Parasites Archives

Blastocysits h., what kind of symptoms?: an article...

Hi
I was looking for the kind of symptoms blastocystis hominis is causing.
I found this article which summaries scientific researches.
For those interested:
((http://www.hc-sc.gc.ca/pphb-dgspsp/publicat/ccdr-rmtc/01vol27/dr2709eb.html))
Mara

BLASTOCYSTIS HOMINIS: A NEW PATHOGEN IN DAY-CARE CENTRES?
Introduction

Blastocystis hominis is a protozoan parasite whose importance as a cause of gastrointestinal pathology is controversial. Studies conducted over the past decade have shed little light on this debate. In 1996 - 1997, 1,700 male food handlers presenting for their Health Clearance Certificate in Egypt were the subject of a study confirming the potential clinical significance of B. hominis(1). Eight and a half percent of individuals who had B. hominis recovered from their stools showed symptoms, whereas 4% were asymptomatic(1). In 1997, 795 German tourists returning from tropical countries were studied, and a link was found between B. hominis and diarrhea
in their group(2). B. hominis was isolated in the stool of 10.8% of symptomatic patients; almost double the rate within the asymptomatic group (5.2%, p = 0.005)(2). It was also observed that the parasite was most frequently acquired during journeys to the Indian subcontinent(2).

Two other large studies attempted to better elaborate the pathogenic role of B. hominis. In 1997, fecal examinations were conducted on > 6,400 Japanese visiting St. Luke’s International Hospital Centre in Tokyo for a routine checkup. Only 0.5% had B. hominis in their stool, and only 7% of these were symptomatic. Colonoscopic observations of asymptomatic patients shedding B. hominis revealed no instance of invasion of host tissue by the organism, and it was concluded that infection with B. hominis rarely gave rise to clinical symptoms(3). In the same year, another study evaluated 2,039 patients in the University Hospital of Valencia, Spain, which revealed a significant association between B. hominis and the presence of clinical manifestations, the most common of which were diarrhea and abdominal pain(4).

Finally, in 1998 and 1999, two more studies investigated 100 Venezuelan and 1,216 Italian adults respectively, which found that only in subjects suffering from immunodepression did B. hominis show a significant association with gastrointestinal symptoms. Consequently, a pathogenic role of the opportunistic type was suggested(5,6).

Epidemiology and Clinical Aspects

Symptoms that have been associated with B. hominis include bloating, flatulence, mild to moderate diarrhea without fecal leukocytes or blood, abdominal pain, and nausea(7-9). Symptoms usually last about 3 to 10 days, but sometimes persist for weeks or months(8). Transmission is believed to be via the fecal-oral route, and transmission from animals may also occur(7-9). The incubation period is still unknown(7). In general, studies from developed countries report approximately a 1.5% to 10% overall prevalence of B. hominis(9). The geographic distribution of B. hominis appears to be global, with infections more common in tropical, subtropical and developing countries(9). Risk factors for transmission are also largely unknown(8,9).

Day-Care Setting

B. hominis in the day-care setting has only briefly been described in scientific literature, with the two studies conducted on asymptomatic individuals in Brazil and Spain. The prevalence of B. hominis was found to be 5.3% to 10.3% in the 11 day-care centres studied in Salamanca, Spain, whereas prevalence was 34.7% in the day-care centres of Botucatu, Brazil(10,11).

Conclusive evidence of an outbreak of B. hominis in the day-care milieu has never been reported in North American day-care centres. Therefore, the presence of this controversially pathogenic parasite has important implications for public health authorities worldwide. The present investigation describes an outbreak of gastro-
enteritis in a day-care centre where an unexpected number of B. hominis positive individuals were discovered. However, the actual role of B. hominis in this setting is still unknown.

Methods

In the first week of March, 2000 the Montreal Regional Public Health Department in Quebec, Canada received laboratory reports confirming diagnoses of giardiasis (a reportable disease) in two brothers frequenting a day-care centre. A preliminary assessment on 3 March, 2000 revealed that approximately 20 other children and educators in this day-care centre also suffered from gastrointestinal symptoms, including diarrhea and abdominal cramps.

Population

The day-care centre enrolment was 78 children, divided into nine groups. Each group was headed by one to two educators, totalling 10 educators. Management, support, and kitchen staff numbered four.

Stool Sampling

All individuals presenting with at least one gastrointestinal complaint at initial assessment (i.e. nausea, vomiting, diarrhea, abdominal cramps, bloating), were asked to provide two separate stool samples for analysis. Samples were sent to the provincial reference laboratory for parasites, in Montreal. Sampling was conducted on 17 individuals between 4 and 8 March, 2000. A further 10 patients were clinically evaluated by their community physicians, and their stool samples were examined by seven other laboratories. These stool samples were collected from 5 February to 13 March, 2000, including the initial two confirmed cases of Giardia lamblia.

Not all laboratories routinely searched for B. hominis. The provincial reference laboratory for parasites reported all parasites found in the samples. In only two of the seven other laboratories was this also done. The five remaining laboratories (involving samples from seven day-care individuals) later stated that they did not actively search for, or report, B. hominis as a matter of course because it was not believed to be pathogenic.

Symptomatology

Following the preliminary assessment, a questionnaire, administered by a nurse, was used to collect detailed information from all symptomatic individuals. The nurse had no knowledge of the subjects’ B. hominis status. Information was obtained by in-person, or telephone, interview, and included age, gender, day-care group, symptomatology (i.e. fever, upper respiratory tract infection [URI], nausea, vomiting, diarrhea, abdominal cramps, bloating, steatorrhea), date of symptom onset, duration of symptoms, and the date of stool sample.

Twenty five interviews were conducted between 8 and 24 March, 2000. Of these 25 subjects, only 20 complained of gastrointestinal symptoms. Because detailed symptom interviews were only conducted after the majority of stool samples had been collected, in the preliminary assessment stage, the five asymptomatic individuals had already provided stool samples.

Symptomatology data were missing for seven individuals who had provided stool samples. These seven subjects either refused to participate or could not be contacted. Excluding these missing seven, it is believed that all symptomatic individuals at the day-care centre were identified.

Results

Symptomatology

Five of 25 individuals assessed were asymptomatic. Of the 20 symptomatic persons, 15 were children, four were educators, and one was the coordinator of the facility. The average age of the symptomatic children was 3.4 years of age (range 1.7 to 5.5) and 60% were male. The average age of the symptomatic adults was 37 years of age (range 28 to 49) and all symptomatic adults were female. Symptomatic individuals were evenly distributed amongst the nine day-care groups. Figure 1 outlines the date of symptom onset for each individual. Table 1 details the symptom patterns observed.

--------------------------------------------------------------------------------
Figure 1: Outbreak of gastrointestinal illness in a day-care centre in Montreal, Quebec, Canada

Date of onset of symptoms in symptomatic individuals (n = 20)

--------------------------------------------------------------------------------

Stool Samples

On 15 March, 2000, the first positive stool sample result (from an educator) reached the Montreal Regional Public Health Department. It was negative for G. lamblia, but tested positive for B. hominis on two separate occasions. Results from the remaining 26 sampled individuals were received between 16 and 29 March, 2000.

Overall, seven individuals (three adults and four children) tested positive for B. hominis. One positive B. hominis stool sample occurred in one of the two original children positive for G. lamblia. Of the seven B. hominis positives, one child was asymptomatic and one child did not complete the symptom questionnaire. The symptom profiles of the remaining five positive individuals (two children and three adults) can be found in Table 1.

--------------------------------------------------------------------------------
Table 1: Outbreak of gastrointestinal illness in a day-care centre in Montreal, Quebec, Canada

Symptom
Pattern of symptoms

% of all symptomatic individuals suffering from symptom (n = 20)*
% of B. hominis positive individuals suffering from symptom (n = 5)
% of B. hominis negative individuals suffering from symptom (n = 6)

Fever
20% (n = 4/20)
40% (n = 2/5)
0% (n = 0/6)

Upper respiratory tract infection
25% (n = 5/20)
40% (n = 2/5)
0% (n = 0/6)

Nausea and vomiting
40% (n = 8/20)
60% (n = 3/5)
33% (n = 2/6)

Bloating
55% (n = 11/20)
40% (n = 2/5)
33% (n = 2/6)

Steatorrhea
60% (n = 12/20)
60% (n = 3/5)
50% (n = 3/6)

Diarrhea
65% (n = 13/20)
40% (n = 2/5)
83% (n = 5/6)

Abdominal cramps
70% (n = 14/20)
60% (n = 3/5)
50% (n = 3/6)

Average duration of symptoms
15.5 days
(SD = 11.4; range 1 - 35 days)
20 days
(SD = 15.4; range = 2 - 35 days)
6.5 days
(SD = 6.22; range = 1 - 14 days)

* Nine symptomatic individuals did not provide stool samples or had undefined stool sample results.

--------------------------------------------------------------------------------

As described in the methods section, since stool samples from seven individuals were assessed by laboratories not actively searching for, or reporting, B. hominis, these individuals’ true B. hominis status was undefined. Of the 20 with clearly defined B. hominis status, six did not complete the symptom-evaluation tool, including one positive for B. hominis. The 14 remaining individuals had both definite laboratory sample status and complete symptomatology records. They, therefore, composed the study sample for further analysis.

Case-Control Analysis

Among the 11 symptomatic individuals, five were positive for B. hominis and six were negative. In the three asymptomatic individuals, one was positive and two were negative for B. hominis. Using the symptomatic individuals (cases) and the representative random sample of asymptomatic individuals (controls) in the day-
care, the odds of being B. hominis positive were 1.7 times greater in symptomatic versus asymptomatic individuals. Fisher’s Exact Test performed on this sample was not significant (p = 0.846), and the exact 95% confidence interval was 0.064 - 118.

The duration of symptoms between B. hominis-positive and B. hominis-negative symptomatic individuals were also compared. On average, symptoms of B. hominis-positive individuals lasted 13.5 days longer than those of B. hominis-negative individuals (Table 1). This finding approached statistical significance (p = 0.073).

Discussion

Results from this report indicate that it may be premature to confirm B. hominis as simply a commensal. The 1.67-fold odds ratio seen in this study, of B. hominis in symptomatic versus asymptomatic individuals, is consistent with the results of other studies documenting this parasitic association(1,2). Symptom patterns and the duration of illness found in this day-care population correspond with previous, albeit limited, knowledge(7,8). B. hominis-positive symptomatic individuals experienced a longer mean symptom duration than B. hominis-negative subjects. Finally, in 11 symptomatic persons with defined stool samples, five were positive for B. hominis, resulting in a higher prevalence than previously described in the literature for symptomatic individuals (8.5% to 13.2%)(1,2,4).

Characteristics and Limitations

To our knowledge, there has been no other reported outbreak of gastro-enteritis implicating B. hominis in a day-care centre. This novel situation warrants further careful examination of B. hominis’ potential for causing morbidity.

This outbreak investigation, however, has inherent limitations. Missing symptom profiles limited the power of the study by reducing sample size. Similarly, several stool samples were not exhaustively examined for B. hominis by some laboratories. Furthermore, risk factors and possible sources of transmission were not identified, because the cause of the illness was unknown at the time. Finally, the presence of B. hominis in stool samples from patients showing gastrointestinal symptoms does not necessarily imply that symptoms are due to this organism. The complete gamut of infective causes other than parasitosis was not sought, nor were non-infective causes of symptoms excluded. For example, lacking three separate stool samples for each individual prohibits excluding G. lamblia as the potential pathogen(12,13).

Conclusions

This investigation suggests that B. hominis may indeed be more than a harmless commensal. The current inability to fulfil Koch’s postulates, primarily because of the lack of experimental animal models, and the difficulty in excluding all other causes of symptoms, means that the role of B. hominis as a causative agent of human disease remains undefined(9). It should, however, be recalled that protozoa such as Cryptosporidium spp. and the microsporidia, which were previously considered to be nonpathogenic or to have low pathogenicity, are now recognised to cause disease, especially in immunocompromised patients.

At present, it is prudent to consider B. hominis a potential pathogen. In outbreak situations, parasitology laboratories should routinely search for, and report, this parasite in stool samples. B. hominis may be a pathogen in day-care centres and may be more common in individuals with gastrointestinal symptoms of long duration. Recognising this will allow public health authorities and clinicians to request appropriate laboratory investigations and properly manage this controversial parasite. It remains uncertain whether this is the first reported outbreak worldwide of Blastocystis hominis in a day-care centre. However, it is clear that further research is in order.

Acknowledgements

The authors wish to thank Dr. Carole Morissette, Dr. Denise Beauséjour, Dr. Monique Letellier, Dr. Michèle Tremblay, Dr. Michèle Bier, Ms. Martine Barrette and Ms. Alicia Urrego of the Montreal Regional Public Health Department for their invaluable help in the management of this outbreak . They also wish to thank Ms. Agnès Cruz and Dr. Benoît Lapierre of the NDG / Montreal-West Local Community Services Centre (CLSC) for their assistance with the outbreak. Finally, they wish to thank Dr. John Carsley of the Montreal Regional Public Health Department for reviewing and revising the manuscript.

References

Sadek Y, el-Fakahany AF, Lashin AH et al. Intestinal parasites among food-handlers in Qualyobia Governorate, with reference to the pathogenic parasite Blastocystis hominis. J Egypt Soc Parasitol 1997;27:471-78.

Jelinek T, Peyerl G, Loscher T et al. The role of Blastocystis hominis as a possible intestinal pathogen in travellers. J Infect 1997;35:63-6.

Horiki N, Maruyama M, Fujita Y et al. Epidemiologic survey of Blastocystis hominis infection in Japan. Am J Trop Med Hyg 1997;56:370-74.

Carbajal JA, Villar J, Lanuza MD et al. Clinical significance of Blastocystis hominis infection: epidemiologic study. Med Clin (Barc) 1997;108:608-12.

Devera R, Azacon B, Jimenez M. Blastocystis hominis in patients at the Ruiz y Paez University Hospital from Bolivar City, Venezuela. Bol Chil Parasitol 1998;53:65-70.

Cirioni O, Giacometti A, Drenaggi D et al. Prevalence and clinical relevance of Blastocystis hominis in diverse patient cohorts. Eur J Epidemiol 1999;15:389-93.

American Academy of Pediatrics. Blastocystis hominis. In: Peter G, ed. 1997 Red Book: Report of the Committee on Infectious Diseases. 24th ed. Elk Grove Village, IL: American Academy of Pediatrics 1997:153.

Blastocystis hominis: commensal or pathogen? [editorial]. Lancet 1991;337:521-22.

Stenzel DJ, Boreham PF. Blastocystis hominis revisited. Clin Microbiol Rev 1996;9:563-84.

Martin-Sanchez AM, Canut-Blasco A, Rodriguez-Hernandez J et al. Epidemiology and clinical significance of Blastocystis hominis in different population groups in Salamanca (Spain). Eur J Epidemiol 1992;8:553-59.

Guimaraes S, Sogayar MI. Blastocystis hominis: occurrence in children and staff members of municipal day-care centres from Botucatu, Sao Paulo State, Brazil. Mem Inst Oswaldo Cruz 1993;88:427-29.

Hill DR. Giardiasis: Issues in management and treatment. Infect Dis Clin North Am 1993;7:503-25.

Wolfe MS. Giardiasis. Clin Microbiol Rev 1992;5:93-100.

Source: AT Koutsavlis, MD CM, MSc, Community Medicine Residency Programme, Faculty of Medicine, McGill University, L Valiquette, MD, MSc, FRCPC, R Allard, MD CM, MSc, FRCPC, J Soto, MD, PhD, Montreal Regional Public Health Department, Montreal, Quebec, Canada.

Re: Blastocystis (Archive in parasites.)