Giardia lamblia Overview
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Questions and Answers

What is the main method by which Giardia trophozoites multiply in the host?

  • Sexual reproduction
  • Bacterial conjugation
  • Binary fission (correct)
  • Budding

    • Which of the following treatments has the highest cure rate for Giardia infections?

  • Furazolidone
  • Metronidazole (correct)
  • Nitazoxamide
  • Tinidazole

    • What is the most effective method to inactivate Giardia cysts in water?

  • Filtration through carbon filters
  • Boiling (correct)
  • Chlorination
  • Chemical treatment

    • During unfavorable conditions, Giardia trophozoites undergo which process?

    <p>Encystment</p> Signup and view all the answers

    What is the infective dose of Giardia cysts needed to cause an infection?

    <p>10–100 cysts</p> Signup and view all the answers

    What is the primary habitat of Giardia lamblia in the human body?

    <p>Duodenum and upper jejunum</p> Signup and view all the answers

    What characteristic feature helps Giardia lamblia attach to the intestinal mucosa?

    <p>Concave sucking disc</p> Signup and view all the answers

    Which form of Giardia lamblia is considered the infective stage?

    <p>Cyst</p> Signup and view all the answers

    What is a common outcome of infection with Giardia lamblia?

    <p>Fat malabsorption (steatorrhea)</p> Signup and view all the answers

    Which populations are more likely to develop giardiasis?

    <p>Individuals with immune defects</p> Signup and view all the answers

    What components are part of the trophozoite structure of Giardia lamblia?

    <p>One pair of nuclei and four pairs of flagella</p> Signup and view all the answers

    What is the primary method through which contaminated water contributes to giardiasis?

    <p>Ingestion of cysts</p> Signup and view all the answers

    Which feature of Giardia lamblia is important for its virulence?

    <p>Variant specific surface proteins (VSSP)</p> Signup and view all the answers

    Giardia lamblia was first observed by Antonie von Leeuwenhoek in his own stools in 1681.

    <p>True</p> Signup and view all the answers

    The cyst form of Giardia lamblia measures 15 μm x 9 μm.

    <p>False</p> Signup and view all the answers

    Enhanced susceptibility to giardiasis is associated with the blood group O.

    <p>False</p> Signup and view all the answers

    The mode of transmission for Giardia lamblia is through contaminated air.

    <p>False</p> Signup and view all the answers

    Giardia lamblia causes the stool to contain blood due to its pathogenicity.

    <p>False</p> Signup and view all the answers

    Giardia lamblia is the only protozoan parasite found in the lumen of the human large intestine.

    <p>False</p> Signup and view all the answers

    The trophozoite of Giardia lamblia has a pair of axostyles running along its midline.

    <p>True</p> Signup and view all the answers

    Cysts of Giardia lamblia can only be found in contaminated plant foods.

    <p>False</p> Signup and view all the answers

    Giardia can survive in soil and water for several weeks due to its cyst form.

    <p>True</p> Signup and view all the answers

    The infectious dose for Giardia consists of 500–600 cysts.

    <p>False</p> Signup and view all the answers

    Treatment with tinidazole is less effective than treatment with metronidazole.

    <p>False</p> Signup and view all the answers

    Encystment of Giardia typically occurs in the duodenum.

    <p>False</p> Signup and view all the answers

    Proper disposal of wastewater and feces is a key method of prophylaxis against Giardia infections.

    <p>True</p> Signup and view all the answers

    What role do trophozoites play in the transmission of Giardia infection once they are ingested?

    <p>Trophozoites hatch from cysts and multiply in the duodenum, leading to colonization and subsequent shedding of cysts in stool.</p> Signup and view all the answers

    How does the encystment process benefit Giardia in unfavorable conditions?

    <p>Encystment allows Giardia to survive harsh conditions, facilitating its transmission through viable cysts in the environment.</p> Signup and view all the answers

    What are the implications of having a high number of cysts passed per gram of feces on public health?

    <p>The high cyst count increases the risk of environmental contamination and potential outbreaks of giardiasis in populations.</p> Signup and view all the answers

    Discuss the benefits and limitations of using metronidazole as a treatment for giardiasis.

    <p>Metronidazole has a high cure rate but may have adverse effects, suggesting careful consideration in treatment choices, especially for vulnerable groups.</p> Signup and view all the answers

    What are critical components of effective prophylaxis against giardiasis, based on environmental factors?

    <p>Proper disposal of waste and practicing personal hygiene are essential to break the cycle of infection and prevent Giardia transmission.</p> Signup and view all the answers

    What significant role do variant specific surface proteins (VSSP) play in Giardia lamblia?

    <p>VSSP contribute to the virulence and infectivity of Giardia lamblia.</p> Signup and view all the answers

    Describe the symptoms associated with giardiasis caused by Giardia lamblia.

    <p>Symptoms include mucus diarrhea, fat malabsorption (steatorrhea), dull epigastric pain, and flatulence.</p> Signup and view all the answers

    What are the dimensions of the Giardia lamblia cyst, and why is its structure significant?

    <p>The cyst measures 12 μm x 8 μm and its structure allows it to be the infective form, helping it survive outside the host.</p> Signup and view all the answers

    Identify two environmental or health factors that enhance susceptibility to giardiasis.

    <p>Blood group A and chronic pancreatitis are factors that enhance susceptibility to giardiasis.</p> Signup and view all the answers

    How do the trophozoites of Giardia lamblia move, and what does this resemble?

    <p>Trophozoites exhibit slow oscillation about their long axis, resembling a falling leaf.</p> Signup and view all the answers

    Discuss how Giardia lamblia affects intestinal villous architecture.

    <p>Giardia lamblia causes abnormalities in villous architecture through cell apoptosis and increased lymphatic infiltration.</p> Signup and view all the answers

    Explain the transmission route of Giardia lamblia infection in humans.

    <p>Humans acquire Giardia lamblia infection by ingesting cysts present in contaminated water and food.</p> Signup and view all the answers

    What are the main structural components of the Giardia lamblia trophozoite?

    <p>The main structural components include 1 pair of nuclei, 4 pairs of flagella, and 1 pair of axostyles.</p> Signup and view all the answers

    Giardia may colonize the gall bladder, causing biliary colic and ______.

    <p>jaundice</p> Signup and view all the answers

    The trophozoites of Giardia live in the duodenum and upper part of the ______.

    <p>jejunum</p> Signup and view all the answers

    Cysts of Giardia can remain viable in soil and ______ for several weeks.

    <p>water</p> Signup and view all the answers

    Metronidazole can be administered at a dosage of ______ mg, thrice daily for 5-7 days.

    <p>250</p> Signup and view all the answers

    During adverse conditions, Giardia undergoes ______, forming a protective cyst.

    <p>encystment</p> Signup and view all the answers

    Giardia lamblia was first observed by Dutch scientist Antonie von ______ in his own stools.

    <p>Leeuwenhoek</p> Signup and view all the answers

    The infective form of Giardia lamblia is the ______.

    <p>cyst</p> Signup and view all the answers

    Giardia lamblia causes abnormalities of villous architecture by cell ______ and increased lymphatic infiltration.

    <p>apoptosis</p> Signup and view all the answers

    Giardia lamblia primarily lives in the ______ and upper jejunum of the human small intestine.

    <p>duodenum</p> Signup and view all the answers

    A young cyst of Giardia lamblia contains ______ pair of nuclei.

    <p>1</p> Signup and view all the answers

    Enhanced susceptibility to giardiasis is associated with blood group ______.

    <p>A</p> Signup and view all the answers

    The trophozoite of Giardia lamblia possesses ______ pairs of flagella.

    <p>4</p> Signup and view all the answers

    The stool of an individual infected with Giardia lamblia may contain excess mucus and ______, but no blood.

    <p>fat</p> Signup and view all the answers

    Match the following Giardia lamblia life cycle phases with their characteristics:

    <p>Cyst = Infective form passed in stool Trophozoite = Motile feeding form in the intestine Encystment = Formed during unfavorable conditions Binary fission = Method of asexual reproduction</p> Signup and view all the answers

    Match the following treatments for Giardia with their descriptions:

    <p>Metronidazole = 250 mg thrice daily for 5-7 days Tinidazole = 2 g single dose Furazolidone = Preferred for children with fewer side effects Nitazoxamide = Another option for pediatric treatment</p> Signup and view all the answers

    Match the following aspects of Giardia lamblia infection with their implications:

    <p>200,000 cysts/g feces = High environmental contamination potential Infective dose of 10-100 cysts = Low threshold for infection Chronic diarrhea = Possible nutrient malabsorption Gall bladder colonization = Risk of biliary colic and jaundice</p> Signup and view all the answers

    Match the following prevention methods for Giardia with their effectiveness:

    <p>Boiling water = Effective inactivating method for cysts Chlorination = Ineffective for cyst inactivation Personal hygiene = Reduces transmission risk Filtration by membrane filters = Another effective cyst removal method</p> Signup and view all the answers

    Match the following characteristics of Giardia lamblia with their functions:

    <p>Trophozoites' pinocytosis = Nutrient absorption in the intestine Cysts in soil and water = Environmental survival and transmission Encystment process = Survival in harsh conditions Aminoglycoside treatment = Targeting symptoms in pregnant females</p> Signup and view all the answers

    Match the following structures of Giardia lamblia with their descriptions:

    <p>Trophozoite = Motile form with a concave sucking disc Cyst = Infective form surrounded by a hyaline cyst wall Blepharoplast = Structure from which flagella arise Axostyle = Feature running along the midline of the trophozoite</p> Signup and view all the answers

    Match the following terms related to giardiasis with their meanings:

    <p>Steatorrhea = Fat malabsorption causing fatty stools VSSP = Proteins important for Giardia's virulence Chronic pancreatitis = Condition that enhances susceptibility to giardiasis Hyaline = Describes the cyst wall structure of Giardia</p> Signup and view all the answers

    Match the following symptoms with their related conditions caused by Giardia lamblia:

    <p>Mucus diarrhea = Excess mucus in stool Dull epigastric pain = Abdominal pain related to giardiasis Increased lymphatic infiltration = Pathogenicity affecting intestinal architecture Flatulence = Gas production due to fat malabsorption</p> Signup and view all the answers

    Match the following transmission methods with their descriptions:

    <p>Ingestion of contaminated water = Primary method of acquiring giardiasis Direct person-to-person transmission = Less common route of infection Ingestion of food = Secondary method for transmission Enhanced susceptibility = Associated with certain health factors</p> Signup and view all the answers

    Match the following observations about Giardia lamblia to their historical context:

    <p>1681 = Year Giardia was first observed by Antonie von Leeuwenhoek Paris = City associated with Professor Giard's contributions Prague = City linked to Professor Lamble and detailed descriptions Worldwide distribution = Characteristic highlighting endemic areas</p> Signup and view all the answers

    Match the following Giardia lamblia characteristics to their roles:

    <p>Convex dorsally = Shape aiding in attachment Bilateral symmetry = Characteristic of the trophozoite structure Small size of cyst = Facilitates survival in the environment Transverse parabasal bodies = Part of the trophozoite’s structural components</p> Signup and view all the answers

    Match the following types of cells/structures with their roles or characteristics in Giardia lamblia:

    <p>Nuclei = Involved in cellular replication and function Flagella = Structures used for locomotion Cyst wall = Protective barrier for cyst form Parabasal bodies = Support organelles in the trophozoite</p> Signup and view all the answers

    Match the following factors to their association with giardiasis susceptibility:

    <p>Blood group A = Enhances susceptibility Malnutrition = Health factor related to infection risk Use of cannabis = Behavioral aspect linked to increased risk Achlorhydria = Physiological condition influencing infection occurrence</p> Signup and view all the answers

    Study Notes

    History and Distribution

    • Giardia lamblia was first observed by Antonie van Leeuwenhoek in 1681.
    • It's named after Professor Giard of Paris and Professor Lamble of Prague.
    • Giardia is the most common protozoan pathogen worldwide.
    • High endemism exists in areas with low sanitation, particularly tropics and subtropics.
    • Travelers to these areas often develop giardiasis due to contaminated water.

    Habitat

    • Giardia lamblia resides in the duodenum and upper jejunum of the human small intestine.

    Trophozoite

    • It measures 15 μm x 9 μm wide and 4 μm thick.
    • It has a convex dorsal side and a concave ventral side with a sucking disc for attachment to the intestinal mucosa.
    • It's bilaterally symmetrical with:
      • 1 pair of nuclei
      • 4 pairs of flagella
      • Blepharoplast
      • 1 pair of axostyles
      • 2 sausage-shaped parabasal or median bodies
    • The trophozoite exhibits slow oscillatory movement, resembling a falling leaf.

    Cyst

    • It's the infective form of the parasite, measuring 12 μm x 8 μm.
    • It's surrounded by a hyaline cyst wall.
    • Internally, it contains 2 pairs of nuclei grouped at one end and a diagonally positioned axostyle.
    • Young cysts contain 1 pair of nuclei and remnants of flagella and the sucking disc.

    Mode of Transmission

    • Humans acquire infection by ingesting cysts in contaminated water and food.
    • Direct person-to-person transmission is also possible.
    • Increased susceptibility to giardiasis is associated with blood group A, achlorhydria, cannabis use, chronic pancreatitis, malnutrition, and immune defects.

    Pathogenicity

    • Giardia can cause abnormalities of villous architecture through cell apoptosis and increased lymphatic infiltration of the lamina propria.
    • Variant specific surface proteins (VSSP) contribute to virulence and infectivity.
    • Giardia may lead to:
      • Mucus diarrhea
      • Fat malabsorption (steatorrhea)
      • Dull epigastric pain
      • Flatulence
    • Stool contains excess mucus and fat but no blood.
    • Children may experience:
      • Chronic diarrhea
      • Malabsorption of fat, vitamin A, and protein
      • Weight loss
    • Giardia can colonize the gallbladder, causing biliary colic and jaundice.
    • Incubation period is generally about 2 weeks.

    Life Cycle

    • Upon ingestion, the cyst hatches into two trophozoites within half an hour.
    • Trophozoites multiply by binary fission in the duodenum.
    • They live in the duodenum and upper jejunum, feeding by pinocytosis.
    • Encystment occurs in the colon under unfavorable conditions.
    • Cysts are passed in stool and remain viable in soil and water for weeks.
    • Feces may contain 200,000 cysts per gram.
    • The infective dose is 10–100 cysts.

    Treatment

    • Metronidazole (250 mg, thrice daily for 5–7 days) and tinidazole (2 g single dose) are the preferred drugs.
    • Metronidazole has a cure rate exceeding 90%.
    • Tinidazole proves more effective than metronidazole.
    • Furuzolidone and nitazoxamide are favored for children due to fewer side effects.
    • Paromomycin, an oral aminoglycoside, is suitable for symptomatic pregnant women.

    Prophylaxis

    • Proper disposal of wastewater and feces.
    • Personal hygiene practices like hand-washing before eating and proper diaper disposal.
    • Prevention of food and water contamination.
    • Community water chlorination is ineffective against cysts.
    • Water boiling and filtration using membrane filters are necessary precautions.

    History and Distribution

    • Giardia lamblia was first observed in 1681
    • Named after Professors Giard and Lamble
    • Most common protozoan pathogen worldwide
    • High endemicity in areas with low sanitation, especially in the tropics and subtropics
    • Traveler's diarrhea is a common symptom of Giardia infection

    Habitat

    • Lives in the duodenum and upper jejunum of the small intestine
    • The only protozoan parasite found in the lumen of the human small intestine

    Trophozoite

    • Measures 15 μm x 9 μm wide and 4 μm thick
    • Dorsally convex, with a concave sucking disc ventrally for attachment to the intestinal mucosa
    • Possesses 1 pair of nuclei, 4 pairs of flagella, blepharoplast, axostyles, and parabasal bodies
    • Motile, with slow oscillation about its long axis

    Cyst

    • Infective form of the parasite
    • Measures 12 μm x 8 μm
    • Surrounded by a hyaline cyst wall
    • Contains 2 pairs of nuclei grouped at one end
    • Axostyle lies diagonally
    • Remnants of flagella and sucking disc may be seen in the young cyst

    Mode of Transmission

    • Infection acquired by ingestion of contaminated water or food
    • Direct person-to-person transmission is possible
    • Enhanced susceptibility to giardiasis is associated with blood group A, achlorhydria, cannabis use, chronic pancreatitis, malnutrition, and immune defects

    Pathogenicity

    • May cause abnormalities of villous architecture by cell apoptosis and increased lymphatic infiltration
    • Variant specific surface proteins (VSSP) play an important role in virulence and infectivity
    • Can lead to mucus diarrhea, fat malabsorption (steatorrhea), dull epigastric pain, and flatulence
    • Stool contains excess mucus and fat but no blood
    • Children may develop chronic diarrhea, malabsorption of fat, vitamin A, protein, and weight loss
    • May colonize the gallbladder, causing biliary colic and jaundice
    • Incubation period is usually around 2 weeks

    Life Cycle

    • Within half an hour of ingestion, cysts hatch into two trophozoites
    • Trophozoites multiply by binary fission and colonize the duodenum
    • Trophozoites feed by pinocytosis
    • Encystment occurs during unfavorable conditions, usually in the colon
    • Cysts passed in stool and remain viable in soil and water for several weeks
    • Up to 200,000 cysts may be passed per gram of feces
    • Infective dose is 10–100 cysts

    Treatment

    • Metronidazole (250 mg, thrice daily for 5–7 days) and tinidazole (2 g single dose) are the drugs of choice
    • Cure rates with metronidazole are more than 90%
    • Tinidazole is more effective than metronidazole
    • Furuzolidone and nitazoxamide are preferred for children due to fewer adverse effects
    • Paromomycin, an oral aminoglycoside can be given to symptomatic pregnant females

    Prophylaxis

    • Proper disposal of waste water and feces
    • Practice of personal hygiene, like hand-washing before eating and proper disposal of diapers
    • Prevention of food and water contamination
    • Community chlorination of water is not effective for inactivating cysts
    • Boiling water and filtration by membrane filters are required

    History and Distribution

    • First observed by Antonie van Leeuwenhoek in 1681
    • Named after Professor Giard and Professor Lamble
    • Most prevalent protozoan pathogen
    • Worldwide distribution
    • Highly endemic in areas with low sanitation, especially tropics and subtropics
    • Causes traveler's diarrhea through contaminated water

    Habitat

    • Found in the duodenum and upper jejunum of the small intestine
    • Only protozoan parasite found in the lumen of the human small intestine

    Trophozoite

    • Measures 15 μm x 9 μm wide and 4 μm thick
    • Dorsally convex, ventrally concave with sucking disc for attachment to intestinal mucosa
    • Bilaterally symmetrical
    • Possesses one pair of nuclei, four pairs of flagella, a blepharoplast (origin of flagella), one pair of axostyles, two sausage-shaped parabasal bodies.
    • Motile with slow oscillation, resembling a falling leaf

    Cyst

    • Infective form of the parasite
    • Oval, measuring 12 μm x 8 μm
    • Enclosed by a hyaline cyst wall
    • Two pairs of nuclei grouped at one end
    • Young cyst has one pair of nuclei
    • Axostyle lies diagonally within the cyst wall
    • Remnants of flagella and sucking disc may be visible

    Mode of Transmission

    • Ingestion of cysts in contaminated water or food
    • Direct transmission from person to person
    • Enhanced susceptibility associated with blood group A, achlorhydria, cannabis use, chronic pancreatitis, malnutrition, and immune defects

    Pathogenicity

    • Can cause villous architecture abnormalities via cell apoptosis and increased lymphatic infiltration
    • Variant specific surface proteins (VSSP) contribute to virulence and infectivity
    • Causes mucus diarrhea, fat malabsorption (steatorrhea), dull epigastric pain, and flatulence
    • Stool contains excess mucus and fat, but no blood
    • In children, can lead to chronic diarrhea, malabsorption of fat, vitamin A, protein, and weight loss
    • Can colonize the gallbladder, causing biliary colic and jaundice
    • Incubation period typically around two weeks

    Life Cycle

    • Cysts hatch into two trophozoites within half an hour of ingestion
    • Trophozoites multiply by binary fission and colonize the duodenum
    • Trophozoites feed by pinocytosis in the duodenum and upper jejunum
    • Encystment occurs in the colon under unfavorable conditions
    • Cysts are passed in stool and remain viable in soil and water for several weeks
    • Up to 200,000 cysts can be passed per gram of feces
    • Infective dose is 10-100 cysts

    Treatment

    • Metronidazole (250 mg, thrice daily for 5-7 days) and tinidazole (2 g single dose) are the drugs of choice
    • Metronidazole cure rate exceeds 90%
    • Tinidazole more effective than metronidazole
    • Furazolidone and nitazoxamide preferred in children due to fewer adverse effects
    • Paromomycin, an oral aminoglycoside, can be given to symptomatic pregnant females

    Prophylaxis

    • Proper disposal of wastewater and feces
    • Practice of personal hygiene like hand-washing before eating
    • Proper disposal of diapers
    • Prevention of food and water contamination
    • Community chlorination of water is ineffective for inactivating cysts
    • Boiling water and filtration by membrane filters are required

    History and Distribution

    • Giardia lamblia was first observed in 1681 by Antonie van Leeuwenhoek.
    • It is named after professors Giard and Lamble who described the parasite.
    • It is the most common protozoan pathogen.
    • Giardia lamblia is found worldwide with high endemism in areas with low sanitation, especially tropics and subtropics.
    • Travelers to such places often develop traveler's diarrhea caused by Giardia lamblia through contaminated water.

    Habitat

    • Giardia lamblia lives in the duodenum and the upper jejunum of the small intestine.
    • It is the only protozoan parasite found in the lumen of the human small intestine.

    Trophozoite

    • The trophozoite measures 15 μm x 9 μm x 4 μm.
    • It has a concave sucking disc on the ventral side which helps it attach to the intestinal mucosa.
    • It is bilaterally symmetrical and possesses: 1 pair of nuclei, 4 pairs of flagella, blepharoplast, 1 pair of axostyles, and 2 parabasal bodies.
    • The trophozoite is motile and oscillates about its long axis.

    Cyst

    • The cyst is the infective form of the parasite.
    • Its size is 12 μm x 8 μm.
    • It has a hyaline cyst wall and contains 2 pairs of nuclei grouped at one end, remnants of flagella and the sucking disc.
    • The axostyle lies diagonally forming a dividing line within the cyst wall.

    Mode of Transmission

    • Infection occurs through ingestion of cysts in contaminated water and food.
    • Direct transmission from person to person is also possible.
    • Enhanced susceptibility to giardiasis is linked to blood group A, achlorhydria, cannabis use, chronic pancreatitis, malnutrition, and immune defects.

    Pathogenicity

    • Giardia lamblia can cause abnormalities in villous architecture by inducing cell apoptosis and increased lymphatic infiltration.
    • Variant specific surface proteins (VSSP) play a critical role in virulence and infectivity.
    • Symptoms include mucus diarrhea, fat malabsorption, epigastric pain, and flatulence.
    • The stool contains excess mucus and fat but no blood.
    • Children may develop chronic diarrhea, malabsorption of fat, vitamin A, protein, and weight loss.
    • Giardia can colonize the gallbladder, causing biliary colic and jaundice.
    • The incubation period is typically 2 weeks.

    Life Cycle

    • Within half an hour of ingestion, the cyst hatches into two trophozoites.
    • These trophozoites multiply through binary fission in the duodenum.
    • Trophozoites feed by pinocytosis.
    • Encystment occurs in the colon during unfavorable conditions.
    • Cysts are passed in stool and are viable in soil and water for several weeks.
    • A gram of feces can contain 200,000 cysts.
    • The infective dose is 10–100 cysts.

    Treatment

    • Metronidazole (250 mg, thrice daily for 5-7 days) and tinidazole (2 gm single dose) are the drugs of choice.
    • Metronidazole has over 90% cure rate.
    • Tinidazole is more effective than metronidazole.
    • Furuzolidone and nitazoxamide are preferred in children due to fewer side effects.
    • Parmomycin can be given to pregnant females.

    Prophylaxis

    • Proper disposal of wastewater and feces is essential.
    • Practice good personal hygiene such as handwashing before eating and proper diaper disposal.
    • Prevent food and water contamination.
    • Community chlorination of water is ineffective for inactivating cysts.
    • Boiling water and using membrane filters are necessary.

    Giardia Lamblia

    • Discovery: First observed by Antoni van Leeuwenhoek in 1681. Named after Professors Giard (Paris) and Lamble (Prague).
    • Distribution: Most common protozoan pathogen found worldwide. High endemism in low sanitation areas like the tropics and subtropics.
    • Habitat: Lives in the duodenum and upper jejunum of the human small intestine. It is the only protozoan parasite found in the lumen of this area.

    Trophozoite

    • Size: Measures 15 μm x 9 μm wide and 4 μm thick.
    • Structure: Bilaterally symmetrical with a concave sucking disc ventrally for attachment. Contains one pair of nuclei, four pairs of flagella arising from the blepharoplast, one pair of axostyles, and two sausage-shaped parabasal bodies.
    • Motility: Moves with a slow oscillation about its long axis, resembling a falling leaf.

    Cyst

    • Infective form: Small oval-shaped, measuring 12 μm x 8 μm. Surrounded by a hyaline cyst wall.
    • Structure: Contains two pairs of nuclei (young cysts contain one), axostyle lies diagonally, remnants of flagella and sucking disc may be present.

    Mode of Transmission

    • Ingestion of cysts: Occurs through contaminated water and food.
    • Direct Person-to-Person Transmission: Possible.
    • Enhanced Susceptibility: Associated with blood group A, achlorhydria, cannabis use, chronic pancreatitis, malnutrition, and immune defects.

    Pathogenicity

    • Villous Architecture: May cause abnormalities by cell apoptosis and increased lymphatic infiltration of the lamina propria.
    • Variant Specific Surface Proteins (VSSP): Play a significant role in parasite virulence and infectivity.
    • Symptoms: Mucus diarrhea, fat malabsorption (steatorrhea), dull epigastric pain, flatulence. Stools contain excess mucus and fat but no blood.
    • Children: May develop chronic diarrhea, malabsorption of fat, vitamin A, protein, and weight loss.
    • Gall Bladder: Giardia can colonize the gall bladder, causing biliary colic and jaundice.
    • Incubation Period: Usually about 2 weeks.

    Life Cycle

    • Cyst Ingestion: Cysts hatch into two trophozoites within half an hour of ingestion.
    • Multiplication: Trophozoites multiply by binary fission and colonize the duodenum.
    • Feeding: Trophozoites feed by pinocytosis.
    • Encystment: Encystment occurs in the colon during unfavorable conditions.
    • Excretion: Cysts are passed in feces and remain viable in soil and water for weeks.
    • Infective Dose: Requires 10-100 cysts.

    Treatment

    • Drugs of Choice: Metronidazole (250 mg, thrice daily for 5-7 days) and tinidazole (2g single dose).
    • Cure Rates: Metronidazole has a cure rate of over 90%. Tinidazole is more effective than metronidazole.
    • Children: Furuzolidone and nitazoxamide are preferred due to fewer adverse effects.
    • Pregnant Females: Paromomycin, an oral aminoglycoside, is used for symptomatic pregnant females.

    Prophylaxis

    • Waste Disposal: Proper disposal of wastewater and feces.
    • Personal Hygiene: Hand washing before eating and proper disposal of diapers.
    • Food and Water Contamination: Prevention.
    • Water Chlorination: Community chlorination is ineffective for inactivating cysts. Boiling water and filtration using membrane filters are required.

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    This quiz covers the biology and distribution of Giardia lamblia, highlighting its discovery, habitat, and morphology. Explore the characteristics of its trophozoite and cyst forms, as well as the implications for public health, especially in areas with low sanitation. Test your knowledge about this common protozoan pathogen.

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