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The diagnosis of amoebiasis presents problems, particularly if one relies on finding the organism. Thus, serologic tests are expedient. A gel diffusion precipitin test (GDP), commercially available, simple to perform, and inexpensive, was compared with the indirect hemagglutination test (IHA). 257 Patients' sera were tested; 14 had amoebic colitis, 21 had amoebic liver abscess, 63 had suspected amoebic liver abscess, and 46 had inflammatory bowel disease. GDP tests were positive in 85% of amoebic colitis and 95% of amoebic liver abscess patients; IHA was positive in 91% of amoebic colitis and 94% of abscess patients. Within 6 mo, GDP tests became negative in 66% of patients. IHA tests were observed positive up to 20 yr. The performance characteristics of diagnostic methods in amoebiasis, fecal examination, IHA and GDP, show serologic tests have superior sensitivity and predictive value in recognizing invasive disease.

An asymptomatic infection with Babesia sp. was diagnosed in an epidemiologic investigation of transfusion-acquired malaria. This is the seventh human piroplasmosis infection that has been reported in the literature.

The prevalence of microfilaremia among Indians in 13 Amazon Indian villages was determined by examining Giemsa-stained peripheral blood smears and preparations from peripheral blood lymphocyte cultures. Mansonella ozzardi was the only species found in the 601 persons tested. Prevalence was highly village-specific, ranging from 0% in four villages to as high as 93% among persons aged 10 years and older in others. Comparisons of the two methods showed that the concentration effect of the peripheral blood lymphocyte culture preparations allowed the detection of a greater number of microfilaria-positive persons, especially women and children with lower levels of parasitemia.

We used an indirect immunofluorescence test with Giardia lamblia trophozoites as antigen to detect anti-G. lamblia antibodies in serum. Seventy-one patients and control subjects were studied in a blinded protocol. Titers in 29 of 30 patients with symptomatic giardiasis (1:16 to 1:1024) did not overlap titers in 19 healthy control subjects (1:2 to 1:4); titers in 15 patients with hookworm, Entamoeba histolytica, or intestinal bacterial overgrowth were 1:16 or less Absorption of giardiasis patients' sera with G. lamblia trophozoites but not with E. histolytica, Trichomonas vaginalis, or Escherichia coli reduced the titers to, or nearly to, control values. Titers in individual sera were 93.9% reproducible within a fourfold or less dilution. Our results indicate that G. lamblia, an intestinal parasite often regarded as noninvasive, induces a systemic antibody response. The indirect immunofluorescence test for anti-G. lamblia antibodies is specific and reproducible; it may be useful in epidemiologic and immunologic studies of giardiasis.

To determine whether gerbils can be used as a suitable animal model for giardiasis, we attempted to infect Mongolian gerbils with cysts of Giardia lamblia isolated from the stools of 10 humans with symptomatic and asymptomatic giardiasis. We obtained 100% infection with one isolate (CDC:0284:1), as evidenced by the presence of numerous trophozoites in the intestines of the gerbil and cysts in the feces. Cysts from four patients were not infective, while cysts from the other five patients produced infections in 11 to 75% of the animals. On the basis of these and other experiments, we concluded that (i) only certain isolates of human G. lamblia infect gerbils, colonize the intestine, and complete their life cycle by undergoing differentiation into cysts; (ii) the infection could last for about 39 days, but the animals excreted maximum numbers of cysts on about day 13 postinfection; (iii) the pattern of cyst excretion was irregular, and some gerbils, like humans, excreted cysts intermittently; (iv) the minimum number of cysts needed to establish an infection in 50% of the gerbils was 100; and (v) only certain strains retained the ability to infect gerbils even after repeated animal passage.

Only recently has it been recognized that hemotropic animal parasites of the genus babesia are also human pathogens. Similar to malaria in both symptoms and laboratory findings, acute babesiosis generally results in self-limited illness, but it can be fatal in the asplenic patient. The widely disseminated vector tick, Ixodes dammini, can transmit infection at each stage of its development, larva and nymph as well as adult.

Over a 2-year period two cases of dermal leishmaniasis of special interest were recognized in Texas. The first occurred in 1972 in a 74-year-old woman who had residences in Dilworth and Gahzales, Gonzales County, and the other was in a 56-year-old man from Kenedy, Karnes County, in 1974. Both cases were biopsy- and culture-positive, and the second patient exhibited anti-Leishmania antibodies by indirect immunofluorescent antibody and direct agglutination tests. Epidemiologic investigation revealed no association between the two cases and suggested that both patients had acquired their infections locally in southern Texas. Moreover, serologic evidence of Leishmania infection was uncovered in a neighbor of the second case and in 3 dogs living nearby. Potential sylvatic reservoirs and arthropod vectors of the disease are resident in the area. Epidemiologic data suggest that dermal leishmaniasis is endemic in south-central Texas.

Trichomonas vaginalis is a widely prevalent, sexually transmitted protozoan infecting both males and females. Despite its prevalence, little is known about its contribution to the morbidity rates for urogenital-tract infections. Currently accepted diagnostic methods are limited to the demonstration of the organism in fresh material, identification in stained material, or in vitro cultivation of organisms from the urogenital tract. We have evaluated the indirect hemagglutination test and the gel diffusion test for efficacy in detecting antibodies in serum samples drawn from two population groups. Sera from patients attending a vaginitis clinic had a seropositivity rate of 69% by indirect hemagglutination and 34% by gel diffusion. Seropositivity rates among culture-positive patients were 78% with indirect hemagglutination and 43% with gel diffusion. A group of normal female hospital employees showed seropositivity rates of 30% by indirect hemagglutination and 3% by gel diffusion. Absorption of reactive sera with Trichomonas antigens reduced or abolished the serological reactivity, confirming the specificity of the test. Serological methods can provide a rapid, sensitive, and economical tool to study the epidemiology of this common protozoan infection.

Large numbers of Blastocystis hominis were found in fecal samples from a pig-tailed macaque (Macaca nemestrina) with chronic diarrhea that was refractory to conventional therapy. The animal's condition improved and fecal samples showed minimal numbers of Blastocystis hominis following therapy with an antiprotozoal agent. This organism, recently reclassified as a protozoa, appeared to be causally related to the diarrhea. The cytologic and ultrastructural features of the monkey Blastocystis were comparable to those reported for similar organisms from man.

The 161A strain of Naegleria isolated from a human nasal swab and reported earlier was further studied for its growth pattern, cyst-wall appearance, cytopathic effect on primary monkey kidney cells, and pathogenicity in mice. Results obtained in the study establish the pathogenic status of this strain. This constitutes the first isolation of a pathogenic Naegleria from a human nasal cavity.

Blood smears from 13 patients infected with Babesia microti were reviewed to define the range of morphologic characteristics of the organism. Organisms resembling rings of Plasmodium falciparum were the predominant forms in all patients' blood smears. Babesia microti and Plasmodium spp. may be differentiated by the presence of pigment deposits in erythrocytes parasitized with mature stages of Plasmodium.

Ophthalmomyiasis interna caused severe intraocular inflammation and loss of vision in two eyes. In the first eye, the organism was found in the vitreous and created a severe uveitis; a second-stage larva of Hypoderma lineatum was later removed from the anterior chamber. Phthisis bulbi ensued with loss of all vision. In a second eye, a subretinal maggot was observed to produce tracks in the pigment epithelium, with subretinal and vitreous hemorrhage. Severe uveitis and traction retinal detachment later developed. Despite successful reattachment of the retina, visual acuity remained only light perception. These cases demonstrate that ophthalmomyiasis interna is not always a benign condition.

An indirect immunofluorescent test was used to determine antibody titers to Babesia microti in serum samples collected from 16 patients between 1 week and 1 year after the onset of illness. Titers rose to greater than or equal to 1:1,024 during the first few weeks of illness and then fell gradually to 1:16 to 1:256 over the next 5-6 months.

From June 1978 through December 1980, at least 36 cases of amebiasis occurred in persons who had had colonic-irrigation therapy at a chiropractic clinic in western Colorado. Of 10 persons who required colectomy, six did. Of 176 persons who had been to the clinic in the last four months of 1980, 80 had received other forms of treatment. Twenty-one per cent of the colonic-irrigation group had bloody diarrhea, as compared with 1 per cent of the non-irrigation group (P = 0.00013). Thirty-seven per cent of the colonic-irrigation group who submitted specimens had evidence of amebic infection on either stool examination or serum titer, as compared with 2.4 per cent in the non-irrigation group (P = 0.00012). Persons who were given colonic irrigation immediately after a person with bloody diarrhea received it were at the highest risk for the development of amebiasis. Tests of the colonic-irrigation machine after routine cleaning showed heavy contamination with fecal coliform bacteria. The severity of disease in this outbreak may have been related to the route of inoculation.

Trichomonas vaginalis was isolated from the respiratory tracts of two infants with respiratory disease. Bacterial and viral cultures of tracheal aspirates and nasopharyngeal specimens did not detect bacterial pathogens or viruses; however, T vaginalis was found to be present in inoculated cell cultures. Both infants were delivered vaginally by mothers with known previous episodes of T vaginalis infection. The possibility that this organism may, on occasion, cause respiratory tract disease needs further evaluation.

The 161A strain of Naegleria isolated from the nasal swab of a boy (9) was grown axenically in Nelson's medium. When 10,000 amoebae from the axenic medium were inoculated onto each monkey kidney cell (Vero) culture, characteristic cytopathic effects (CPE) were noticed in 4 to 5 days. The CPE consisted of granulation of the host cell cytoplasm, cell shrinkage, nuclear pycnosis, and discontinuity of cell sheet. When 10,000 amoebae were instilled intranasally into a group of ten 2- to 3-week-old mice, 8 of the 10 mice exhibited characteristic symptoms of primary amoebic meningoencephalitis and died within 10 to 12 days. Histopathology of the brain revealed necrotic tissue and an acute inflammatory reaction in the superficial regions of the brain. In the gel diffusion and immunoelectrophoresis tests the sonically disrupted antigens of 161A amoebae reacted extensively with the hyper-immune sera against 3 strains (CA, CJ, HB-1) of pathogenic N. fowleri and produced patterns very similar to those produced by the homologous systems. Further, anti-HB-1 serum absorbed with the 161A antigens failed to react with the antigens of HB-1, CA, CJ, and 161A strains thus indicating antigenic identity of 161A strain with N. fowleri. In view of these observations it was concluded that the strain 161A is pathogenic and should be reclassified as N. fowleri.

Three hundred fifty residents of Rome, New York, had laboratory-confirmed cases of giardiasis between 1 November 1974 and 7 June 1975. A random household survey showed an overall attack rate for giardiasis (defined as a diarrheal illness of 5 days or more) of 10.6%. A significant association was discovered between having giardiasis and using city water and between having illness and drinking 1 or more glasses of water a day. The presence of human settlements in the Rome watershed area suggested that the water supply could have been contaminated by untreated human waste. The infectivity of municipal water was confirmed by producing giardiasis in specific pathogen-free dogs fed sediment samples of raw water obtained from an inlet of a city reservoir. A microscopic examination of the water sediments uncovered a Giardia lamblia cyst in one sample. This was the first time that a G. lamblia cyst has been found in municipal water in an epidemic and the first time that such water has been shown to infect laboratory animals.

Antigens prepared from each of five strains (CA, CJ, HB-1, HB-3, and TY) of pathogenic Naegleria and the EG strain of nonpathogenic Naegleria gruberi were compared by the gel diffusion and immunoelectrophoresis techniques. Axenically grown amoebae were used as sources of antigens. Antisera were produced in individual rabbits against three strains (CA, CJ, and HB-1) of pathogenic Naegleria and the EG strain of N. gruberi. In the gel diffusion experiment each of the six antigens was reacted with each of the four antisera in agar gel. The results of these experiments revealed that the antigens of N. gruberi reacted strongly with the homologous antiserum but minimally with each of the three heterologous antisera. The antigens of all five pathogenic strains reacted extensively with the anti-CA, anti-CJ, and anti-HB-1 sera and moderately with the anti-EG serum. In the immunoelectrophoresis test each of the six antigens was separated electrophoretically in agar gel and reacted with each of the four antisera. The EG strain reacted extensively with its homologous antiserum and produced multiple precipitin arcs; it reacted minimally with anti-CA, anti-CJ, and anti-HB-1 sera and produced only three arcs. The antigens of all five strains of Naegleria fowleri reacted very strongly with anti-CA, anti-CJ, and anti-HB-1 sera and produced multiple precipitin arcs. They, however, reacted variably with the anti-EG serum and produced three to six precipitin arcs. Comparative immunoelectrophoretic analysis carried out on the CA and HB-1 strains revealed the antigenic identity of these two strains. Based on these results, together with those from the reciprocal absorption experiments, it was concluded that (i) the pathogenic strains of Naegleria, though they shared three to six common antigens with N. gruberi, were nevertheless distinct from it, and (ii) the five pathogenic strains were antigenically close and belonged in the same species. Antigens of Acanthamoeba castellanii, A. culbertsoni, and Entamoeba histolytica were also reacted with the four anti-Naegleria sera in gel diffusion experiments. Results of these tests indicate that these three organisms are antigenically distinct from Naegleria.

Examination of blood films from six species of rodents and lagomorphs on Nantucket Island disclosed infections with Babesia microti in all of five Microtus pennsylvanicus (field mice) and 31 of 39 Peromyscus leucopus (white-footed or deer mice). Six human cases of clinical babesiosis have recently been diagnosed on the island.

Several immunodiagnostic tests that detect antibody to Entamoeba histolytica are now available. Such tests are useful when demonstration of the etiologic agent is difficult (as in liver abscess), when routine diagnostic tests fail to disclose the organisms (as in severe intestinal disease compromised by failure of the laboratory to identify the organism or by the patient's use of interfering substances), and as epidemiologic tools for determining the prevalence of invasive disease in populations. Knowledge of the prevalence of amebiasis in the United States is incomplete because the disease is not routinely reported. Information currently available on the prevalence of amebiasis has accumulated from studies of selected groups that include children, institutionalized persons, members of extended families, immigrants, and male homosexuals.

We describe babesiosis transmitted by transfusion. The infected blood donor was identified and a minimum period of infectivity of the donor's blood was established. We report a new modality for chemotherapy consisting of quinine plus clindamycin, and a new endemic focus for this zoonosis on Fire Island, New York. There are insufficient data to establish a reasonably safe period after which visitors and residents of Babesia-endemic foci can become blood donors. Screening of such persons by a rapid serologic test, such as the ELISA or immunofluorescent antibody tests, is suggested.

Seven investigations of suspected foci of amebiasis between October 1971 and June 1974 lead to three conclusions. (1) A number of laboratories have vastly overdiagnosed amebiasis and have reported leukocytes in stools as Entamoeba histolytica. Two laboratories found to be in error were in community hospitals, and one was at a teaching hospital associated with a medical school and a school of public health. These three laboratories had been diagnosing more than 1200 cases of amebiasis a year for 20 years. (2) When amebiasis does occur, it is likely to be misdiagnosed. In one outbreak with four cases and three deaths, amebiasis was not diagnosed until two patients had died and another was critically ill. Sporadic cases may be mistakenly diagnosed as ulcerative colitis and inappropriately treated with steroids. (3) Foci of endemic amebiasis continue to exist in the United States, both in institutions and in noninstitutional settings.

Acanthamoeba culbertsoni was identified retrospectively in a case of amoebic meningoencephalitis, previously reported by Jager and Stamm (Lancet, 2, 1343, 1972). This is the second report of this species causing secondary infection in man. Positive results were obtained only with anti-A. culbertsoni sera when the brain sections were stained by the indirect immunofluorescence antibody test with various antisera produced against different Acanthamoeba species. Antiserum raised against purified plasma membranes of A. culbertsoni showed once more its highly specific diagnostic value.

We have observed two cases of human infection with intraerythrocytic protozoa. The organisms appeared to be in the Entopolypoides group, which had not previously been associated with human infection. One patient was asplenic. Both patients had hepatic dysfunction, and their serum samples contained blocking factors that interfered in vitro with the stimulation of normal lymphocytes by phytohemagglutinin. It appears that in humans, as well as in experimental animals, host factors are important in resistance to infection by intraerythrocytic parasites. These factors include the presence of a spleen and cell-mediated and humoral immunities. Possibly similar infections will be observed in patients with other impairments of T-cell function, such as those induced by malignancy, thymic dysfunction, or immunosuppressive drugs.

The prevalences of intestinal parasites among the residents of three South American Indian villages in the process of acculturation were compared with those found in earlier unpublished surveys in two newly contracted village.s Although one individual in an acculturating village harbored 11 different intestinal parasites, in general the average number of different parasitic species carried per person was somewhat higher in the newly contacted villages. Helminth egg counts, performed on direct smears of each specimen from one newly contacted village, were low. There were no sex-associated differences in prevalences. The overall prevalences, unadjusted for age, were among the highest recorded for Amerindians. No Taenia species were present. Balantidium coli was present in two acculturating villages, concomitant with the beginning of agricultural practices which include raising swine. No cases of moderate or severe protein-calorie malnutrition was observed in any of the villages during the surveys. These limited data provide a baseline for future comparisons and, perhaps, a glimpse into the past.

Serologic and parasitologic studies were done in El Salvador, C.A., from 1974-1978 to examine the reliability of the diagnosis of Entamoeba histolytica infection in an endemic area and to confirm the estimates of morbidity and mortality due to amebiasis. The results suggest that infection with E. histolytica is common, but the estimated prevalence is too high. Misdiagnosis occurring in hospital and public health laboratories was documented. Data collected from examining family members of persons with E. histolytica infection and disease indicate that most infections are asymptomatic, and support the hypothesis that estimates of morbidity and mortality rates are excessive.

Between 1969 and 1977, 14 persons with parasitologically confirmed Babesia microti infections and seven persons with antibody titers to B. microti greater than or equal to 1:1,024 were identified on Nantucket Island, Massachusetts. Nineteen of these 21 persons were interviewed. About half were permanent residents of Nantucket; the others spent most of their summers on the island. There were 12 women and seven men. Patients ranged in age from 23 to 86 years; all of those with parasitologically confirmed infections were at least 49 years old. Fifteen patients had illnesses characterized by fever, chills, myalgia and fatigue. Five reported being bitten by a tick from 7 to 28 days before the onset of illness. Most cases occurred during July or August. There appeared to be no association between B. microti infection and direct contact with wild or domestic animals or specific outdoor activities. The unusual age distribution of patients with parasitologically confirmed B. microti infections may result because older persons tend to have more severe illnesses and thus are more likely to come to medical attention.

In this preliminary report, we describe a polyacrylamide gel electrophoresis technique for the resolution of isoenzyme patterns of four isolates of Entamoeba histolytica and one isolate of Entamoeba coli. Our findings were similar to previous findings for three enzyme systems: maleic enzyme (malate dehydrogenase [EC 1.1.1.40]), hexokinase (EC 2.7.1.1), and phosphoglucomutase (EC 2.7.5.1). We found preliminary evidence that glucosephosphate isomerase (EC 5.3.1.9) may also differentiate invasive amoebae from noninvasive amoebae, when the isoenzymes are separated by polyacrylamide gel electrophoresis, whereas this differentiation is not evident with starch-gel electrophoresis. We used an Rf system to relate isoenzyme band mobility to the migration distance of a standard E. histolytica strain (HK-9). The numerical identification of isoenzyme bands can simplify the grouping of isolates into zymodemes.

Between 20 July and 15 Octoboer 1975, five cases of human infection with Babesia microti were diagnosed on Nantucket Island, Massachusetts. The illness was characterized by fever, drenching sweats, shaking chills, myalgia, arthralgia, extreme fatigue, and a mild-to-moderate hemolytic anemia. None of the patients had a history of splenetomy. Although all patients responded symptomatically to treatment with oral chloroquine phosphate, parasitemia and fatigue frequently persisted for several weeks to months.

Human "O" cells were fixed with pyruvic aldehyde, treated with tannic acid, and fixed with glutaraldehyde. The cells were sensitized with amoeba antigen and stored in a refrigerator. The sensitized cells were used periodically for the indirect hemagglutination test with a battery of sera from patients with intestinal amebiasis and confirmed and unconfirmed amebic liver abscess, and also from negative controls. The same battery was tested with cells sensitized with different batches of antigen and also with fresh sheep cells. None of the cells showed any reaction with negative control sera. The fixed cells remained sensitive and stable throughout the study. Reproducibility of the titers with the fixed cells within each day and from day to day was satisfactory. The titers with fixed human "O" cells were slightly lower than were the titers with fresh sheep cells. The advantages of using stable, sensitized cells are pointed out.

An indirect immunofluorescent antibody test was used to detect antibody to Babesia microti in human sera. Nine patients from Nantucket Island, Massachusetts infected with B. microti had serum titers greater than or equal to 1,024. Of 84 control sera from New York City residents, 246 sera from patients with possible exposure to ticks, and 36 sera from patients with suspected or confirmed tick bites, none was reactive at titers of 1:16 or above. The within-test reproducibility was within one fourfold dilution in 95% of trials. Test-to-test reproducibility was within one fourfold dilution in 33% of trials and within two fourfold dilutions in 100% of trials. Although cross-reactions among infected patients' sera and antigens of B. argentina, B. equi, B. bigemina, Plasmodium vivax, P. falciparum, and P. brasilianum were common, titers were highest to the homologous antigen.

We used high-resolution polyacrylamide gradient gel electrophoresis (PGGE) to separate four babesial enzymes to aid in the identification of two Babesia microti isolates established in hamsters. The isolates were compared to two different hamsters passages of the "Gray" strain. All isoenzymes patterns from the two isolates and the "Gray" strain were similar except glucose phosphate isomerase (GPI) from one of the "Gray" strain passages. It showed a polymorphic GPI pattern as opposed to a monomorphic GPI pattern seen in the other "Gray" strain passage and the two isolates. The observed differences suggested that some population of B. microti are capable of having polymorphic GPI, that the "Gray" strain originally contained (and may still contain) a heterogeneous population of B. microti, and that the population possessing polymorphic GPI was selected over that with monomorphic GPI. This information was obtained by a PGGE method that eliminated hemoglobin from gels and allowed, for the first time, detection of babesial leucine amino peptidase (LAP) and isocitrate dehydrogenase (IDH). In addition, this method provided molecular weight estimations on babesial GPI, LAP, IDH, and glutamate dehydrogenase (GDH), and it proved useful in the identification and characterization of the B. microti isolates.

Eight non-splenectomized Macaca mulatta were inoculated intravenously with strains of Babesia microti that originally were isolated from 2 human cases of babesiosis and then were maintained in hamsters in the laboratory. Patent infections developed in 7 animals with peak parasitemias of 496 to 3,906 organisms/mm3 blood. Prepatent periods ranged from 15 to 46 days. Parasitemia persisted for at least 90 days in all animals and in one, organisms were still present 559 days after inoculation.

Radiological and serological tests are valuable tools commonly used in diagnosing amebic liver abscess. The limitations in sensitivity and specificity of the various imaging procedures should be recognized in order to avoid misinterpretation of test results. Serodiagnostic methods present potential pitfalls primarily because of their frequent inability to differentiate previous disease from active infection, and must therefore be interpreted carefully.