Giardia lamblia is a parasitic species of protozoa that was first recognized as harmful in the 1970s. Globally, infection by this organism is responsible for a large proportion of cases of diarrheal illness. It has a prevalence of up to 42 percent in developing countries, and in the United Kingdom is the most common parasite of the gut. In the United States, G. lamblia is the most commonly identified intestinal pathogen in water and is present in up to 80 percent of the country’s water supplies obtained from ponds, lakes and streams. This organism is also known as Giardia duodenalis and Giardia intestinalis.
The lifecycle of the Giardia lamblia protozoan has two stages. In the first stage, the organism lives in the human small intestine and is referred to as a trophozoite. After living and feeding in the small intestine, the trophozoite passes through to the bowel, where cyst formation is triggered by the neutral pH there. Giardia lamblia cysts are then excreted during bowel movements.
The cysts can remain dormant for a considerable period of time, until they are exposed to a pH of between 1.3 and 2.7, such as what exists in the human stomach. Infection of a new host occurs via contact with cysts in contaminated food or water, or via direct contact with an infected person. It is believed that as few as 10 cysts might be enough to cause infection.
An estimated 15 percent of cases of infection caused by G. lamblia are asymptomatic, but cyst excretion still occurs. Giardia lamblia symptoms are present in about 50 percent of cases. Symptoms might include diarrhea, abdominal cramping, bloating and flatulence. People with chronic infection can become malnourished, and a weight loss of up to 15 pounds is not uncommon. Children in developing countries are particularly at risk of chronic infection and malnutrition, which may lead to delayed growth.
Standard Giardia lamblia treatment includes a course of antibiotics capable of killing the parasites. These include metronidazole, albendazole and furazolidone. People infected with this parasite should ensure they receive an adequate intake of fluids and nourishment.
There are no special dietary requirements for people with an active infection, but most people find that bland foods such as rice, potatoes and crackers are well-tolerated. After an infection, many people become temporarily lactose intolerant and might need to eliminate dairy products for up to several months. Because cysts can be transmitted through person-to-person contact, observing good hygiene is crucial to prevent the infection from spreading.
When a person becomes infected with the parasite that causes giardiasis (Giardia lamblia), the parasite begins to multiply within the intestines. Within one to two weeks (the average is seven days), the infected individual will begin to develop Giardia lamblia symptoms. This period between initial infection and the start of symptoms is called the "Giardia incubation period."
Symptoms of Giardia lamblia may begin gradually or develop without warning. Some people who have giardiasis may not have any symptoms at all, while others may experience severe symptoms.
Symptoms often vary from patient to patient, but the most common intestinal symptoms include:
Diarrhea
Upset stomach or nausea
Vomiting
Greasy stools that tend to float
Stomach cramps
Gas or flatulence
Abdominal pain
Bloating
Belching.
These symptoms may lead to weight loss and dehydration.
Chronic giardiasis is a more severe form of the condition and can last for months or even years. The symptoms seen in patients with chronic giardiasis can be different from those who develop an acute Giardia infection. Common symptoms of chronic giardiasis include:
Increased gas (flatus)
Dehydration
Burping
Loose stools
Slowed growth.
These chronic symptoms may come and go or always be present.
In some cases, giardiasis goes away on its own in about one month. Other people need antibiotics (e.g., metronidazole, paromomycin) to shorten the duration of the infection and to kill the parasite.
Because the disease can spread quickly, your doctor may suggest that the whole family be treated at the same time. Your doctor may also suggest that you take your medication for a longer time or change your medication depending on the severity of your illness. It is very important that you let your doctor know if you are pregnant because some medications used to treat this condition can harm the fetus.
Finally, it is very important that you drink enough water and electrolyte-rich drinks (solutions containing sugar and salts) because your body will be losing water due to diarrhea. Signs of dehydration are extreme tiredness; dry skin, mouth, and tongue; sunken eyes; and very little production of urine or tears.
Children are at a higher risk of dehydration than adults due to their small body size, so parents or caregivers should watch for signs of dehydration and ensure that the child drinks plenty of water. Oral rehydration solutions, which are available at pharmacies as liquids or powder packets to mix with water, are an excellent way to keep a child hydrated. If you are mixing electrolyte powder with water, make sure the water is clean to avoid reinfection.
There are several effective ways to avoid getting or spreading this infection. Keep these tips in mind:
Do not drink or brush your teeth and wash food or dishes with untreated water from streams, rivers, or lakes, even if they look sparkling clean. Make sure you boil water from these sources for 1 to 2 minutes (or 3 minutes if you are at a high altitude) before use.
Wash your hands thoroughly with soap and water before and after eating, preparing food, changing diapers, and using the toilet.
Do not send a child who is infected and cannot control his or her bowel movements to daycare or school.
Avoid swallowing water when swimming in public pools or lakes. Chlorine commonly used in swimming pools will not kill the cysts.
Try to eat well-cooked hot foods and always peel raw vegetables and fruit.