uncommon, present in less than one-third of the cases The condition can be differentiated from that of bacillary dysentery by the demonstration of RBCs, Charcot-Leyden crystals and haematophagous amoebic trophozoites in the amoebic ⑧ Complications of symptomatic intestinal amoebiasis: Thick megacolon(巨结肠) occurs In less than 0.5 percent cases. It is resistant to treatment with anti amoebic drugs, hence require colectomy Fuhninant amoebic colitis(阿米巴性结肠炎) has a high mortality and tends to occur more in pregnant women, malnourished persons and persons receiving corticosteroids(皮质类固醇).The onset is abrupt with high fever, widespread abdominal pain, leucocytosis(白细胞增多), profuse bloody, mucosal diarrhoea with tenesmus(里急后重). The patients have necrotic involvement of their colon Colonic perforation and haemorrhage frequently occur in this condition Amoeboma(阿米巴肿) is a pseudo- tumoral condition. Lesion may be single or multiple and occurs commonly in the colon, caecum or rectum. Anti-amoebic antibodies are present in the patient serum Complicated intestinal amoebiasis: This condition includes peritonitis, perianal ulceration, urogenital infection, colonic stricture, intussusception (E A)and haemorrhage. These complications relatively are uncommon. 2)Err- intestinal amoebiasis(肠外阿米巴病) Clinical manifestations of extra-intestinal amoebiasis depends upon the organ involved. It can be Hepatic amoebiasis, pulmonary amoebiasis, cerebral amoebiasis, genitourinary amoebiasis and splenic amoebiasis ① Hepatic amoebiasis(肝阿米巴病) begins with the hepatic involvement(non suppurative amoebic hepatitis) and progress to form suppurative lesions in the liver (amoebic liver abscess) Non- suppurative amoebic hepatitis(非化脓性阿米巴肝炎) This refers to a syndrome (sRAE)of tender hepatomegaly, right upper quadrant pain, fever and leucocytosis in persons with amoebic dysentery. This results from non-specific peripheral inflammation of the liver occurring during colitis Amoebic liver abscess(阿米巴肝脓肿): Onset is insidious. The condition is associated with ver, sweating, loss of weight and abdominal pain. Nearly, half of the patients presenting with acute manifestations have a single abscess situated most common only in the postero-superior surface of the right lobe of the liver Abdominal pain and tenderness in the right hypochondrium(AJ Hp )is the earliest important manifestation. It is caused by stretching of the liver capsule. Abdominal pain is frequently referred to the shoulder and is accompanied by a non-productive cough. On physical examination, the lower part of the liver is palpable below the costal margin and is tender. Point tenderness can be elicited in the postero-lateral part of the lower-right intercostal space. In less than halfofthe cases, hepatomegaly is usually present. In the base of the right lung, dullness and les are common. Peritoneal signs and jaundice are unusual ② Pulmonary amoebiasis(肺阿米巴病: It is the most common complication(并发症)of amoebic liver abscess and is caused by rupture of a superior right lobe abscess through the diaphragm(Ht PE SD)into the lung parenchyma. It occurs in 10 to 20 percent of patients. Cough, pleuritic pain and dyspnoea are the common clinical manifestations
26 uncommon, present in less than one-third of the cases. The condition can be differentiated from that of bacillary dysentery by the demonstration of RBCs, Charcot-Leyden crystals and haematophagous amoebic trophozoites in the amoebic dysenteric stool. ③Complications of symptomatic intestinal amoebiasis: Thick megacolon (巨结肠) occurs in less than 0.5 percent cases. It is resistant to treatment with anti amoebic drugs, hence requires colectomy. Fuhninant amoebic colitis (阿米巴性结肠炎) has a high mortality and tends to occur more in pregnant women, malnourished persons and persons receiving corticosteroids (皮质类固醇). The onset is abrupt with high fever, widespread abdominal pain, leucocytosis (白细胞增多), profuse bloody ,mucosal diarrhoea with tenesmus (里急后重). The patients have necrotic involvement of their colon. Colonic perforation and haemorrhage frequently occur in this condition. Amoeboma (阿米巴肿) is a pseudo-tumoral condition. Lesion may be single or multiple and occurs commonly in the colon, caecum or rectum. Anti-amoebic antibodies are present in the patient serum. Complicated intestinal amoebiasis: This condition includes peritonitis, perianal ulceration, urogenital infection, colonic stricture, intussusception ( 肠 套叠) and haemorrhage. These complications relatively are uncommon. 2) Extra-intestinal amoebiasis(肠外阿米巴病) Clinical manifestations of extra-intestinal amoebiasis depends upon the organ involved. It can be Hepatic amoebiasis, pulmonary amoebiasis, cerebral amoebiasis, genitourinary amoebiasis, and splenic amoebiasis. ①Hepatic amoebiasis (肝阿米巴病) begins with the hepatic involvement (non suppurative amoebic hepatitis) and progress to form suppurative lesions in the liver (amoebic liver abscess). Non-suppurative amoebic hepatitis(非化脓性阿米巴肝炎): This refers to a syndrome (综合症)of tender hepatomegaly, right upper quadrant pain, fever and leucocytosis in persons with amoebic dysentery. This results from non-specific peripheral inflammation of the liver, occurring during colitis. Amoebic liver abscess(阿米巴肝脓肿): Onset is insidious. The condition is associated with fever, sweating, loss of weight and abdominal pain. Nearly, half of the patients presenting with acute manifestations have a single abscess situated most common only in the postero-superior surface of the right lobe of the liver. Abdominal pain and tenderness in the right hypochondrium (季肋部) is the earliest important manifestation. It is caused by stretching of the liver capsule. Abdominal pain is frequently referred to the shoulder and is accompanied by a non-productive cough. On physical examination, the lower part of the liver is palpable below the costal margin and is tender. Point tenderness can be elicited in the postero-lateral part of the lower-right intercostal space. In less than halfofthe cases, hepatomegaly is usually present. In the base of the right lung, dullness and tales are common. Peritoneal signs and jaundice are unusual. ②Pulmonary amoebiasis (肺阿米巴病): It is the most common complication (并发症) of amoebic liver abscess and is caused by rupture of a superior right lobe abscess through the diaphragm (横隔膜)into the lung parenchyma. It occurs in 10 to 20 percent of patients. Cough, pleuritic pain and dyspnoea are the common clinical manifestations
③ Cerebral amoebiasis(脑阿米巴病): Amoebic brain abscess is very unusua. The abscess is single, small and is located in the cerebral hemisphere. It is difficult to diagnose the condition nica ④ Genito-urinary amoebiasis(泌尿生殖系阿米巴病): It is a rare condition amoo the penis caused by E. histolytica is acquired during vaginal or anal intercourse. In females, recto vaginal fistula causes amoebic trophozoites spread to the genito urinary tract ⑥ Splenic amoebiasis(脾阿米巴病) is very unusual and is caused by transmission of amoebic trophozoites directly through an adherent splenic flexure of the intestine DIAGNOSIS Clinically, it is difficult to establish the diagnosis of amoebiasis, either intestinal or extra-intestinal. It is always supplemented by the laboratory diagnosis Laboratory diagnosis includes parasitic diagnosis, serodiagnosis, biochemical diagnosis, and radio-imaging diagnosis Parasitic diagnosis(病原诊断) The specific diagnosis of intestinal amoebiasis is established by the demonstration of E. histolytica in the stool, rectal exudate and material collected from the base of rectal ulcers The stool is collected in wide-mouthed, chemically clean containers. Substances that interfere with stool examination should not be administered in an individual at east 10 days before the collection of stool. These include Kaolin, bismuth, barium sulphate, antimicrobial and anti-malarial drugs, liquid paraffin and anti-diarrhea agents. Since exeretion of cysts in the stool is often intermittent, at least three consecutive specimens should be examined before excluding the diagnosis of amoebiasis Stool should be examined immediately within 15 minutes of the passage, for the detection of trophozoites. The cysts can be demonstrated even in the 3 days old formed stool specimen Stool is usually examined by microscopy, concentration and culture Stoo 1)Microscopy: Trophozoites are demonstrated in the saline wet mount of fresh diarrhoeal These are identified by their unidirectional motility with the help of finger-like pseudopodia. Permanent staining of the faecal smear by iron-haematoxylin or trichrome staining allows the best identification of haematophagous trophozoites of E. hislolvica. Cysts can be demonstrated by lodine wet mount preparation of the diarrhoeal and formed stool. These cysts need to differentiated from the cysts of other amoebae 2) Concentration Concentration is a better method for the concentration of amoebic cysts in the stool. No method is available yet for concentration of trophozoites. The concentration method is useful when the numbers of amoebae in the stool are scanty 3)Culture: Robinsons's medium and Nih polyxenic culture media are frequently used for culture and isolation of the amoebae from the stool. Serum, bacterial flora and starch present in the media provide nutrients and growth factors for E. histolytica Stool culture is helpful especially in the cases of chronic and asymptomatic intestinal infections, excreting less number of cysts in the faeces Rectal exudate: The amoebic trophozoites are demonstrated in tile exudate covering the rectal Rectal ulcer tissue: Trophozoitcs also are demonstrated, but less frequently, in the necrotic tissue at the base of rectal ulcer
27 ③Cerebral amoebiasis(脑阿米巴病): Amoebic brain abscess is very unusual. The abscess is single, small and is located in the cerebral hemisphere. It is difficult to diagnose the condition clinically. ④Genito-urinary amoebiasis(泌尿生殖系阿米巴病): It is a rare condition. Amoebiasis of the penis caused by E. histolytica is acquired during vaginal or anal intercourse. In females, recto vaginal fistula causes amoebic trophozoites spread to the genito urinary tract. ⑤Splenic amoebiasis (脾阿米巴病) is very unusual and is caused by transmission of amoebic trophozoites directly through an adherent splenic flexure of the intestine. DIAGNOSIS Clinically, it is difficult to establish the diagnosis of amoebiasis, either intestinal or extra-intestinal. It is always supplemented by the laboratory diagnosis. Laboratory diagnosis includes parasitic diagnosis, serodiagnosis, biochemical diagnosis, and radio-imaging diagnosis. Parasitic diagnosis (病原诊断) The specific diagnosis of intestinal amoebiasis is established by the demonstration of E. histolytica in the stool, rectal exudate and material collected from the base of rectal ulcers. The stool is collected in wide-mouthed, chemically clean containers. Substances that interfere with stool examination should not be administered in an individual at east 10 days before the collection of stool. These include Kaolin, bismuth, barium sulphate, antimicrobial and anti-malarial drugs, liquid paraffin and anti-diarrhea agents. Since exeretion of cysts in the stool is often intermittent, at least three consecutive specimens should be examined before excluding the diagnosis of amoebiasis. Stool should be examined immediately within 15 minutes of the passage, for the detection of trophozoites. The cysts can be demonstrated even in the 3 days old formed stool specimen. Stool is usually examined by microscopy, concentration and culture. 1)Microscopy: Trophozoites are demonstrated in the saline wet mount of fresh diarrhoeal stool. These are identified by their unidirectional motility with the help of finger-like pseudopodia. Permanent staining of the faecal smear by iron-haematoxylin or trichrome staining allows the best identification of haematophagous trophozoites of E. hislolvlica. Cysts can be demonstrated by iodine wet mount preparation of the diarrhoeal and formed stool. These cysts need to be differentiated from the cysts of other amoebae. 2)Concentration Concentration is a better method for the concentration of amoebic cysts in the stool. No method is available yet for concentration of trophozoites. The concentration method is useful when the numbers of amoebae in the stool are scanty. 3)Culture: Robinsons's medium and NIH polyxenic culture media are frequently used for culture and isolation of the amoebae from the stool. Serum, bacterial flora and starch present in the media provide nutrients and growth factors for E. histolytica. Stool culture is helpful especially in the cases of chronic and asymptomatic intestinal infections, excreting less number of cysts in the faeces. Rectal exudate: The amoebic trophozoites are demonstrated in tile exudate covering the rectal mucosa. Rectal ulcer tissue: Trophozoitcs also are demonstrated, but less frequently, in the necrotic tissue at the base of rectal ulcer
For amoebic liver abscess, demonstration of amoebic trophozoites in the aspirated pus by microscopy or culture establishes the specific diagnosis of amoebic liver abscess. The parasitic diagnosis, however, is difficult. Trophozoites can only be demonstrated ill the pus in less than 15 of cases of amoebic liver abscess Serodiagnosis 1)Antibody Detection Amoebic antibodies frequently appear in the amoebiasis. Antibody detection is most useful in patients with extraintestinal disease, i.e., amebic liver abscess, when organisms are not generally found on stool examination. Indirect haemagglutination(IHA), indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay(ELISA),etc,are frequently used tests to detect the serum amoebic antibodies amoebiasis. However, these serological test are of no or little value in the diagnosis of asymptomatic cyst passers, as amoebic antibodies fail to appear in their sera. 2)Antigen Detection Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish between pathogenic and non-pathogenic infections. Recent studies indicate improved sensitivity and specificity of fecal antigen assays with the use of monoclonal antibodies which can distinguish between E. histolytica and E. dispar infections. At least one commercial kit is available which detects only pathogenic E. histolytica infection in stool; several kits are available which detect E. histolytica antigens in stool but do not exclude E. dispar infections cHar In reference diagnosis laboratories PCr is the method of choice for discriminating between E. dispar) Radio diagnosis Various imaging techniques have been used to demonstrate the presence of space occupying amoebic lesions in the liver and other organs. These include ultrasound, CT scan, magnetic resonance imaging(MRI) and GA scan. None of these methods however are absolutely specific These can not differentiate amoebic liver abscess from those of pyogenic liver abscess and tumour Ultrasound is rapid, slightly sensitive than CT scan for the amoebic liver abscess. The CT scan is sensitive but not specific for amoebic liver abscess. MRI is sensitive like those of CT and ultrasound EPIDEMIOLOGY Geographical distribution Amoebiasis has a worldwide distribution. Amoebiasis is a major health problem in Africa, South-east Asia, Latin America, especially Mexico. More than 10 percent of the worlds population is estimated to be infected by E. histolytica. 50 million cases of invasive amoebic diseases have been reported from the world. Every year, more than 100,000 persons die due to amoebic disease Source of transmission and infection Food and water contaminated by human faeces that contain cysts are the main sources of infection. Infected man himself, especially carriers, are the principal source of transmission infection Infective form Four nucleus cyst is the infective form Susceptible population All age of humans are susceptive for E. histolytica Transmission ways
28 For amoebic liver abscess, demonstration of amoebic trophozoites in the aspirated pus by microscopy or culture establishes the specific diagnosis of amoebic liver abscess. The parasitic diagnosis, however, is difficult. Trophozoites can only be demonstrated ill the pus in less than 15% of cases of amoebic liver abscess. Serodiagnosis. 1) Antibody Detection Amoebic antibodies frequently appear in the amoebiasis. Antibody detection is most useful in patients with extraintestinal disease, i.e., amebic liver abscess, when organisms are not generally found on stool examination. Indirect haemagglutination (IHA), indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), etc., are frequently used tests to detect the serum amoebic antibodies amoebiasis. However, these serological test are of no or little value in the diagnosis of asymptomatic cyst passers, as amoebic antibodies fail to appear in their sera. 2) Antigen Detection Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish between pathogenic and non-pathogenic infections. Recent studies indicate improved sensitivity and specificity of fecal antigen assays with the use of monoclonal antibodies which can distinguish between E. histolytica and E. dispar infections. At least one commercial kit is available which detects only pathogenic E. histolytica infection in stool; several kits are available which detect E. histolytica antigens in stool but do not exclude E. dispar infections. Molecular diagnosis In reference diagnosis laboratories, PCR is the method of choice for discriminating between the pathogenic species (E. histolytica) from the non-pathogenic species (E. dispar). Radio diagnosis Various imaging techniques have been used to demonstrate the presence of space occupying amoebic lesions in the liver and other organs.These include ultrasound, CT scan, magnetic resonance imaging (MRI) and GA scan. None of these methods however are absolutely specific. These can not differentiate amoebic liver abscess from those of pyogenic liver abscess and tumour. Ultrasound is rapid, slightly sensitive than CT scan for the amoebic liver abscess. The CT scan is sensitive but not specific for amoebic liver abscess. MRI is sensitive like those of CT and ultrasound. EPIDEMIOLOGY Geographical distribution Amoebiasis has a worldwide distribution. Amoebiasis is a major health problem in Africa, South-east Asia, Latin America, especially Mexico. More than 10 percent of the world's population is estimated to be infected by E. histolytica. 50 million cases of invasive amoebic diseases have been reported from the world . Every year, more than 100,000 persons die due to amoebic disease. Source of transmission and infection Food and water contaminated by human faeces that contain cysts are the main sources of infection. Infected man himself, especially carriers, are the principal source of transmission. infection. Infective form Four nucleus cyst is the infective form. Susceptible population All age of humans are susceptive for E. histolytica. Transmission ways
Infection is transmitted from one person to another by following methods 1)Faecal-oral route Amoebiasis is transmitted orally by ingestion of water, vegetable and food contaminated by faeces containing cysts. Water is contaminated by accidental leakage of sewage into treated water supplies. Water and food also are contaminated by unhygienic handling of food by food handlers such as cook. The infection is transmitted among the individuals with poor personal hygiene. In areas, where human faeces are used as fertilizers in the fields for cultivation of vegetables, crops, etc, the infection is transmitted by eating those vegetables raw 2)Vectors Flies and cockroaches mechanically may transmit cysts from the faeces to the nprotected food and water 3)Sexual contact E. histolytica is sexually transmitted among sexually promiscuous male homosexuals. The amoebae are transmitted by the sexual practice that allows faecal-oral contact E. histolytica is a leading cause of larrnoea wor rldwide. It is an important cause of diarrhoea in persons with the acquired immunodeficiency syndrome(AIDS ) Amoebiasis tends to be severe in pregnant and lactating mothers, and, in children especially in neonates PREVENTION AND CONTROI Treating the infected persons Treatment of amoebiasis is broadly based on: eradication of amoebae by the use of amoebicides, replacement of fluid, electrolyte and blood, and relief from the constitutional syn oebae may be found in the lumen of the intestine, in the intestinal submucosa or in the extra-intestinal sites such as liver, lungs, etc. None of the amoebicidal drugs availabl now are effective against the amoebae found in all these sites. These amoebicidal drugs depending upon their sites of action can be grouped as follows Luminal amoebicides: They act on the amoebic trophozoites present in the lumen of the bowel ney are ineffective against tissue amoebae. These include: a)diloxanide fiuorate, b) diiodohydre Tissue amoebicides: They act on tissue amoebae present ill different tissues. The tissue amoebicides which act on all the tissues include: metronidazole(灭滴灵), tinidazole(硝砜咪唑) emetine hydrochloride and 2-dehydroemetin. Amoebicides which act only on liver tissue is chloroquine(氯喹). Tetracycline(四环素) and erythromycin act only on the intestinal wall Control and prevention The amoebic infections can be controlled and prevented by individual prophylaxis and community prophylaxis 1) Individual prophylaxis(个人防护) consists of O Avoiding faecal contamination of food and water 2 boiling the drinking water to kill all the amoebic cysts. The cysts also are killed by th routinely used chlorine concentration in the drinking water 3 Treating vegetables with acetic acid and vinegar at least for 15 minutes before consumption as salad. 4 In homosexuals, by avoiding sexual practices that allow faecal-oral contact and 5 Improved personal hygiene such as washing hand before eating and after defecate 2)Community prophylaxis consists of Improvement of general sanitation by proper disposal of faeces
29 Infection is transmitted from one person to another by following methods: 1) Faecal-oral route Amoebiasis is transmitted orally by ingestion of water, vegetable and food contaminated by faeces containing cysts. Water is contaminated by accidental leakage of sewage into treated water supplies. Water and food also are contaminated by unhygienic handling of food by food handlers such as cook. The infection is transmitted among the individuals with poor personal hygiene. In areas, where human faeces are used as fertilizers in the fields for cultivation of vegetables, crops, etc, the infection is transmitted by eating those vegetables raw. 2) Vectors Flies and cockroaches mechanically may transmit cysts from the faeces to the unprotected food and water. 3) Sexual contact E. histolytica is sexually transmitted among sexually promiscuous male homosexuals. The amoebae are transmitted by the sexual practice that allows faecal-oral contact. E. histolytica is a leading cause of diarrhoea worldwide. It is an important cause of diarrhoea in persons with the acquired immunodeficiency syndrome(AIDS). Amoebiasis tends to be severe in pregnant and lactating mothers, and.in children especially in neonates. PREVENTION AND CONTROL Treating the infected persons Treatment of amoebiasis is broadly based on: eradication of amoebae by the use of amoebicides,replacement of fluid, electrolyte and blood, and relief from the constitutional symptoms. Amoebae may be found in the lumen of the intestine, in the intestinal submucosa or in the extra-intestinal sites such as liver, lungs, etc. None of the amoebicidal drugs available now are effective against the amoebae found in all these sites. These amoebicidal drugs depending upon their sites of action can be grouped as follows Luminal amoebicides:They act on the amoebic trophozoites present in the lumen of the bowel. They are ineffective against tissue amoebae. These include: a) diloxanide fiuorate, b) diiodohydroxyquin and c) paromomycin. Tissue amoebicides: They act on tissue amoebae present ill different tissues. The tissue amoebicides which act on all the tissues include: metronidazole (灭滴灵), tinidazole (硝砜咪唑), emetine hydrochloride and 2-dehydroemetin. Amoebicides which act only on liver tissue is chloroquine (氯喹). Tetracycline (四环素) and erythromycin act only on the intestinal wall. Control and prevention The amoebic infections can be controlled and prevented by individual prophylaxis and community prophylaxis. 1) Individual prophylaxis (个人防护) consists of: ① Avoiding faecal contamination of food and water. ② Boiling the drinking water to kill all the amoebic cysts. The cysts also are killed by the routinely used chlorine concentration in the drinking water. ③ Treating vegetables with acetic acid and vinegar at least for 15 minutes before consumption as salad. ④ In homosexuals, by avoiding sexual practices that allow faecal-oral contact and ⑤ lmproved personal hygiene such as washing hand before eating and after defecation. 2) Community prophylaxis consists of ① Improvement of general sanitation by proper disposal of faeces
(2 Prevention of water supplies from faecal contamination, and Better managernent of cases by an early and rapid detection and subsequent treatment of cases
30 ② Prevention of'water supplies from faecal contamination, and ③ Better managernent of cases by an early and rapid detection and subsequent treatment of cases