Download Human Infection with Entamoeba polecki

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
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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.
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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
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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.
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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