Giardia Lamblia Pdf

[Marketta Filipovich]

Cystsare resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) . The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route (hands or fomites) . In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites) . Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk . Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces . Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear.

The spectrum varies from asymptomatic carriage to severe diarrhea and malabsorption. Acute giardiasis develops after an incubation period of 1 to 14 days (average of 7 days) and usually lasts 1 to 3 weeks. Symptoms include diarrhea, abdominal pain, bloating, nausea, and vomiting. In chronic giardiasis the symptoms are recurrent and malabsorption and debilitation may occur.

Giardiasis is diagnosed by the identification of cysts or trophozoites in the feces, using direct mounts as well as concentration procedures. Cysts are typically seen in wet mount preparations, while trophozoites are seen in permanent mounts (i.e. trichrome). Repeated samplings may be necessary. In addition, samples of duodenal fluid (e.g., Enterotest) or duodenal biopsy may demonstrate trophozoites. Alternate methods for detection include antigen detection tests by enzyme immunoassays, and detection of parasites by immunofluorescence. Both methods are available in commercial kits.

A direct immunofluorescence assay (DFA) is available for diagnosing Giardia duodenalis infections. Antibodies tagged with fluorescent markers are added to stool and incubated. Visualization under a fluorescent microscope shows the Giardia cysts as green, glowing ovoid objects. This test includes antibodies for Cryptosporidium and both diseases can be tested for simultaneously.

Giardia infection is an intestinal infection marked by stomach cramps, bloating, nausea and bouts of watery diarrhea. Giardia infection is caused by a microscopic parasite that is found worldwide, especially in areas with poor sanitation and unsafe water.

Giardia infection (giardiasis) is one of the most common causes of waterborne disease in the United States. The parasites are found in backcountry streams and lakes but also in public water supplies, swimming pools, whirlpool spas and wells. Giardia infection can be spread through food and person-to-person contact.

Giardia infections usually clear up within a few weeks. But you may have intestinal problems long after the parasites are gone. Several drugs are generally effective against giardia parasites, but not everyone responds to them. Prevention is your best defense.

Some people with giardia infection never develop signs or symptoms, but they still carry the parasite and can spread it to others through their stool. For those who do get sick, signs and symptoms usually appear one to three weeks after exposure and may include:

Giardia parasites live in the intestines of people and animals. Before the microscopic parasites are passed in stool, they become encased within hard shells called cysts, which allows them to survive outside the intestines for months. Once inside a host, the cysts dissolve and the parasites are released.

The most common way to become infected with giardia is after swallowing unsafe (contaminated) water. Giardia parasites are found in lakes, ponds, rivers and streams worldwide, as well as in public water supplies, wells, cisterns, swimming pools, water parks and spas. Ground and surface water can become infected with giardia from agricultural runoff, wastewater discharge or animal feces. Children in diapers and people with diarrhea may accidentally contaminate pools and spas.

Giardia infection is almost never fatal in industrialized countries. But it can cause lingering symptoms and serious complications, especially in infants and children. The most common complications include:

Giardia duodenalis, also known as Giardia intestinalis and Giardia lamblia, is a flagellated parasitic protozoan microorganism of the genus Giardia that colonizes the small intestine, causing a diarrheal condition known as giardiasis.[1][2][3] The parasite attaches to the intestinal epithelium by an adhesive disc or sucker, and reproduces via binary fission.[4] Giardiasis does not spread to other parts of the gastrointestinal tract, but remains confined to the lumen of the small intestine.[5] The microorganism has an outer membrane that makes it possible to survive even when outside of its host, and which can render it tolerant to certain disinfectants. Giardia trophozoites are anaerobic, and absorb their nutrients from the intestinal lumen. If the organism is stained, its characteristic pattern resembles the familiar "smiley face" symbol.[6]

Chief pathways of human infection include ingestion of untreated drinking water (which is the most common method of transmission for this parasite),[3] food, soil contaminated with human feces, and sewage, a phenomenon particularly common in many developing countries.[7][3] Contamination of natural waters also occurs in watersheds where intensive grazing occurs.

Giardia infections occur worldwide. It is the most commonly identified intestinal parasite among children in day-care centers, hikers, immunocompromised adults and their family members in the United States and Canada. About 20,000 cases per year in the United States are reported.[8]

The trophozoite has an elaborate structure with two nuclei and four pairs of flagella which allow it to swim within the intestinal lumen of the host. It also has an adhesive disk on its ventral surface that enables it to adhere to the intestinal epithelium. The organism lacks Golgi or mitochondria but has mitosomes, which probably evolved from mitochondria.[13] The mitosomes lack mitochondrial genomes but contain proteins from former mitochondrial genes that migrated to the cell nucleus. The trophozoite changes into the cyst form when it comes into contact with certain environmental stressors such as a high pH. The cyst form primarily contains the nucleus, and lacks most structures of the trophozoite form such as the flagella and adhesive disks. This allows the cyst to remain dormant until it is ingested by a new host. At that point, it transforms back into the trophozoite form.[14]

The parasite Giardia duodenalis can be found all over the world, in both developing and industrialized nations. However, it is most commonly found in tropical and temperate climates.[15] Giardia duodenalis is common around the world because the parasite resides in bodies of water; typically rivers, lakes, and recreational swimming pools.[16] Additionally, cases of giardiasis tend to be more frequent in developing countries, where the sanitation and overall hygiene is poorer, compared to countries that are more developed and have more advanced sanitary regulations and procedures.[17] In developed nations, giardiasis has a prevalence of 2%-5%, and in developing nations giardiasis has a prevalence of 20%-30%.[18] Giardiasis is the most common intestinal infection that is derived from parasites in both the United States[17] and the United Kingdom.[19] In the United States, it has been discovered that a majority of whom are infected by the Giardia duodenalis parasite tend to reside in more urban areas, and, patients who are infected are more likely to live in the Southern United States.[20]

G. duodenalis causes an infection called giardiasis. This disease is the cause of both endemic and epidemic disease worldwide and is the most frequently identified intestinal parasite in the United States and Canada. It is estimated to infect over 280 million people world every year[18]resulting over 500,000 deaths. The most affected demographic is children 0 to 4 years of age. Globally G. duodenalis is the most commonly identified protozoal intestinal parasite. In high-income countries, there is an infection rate between 2-5%, and in low and middle-income countries there is an infection rate between 20% and 30%.[17]Giardia has common seasonal patterns in the distribution of infection rates with highest peaks in the late summer to early fall.[21]

The cyst can survive for weeks to months in cold water, [11] so can be present in contaminated wells and water systems, especially stagnant water sources, such as naturally occurring ponds, storm-water storage systems, and even clean-looking mountain streams. Cysts can also be found on surfaces, soil, food, or water that have been contaminated with feces from infected humans or animals.[22] They may also occur in city reservoirs and persist after water treatment, as the cysts are resistant to conventional water-treatment methods, such as chlorination and ozonolysis.[11] Zoonotic transmission is also possible, so Giardia infection is a concern for people camping in the wilderness or swimming in contaminated streams or lakes, especially the artificial lakes formed by beaver dams (hence the popular name for giardiasis, "beaver fever").[citation needed]

In addition to waterborne sources, Giardia infections are more commonly found in children than adults, this is believed to be due to fecal-oral transmission of the cysts. Depending on the geographical area, from 1-68% of children may be infected. Those who work with children are also at risk of being infected, as are family members of infected individuals. 7% of children aged 1 to 3 years and 11% of infants and toddlers tested for admission to day-care centers were found to be infected.[17] Not all Giardia infections are symptomatic, and many people can unknowingly serve as carriers of the parasite. Re- infection and chronic infections of the parasite can occur. [18][citation needed]

3a8082e126