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ABSTRACT |
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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In developing countries, cyclosporiasis and associated symptoms occur more often in children.1–3 Infection rates as high as 20% have been reported4 and asymptomatic infections have been documented.4,5 In Venezuela, the prevalence and significance of the coccidium as a causal agent of enteric disease is largely undefined. In individuals with diarrhea, infection rates of 5.3% in children and 9.8% in patients with AIDS have been reported.6 The majority of epidemiologic studies on Cyclospora has involved highly selective populations, and there are virtually no community-based reports1 with the exception of two studies from Peru5 and Haiti.4 However, the former was a prospective study limited to children less than 2.5 years of age and the latter involved only groups of mothers and children. Two reports from Guatemala based mainly on health care populations also included data and surveillance collected in cohorts of raspberry farm workers.2,7,8 Thus, the epidemiologic features of the parasite are unknown and investigations based in whole populations are needed.
To assess the prevalence and pathogenic role of this coccidium in Venezuela, a retrospective study was designed involving a community previously evaluated by our group for other intestinal parasites.9
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MATERIALS AND METHODS |
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The study settlement was San Luis, which is located in the coastal lowlands near Lake Maracaibo in the Zulia State of northwestern Venezuela. The mean annual temperature, relative humidity, and amount of rainfall were 28°C, 78%, and 747 mm, respectively. The sanitary and socioeconomic standards were low. Thirty-eight percent of the individuals were unemployed and 40% were illiterate. Sixty-five percent of the housing units had indoor plumbing and 35% had piped water. Fifty-six percent had flush toilets and 3.7% had latrines. Forty percent of the individuals defecated in the backyards of the houses. Overflowing sewage and piles of rubbish were frequently observed. Households often had one or two dormitories for six or more occupants, providing the opportunity for frequent contact among residents. Domestic animals such as cats, dogs, pigs, and poultry were common.
Fifty-four families were selected by random sampling and then visited to ensure understanding of the aim of the study and acceptability and cooperation of the householders. Data pertaining to family identification, socioeconomic conditions, and gastrointestinal symptoms at the time of the survey and during the previous month were recorded. Single fecal specimens were collected from 212 individuals (age range = two months to 70 years) who provided representative coverage of the whole population, which was approximately 2,000 inhabitants. Specimens were obtained and processed within two hours after collection.
Data on age, sex, and gastrointestinal complaints were reviewed in the clinical evaluation records of this population. For identification of Cyclospora oocysts, modified Ziehl-Neelsen carbolfuchsin staining of formalin-ether concentrates were used.10 The stained smears were examined under dry magnification (400x) and an ocular micrometer was used to measure the size of the oocysts. For other pathogenic parasites, parasitologic records of iron-hematoxylin–stained fecal smears11 and formalin-ether concentrate examinations12 were also reviewed. For data analysis, the chi-square and Fisher’s exact tests were used. Results were considered significant if the P value was less than 0.05.
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RESULTS |
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Of the 13 subjects shedding oocysts, 11(84.6%) were asymptomatic at the time of sampling or during the previous month and two (15.4%) had diarrhea that lasted from four to ten days by the time of the survey. Both patients were infants, including one of five months of age, who had the coccidium as sole pathogenic parasite detected. Of the 13 Cyclospora-positive individuals, 11(84.6%) were coinfected with other pathogens, including helminths and other protozoa. Among the latter, Giardia lamblia was the most frequent (30.8%).
The distribution of Cyclospora infections among age groups showed a tendency for a higher occurrence in individuals 6–15 years of age, although no significant differences were found (Table 1
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DISCUSSION |
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The age distribution of Cyclospora infections suggest that subjects are exposed to the parasite at a very early age and that infections tend to be more common in the 6–15-year-old children, although no significant differences were obtained among the age groups. This statistical result may be due to the small sample size of the infections since some reports have suggested that children less than nine years of age are more susceptible to infection.2,3 However, these studies were based in health center populations and were thus skewed toward younger children who appear to be more susceptible to clinical manifestations in tropical countries.1–3 The detection of Cyclospora in adolescents and adults in this impoverished area contrasts with the absence of the parasite in those 
11 years of age in slums from Peru.13
Diarrhea was not a prominent feature of Cyclospora infection in this study. Only two (15.4%) infants had diarrheal illness that could be related to the parasite. However, other etiologic agents were not identified. The high proportion (84.6%) of asymptomatic infections was remarkable. However, since stool specimens were collected at one point in time and diarrheal symptoms were analyzed retrospectively, it is not known how many of these infections occurred during the incubation period prior to the developing of symptoms. Indeed, a study from Nepal showed one patient with histopathologic changes consistent with infection with Cyclospora who was asymptomatic, but developed diarrhea within five days of endoscopy.14 Despite this limitation, the appreciable rates (72–94%) of asymptomatic infections, even in children less than three years old, which was documented in longitudinal studies of indigenous populations from Haiti4 and Peru,5 support our results. Thus, it appears that in developing countries, the situation at the general population level is quite different than that observed in health center populations in whom a strong association of the parasite with diarrhea has been recognized.1
In this study, the high rate of asymptomatic carriage of the coccidium suggests that it may not play a consistent pathogenic role in this population. Thus, the probability that individuals shedding oocysts could have developed diarrhea after the primary infection with the parasite should not be minimized. In tropical countries, asymptomatic excretion of intestinal pathogens is frequently observed.15 Similarly, a high proportion (71.4%) of asymptomatic Cryptosporidium infections in the study community was previously reported.9 The overwhelming parasitism also found in this area9 reflects its unsanitary living conditions. In this kind of setting, continuous exposure to Cyclospora may be associated with protection against parasite-associated symptoms. In this study, the age distribution of diarrheal illness affecting only infants and the presence of asymptomatic infections in all the other age groups appear to suggest the development of partial immunity that protects from the pathogenic effects of the coccidium, but not from reinfections. Studies from Peruvian shanty towns suggest that immunity becomes complete by adolescence.13
In conclusion, our findings suggest that Cyclospora infections are relatively common and often asymptomatic in the general population of this Venezuelan region. However, further studies are needed to better characterize the epidemiology and significance of C. cayetanensis in this country.
Received May 4, 2002. Accepted for publication November 20, 2002.
Authors’ addresses: Leonor Chacin-Bonilla, Margot Mejia de Young, and Jesús Estévez, Instituto de Investigaciones Clinicas, Universidad del Zulia, Apartado Postal 1151, Maracaibo, Venezuela, Telephone: 58-261-759-7247, Fax: 58-261-783-5587, E-mail: ebonillaro{at}yahoo.com
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This article has been cited by other articles:
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  B. Sancak, Y. Akyon, and S. Erguven Cyclospora infection in five immunocompetent patients in a Turkish university hospital. J. Med. Microbiol., April 1, 2006; 55(Pt 4): 459 - 462. [Abstract] [Full Text] [PDF]
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