ABSTRACT
An operating error in a sewage treatment plant led to severe drinking water contamination in a well-defined district of a suburban municipality of Zurich, Switzerland. Despite the alert issued to the local population on the same day advising people not to consume the contaminated water, cases of acute gastroenteric diseases were subsequently observed. Considerable faecal contamination was detected the day after the incident in water samples taken up to 500 m from the sewage plant. In a retrospective epidemiological study involving 240 persons living in the affected area, 126 cases of acute gastrointestinal illness were documented. The epidemic curve revealed a peak incidence two days after the event. Stool samples from 11 of 20 patients were positive for noroviruses or Campylobacter jejuni. Although these microorganisms were not detected in the contaminated water, the subsequently conducted case-control study among the surveyed population showed that consumption of contaminated drinking water was associated with gastrointestinal illness (odds ratio 29.1; 95% confidence interval: 9.8-86.4; p = 0.001). The study also revealed the very probable time period of infection. We present the dimension and chronology of this outbreak and discuss the reasons for its localised and temporary spread.
Subject(s)
Campylobacter Infections/epidemiology , Campylobacter Infections/transmission , Drinking Water/microbiology , Gastroenteritis/epidemiology , Gastroenteritis/microbiology , Water Microbiology , Campylobacter jejuni/isolation & purification , Disease Outbreaks , Humans , Norovirus/isolation & purification , Retrospective Studies , Risk Factors , Sewage/microbiology , Surveys and Questionnaires , Switzerland/epidemiology , Water SupplyABSTRACT
The microsporidian species Enterocytozoon bieneusi had emerged as opportunistic pathogen in AIDS patients causing chronic diarrhoea and was found with high prevalences in faeces of asymptomatic pigs. Analysis of the ribosomal RNA gene internal transcribed spacer (rDNA ITS) had revealed that nine distinct but closely related genotypes occur in humans and in swine. Using primers that were designed to be specific for E. bieneusi, we obtained amplicons from the faecal samples of one from twelve cats and from three out of 36 farm dogs. Sequence analysis of the rDNA ITS, which is part of the diagnostic PCR product, revealed that the isolate from the cat is very closely related to the E. bieneusi genotypes of human or swine origin. The corresponding sequence of all three dog-derived isolates were identical among each other and had a sequence similarity to known sequences of only 47.6-48.2%. In addition, part of the small subunit rRNA gene was amplified and sequenced from one dog-derived isolate revealing a similarity to known sequences of human-derived E. bieneusi of 96-98%. Enterocytozoon-like spores could be detected by light microscopy in one canine sample. Together with recent reports of detection of Enterocytozoon in environmental samples, our findings suggest that microsporidia of the genus. Enterocytozoon seem to be ubiquitous and consist of many genotypes in various naturally infected animal species.
Subject(s)
Cat Diseases/diagnosis , Dog Diseases/diagnosis , Microsporidia/genetics , Microsporidiosis/veterinary , AIDS-Related Opportunistic Infections/parasitology , Animals , Cat Diseases/parasitology , Cats , DNA, Protozoan/genetics , DNA, Ribosomal/genetics , Dog Diseases/parasitology , Dogs , Feces/parasitology , Genotype , Humans , Microsporidia/classification , Microsporidia/isolation & purification , Microsporidiosis/diagnosis , Microsporidiosis/transmission , Molecular Sequence Data , PhylogenyABSTRACT
The microsporidial species Enterocytozoon bieneusi is found among immunocompromised, particularly HIV-infected, patients with chronic diarrhoea, and rarely also among immunocompetent persons with self-limited diarrhoea. Only recently, E. bieneusi was detected in 4 pigs in Switzerland raising the question of a potential zoonotic nature of this parasite. We examined faecal samples of 109 pigs, 24 cows, horses and red foxes each for the presence of E. bieneusi by PCR and compared these isolates with isolates obtained from stool samples of 13 HIV-infected patients living in Switzerland. In animals, E. bieneusi was only identified in pigs with a prevalence of 35%. Analysis of the rDNA internal transcribed spacer (ITS) sequence allowed the classification of E. bieneusi from 28 pigs into 4 distinct genotypes which grouped very closely (identity 96.3-98.8%) together with 2 of the 3 human-derived E. bieneusi genotypes. Hence, E. bieneusi seems to be a common parasite in swine, but no genotypes were identified that were found in humans. Nevertheless, swine might serve as a new animal model for enterocytozoonosis.
