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H u m a n Infection with Entamoeba polecki RICHARD L. LEVIN, M.D., AND DEAN E. ARMSTRONG .; Department of Pathology, Washington Hospital Center, 110 Irving Street, N. W., Washington, D. C. 2001 ABSTRACT HUMAN INFECTION with Entamoeba polecki (von Prowazek, 1912), because of its rarity, has often been confused with Entamoeba histolytica infection, even by experienced parasitologists. The literature contains few reports of this entity and in these the clinical information is scanty and incomplete.18,*, e, 7 \ y e recently studied a case of infection due to E. polecki which is clinically well documented and partially supported by serologic and rectal biopsy studies. Report of a Case A 25-year-old woman, a Peace Corps volunteer, was stationed in Uttar Pradesh in northern India from October 1966 to June 1968. The only pertinent animal contact was with pigs which roamed her village. In November 1966 she had diarrhea of approximately 1 week's duration, with numerous, bloody, mucoid stools, but did not seek medical attention. Her husband, also a Peace Corps volunteer, had similar symptoms and was treated for amebic dysentery. The patient first sought medical aid in April 1967 for diarrhea of a similar nature, and was seen in the Clara Swain Hospital in Bareilly, Uttar Pradesh, India. T h e stool Received November 20, 1969; accepted for publication May 8, 1970. was reported to contain cysts of E. coli. The patient was treated with iodochlorhydroxyquin and iron. Hemoglobin was 10.1 Gm. per 100 ml. and the leukocyte count, 6,500 per cu. mm., with a normal differential. No eosinophilia was present. A repeat stool examination 2 weeks later revealed a few cysts of Giardia lamblia, and a 7-day course of atabrine was given. Diarrhea recurred 3 weeks later, accompanied by fever, and the patient was again treated with iodochlorhydroxyquin, sulfadiazine, kaolin, and opiates. After 3 weeks of this regimen, a stool specimen obtained in a "MIF kit" was reported to contain E. histolytica. Diarrhea persisted intermittently until August 1967 when the patient returned to the Bareilly clinic with a history of 20 to 40 loose, bloody, mucoid stools during the previous 3 days. She had a temperature of 101 F., some nausea and vomiting, abdominal cramps, and a suggestion of inspiratory restriction in the right upper quadrant. Because of her weakened condition the patient was admitted to the hospital in Bareilly. Two stool examinations revealed no ova or parasites, and sigmoidoscopic examination showed the mucosa to be ulcerated, hemorrhagic, and indurated. No amebae were found in a 611 Downloaded from http://ajcp.oxfordjournals.org/ by guest on October 13, 2016 Levin, Richard L., and Armstrong, Dean E.: Human infection with Entamoeba polecki. Amer. J. Clin. Path. 54: 611-614, 1970. A case of infection due to Entamoeba polecki in a Peace Corps volunteer is presented. Although the patient was intensively treated for E. histolytica infection for more than a year, no serologic or pathologic confirmation of this diagnosis could be elicited and her clinical condition did not improve significantly. The significance of finding E. polecki in humans is discussed and the tests necessary for detection and the criteria for identification are reviewed. 612 LEVIN AND ARMSTRONG In August 1968 during the patient's prenatal work-up in the Obstetrical Clinic of the Washington Hospital Center, a stool examination was requested in view of her previous medical history. At that time, the patient was still mildly diarrheic, with 3 to 5 stools per day. Microscopic examination of the stool by the saline and the MIF (merthiolate-iodine-formalin) direct smear technics 8 revealed numerous Entamoeba trophozoites and cysts. Permanent mount preparations stained with iron hematoxylin 9 and with the Lawless rapid stain technic,5 revealed trophozoites that had characteristics of both E. histolytica and E. coli. Most of the cysts were uninucleate, with occasional binucleate forms. They had an abundance of polymorphic chromatoid material and contained a darkstained inclusion mass (Fig. 1A-D). Two additional antepartum stools and two postpartum stools revealed findings identical to those in the original specimen. On the basis of the morphologic characteristics of the amebae 2 and because of the previous experience of one of the authors, 1 the diagnosis of E. polecki infection was made. This diagnosis was confirmed by Deaner K. Lawless, Chief, Clinical Parasitology, Clinical Center, National Institutes of Health, Bethesda, Maryland. Rectal biopsy, done after an uneventful delivery of a normal child, revealed only mild chronic inflammation. Multiple step sections of the specimen, using routine and special stains for parasites, failed to reveal any amebae in the tissue. Sigmoidoscopic examination at the time of biopsy was unremarkable. The patient's mild diarrhea continued after delivery, and still was present at follow-up examination one month postpartum. Microscopic examination of the stool one month postpartum still revealed trophozoites and cysts of E. polecki. Hemagglutination and complement-fixation tests for E. histolytica were negative. These tests were performed by the Tropical Health Laboratory, School of Public Health, University of California, Los Angeles, California. Downloaded from http://ajcp.oxfordjournals.org/ by guest on October 13, 2016 specimen obtained at sigmoidoscopy. Treatment at this time consisted of sulfadiazine, chloramphenicol-streptomycin suspension, opiates, kaolin, and retention enemas containing sulfaguanidine and iodochlorhydroxyquin. There was mild improvement in the patient's condition, but she continued to have 6 to 15 bloody stools per day. After 10 days of the above treatment, dehydroemetine was begun, with only mild improvement. The patient was then transferred to Delhi for further medical care. On arrival at the Delhi hospital she was afebrile, with a brawny, pruritic, erythematous rash over the trunk, neck, arms, and back. The clinical impression was that of amebic dysentery and drug allergy, but ulcerative colitis was considered a strong possibility. The patient had lost 25 lb. in weight over the preceding 3 weeks. Complete blood count, blood urea nitrogen, blood sugar, and liver function tests were all within normal limits. A barium enema study was unremarkable. Five consecutive stool examinations, obtained after discontinuance of all medications, revealed no amebae or other parasites. Sigmoidoscopic examination revealed a localized area of inflammation extending from 12 to 15 cm. above the anal verge. Biopsy of this area was obtained and the tissue was sent to the Armed Forces Institute of Pathology, Washington, D. C. The tissue was interpreted as showing slight mucosal hyperplasia, submucosal vascular sclerosis, and chronic inflammation. The changes were felt to be nonspecific and compatible with idcerative colitis or any other inflammatory condition of the colon. Diarrhea decreased to 1 to 2 stools per day and the patient was maintained on Donnatal and hydrocortisone suppositories with a restricted diet. In February 1968 she was diagnosed as being three months pregnant. She was terminated from the Peace Corps in June 1968. At this time her stools were reported to contain cysts of G. lamblia and E. histolytica and she received a 3-week course of diiodohydroxyquin. A.J.C.P.— Vol. 54 October 1970 HUMAN INFECTION WITH ENTAMOEBA POLECKI 613 An attempt was made to culture the organisms utilizing Bacto Entamoeba media, but the organisms disappeared after several passages. Similar findings were reported by Lawless,6 and Burrows and Klink. 3 scussion This case is apparently the nineteenth reported instance of human infection with E. polecki. The organism, first described and named by von Prowazek in 1912, was seen by him in pigs and in a child in Saipan. He named the amoeba after Dr. Poleck, a physician in Samoa. Since the original descriptions, the taxonomy of the organism has been the source o£ many conflicts among parasitologists, but it appears to have become accepted by most contemporary workers in the field of protozoology.3 The ameba usually is considered a parasite of pigs and monkeys, and the mechanism of human infection is unknown, although human-to-human spread of the infection has been postulated. 7 The question whether human infection with E. polecki is ever symptomatic remains to be answered, but several cases, including the present one, strongly suggest that disease attributed to E. histolytica can be due to E. polecki.3'7 None of the amebicidal drugs have been shown to have any Downloaded from http://ajcp.oxfordjournals.org/ by guest on October 13, 2016 FIG. 1. Representative E. polecki cysts. The karyosome is consistently large compared with the nucleus. Chromatoid material is abundant and polymorphic. The cytoplasm ranges from granular to foamy. Iron hematoxylin stain. X 960. 614 LEVIN AND ARMSTRONG may contain as many as 30, some of which resemble cocci or bacilli in size and shape. In retrospect, the present case presents several problems. The first is whether the patient ever had amebic dysentery due to E. histolytica. Material is not available for reviewing the so-called cysts of E. histolytica, but the lack of response to innumerable amebicidal drugs and the absence of serologic or pathologic evidence of E. histolytica infection make the diagnosis quite doubtful. The second problem is whether the patient could have had nonspecific ulcerative colitis with secondary infection by E. polecki. This is entirely possible and cannot be excluded as an explanation for her clinical illness. There is no doubt that the patient is infected with E. polecki, which she could have acquired from pigs in her village in India. However, whether her clinical illness is due solely to this parasitic infection cannot be definitely confirmed. Acknowledgment. Mr. Ray Rew gave technical assistance. References 1. Armstrong, D. E.: Occurrence of Entamoeba polecki in school children in Taiwan. J. Parasit. 52: 700, 1966. 2. Burrows, R. B.: Morphological differentiation of Entamoeba hartmanni and E. polecki from E. histolytica. Amer. J. Trop. Med. 8: 583-589, 1959. 3. Burrows, R. B., and Klink, G. E.: Endamoeba polecki infections in man. Amer. J. Hyg. 62: 156-167, 1955. 4. Kessel, J. F., and Johnstone, H. G.: The occurrence of Endamoeba polecki Prowazek, 1912, in Macaca mulatto and in man. Amer. J. Trop. Med. 29: 311-317, 1949. 5. Lawless, D. K.: A rapid permanent-mount stain technique for the diagnosis of intestinal protozoa. Amer. J. Trop. Med. 2: 1137-1138, 1953. 6. Lawless, D. K.: Report on a human case of Endamoeba polecki, Prowazek, 1912. J. Parasit. 40: 221-228, 1954. 7. Lawless, D. K., and Knight, V.: Human infection with Entamoeba polecki: Report of four cases. Amer. J. Trop. Med. 15: 701-704, 1966. 8. Sapero, J. J., and Lawless, D. K.: The "MIF" stain preservation technique for the identification of intestinal protozoa. Amer. J. Trop. Med. 2: 613-619, 1953. 9. U. S. Naval Medical School: Medical Protozoology and Helminlliology Manual, 1962, pp. 55-56. Downloaded from http://ajcp.oxfordjournals.org/ by guest on October 13, 2016 effect on human E. polecki infections, and the use of potentially toxic agents, as in the present case, could lead to a far more serious clinical situation than infection with the parasite. Differentiation between the trophozoites of E. histolytica, E. coli, and E. polecki can be quite difficult. Extensive study of permanent stain preparations may be required. Because of this fact, the differentiation of these organisms is more easily accomplished through the study of encysted forms. The cysts of E. coli rarely cause a problem in differential diagnosis because of their multinucleation. E. polecki is consistently uninucleate, with only about 2% of the forms reaching the binucleate stage. Whereas E. histolytica cysts can be uninucleate, the persistence of uninucleate forms in multiple stool specimens should raise a strong suspicion of the presence of E. polecki. The nucleus in the cyst of E. polecki is usually about one-fourth to onethird of the diameter of the cyst and contains a comparatively large karyosome with numerous variations in the peripheral chromatin pattern. Contrastingly, the uninucleate cyst of E. histolytica contains a nucleus which is one-third to half the diameter of the cyst, with a comparatively small karyosome and an apparently uniform distribution of peripheral nuclear chromatin. Large glycogen vacuoles are rarely seen in the cytoplasm of E. polecki cysts but are commonly found in those of E. histolytica. Conversely, the so-called inclusion mass seen in the cytoplasm of E. polecki cysts is frequently found. It stains homogeneously and varies in size, sometimes being two to three times the size of the nucleus. The dark-staining body is not seen in cysts of E. histolytica. A final differentiating feature is the number of chromatoid bars in the cysts. Cysts of E. histolytica usually contain fewer than 10 chromatoid bars, whereas those of E. polecki A.J.C.P.—Vol. 54