, the doctor may prescribe it.

If the infection doesn’t clear up with metronidazole, there are other medications that might help like tinidazole, nitazoxanide, mebendazole, albendazole, and paromomycin. Paromomycin, could be used in pregnant patients during their first trimester due to its reduced absorption into the bloodstream, minimizing potential risks to the fetus.

Despite ongoing studies, we’re still not entirely sure which is the most effective treatment for giardiasis. Some research suggests that a drug called albendazole may be just as effective as metronidazole and cause fewer side effects. If symptoms persist even after treatment, a medication from a different class may be chosen.

For those who are carrying the parasite but are not showing any symptoms, treatment is usually not needed, unless it’s to prevent spreading the infection to others at home, particularly to pregnant women or people with cystic fibrosis. Also, patients who are having other infections needing oral antibiotics and have digestion issues due to Giardia, may need to be treated. People who’ve been in close contact with a person diagnosed with giardiasis should get themselves checked for the infection and get treated, if needed.

What else can Giardiasis be?

When suspecting giardiasis, a kind of parasitic infection, several other conditions may produce similar symptoms and should also be considered. These include:

• Traveler’s diarrhea (common for people traveling internationally)
• Lactose intolerance (difficulty digesting lactose)
• Inflammatory bowel disease (chronic inflammation of the digestive tract)
• Cryptosporidiosis (another type of parasitic infection)
• Tropical sprue (a disease affecting absorption of food in the small intestine)
• Irritable bowel syndrome (a common disorder that affects the large intestine)
• Strongyloidiasis (another parasitic disease)
• Viral gastroenteritis (also known as the stomach flu)

What to expect with Giardiasis

Giardiasis, an infection typically picked up from contaminated water, usually has a positive outlook for people who contract it. This is because the infection is often self-limiting, meaning it goes away on its own without treatment. The risk of death from giardiasis is low, but can be slightly higher in babies and malnourished children if extreme dehydration occurs.

There are several antibiotics available that can successfully shorten the duration of the illness. However, there have been cases where the giardia parasite has resisted these drugs. If giardiasis isn’t treated, it can stay in the body for weeks. This is because the parasite can stay in a person’s stools, and re-infection is possible.

Complications can arise from giardiasis, including weight loss, trouble digesting certain sugars (disaccharidase deficiency), stunted growth, and malabsorption, which is when your intestines aren’t absorbing nutrients properly. The giardia parasite is often the primary cause of stunted growth in affected children, even after controlling for other possible causes of diarrhea.

Possible Complications When Diagnosed with Giardiasis

Giardiasis, a parasitic infection, can cause a range of complications, including:

• Irritable bowel syndrome
• Long-term illness leading to weight loss
• Malabsorption syndrome (a condition where nutrients are not properly absorbed)
• Disaccharidase deficiency (a condition where the body lacks certain enzymes to digest sugars)
• Chronic fatigue syndrome
• Food allergies
• Reactive arthritis (a type of arthritis triggered by infection in another part of the body)
• Zinc deficiency, particularly in school-aged children
• Persistent stomach and gastrointestinal symptoms

If patients are showing these symptoms, doctors should check if they could have been exposed to Giardia.

Preventing Giardiasis

People who are at risk should be educated on the correct way to maintain cleanliness and also learn how to identify signs of infection. It’s particularly important to thoroughly wash your hands after changing a baby’s diaper. On top of this, those working in childcare centers should be extra careful about keeping their hands clean. This is to minimize the possibility of spreading germs between children and staff.