Podcast
Questions and Answers
Where are liver abscesses usually located in cases of hepatic amoebiasis?
Where are liver abscesses usually located in cases of hepatic amoebiasis?
What is a common complication of untreated liver abscesses?
What is a common complication of untreated liver abscesses?
Which of the following is a luminal amoebicide used for treating amoebic infections?
Which of the following is a luminal amoebicide used for treating amoebic infections?
In the treatment of amoebic liver abscess, what is the initial dosage of chloroquine recommended?
In the treatment of amoebic liver abscess, what is the initial dosage of chloroquine recommended?
Signup and view all the answers
What is a critical measure for the prophylaxis of hepatic amoebiasis?
What is a critical measure for the prophylaxis of hepatic amoebiasis?
Signup and view all the answers
What characterizes the mature cyst of E. histolytica?
What characterizes the mature cyst of E. histolytica?
Signup and view all the answers
In what part of the ileum does excystation of E. histolytica occur?
In what part of the ileum does excystation of E. histolytica occur?
Signup and view all the answers
Which staining method shows nuclear chromatin and chromatoid bodies appearing deep blue or black?
Which staining method shows nuclear chromatin and chromatoid bodies appearing deep blue or black?
Signup and view all the answers
Which stage of E. histolytica is characterized by amoeboid movements and liberation of quadrinucleate amoeba?
Which stage of E. histolytica is characterized by amoeboid movements and liberation of quadrinucleate amoeba?
Signup and view all the answers
What role does the lytic enzyme histolysin play in E. histolytica pathogenesis?
What role does the lytic enzyme histolysin play in E. histolytica pathogenesis?
Signup and view all the answers
What is the typical lesion seen in intestinal amoebiasis?
What is the typical lesion seen in intestinal amoebiasis?
Signup and view all the answers
What is the primary form of transmission for E. histolytica?
What is the primary form of transmission for E. histolytica?
Signup and view all the answers
What outcome does the invasion of metacystic trophozoites typically lead to in the colon?
What outcome does the invasion of metacystic trophozoites typically lead to in the colon?
Signup and view all the answers
Which protozoan is known to cause amoebic dysentery and is prevalent in tropical regions?
Which protozoan is known to cause amoebic dysentery and is prevalent in tropical regions?
Signup and view all the answers
What is the average size of a trophozoite of Entamoeba histolytica?
What is the average size of a trophozoite of Entamoeba histolytica?
Signup and view all the answers
At what temperature can trophozoites of Entamoeba histolytica survive for a limited time?
At what temperature can trophozoites of Entamoeba histolytica survive for a limited time?
Signup and view all the answers
Which of the following statements is TRUE regarding the trophozoites of Entamoeba histolytica?
Which of the following statements is TRUE regarding the trophozoites of Entamoeba histolytica?
Signup and view all the answers
In which stage does Entamoeba histolytica undergo a transformation to form a cyst?
In which stage does Entamoeba histolytica undergo a transformation to form a cyst?
Signup and view all the answers
What is a distinguishing feature of trophozoites in acute dysentery compared to other intestinal amoebae?
What is a distinguishing feature of trophozoites in acute dysentery compared to other intestinal amoebae?
Signup and view all the answers
Which cystic stage is identifiable as having a defined cyst wall?
Which cystic stage is identifiable as having a defined cyst wall?
Signup and view all the answers
What is the spherical size range of a cyst of Entamoeba histolytica?
What is the spherical size range of a cyst of Entamoeba histolytica?
Signup and view all the answers
What is the typical shape of an amoebic ulcer in cross section?
What is the typical shape of an amoebic ulcer in cross section?
Signup and view all the answers
How far do the ulcers typically extend into the intestinal wall?
How far do the ulcers typically extend into the intestinal wall?
Signup and view all the answers
What is a common characteristic of the stools in typical amoebic dysentery?
What is a common characteristic of the stools in typical amoebic dysentery?
Signup and view all the answers
What complication may arise from chronic involvement of the caecum due to amoebic infection?
What complication may arise from chronic involvement of the caecum due to amoebic infection?
Signup and view all the answers
What type of abscess may occur in about 5-10% of patients with intestinal amoebiasis?
What type of abscess may occur in about 5-10% of patients with intestinal amoebiasis?
Signup and view all the answers
What does the center of a hepatic amoebic abscess typically contain?
What does the center of a hepatic amoebic abscess typically contain?
Signup and view all the answers
Which clinical feature is typically seen in patients with fulminant colitis due to amoebic infection?
Which clinical feature is typically seen in patients with fulminant colitis due to amoebic infection?
Signup and view all the answers
What is the incubation period variability range for intestinal amoebiasis?
What is the incubation period variability range for intestinal amoebiasis?
Signup and view all the answers
Liver abscesses in hepatic amoebiasis are most commonly found in the upper left lobe of the liver.
Liver abscesses in hepatic amoebiasis are most commonly found in the upper left lobe of the liver.
Signup and view all the answers
Chocolate brown sputum is a characteristic symptom in pulmonary amoebiasis due to hepatobronchial fistula.
Chocolate brown sputum is a characteristic symptom in pulmonary amoebiasis due to hepatobronchial fistula.
Signup and view all the answers
Chloroquine is the preferred luminal amoebicide for treating amoebic liver abscess.
Chloroquine is the preferred luminal amoebicide for treating amoebic liver abscess.
Signup and view all the answers
The incidence of liver abscess is more common in women compared to men.
The incidence of liver abscess is more common in women compared to men.
Signup and view all the answers
Both luminal and tissue amoebicides can effectively treat amoebic colitis and amoebic liver abscess.
Both luminal and tissue amoebicides can effectively treat amoebic colitis and amoebic liver abscess.
Signup and view all the answers
Entamoeba histolytica is primarily found in temperate climate regions.
Entamoeba histolytica is primarily found in temperate climate regions.
Signup and view all the answers
The trophozoite stage of Entamoeba histolytica divides by binary fission approximately every 8 hours.
The trophozoite stage of Entamoeba histolytica divides by binary fission approximately every 8 hours.
Signup and view all the answers
Cysts of Entamoeba histolytica are oval in shape and typically measure 20–30 μm in size.
Cysts of Entamoeba histolytica are oval in shape and typically measure 20–30 μm in size.
Signup and view all the answers
The outer ectoplasm of a trophozoite is typically granular in appearance.
The outer ectoplasm of a trophozoite is typically granular in appearance.
Signup and view all the answers
Phagocytosed erythrocytes in trophozoites are a diagnostic feature specific to Entamoeba histolytica.
Phagocytosed erythrocytes in trophozoites are a diagnostic feature specific to Entamoeba histolytica.
Signup and view all the answers
Trophozoites can initiate infections if they survive in the stomach after being ingested.
Trophozoites can initiate infections if they survive in the stomach after being ingested.
Signup and view all the answers
Entamoeba histolytica is the fourth leading cause of parasitic mortality after malaria, schistosomiasis, and leishmaniasis.
Entamoeba histolytica is the fourth leading cause of parasitic mortality after malaria, schistosomiasis, and leishmaniasis.
Signup and view all the answers
The average size of a trophozoite of Entamoeba histolytica is around 30 μm.
The average size of a trophozoite of Entamoeba histolytica is around 30 μm.
Signup and view all the answers
The early cyst of E.histolytica contains four nuclei.
The early cyst of E.histolytica contains four nuclei.
Signup and view all the answers
Excystation occurs in the duodenum after the cyst wall is damaged by trypsin.
Excystation occurs in the duodenum after the cyst wall is damaged by trypsin.
Signup and view all the answers
With iodine stain, chromatoid bodies appear bright yellow.
With iodine stain, chromatoid bodies appear bright yellow.
Signup and view all the answers
The typical amoebic ulcer in intestinal amoebiasis does not extend deeper than the muscular layer.
The typical amoebic ulcer in intestinal amoebiasis does not extend deeper than the muscular layer.
Signup and view all the answers
The optimal habitat for metacystic trophozoites is in the mucosal tissue of the stomach.
The optimal habitat for metacystic trophozoites is in the mucosal tissue of the stomach.
Signup and view all the answers
In hepatic amoebiasis, the center of the abscess is filled with thick yellow pus.
In hepatic amoebiasis, the center of the abscess is filled with thick yellow pus.
Signup and view all the answers
The incubation period for amoebiasis is always 4 days.
The incubation period for amoebiasis is always 4 days.
Signup and view all the answers
Patients with intestinal amoebiasis are typically febrile and toxic.
Patients with intestinal amoebiasis are typically febrile and toxic.
Signup and view all the answers
Amoebic dysentery is characterized by small, odorless stools that contain mucus.
Amoebic dysentery is characterized by small, odorless stools that contain mucus.
Signup and view all the answers
Amoebic ulcers are characteristically solitary and confined to the rectum.
Amoebic ulcers are characteristically solitary and confined to the rectum.
Signup and view all the answers
The incubation period for intestinal amoebiasis can vary between 1 week and 4 months.
The incubation period for intestinal amoebiasis can vary between 1 week and 4 months.
Signup and view all the answers
Metacystic trophozoites undergo division to form eight nuclei, each surrounded by cytoplasm.
Metacystic trophozoites undergo division to form eight nuclei, each surrounded by cytoplasm.
Signup and view all the answers
Histolysin is a protective enzyme that enhances the healing of ulcers caused by E.histolytica.
Histolysin is a protective enzyme that enhances the healing of ulcers caused by E.histolytica.
Signup and view all the answers
The ulcers in intestinal amoebiasis can lead to strictures and thickening of the gut wall.
The ulcers in intestinal amoebiasis can lead to strictures and thickening of the gut wall.
Signup and view all the answers
Only about 1% of individuals with intestinal amoebiasis develop liver abscesses.
Only about 1% of individuals with intestinal amoebiasis develop liver abscesses.
Signup and view all the answers
Chronic involvement of the caecum due to amoebic infection can present symptoms resembling appendicitis.
Chronic involvement of the caecum due to amoebic infection can present symptoms resembling appendicitis.
Signup and view all the answers
What are the three forms of Entamoeba histolytica?
What are the three forms of Entamoeba histolytica?
Signup and view all the answers
What characteristic distinguishes the trophozoites of Entamoeba histolytica found in dysenteric stools?
What characteristic distinguishes the trophozoites of Entamoeba histolytica found in dysenteric stools?
Signup and view all the answers
At what temperature can trophozoites of Entamoeba histolytica survive, and how long do they live at that temperature?
At what temperature can trophozoites of Entamoeba histolytica survive, and how long do they live at that temperature?
Signup and view all the answers
What occurs during the encystment of trophozoites in Entamoeba histolytica?
What occurs during the encystment of trophozoites in Entamoeba histolytica?
Signup and view all the answers
What is the range of sizes (in μm) for a mature cyst of Entamoeba histolytica?
What is the range of sizes (in μm) for a mature cyst of Entamoeba histolytica?
Signup and view all the answers
How often do trophozoites of Entamoeba histolytica divide by binary fission?
How often do trophozoites of Entamoeba histolytica divide by binary fission?
Signup and view all the answers
What is a notable feature of the endoplasm of the trophozoite stage of Entamoeba histolytica?
What is a notable feature of the endoplasm of the trophozoite stage of Entamoeba histolytica?
Signup and view all the answers
Why are live trophozoites not transmitted through stool ingestion in Entamoeba histolytica infections?
Why are live trophozoites not transmitted through stool ingestion in Entamoeba histolytica infections?
Signup and view all the answers
What is the expected outcome if untreated liver abscesses in hepatic amoebiasis rupture?
What is the expected outcome if untreated liver abscesses in hepatic amoebiasis rupture?
Signup and view all the answers
Describe the characteristics of the sputum produced in cases of pulmonary amoebiasis.
Describe the characteristics of the sputum produced in cases of pulmonary amoebiasis.
Signup and view all the answers
How do luminal amoebicides differ from tissue amoebicides in the treatment of amoebic infections?
How do luminal amoebicides differ from tissue amoebicides in the treatment of amoebic infections?
Signup and view all the answers
What population is at a lower risk for developing liver abscesses in the context of hepatic amoebiasis?
What population is at a lower risk for developing liver abscesses in the context of hepatic amoebiasis?
Signup and view all the answers
What role does health education play in the prophylaxis of hepatic amoebiasis?
What role does health education play in the prophylaxis of hepatic amoebiasis?
Signup and view all the answers
What is the characteristic appearance of the typical amoebic ulcer in cross section?
What is the characteristic appearance of the typical amoebic ulcer in cross section?
Signup and view all the answers
In cases of fulminant colitis, how does the clinical presentation differ from typical intestinal amoebiasis?
In cases of fulminant colitis, how does the clinical presentation differ from typical intestinal amoebiasis?
Signup and view all the answers
What type of pus is commonly found in the center of a hepatic amoebic abscess?
What type of pus is commonly found in the center of a hepatic amoebic abscess?
Signup and view all the answers
Describe the typical stool characteristics associated with amoebic dysentery.
Describe the typical stool characteristics associated with amoebic dysentery.
Signup and view all the answers
What complications can arise from chronic involvement of the cecum due to amoebic infection?
What complications can arise from chronic involvement of the cecum due to amoebic infection?
Signup and view all the answers
During the incubation period of intestinal amoebiasis, what symptomatology is generally observed?
During the incubation period of intestinal amoebiasis, what symptomatology is generally observed?
Signup and view all the answers
How can amoebic granulomas be misdiagnosed, and why is this significant?
How can amoebic granulomas be misdiagnosed, and why is this significant?
Signup and view all the answers
What role do lysosomal enzymes and cytokines play in hepatic amoebiasis?
What role do lysosomal enzymes and cytokines play in hepatic amoebiasis?
Signup and view all the answers
What structural change occurs to the cyst wall during excystation in E. histolytica?
What structural change occurs to the cyst wall during excystation in E. histolytica?
Signup and view all the answers
What is the role of the histolysin enzyme in the pathogenesis of E. histolytica?
What is the role of the histolysin enzyme in the pathogenesis of E. histolytica?
Signup and view all the answers
Describe the typical appearance of amoebic ulcers in intestinal amoebiasis.
Describe the typical appearance of amoebic ulcers in intestinal amoebiasis.
Signup and view all the answers
What distinguishes the metacystic trophozoite stage from the earlier cyst stage of E. histolytica?
What distinguishes the metacystic trophozoite stage from the earlier cyst stage of E. histolytica?
Signup and view all the answers
Which part of the gastrointestinal tract is optimal for the survival of metacystic trophozoites?
Which part of the gastrointestinal tract is optimal for the survival of metacystic trophozoites?
Signup and view all the answers
How does the staining with iron hemotoxylin assist in identifying E. histolytica?
How does the staining with iron hemotoxylin assist in identifying E. histolytica?
Signup and view all the answers
What impact does the motility of trophozoites have on the severity of intestinal amoebiasis?
What impact does the motility of trophozoites have on the severity of intestinal amoebiasis?
Signup and view all the answers
How does the lifecycle of E. histolytica complete its transmission cycle?
How does the lifecycle of E. histolytica complete its transmission cycle?
Signup and view all the answers
Entamoeba histolytica is the third leading parasitic cause of mortality, after malaria and ______.
Entamoeba histolytica is the third leading parasitic cause of mortality, after malaria and ______.
Signup and view all the answers
The trophozoite is the only form of Entamoeba histolytica present in ______.
The trophozoite is the only form of Entamoeba histolytica present in ______.
Signup and view all the answers
The cyst of Entamoeba histolytica is approximately ______ μm in size.
The cyst of Entamoeba histolytica is approximately ______ μm in size.
Signup and view all the answers
Trophozoites divide by ______ fission approximately every 8 hours.
Trophozoites divide by ______ fission approximately every 8 hours.
Signup and view all the answers
The trophozoites from acute dysenteric stools often contain phagocytosed ______.
The trophozoites from acute dysenteric stools often contain phagocytosed ______.
Signup and view all the answers
Entamoeba histolytica undergoes ______ in the intestinal lumen before forming a cyst.
Entamoeba histolytica undergoes ______ in the intestinal lumen before forming a cyst.
Signup and view all the answers
The outer ectoplasm of a trophozoite is clear, transparent, and ______.
The outer ectoplasm of a trophozoite is clear, transparent, and ______.
Signup and view all the answers
Typical amoeboid motility is a crawling or ______ movement, not a free swimming one.
Typical amoeboid motility is a crawling or ______ movement, not a free swimming one.
Signup and view all the answers
The mature cyst of E.histolytica is characterized as being ______
The mature cyst of E.histolytica is characterized as being ______
Signup and view all the answers
E.histolytica passes its life cycle only in ______
E.histolytica passes its life cycle only in ______
Signup and view all the answers
The optimal habitat for the metacystic trophozoite is the submucosal tissue of the ______ and colon
The optimal habitat for the metacystic trophozoite is the submucosal tissue of the ______ and colon
Signup and view all the answers
Excystation occurs when the cyst reaches the lower part of the ______
Excystation occurs when the cyst reaches the lower part of the ______
Signup and view all the answers
Penetration of the amoeba is facilitated by motility and the tissue lytic enzyme, ______
Penetration of the amoeba is facilitated by motility and the tissue lytic enzyme, ______
Signup and view all the answers
The cysts pass through the stomach ______ and enter the small intestine
The cysts pass through the stomach ______ and enter the small intestine
Signup and view all the answers
Amoebic ulcers typically appear initially as raised nodules with ______ edges
Amoebic ulcers typically appear initially as raised nodules with ______ edges
Signup and view all the answers
The average incubation period for amoebiasis ranges from ______ to 4 months
The average incubation period for amoebiasis ranges from ______ to 4 months
Signup and view all the answers
Liver abscesses are usually located in the upper right lobe of the ______.
Liver abscesses are usually located in the upper right lobe of the ______.
Signup and view all the answers
A hepatobronchial fistula may result in expectoration of ______ brown sputum.
A hepatobronchial fistula may result in expectoration of ______ brown sputum.
Signup and view all the answers
Luminal amoebicides act in the intestinal lumen but not in ______.
Luminal amoebicides act in the intestinal lumen but not in ______.
Signup and view all the answers
Metronidazole is the drug of choice for treating both amoebic colitis and amoebic liver ______.
Metronidazole is the drug of choice for treating both amoebic colitis and amoebic liver ______.
Signup and view all the answers
General prophylaxis for hepatic amoebiasis includes protecting food and water from ______ with human excreta.
General prophylaxis for hepatic amoebiasis includes protecting food and water from ______ with human excreta.
Signup and view all the answers
The typical amoebic ulcer is ______-shaped in cross section.
The typical amoebic ulcer is ______-shaped in cross section.
Signup and view all the answers
In chronic amoebic infections, the ______ of the gut wall may occur.
In chronic amoebic infections, the ______ of the gut wall may occur.
Signup and view all the answers
The ulcers in intestinal amoebiasis do not extend deeper than the ______ layer.
The ulcers in intestinal amoebiasis do not extend deeper than the ______ layer.
Signup and view all the answers
The stools in typical amoebic dysentery are large, foul-smelling, and often ______ with bloodstreaked mucus.
The stools in typical amoebic dysentery are large, foul-smelling, and often ______ with bloodstreaked mucus.
Signup and view all the answers
Hepatic amoebiasis may lead to the formation of liver ______.
Hepatic amoebiasis may lead to the formation of liver ______.
Signup and view all the answers
The center of a hepatic amoebic abscess contains thick ______ pus.
The center of a hepatic amoebic abscess contains thick ______ pus.
Signup and view all the answers
The patient with fulminant colitis often presents as ______ and toxic.
The patient with fulminant colitis often presents as ______ and toxic.
Signup and view all the answers
The incubation period for intestinal amoebiasis is highly variable, ranging from 1 to ______ months.
The incubation period for intestinal amoebiasis is highly variable, ranging from 1 to ______ months.
Signup and view all the answers
Match the following amoebicides with their classification:
Match the following amoebicides with their classification:
Signup and view all the answers
Match the following clinical features with their corresponding conditions:
Match the following clinical features with their corresponding conditions:
Signup and view all the answers
Match the following treatment dosages with the respective drug:
Match the following treatment dosages with the respective drug:
Signup and view all the answers
Match the following preventive measures with their descriptions:
Match the following preventive measures with their descriptions:
Signup and view all the answers
Match the following statements with their accuracy:
Match the following statements with their accuracy:
Signup and view all the answers
Match the stages of Entamoeba histolytica with their characteristics:
Match the stages of Entamoeba histolytica with their characteristics:
Signup and view all the answers
Match the staining methods with their observed results:
Match the staining methods with their observed results:
Signup and view all the answers
Match the forms of amoebiasis with their descriptions:
Match the forms of amoebiasis with their descriptions:
Signup and view all the answers
Match the life cycle stages of E. histolytica with their respective roles:
Match the life cycle stages of E. histolytica with their respective roles:
Signup and view all the answers
Match the pathological effects of E. histolytica with their outcomes:
Match the pathological effects of E. histolytica with their outcomes:
Signup and view all the answers
Match the characteristics of cysts found in E. histolytica with their details:
Match the characteristics of cysts found in E. histolytica with their details:
Signup and view all the answers
Match the incubation periods with their respective durations:
Match the incubation periods with their respective durations:
Signup and view all the answers
Match the transmission methods with their mechanisms:
Match the transmission methods with their mechanisms:
Signup and view all the answers
Match the amoebic diseases with their related clinical features:
Match the amoebic diseases with their related clinical features:
Signup and view all the answers
Match the specific features with the type of amoebic infection:
Match the specific features with the type of amoebic infection:
Signup and view all the answers
Match the symptoms with their respective amoebic conditions:
Match the symptoms with their respective amoebic conditions:
Signup and view all the answers
Match the abscess characteristics with their corresponding type of amoebiasis:
Match the abscess characteristics with their corresponding type of amoebiasis:
Signup and view all the answers
Match the incubation periods with their corresponding amoebic infections:
Match the incubation periods with their corresponding amoebic infections:
Signup and view all the answers
Match the amoebic ulcer characteristics with their descriptions:
Match the amoebic ulcer characteristics with their descriptions:
Signup and view all the answers
Match the following stages of Entamoeba histolytica with their descriptions:
Match the following stages of Entamoeba histolytica with their descriptions:
Signup and view all the answers
Match the amoebic manifestations with their clinical importance:
Match the amoebic manifestations with their clinical importance:
Signup and view all the answers
Match the types of amoebic infections with their associated complications:
Match the types of amoebic infections with their associated complications:
Signup and view all the answers
Match the following characteristics with the correct forms of Entamoeba histolytica:
Match the following characteristics with the correct forms of Entamoeba histolytica:
Signup and view all the answers
Match the following terms related to Entamoeba histolytica with their meanings:
Match the following terms related to Entamoeba histolytica with their meanings:
Signup and view all the answers
Match the following descriptions of Entamoeba histolytica with their corresponding forms:
Match the following descriptions of Entamoeba histolytica with their corresponding forms:
Signup and view all the answers
Match the following diseases with their causative form of Entamoeba histolytica:
Match the following diseases with their causative form of Entamoeba histolytica:
Signup and view all the answers
Match the following features with the correct stage of Entamoeba histolytica:
Match the following features with the correct stage of Entamoeba histolytica:
Signup and view all the answers
Match the following terms with their specific characteristics concerning Entamoeba histolytica:
Match the following terms with their specific characteristics concerning Entamoeba histolytica:
Signup and view all the answers
Match the following components of the life cycle of Entamoeba histolytica with their functions:
Match the following components of the life cycle of Entamoeba histolytica with their functions:
Signup and view all the answers
Study Notes
Entamoeba Histolytica
- Entamoeba histolytica is a protozoan parasite that causes amoebic dysentery and amoebic liver abscess.
- The parasite is found worldwide but is more common in tropical regions.
- It's estimated that 10% of the global population and 50% of people in developing countries are infected with the parasite.
- E. histolytica is a leading cause of parasitic mortality, ranking third after malaria and schistosomiasis.
Morphology
- E. histolytica exists in three forms: trophozoite, precystic stage, and cyst.
- The trophozoite is the vegetative or active form of the parasite.
- It's the only form present in tissues, ranging in size from 12-60 µm with an average of 20 µm.
- Trophozoites are characterized by their irregular shape and amoeboid movement.
- They have a clear outer ectoplasm and a finely granular inner endoplasm.
- Trophozoites in acute dysenteric stool often contain ingested red blood cells (RBCs), which is a diagnostic feature.
- Trophozoites divide by binary fission (splitting into two) every 8 hours.
- They can survive for up to 5 hours at 37°C and are killed by drying, heat, and chemical sterilization.
- Infection is not transmitted by trophozoites because they cannot survive outside the body to initiate infection.
- The precystic stage is a transition phase where the trophozoite prepares for encystment.
- The cyst is the spherical, dormant form of the parasite.
- It's 10-20 µm in size and can contain one to four nuclei.
Life Cycle
- E. histolytica completes its life cycle solely in humans.
- The mature cyst with four nuclei is the infective stage.
- Infection occurs when humans ingest food or water contaminated with cysts.
- Cysts survive passage through the stomach and reach the small intestine, where excystation occurs.
- During excystation, the cyst wall breaks down due to trypsin.
- The liberated quadrinucleate amoeba then divides into eight smaller metacystic trophozoites.
- These trophozoites are found in the submucosal tissue of the caecum and colon.
- Some metacystic trophozoites develop into precystic forms and cysts.
- Cysts are passed in feces, completing the cycle.
Pathogenesis
- E. histolytica can cause both intestinal and extraintestinal amoebiasis.
- The incubation period is highly variable, typically ranging from four days to four months.
- Symptoms and severity depend on the organ affected and the extent of damage.
Intestinal Amoebiasis
- Metacystic trophozoites penetrate the colon's epithelial lining.
- Penetration is aided by the amoeba's motility and the enzyme "histolysin," which damages the mucosal cells.
- Amoeba penetration creates distinctive ulcers with a pinhead center and raised edges.
- Amoebic ulcers are the characteristic lesion of intestinal amoebiasis.
- Ulcers are often multiple and concentrated in the caecum and sigmoidorectal region.
- The ulcers can undermine and spread laterally, causing extensive mucosal loss.
- Occasionally, ulcers penetrate deeper into the colon wall, leading to perforation and peritonitis.
- Deep ulcers can form scars that constrict the colon, leading to obstruction.
- These amoebic granulomas can be mistaken for malignant tumors.
Clinical Features
- Amoebic dysentery is the typical manifestation of intestinal amoebiasis.
- Patients experience large, foul-smelling, bloody stools with mucus.
- The stools contain clumped, reddish-brown RBCs.
- Trophozoites with ingested RBCs can be observed in the stool.
- Patients are usually afebrile (not feverish) and nontoxic.
- Fulminant colitis (acute inflammation of the colon) causes confluent ulceration and necrosis.
- Other intestinal symptoms like diarrhea or vague abdominal discomfort can occur.
- Chronic involvement of the caecum can mimic appendicitis.
Extraintestinal Amoebiasis
- E. histolytica can spread beyond the intestines and cause complications in other organs.
- The most common extraintestinal complication is hepatic amoebiasis, which can lead to liver abscesses.
- Pulmonary amoebiasis can occur due to the spread of liver abscesses to the lungs.
- Metastatic amoebiasis can involve other organs like the brain, skin, and genitourinary tract.
Hepatic Amoebiasis
- Liver damage might not be directly caused by amoeba but by enzymes and inflammatory mediators released by surrounding cells.
- Liver abscesses are present in about 5%-10% of patients with intestinal amoebiasis.
- Abscesses typically occur in the upper right lobe of the liver and contain thick, chocolate-brown pus.
- Abscesses can rupture into surrounding tissues, causing complications depending on the location.
- Liver abscesses are less common in women and rare in children under 10 years old.
Pulmonary Amoebiasis
- Pulmonary amoebiasis often results from a hepatobronchial fistula and can lead to amoebic empyema.
- Patients present with chest pain, dyspnea (difficulty breathing), and non-productive coughs.
Treatment
- Luminal amoebicides like diloxanide furoate, iodoquinol, paromomycin, and tetracycline target the intestinal lumen but have limited effect on tissue amoebae.
- Tissue amoebicides such as emetine and chloroquine are effective against systemic infection but less potent against intestinal amoebae.
- Metronidazole and its related compounds (tinidazole, ornidazole) are the drugs of choice for treating both intestinal and liver involvement.
- Metronidazole dosage for liver abscess is 1 g for two days, followed by 5 g daily for three weeks.
Prophylaxis
- General prophylaxis measures for fecal-oral infections are crucial.
- Food and water must be protected from contamination with human excreta.
- Detection and treatment of carriers and their exclusion from food handling jobs help limit infection spread.
- Healthy personal hygiene practices and education contribute to control efforts.
Entamoeba Histolytica: A Brief Overview
- Entamoeba histolytica is responsible for amoebic dysentery and amoebic liver abscess.
- Its prevalence is widespread, particularly in tropical regions.
- Around 10% of the global population and 50% of inhabitants in developing countries are estimated to be infected.
Morphology of Entamoeba Histolytica
- Entamoeba histolytica exists in three forms: trophozoite, precystic stage, and cyst.
-
Trophozoite: The vegetative or growing stage, present only in tissues.
- Size: 12–60 μm, averaging 20 μm
- Active in fresh dysenteric stool, smaller in convalescents and carriers.
- Cytoplasm: Consists of clear, transparent outer ectoplasm and finely granular inner endoplasm.
- Motility: Exhibits amoeboid movement, crawling or gliding, driven by pseudopodia.
- Nucleus: Spherical, 4–6 μm, containing a central karyosome.
- Important diagnostic feature: Contains phagocytosed erythrocytes, not found in other intestinal amoebae.
- Divides via binary fission every 8 hours.
- Survival: Survives for up to 5 hours at 37°C. Killed by drying, heat, and chemical sterilization.
-
Precystic Stage:
- Forms in the intestinal lumen during encystment.
- Trophozoites round or oval, extruding food vacuoles.
- Contains a large glycogen vacuole and two chromatid bars.
- Secretes a cyst wall, transforming into a cyst.
-
Cystic Stage:
- Spherical shape, 10–20 μm.
- Early cyst: Contains a single nucleus and two chromatid bars.
- Mature cyst: Contains four nuclei, known as a quadrinucleate cyst.
- Staining:
- Hematoxylin: Nuclear chromatin and chromatoid bodies appear blue or black.
- Iodine: Nuclear chromatin and karyosome bright yellow, chromatoid bodies appear clear (unstained).
The Life Cycle of Entamoeba Histolytica
- Involves only one host: Humans.
- Infective form: Mature quadrinucleate cyst.
- Transmission: Ingestion of contaminated food and water containing cysts.
- Cysts pass through the stomach unharmed, reaching the small intestine.
- Excystation: In the lower ileum, trypsin damages the cyst wall, leading to excystation.
- Metacyst stage: The cytoplasm detaches from the cyst wall, freeing the quadrinucleate amoeba.
- Metacystic trophozoites: The nuclei divide, forming 8 nuclei, each surrounded by cytoplasm, resulting in 8 small metacystic trophozoites.
- Optimal habitat: Submucosal tissue of the caecum and colon.
- Some metacystic trophozoites develop into precystic forms and cysts, which are eliminated in feces, continuing the cycle.
Pathogenesis of Entamoeba Histolytica
- Causes intestinal and extraintestinal amoebiasis.
- Incubation period: Variable, ranging from 4 days to 4 months.
- Forms and severity of amoebiasis depend on the affected organ and extent of damage.
Intestinal Amoebiasis
- Metacystic trophozoites invade the columnar epithelial cells of the colon.
- Penetration facilitated by trophozoite motility and the tissue lytic enzyme, histolysin, which breaks down the mucosal epithelium.
- Results in ulcers with pinhead centers and raised edges.
- May heal spontaneously if invasion remains superficial.
- More often, amoebae penetrate the submucosal layer, multiplying rapidly and causing lytic necrosis, leading to abscess formation.
- Abscesses break down, forming ulcers.
- Ulcers are multiple, mainly located in the caecum and the sigmoidorectal region.
- Initially appear as raised nodules with pouting edges, later breaking down, releasing brownish necrotic material containing numerous trophozoites.
- Typical amoebic ulcer is flask-shaped with a narrow mouth and neck, and a large, rounded base.
- Ulcers generally don't extend beyond the submucosal layer but spread laterally in the submucosa, causing undermining and patchy mucosal loss.
- Amoebae are found at the periphery of the lesions and extend into surrounding healthy tissues.
- In rare instances, ulcers may affect the muscular and serous coats of the colon, causing perforation and peritonitis.
- Deep ulcers form scars, leading to strictures, partial obstruction, and thickening of the gut wall.
- This amoebic granuloma or amoeboma may be mistaken for a malignant tumor.
Clinical Features of Intestinal Amoebiasis
- Incubation period: Variable, ranging from 1 to 4 months.
- Clinical course: Characterized by prolonged latency, relapses, and intermissions.
- Amoebic dysentery:
- Large, foul-smelling, brownish-black stools with blood-streaked mucus and feces.
- Erythrocytes in stools appear clumped and reddish-brown.
- Presence of E.histolytica trophozoites with ingested erythrocytes is a key diagnostic feature.
- Patient is usually afebrile and non-toxic.
- Fulminant colitis: Confluent ulceration and necrosis of the colon, accompanied by fever and toxicity.
- Not all intestinal amoebiasis manifests as dysentery.
- It can present as diarrhea or vague abdominal symptoms.
- Chronic involvement of the caecum can mimic appendicitis.
Extraintestinal Amoebiasis
- Entamoeba histolytica can affect organs beyond the intestines.
- Major sites of extraintestinal amoebiasis:
- Hepatic amoebiasis (including liver abscesses)
- Pulmonary amoebiasis
- Metastatic amoebiasis
- Cutaneous amoebiasis
- Genitourinary amoebiasis
Hepatic Amoebiasis
- Liver enlargement and tenderness are common, without significant liver function impairment or fever.
- Damage may not be directly caused by amoebae but by lysosomal enzymes and cytokines from inflammatory cells surrounding the trophozoites.
- Liver abscesses occur in 5–10% of individuals with intestinal amoebiasis.
- Liver abscesses usually solitary, located in the upper right lobe of the liver, contain thick chocolate brown pus.
- Multiple abscesses and abscesses pressing on the biliary tract can lead to jaundice.
- Uncontrolled abscesses can rupture into surrounding tissues, including the lung, pleural cavity, pericardium, peritoneal cavity, stomach, intestine, inferior vena cava, or externally through the abdominal wall and skin.
- Lower incidence in women and rare in children younger than 10 years.
Pulmonary Amoebiasis
- Often results from a hepatobronchial fistula, characterized by expectoration of chocolate brown sputum.
- Less commonly, amoebic empyema can develop.
- Clinical presentation: Severe pleuritic chest pain, dyspnea (difficulty breathing), and non-productive cough.
Treatment of Amoebiasis
-
Luminal amoebicides:
- Diloxanide furoate, iodoquinol, paromomycin, and tetracycline act within the intestinal lumen but not in tissues.
-
Tissue amoebicides:
- Emetine, chloroquine, etc., effective in systemic infections, but less so in the intestine.
- Dosage of chloroquine for amoebic liver abscess: 1 g for 2 days followed by 500 mg daily for 3 weeks.
-
Both luminal and tissue amoebicides:
- Metronidazole and related compounds (tinidazole and ornidazole) are effective in both the intestine and tissues, and are preferred for treating amoebic colitis and amoebic liver abscess.
Prophylaxis
- General measures:
- Similar to other fecal-oral infections.
- Food and water must be protected from contamination with human excreta.
- Additional approaches:
- Detection and treatment of carriers.
- Exclusion of carriers from food-handling professions.
- Health education and promotion of healthy personal hygiene habits.
Entamoeba histolytica
- A parasitic protozoan responsible for amoebic dysentery and amoebic liver abscess.
- Found globally, with higher prevalence in tropical regions.
- Estimated to infect 10% of the world's population and 50% of those in developing countries.
- Third leading parasitic cause of death worldwide, after malaria and schistosomiasis.
Morphology
- Entamoeba histolytica exists in three forms:
- Trophozoite: The vegetative or growing stage. Present in tissues. Irregular shape, 12-60 μm in size. Actively motile in dysenteric stool.
- Precyst: Transition stage between trophozoite and cyst.
- Cyst: The infective stage, passed in feces. Spherical, 10-20 μm in size.
Life Cycle
- Entamoeba histolytica has a single-host life cycle (human).
- Infective form: Mature quadrinucleate cyst
- Transmission: Ingestion of contaminated food and water containing cysts.
- Excystation occurs in the ileum, releasing metacystic trophozoites.
- Metacystic trophozoites multiply in the colon.
- Some trophozoites transform into precystic stages and cysts, completing the cycle.
Pathogenesis
- Causes intestinal and extraintestinal amoebiasis.
- Incubation period varies from 4 days to 4 months.
- Intestinal amoebiasis:
- Metacystic trophozoites penetrate the colonic epithelium, causing ulcers.
- Amoeba utilize histolysin to penetrate the mucosal barrier.
- Ulcers may be superficial or deep.
- Deep ulcers may lead to scarring, strictures, and amoebomas.
Clinical Features
- Intestinal amoebiasis presents as:
- Amoebic dysentery: Characterized by bloody, foul-smelling stools.
- Diarrhea: Often asymptomatic or with vague abdominal complaints.
- Chronic caecal involvement: Mimicking appendicitis.
Extraintestinal Amoebiasis
- Hepatic Amoebiasis:
- Liver abscesses: Usually solitary, located in the right lobe.
- Characterized by chocolate-brown pus (anchovy sauce pus).
- May lead to complications such as rupture into surrounding organs.
- Pulmonary Amoebiasis:
- Often secondary to liver abscesses.
- Results in hepatobronchial fistula with expectoration of chocolate brown sputum.
- Other forms:
- Metastatic amoebiasis: Affecting various organs.
- Cutaneous amoebiasis: Skin infections.
- Genitourinary amoebiasis: Affecting reproductive organs.
Treatment
- Luminal amoebicides: Act in the intestinal lumen (Diloxanide furoate, iodoquinol, paromomycin, Tetracycline)
- Tissue amoebicides: Act systemically (Emetine, chloroquine)
- Both luminal and tissue amoebicides: Preferred treatment (Metronidazole, tinidazole, ornidazole)
Prophylaxis
- General measures for fecal-oral infections.
- Food and water protection from contamination with human excreta.
- Detection and treatment of carriers, exclusion from food handling.
- Health education and promotion of healthy personal habits.
Entamoeba histolytica
- Entamoeba histolytica causes amoebic dysentery and amoebic liver abscess
- It is a common parasite, particularly in tropical regions
- It is the third leading parasitic cause of death worldwide
Morphology
- Entamoeba histolytica exists in three forms: trophozoite, precystic, and cyst
- The trophozoite is the active, feeding stage, found in tissues
- It is irregular in shape, ranging from 12-60 µm in size
- The trophozoite displays amoeboid movement with finger-like projections
- It contains a single nucleus with a central karyosome
- Trophozoites from acute dysenteric stools often contain phagocytosed red blood cells, a distinguishing feature
- The trophozoite divides by binary fission
- The precystic stage is a transition form, losing food vacuoles and becoming rounder
- It contains a glycogen vacuole and two chromatid bars
- The cyst is the infective stage, spherical and 10-20 µm in size
- Mature cysts contain four nuclei (quadrinucleate)
- Cysts are resistant to environmental conditions and can survive for extended periods
Life Cycle
- The life cycle of Entamoeba histolytica occurs solely in humans
- Infection occurs through ingestion of mature cysts
- Cysts reach the small intestine unharmed and undergo excystation
- The metacyst stage releases quadrinucleate amoebae which then divide to form 8 metacystic trophozoites
- Optimal habitat for metacystic trophozoites is the submucosal tissue of the caecum and colon
Pathogenesis
- E. histolytica causes both intestinal and extraintestinal amoebiasis
- Incubation period ranges from 4 days to 4 months
- The severity and manifestation of amoebiasis depend on the affected organ and extent of damage
Intestinal Amoebiasis
- Metacystic trophozoites penetrate the colon's epithelium
- Penetration is facilitated by the amoebae's motility and histolysin, a tissue lytic enzyme
- Amoebic penetration creates discrete ulcers with a central pinhead and raised edges
- Deeper penetration leads to submucosal abscess formation
- Amoebic ulcers are flask-shaped, forming scar tissue that may lead to strictures and thickening of the gut wall
Clinical Features
- Intestinal amoebiasis presents with diverse symptoms, from mild diarrhea to severe dysentery
- Patients with amoebic dysentery experience bloody, foul-smelling stools and can exhibit fever and toxicity in more severe cases
- In chronic cases, involvement of the caecum can mimic appendicitis
Extraintestinal Amoebiasis
- Liver abscess is the most common extraintestinal manifestation
- Other forms include pulmonary, metastatic, cutaneous, and genitourinary amoebiasis
Hepatic Amoebiasis
- Liver abscesses are often solitary and located in the upper right lobe
- Jaundice occurs with multiple abscesses or blockage of the biliary tract
- Untreated abscesses can rupture into surrounding tissues, including the lung, pleura, pericardium, and peritoneum
Pulmonary Amoebiasis
- Often arises from a hepatobronchial fistula, resulting in brown sputum
- Symptoms include pleuritic chest pain, dyspnea, and non-productive cough
Treatment
- Luminal amoebicides (diloxanide furoate, iodoquinol, paromomycin, and tetracycline) act in the intestinal lumen but not tissues
- Tissue amoebicides (emetine, chloroquine) target systemic infection and are less effective in the intestine
- Metronidazole and related compounds (tinidazole, ornidazole) are the drugs of choice for both intestinal and systemic amoebiasis
Prophylaxis
- Prevention measures focus on avoiding fecal-oral contamination of food and water
- Detection and treatment of carriers are essential
- Promoting healthy personal habits and sanitation practices is vital for control
Entamoeba Histolytica
- A parasitic protozoan that causes amoebic dysentery and amoebic liver abscess.
- Globally prevalent, with higher rates in tropical regions.
- Estimated to infect 10% of the world population and 50% of those in developing countries.
- Third leading parasitic cause of death, after malaria and schistosomiasis.
Morphology
- Exists in three forms: trophozoite, precyst, and cyst.
-
Trophozoite:
- Active, growing stage.
- Found in tissues, irregularly shaped, 12-60 μm in size (average 20 μm).
- Larger and more active in dysenteric stool, smaller in convalescent and carrier stages.
- Cytoplasm: clear outer ectoplasm and finely granular inner endoplasm.
- Possesses finger-like pseudopodia for movement.
- Contains a spherical nucleus (4-6 μm) with a central karyosome.
- Often contain phagocytosed red blood cells, a diagnostic feature.
- Divides via binary fission every 8 hours.
- Survives for up to 5 hours at 37°C, but is killed by drying, heat, and chemical sterilization.
-
Precystic Stage:
- Formed when trophozoites undergo encystment in the intestinal lumen.
- Round or oval shape with a large glycogen vacuole and two chromatid bars.
- Secretes a cyst wall around itself.
-
Cystic Stage:
- Spherical, 10-20 μm in diameter.
- Early cyst has one nucleus and two chromatid bars.
- Mature cyst has four nuclei.
- Nuclear chromatin and chromatoid bodies stain dark blue or black with hematoxylin.
- With iodine stain, nuclear chromatin and karyosome appear bright yellow, while chromatoid bodies remain clear.
Life Cycle
- Only occurs in humans.
- Infective form: Mature quadrinucleate cyst.
- Mode of transmission: Ingestion of cysts through contaminated food and water.
- Excystation: Cyst wall breaks down in the ileum by trypsin, releasing the amoeba.
- Metacystic stage: The amoeba (now quadrinucleate) detaches from the cyst wall.
- Metacystic trophozoites: The amoeba undergoes division to form 8 nuclei, each surrounded by cytoplasm, resulting in smaller metacystic trophozoites.
- Ideal habitat: Submucosal tissue of the caecum and colon.
- Some trophozoites develop into precystic forms and cysts, which are excreted in feces, completing the cycle.
Pathogenesis
- Causes intestinal and extraintestinal amoebiasis.
- Incubation period: Highly variable, typically 4 days to 4 months.
- Amoebiasis severity depends on the affected organ and extent of damage.
Intestinal Amoebiasis
- Metacystic trophozoites penetrate the colon's epithelial cells, facilitated by their motility and the enzyme histolysin.
- Penetration creates small ulcers with raised edges.
- Some invasions are superficial and heal spontaneously.
- Deeper penetration results in submucosal abscesses due to amoeba multiplication and tissue lysis.
- Abscess rupture leads to ulcers, which are often multiple and primarily localized in the caecum and sigmoidorectal region.
- Amoebic ulcers appear as raised nodules with pouting edges and later discharge necrotic material with trophozoites.
- Typically flask-shaped in cross-section, with a narrow mouth and a wide, rounded base.
- Amoebae spread laterally in the submucosa, causing undermining and mucosal loss.
- Ulceration may involve the muscular and serous coats, leading to perforation, peritonitis, and scarring.
- Scarring can result in strictures, obstruction, and thickening of the gut wall.
- Amoebic granulomas (amoebomas) may mimic malignant tumors.
Clinical Features
- Incubation period: 1-4 months.
- Symptoms:
- Prolonged latency, relapses, and intermissions.
- Amoebic dysentery: characterized by large, foul-smelling stools with bloodstreaked mucus.
- Erythrocytes in stools are clumped and reddish-brown.
- Fever and toxicity are usually absent.
- Fulminant colitis: Extensive ulceration and necrosis of the colon are present.
- Diarrhea or vague abdominal discomfort (uncomfortable belly or growling abdomen).
- Chronic caecal involvement mimicking appendicitis.
Extraintestinal Amoebiasis
- Occurs when the amoeba spreads beyond the intestines.
- Common forms:
- Hepatic amoebiasis (liver abscess)
- Pulmonary amoebiasis
- Metastatic amoebiasis
- Cutaneous amoebiasis
- Genitourinary amoebiasis
Hepatic Amoebiasis
- Enlarged, tender liver without significant liver dysfunction or fever.
- Liver damage may be caused indirectly by enzymes and cytokines from inflammatory cells surrounding the amoeba.
- Amoebic liver abscesses develop in 5-10% of cases.
- Abscesses contain thick, chocolate-brown pus (anchovy sauce pus) composed of liquefied necrotic liver tissue.
- Usually solitary and located in the upper right lobe of the liver.
- Multiple abscesses can cause jaundice by pressing on the biliary tract.
- Untreated abscesses can rupture into adjacent tissues, such as the lung, pleural cavity, pericardium, peritoneal cavity, stomach, intestine, inferior vena cava, or externally through the abdomen and skin.
- Less common in women and rare in children under 10 years old.
Pulmonary Amoebiasis
- Results from a hepatobronchial fistula, leading to expectoration of chocolate-brown sputum.
- Less commonly, amoebic empyema develops.
- Symptoms: Severe pleuritic chest pain, dyspnea, and non-productive cough.
Treatment
-
Luminal amoebicides:
- Target amoebae in the intestinal lumen.
- Include diloxanide furoate, iodoquinol, paromomycin, and tetracycline.
-
Tissue amoebicides:
- Effective for systemic infections but less effective in the intestine.
- Examples include emetine and chloroquine.
- Chloroquine dosage for amoebic liver abscess: 1 g for 2 days followed by 5 g daily for 3 weeks.
-
Both luminal and tissue amoebicides:
- Preferred for treating amoebic colitis and liver abscess.
- Examples include metronidazole, tinidazole, and ornidazole.
Prophylaxis
- Similar to other fecal-oral infections.
- Prevention includes protecting food and water from contamination with human excreta.
- Detecting and treating carriers and excluding them from food handling helps control spread.
- Promoting healthy personal habits and education are essential.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the essential aspects of Entamoeba histolytica, a protozoan parasite responsible for amoebic dysentery. Explore its morphology, lifecycle stages, and global impact on human health. Understanding this parasite is crucial for studying infectious diseases.