The seroepidemiology of toxoplasmosis in the lower Fraser Valley of British Columbia.

OBJECTIVE: To determine the seroprevalence of toxoplasmosis in vegetarian and nonvegetarian members of different ethnic communities in the lower Fraser Valley of British Columbia. DESIGN: Serum samples were collected from 2027 participants drawn from various ethnic groups and tested by elisa for the presence of immunoglobulin (Ig) G and IgM antibodies to Toxoplasma gondii. Coded questionnaires requesting information relevant to the study were completed by each participant. The study population comprised 1334 females and 693 males; ages ranged from 17 to 102 years. MAIN RESULTS: Four hundred and nineteen (20.7%) individuals were IgG positive with titres ranging from 1:100 to 1:3200. IgM antibodies were detected in only four individuals. The seroprevalence rose with increase in age but there was no significant difference between males and females. A positive correlation was shown between ingestion of meat and between consumption of unpasteurized milk and antibodies to T gondii. Eighty per cent of females between the ages of 17 and 40, of all ethnic origins, were seronegative. Seropositivity did not differ between cat owners and non-cat owners. CONCLUSIONS: Women of childbearing age are at risk of acquiring toxoplasmosis during pregnancy and of transmitting the infection transplacentally. Consumption of undercooked meat and unpasteurized milk may result in the acquisition of toxoplasmosis. Data suggest that acquisition of toxoplasmosis is more likely via environmental oocysts or cysts in food source animals than by direct contact with cats.

Tunga penetrans acquired while traveling in Africa.

Three cases of tungiasis acquired in the course of travel are briefly described, and the biology of the jigger flea, Tunga penetrans, is reviewed.

Enhanced killing of Acanthamoeba cysts in vitro using dimethylsulfoxide.

PURPOSE: Acanthamoeba keratitis is difficult to treat and requires prolonged therapy despite the well-documented in vitro effectiveness of a variety of drugs. The authors propose that this may be due to the cysts formed by the organism in response to hostile conditions. Consequently, the study concentrates on increasing penetration of drugs effective against the parasite into the cysts using dimethylsulfoxide (DMSO). METHODS: The organism is forced to encyst in vitro on solid media by nutrient deprivation. In the first set of experiments, serial dilutions of a standard treatment regimen are applied to the organisms, and these treated cysts are then subcultured onto nutrient-rich material and observed for growth. The experiments are then repeated with DMSO added to the serially diluted standards. In a second set of experiments, the effects of retreatment on a larger concentration of organisms is examined. RESULTS: When applied to a cyst-only population of Acanthamoeba, none of three standard drugs, propamidine isethionate 0.1%, neomycin 1%, or miconazole 1%, was cysticidal. When combined with DMSO 30%, propamidine isethionate was clearly cysticidal even in low dilution. This was confirmed by the retreatment experiments using a larger, standardized cyst population. CONCLUSION: The authors propose that DMSO is acting as a "carrier" for the propamidine isethionate and increases its penetration into the normally drug-resistant cyst form of the organism. Because DMSO has been used topically in the past and shown to be quite safe, this may be a viable new therapy for this difficult condition.

Laboratory diagnosis of amebiasis.

The procedure used to diagnose amebiasis varies depending on the geographic location of the laboratory. However, in general, the microscopic diagnosis and differentiation of E. histolytica from other intestinal amebae is most satisfactorily achieved when the specimen is preserved immediately and both a concentration and stained smear are examined. The number of additional positive findings achieved by the cultivation of fecal material does not justify the time and cost involved. On the other hand, serology is a useful adjunct to diagnosis, especially in patients with extraintestinal amebiasis. The commercial development of antigen detection kits and DNA probes may provide more rapid, accurate, and less costly diagnostic procedures for the future. New guidelines need to be formulated regarding the number of specimens to be submitted, and the cost effectiveness of various diagnostic procedures should be evaluated.

Etiology of childhood diarrhea in Beijing, China.

To determine the role of recently recognized enteropathogens in childhood diarrhea in China, 221 children with diarrhea and 108 controls seen at the Beijing Children's Hospital were studied during April and May 1989. Stools were examined for ova, parasites, and rotavirus, cultured for bacterial pathogens, and probed for enterotoxigenic Escherichia coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC), and enteropathogenic adherence factor-positive (EAF+) E. coli. Pathogens were identified in 56.5% of children with diarrhea and 43.5% of controls (P = 0.04). Detection of enteropathogens was significantly greater in patients examined within 1 week of symptom onset (65%) than in patients examined later (39%; P = 0.01). ETEC was the most frequently detected pathogen in children with diarrhea, accounting for 20% of the cases. Other agents identified in patients included the following: salmonellae, 12%; rotavirus, 7%; EIEC, 7%; EHEC, 7%; members of the Aeromonas hydrophila group, 6%; EAF+ E. coli, 5%; Ascaris lumbricoides, 3%; shigellae, 3%; campylobacters, 2%; and Vibrio spp., 0.5%. The isolation rates of salmonellae (P = 0.02), EAF+ E. coli (P = 0.04), and mixed pathogens (P = 0.05) were significantly greater for diarrhea patients than for controls. Resistance to multiple antimicrobial agents occurred in 39% of the Salmonella isolates, 22% of the Aeromonas isolates, and 17% of the Shigella isolates. Multiresistant salmonellae (P = 0.05) and shigellae were recovered from diarrheal stools only. Ciprofloxacin, cefotaxime, and imipenem were the only agents tested to which all bacterial isolates were susceptible in vitro. These results suggest that both traditional and newly recognized agents are important causes of childhood diarrhea in Beijing and that therapy may be complicated by indigenous antimicrobial resistance.

Epidemiology and pathogenicity of Blastocystis hominis.

A prospective study was performed on a large outpatient population to evaluate the epidemiology and pathogenicity of Blastocystis hominis. Patients with stool specimens positive for B. hominis and negative for other bacterial and parasitic pathogens were sent a questionnaire and were requested to submit a follow-up specimen for ova-and-parasite examination. B. hominis was identified in 530 of 16,545 specimens (3.2%). There was a spectrum of clinical-pathological presentations in the 143 patients evaluated. An asymptomatic carrier state was seen in 19 patients. Fifteen patients had an illness consistent with acute self-limited B. hominis gastroenteritis, and 21 patients had chronic gastroenteritis associated with B. hominis. In the epidemiological evaluation of 130 patients, the most common symptoms were watery diarrhea, abdominal pain, and gas. We did not find a statistically significant association between the number of organisms present and the disease state. In summary, our results are consistent with a role for B. hominis in acute and chronic gastroenteritis; however, further detailed studies are necessary to determine whether that role is one of association or causation.

Isoenzyme analysis of human and animal isolates of Giardia duodenalis from British Columbia, Canada.

Isoenzyme patterns of 32 isolates of Giardia duodenalis, obtained from 6 beavers and 11 humans from British Columbia, plus 15 other isolates were evaluated using thin-layer starch-gel electrophoresis. We attempted to use 12 enzymes; 9 gave reproducible and interpretable results. The isoenzyme patterns of the isolates were classified into 12 groups with 17 (53%) of the 32 isolates confined to 1 group. The other 11 groups each comprised only 1 or 2 isolates. There was no obvious correlation between clinical symptoms and isoenzyme patterns. Our findings suggest that beavers, like humans and gerbils are receptive to organisms with many different isoenzyme patterns.

Isoenzyme patterns of isolates of Trichomonas vaginalis from Vancouver.

Isoenzyme patterns of 63 isolates of Trichomonas vaginalis obtained in Vancouver were evaluated by use of thin-layer starch-gel electrophoresis. We attempted to use eight enzymes, but only four gave reproducible and interpretable results. There were four patterns with malic enzyme, two with malate dehydrogenase, one with hexokinase, and four with lactate dehydrogenase. The isoenzyme patterns of the 63 isolates were classified into 15 groups, but 49 (78%) fell into five groups and 14 (22%) fell into ten groups. There was no obvious correlation between groups and magnitude of symptoms and signs, past history of trichomoniasis, or likelihood of treatment failure. Results were consistent for isolates obtained from the same patient on different days. This system will allow differentiation of isolates into groups, a procedure that could be useful. However, groups do not appear to correlate with clinical or historical features or with outcome of treatment.

Enzyme-linked immunosorbent assay for the diagnosis of trichomoniasis in women.

An enzyme-linked immunosorbent assay-(ELISA) using whole Trichomonas vaginalis as antigen was developed for measurement of serum antibody to T. vaginalis. Sera from six women who denied ever having had genital contact were used as the negative control. Of 38 women with proved T. vaginalis infection, 25 (66%) had elevated ELISA values. Values were usually very stable over weeks to months of follow-up. Among a matched comparison group of 38 women attending the same clinic who did not have T. vaginalis infection (as detected by wet mounts), an elevated value was present in only eight (21%) of 38 (P less than 0.001). Thus, in this group of women, the sensitivity was 66%, the specificity, 79%, the predictive value of a positive test, 76%, and the predictive value of a negative test, 70%. Our ELISA clearly demonstrates more reactivity in women with T. vaginalis. Its usefulness as a marker of current infection is probably limited, but it could be of considerable value for seroepidemiologic studies.

The electrophoretic isoenzyme patterns of strains of Entamoeba histolytica isolated in two major cities in Canada.

The isoenzyme patterns of 92 isolates of Entamoeba histolytica from British Columbia and 28 from Ontario were determined. Seropositivity for E. histolytica was assessed by indirect hemagglutination and enzyme-linked immunosorbent assay in the one center and by ELISA and amebic gel diffusion in the other. In both British Columbia and Ontario nonpathogenic zymodemes I and III were most common. A newly described isoenzyme pattern was identified in Ontario. Only 9 of 120 zymodeme patterns identified were found to be pathogenic strains of E. histolytica. Pathogenic isolates were strongly correlated with clinical symptoms and seropositivity.

Cell culture compared with broth for detection of Trichomonas vaginalis.

Trichomonas vaginalis can be grown in cell culture. We studied the growth kinetics of T. vaginalis in McCoy cell culture compared with that in a conventional broth medium (Diamond TYI-S-33 medium supplemented with 10% heat-inactivated bovine serum [TYI]). In the presence of McCoy cells and two parts cell culture medium to one part TYI, a peak concentration of 2 X 10(6) to 6 X 10(6) T. vaginalis per ml was consistently achieved with inocula as low as three T. vaginalis cells per ml. Without cells, this medium did not support growth of T. vaginalis. T. vaginalis in TYI in 1-ml vials with or without McCoy cells demonstrated poor growth. In tubes containing 10 ml of TYI, inocula grew to 2 X 10(6) to 6 X 10(6) T. vaginalis per ml, but at least 3 X 10(3) T. vaginalis per tube was required to initiate growth. Thus, in vitro, cell culture was more sensitive than TYI broth in detecting low numbers of T. vaginalis. In a subsequent clinical comparison of broth and cell culture for isolation of T. vaginalis from 188 vaginal specimens and 21 urethral specimens from men, the results were in agreement for 206 specimens (98.6%). There were no situations in which culture was negative and a saline preparation showed motile trichomonads. For women, using a positive culture as the indicator of true positivity, the sensitivity of detection of T. vaginalis was 83% with the Pappenheim stain and 77% with saline preparations. These studies show that cell culture can be used for isolation of T. vaginalis from clinical specimens; it gave results comparable to those of broth culture for the group of mainly symptomatic women. Further studies should be performed to determine its utility in clinical populations such as asymptomatic women and men with and without symptoms, in which T. vaginalis is more likely to be present in low numbers.

Endemic institutional strongyloidiasis in British Columbia.

The incidental finding in 1984 of Strongyloides stercoralis larvae in a resident of a chronic care institution who had a vague clinical illness prompted a review of the other residents. Five other cases were identified after exhaustive laboratory investigations. Fecal-oral spread was considered the most likely manner of the spread of infection. The possibility of endemic strongyloidiasis in institutions should be considered, even in temperate climates, when there is unexplained persistent illness or high eosinophil counts. Serologic testing is a useful adjunct to fecal examination in such situations.

Cryptosporidium infections: a laboratory survey.

Between Oct. 1, 1983, and June 30, 1985, Cryptosporidium oocysts were identified in stool specimens from 74 patients who presented with gastrointestinal symptoms to their physicians. Questionnaires prepared to determine travel history, symptoms, duration of illness and epidemiologic characteristics of the infection were completed for 67 (90%) of the patients by their physicians; the information on the other 7 patients was obtained from the requisitions accompanying the specimens. Of the 67, 35 (52%) had recently been to Mexico. The infection was likely transmitted through contaminated water, food and, possibly, milk. The infections in patients who had not travelled were thought to be due to contact with infected pets or farm animals or with infected children attending daycare centres. Diarrhea, vomiting, fever and nausea usually lasted for 1 to 2 weeks, except in those with immune deficiency, in whom the symptoms persisted for up to 6 months. The condition was diagnosed by identification of oocysts in stool specimens that underwent formalin-ether sedimentation and modified cold Kinyoun staining.

Immunogenic proteins of Trichomonas vaginalis as demonstrated by the immunoblot technique.

Fifteen clinical isolates of Trichomonas vaginalis were evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with transfer to nitrocellulose and by immunoblots probed with human sera. All T. vaginalis isolates showed similar banding patterns by Coomassie brilliant blue and silver staining of the electrophoresis gels and by amido black staining of the nitrocellulose. However, by the immunoblot technique, differences in banding patterns were noted, particularly in the high-molecular-weight zone (greater than 1.5 X 10(5], which were consistent in numerous experiments. A common immunogenic band was noted at a molecular weight of approximately 100,000 in all T. vaginalis isolates probed with six sera reactive in an enzyme-linked immunosorbent assay but was not seen or was only faintly visible when isolates were probed with sera considered to be nonreactive by the assay. Many other bands were identified, some of which appeared common to all isolates, but were not recognized by all sera tested. These studies demonstrate the antigenic heterogeneity of T. vaginalis and show that different individuals appear to respond immunologically to different T. vaginalis antigens.

Strongyloidiasis in Canadian Far East war veterans.

A survey was done of Canadians who had been interned by the Japanese during World War II to assess the prevalence of latent infection with Strongyloides stercoralis in this group. Packages containing three mail-in kits and a questionnaire were sent to 992 men, 694 (70%) of whom responded. Larvae were found in the stool specimens of four of the respondents. Examination of stool specimens after formalin-ether concentration was the most successful method of detecting Strongyloides larvae. The Baermann concentration technique yielded negative results in all four men. Three of the four cases of strongyloidiasis were detected after sampling of three fecal specimens. In the fourth case additional specimens were requested on the basis of data derived from the questionnaire. The most frequently cited clinical manifestations were abdominal pain, weight loss, diarrhea and rashes.