Risk factors for endemic giardiasis

Retrospective Survey of Dog and Cat Endoparasites in Ireland: Antigen Detection

Endoparasites of dogs and cats, play an important role in both veterinary medicine and public health. Untreated and stray dogs and cats, in particular, play an important role in contaminating the environment with important zoonotic parasites. Thus, the aim of this study was to estimate the prevalence of intestinal parasites in stray dogs and cats using highly sensitive and specific copro-antigen tests. Archive faecal samples from previous surveys conducted between 2016−2019 from dogs (n = 789) and cats (n = 241) were included in this study. The IDEXX Fecal Dx™ antigen panel was used for the detection of Toxocara, hookworms, Trichuris and the SNAP™ Giardia antigen assay was used for the detection of Giardia infection. Giardia duodenalis was the most common parasite (26%, n = 205) detected in the dogs, followed by ascarids (17.6%, n = 139) and hookworms (5.3%, n = 42). Trichuris vulpis was only detected in 1 dog. Ascarids (23.2%, n = 56) was the most common parasite detected in the cats, followed by Giardia (12.9%, n = 31) and hookworms (n = 7, 2.9%). No whipworms were detected in cats. Overall, there was little difference in the positivity between sexes in both dogs and cats. However, in terms of age, adolescent dogs (<3 years) and kittens (<1 year) had the highest parasite prevalence overall, with G. duodenalis and ascarids being the most prevalent. This study shows a high prevalence of parasite infection in untreated and stray dogs and cats in the greater Dublin area in Ireland. Since they live in synanthropic conditions and can roam over vast distances they can contaminate public areas and pose a risk to both humans and owned pets that utilise these spaces. It is therefore important to raise public awareness and increase the knowledge on zoonotic parasites.

Giardiasis notifications are associated with socioeconomic status in Sydney, Australia: a spatial analysis

OBJECTIVE

In developed countries prolonged symptoms due to, or following, Giardia intestinalis infection can have a significant impact on the quality of life. In this research, we investigate the presence of a socioeconomic status (SES) gradient in the reporting of giardiasis in South West Sydney Local Health District (SWSLHD), New South Wales (NSW), Australia, across geographic scales.

METHODS

We used a large database, spatial-cluster analysis and a linear model.

RESULTS

Firstly, we found one spatial cluster of giardiasis in one of the most advantaged neighbourhoods of SWSLHD. Secondly, rates of giardiasis notifications were significantly and consistently lower in SWSLHD compared to an unnamed advantaged Local Health District and NSW over multiple years. Finally, we found an overall significant positive dose-response relationship between counts of giardiasis and area-level SES.

CONCLUSIONS

Lower reporting in disadvantaged areas may represent true differences in incidence across SES groups or may result from differential use of health services and reporting. Implications for public health: If the disparities result from differential use of health services, research should be directed toward identifying barriers and facilitators of use. If disparities result from a true difference in incidence, then the behavioural mediators between SES and giardiasis should be identified and addressed.

Risk factors for sporadic Giardia infection in the USA: a case-control study in Colorado and Minnesota

Giardia duodenalis is the most common intestinal parasite of humans in the USA, but the risk factors for sporadic (non-outbreak) giardiasis are not well described. The Centers for Disease Control and Prevention and the Colorado and Minnesota public health departments conducted a case-control study to assess risk factors for sporadic giardiasis in the USA. Cases (N = 199) were patients with non-outbreak-associated laboratory-confirmed Giardia infection in Colorado and Minnesota, and controls (N = 381) were matched by age and site. Identified risk factors included international travel (aOR = 13.9; 95% CI 4.9-39.8), drinking water from a river, lake, stream, or spring (aOR = 6.5; 95% CI 2.0-20.6), swimming in a natural body of water (aOR = 3.3; 95% CI 1.5-7.0), male-male sexual behaviour (aOR = 45.7; 95% CI 5.8-362.0), having contact with children in diapers (aOR = 1.6; 95% CI 1.01-2.6), taking antibiotics (aOR = 2.5; 95% CI 1.2-5.0) and having a chronic gastrointestinal condition (aOR = 1.8; 95% CI 1.1-3.0). Eating raw produce was inversely associated with infection (aOR = 0.2; 95% CI 0.1-0.7). Our results highlight the diversity of risk factors for sporadic giardiasis and the importance of non-international-travel-associated risk factors, particularly those involving person-to-person transmission. Prevention measures should focus on reducing risks associated with diaper handling, sexual contact, swimming in untreated water, and drinking untreated water.

Giardiasis Diagnosis and Treatment Practices Among Commercially Insured Persons in the United States

Background

Giardiasis, the most common enteric parasitic infection in the United States, causes an estimated 1.2 million episodes of illness annually. Published clinical recommendations include readily available Giardia-specific diagnostic testing and antiparasitic drugs. We investigated sequences of giardiasis diagnostic and treatment events using MarketScan, a large health insurance claims database.

Methods

We created a longitudinal cohort of 2995 persons diagnosed with giardiasis (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 007.1) from 2006 to 2010, and analyzed claims occurring 90 days before to 90 days after initial diagnosis. We evaluated differences in number and sequence of visits, diagnostic tests, and prescriptions by age group (children 1-17 years, adults 18-64 years) using χ2 tests and data visualization software.

Results

Among 2995 patients (212433 claims), 18% had a Giardia-specific test followed by or concurrent with an effective antiparasitic drug, without ineffective antibiotics. Almost two-thirds of patients had an antiparasitic and 27% had an antibiotic during the study window. Compared with children, adults more often had ≥3 visits before diagnosis (19% vs 15%; P = .02). Adults were also less likely to have a Giardia-specific diagnostic test (48% vs 58%; P < .001) and more likely to have an antibiotic prescription (28% vs 25%; P = .04). When Giardia-specific tests and antiparasitic and antibiotic prescriptions were examined, pediatric clinical event sequences most frequently began with a Giardia-specific test, whereas adult sequences most frequently began with an antiparasitic prescription.

Conclusions

Giardiasis care infrequently follows all aspects of clinical recommendations. Multiple differences between pediatric and adult care, despite age-agnostic recommendations, suggest opportunities for provider education or tailored guidance.

Giardiasis in the United States - an epidemiologic and geospatial analysis of county-level drinking water and sanitation data, 1993-2010

Giardiasis is the most commonly reported intestinal parasitic infection in the United States. Outbreak investigations have implicated poorly maintained private wells, and hypothesized a role for wastewater systems in giardiasis transmission. Surveillance data consistently show geographic variability in reported giardiasis incidence. We explored county-level associations between giardiasis cases, household water and sanitation (1990 census), and US Census division. Using 368,847 reported giardiasis cases (1993-2010), we mapped county-level giardiasis incidence rates, private well reliance, and septic system reliance, and assessed spatiotemporal clustering of giardiasis. We used negative binomial regression to evaluate county-level associations between giardiasis rates, region, and well and septic reliance, adjusted for demographics. Adjusted giardiasis incidence rate ratios (aIRRs) were highest (aIRR 1.3; 95% confidence interval 1.2-1.5) in counties with higher private well reliance. There was no significant association between giardiasis and septic system reliance in adjusted models. Consistent with visual geographic distributions, the aIRR of giardiasis was highest in New England (aIRR 3.3; 95% CI 2.9-3.9; reference West South Central region). Our results suggest that, in the USA, private wells are relevant to giardiasis transmission; giardiasis risk factors might vary regionally; and up-to-date, location-specific national data on water sources and sanitation methods are needed.

Forest fragmentation and risk of giardiasis in New York State

In the United States, giardiasis is endemic in northern and northeastern states, but its ecology and epidemiology remain elusive. The underlying physical landscape may play a role in shaping points of contact between humans, animals, and Giardia cysts. This study examined 11 years of surveillance data in New York State to measure the relationship between forest fragmentation and the incidence of giardiasis. Adjusted Poisson models showed that increasing points of contact between forested land and developed land, as measured by their shared edges [incident rate ratio (IRR) = 1.003; P < 0.001] and by the perimeter length of forested patches (IRR = 1.31; P = 0.01), were associated with higher incidence of giardiasis cases, whereas increasing forest density was associated with a lower incidence (IRR = 0.97; P < 0.001). These associations were independent of both temperature and surface water area. While these results are only suggestive due to the county-level aggregated data, the findings do identify a potentially important signal in the landscape epidemiology of giardiasis and highlight the need for better, more targeted, field studies on individual water sources for household consumption, inter-species contact in ecotones, surface water contamination, and human giardiasis cases.

Drugs for treating giardiasis

BACKGROUND

Giardiasis infection may be asymptomatic, or can cause diarrhoea (sometimes severe), weight loss, malabsorption, and, in children, failure to thrive. It is usually treated with metronidazole given three times daily for five to 10 days.

OBJECTIVES

To evaluate the relative effectiveness of alternative antibiotic regimens for treating adults or children with symptomatic giardiasis.

SEARCH METHODS

We searched the Cochrane Infectious Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 6 2012); MEDLINE, EMBASE, LILACS and the International Clinical Trials Registry Platform Search Portal (3 July 2012).

SELECTION CRITERIA

We included randomized controlled trials (RCT) comparing metronidazole administered for five to 10 days with any of the following drugs: metronidazole (single dose), tinidazole, albendazole, mebendazole, and nitazoxanide. The primary outcomes were parasitological and clinical cure.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion, performed the risk of bias assessment, and extracted data. We summarized data using risk ratios and mean differences and we presented the results in forest plots and performed meta-analyses where possible. We assessed heterogeneity using the Chi(2) test, I(2) statistic and visual inspection; and we explored this by using subgroup analyses.We assessed the quality of evidence by using the GRADE approach.

MAIN RESULTS

We included 19 trials, involving 1817 participants, of which 1441 were children. Studies were generally small, with poor methods reporting. . Most reported parasitological outcomes rather than clinical improvement.Ten trials, from India, Mexico, Peru, Iran, Cuba, and Turkey, compared albendazole (400 mg once daily for five to 10 days) with metronidazole (250 mg to 500 mg three times daily for five to 10 days). This once-daily regimen of albendazole is probably equivalent to metronidazole at achieving parasitological cure (RR 0.99, 95% CI 0.95 to 1.03; 932 participants, 10 trials; moderate quality evidence), and improving symptoms (RR 0.98, 95% confidence interval (CI) 0.93 to 1.04; 483 participants, five trials; moderate quality evidence), but the duration of follow-up was short (two to three weeks). Albendazole probably has fewer side effects than metronidazole (gastrointestinal side effects: RR 0.29, 95% CI 0.13 to 0.63; 717 participants, eight trials; moderate quality evidence; neurological side effects: RR 0.34, 95% CI 0.18 to 0.64; 453 participants, five trials; low quality evidence).Five trials from Turkey, Spain and the UK compared mebendazole (200 mg three times daily for five to 10 days) with metronidazole (5 mg/kg (or 250 mg) three times daily for five to 10 days). These trials were small in size, and at high risk of bias. Consequently, reliable conclusions on the relative effectiveness cannot be made (very low quality evidence).Five further trials, from Iran, Spain and Peru, have evaluated shortened regimens of tinidazole (single dose; 179 participants, three trials), metronidazole (single dose; 55 participants, one trial), and nitazoxanide (three days; 55 participants, one trial). Again, these trials were at high risk of bias and too small to reliably detect or exclude important differences (very low quality evidence).

AUTHORS' CONCLUSIONS

Albendazole may be of similar effectiveness to metronidazole, may have fewer side effects, and has the advantage of a simplified regimen. Large, high quality trials, assessing clinical outcomes (such as diarrhoea) will help assess further alternatives.

A systematic review and meta-analysis of the association between Giardia lamblia and endemic pediatric diarrhea in developing countries

We performed a systematic literature review and meta-analysis examining the association between diarrhea in young children in nonindustrialized settings and Giardia lamblia infection. Eligible were case/control and longitudinal studies that defined the outcome as acute or persistent (>14 days) diarrhea, adjusted for confounders and lasting for at least 1 year. Data on G. lamblia detection (mainly in stools) from diarrhea patients and controls without diarrhea were abstracted. Random effects model meta-analysis obtained pooled odds ratios (ORs) and 95% confidence intervals (CIs). Twelve nonindustrialized-setting acute pediatric diarrhea studies met the meta-analysis inclusion criteria. Random-effects model meta-analysis of combined results (9774 acute diarrhea cases and 8766 controls) yielded a pooled OR of 0.60 (95% CI, .38-.94; P = .03), indicating that G. lamblia was not associated with acute diarrhea. However, limited data suggest that initial Giardia infections in early infancy may be positively associated with diarrhea. Meta-analysis of 5 persistent diarrhea studies showed a pooled OR of 3.18 (95% CI, 1.50-6.76; P < .001), positively linking Giardia with that syndrome. The well-powered Global Enteric Multicenter Study (GEMS) is prospectively addressing the association between G. lamblia infection and diarrhea in children in developing countries.

Giardiasis among different tribes of Orang Asli in Malaysia: highlighting the presence of other family members infected with Giardia intestinalis as a main risk factor

The flagellate protozoan parasite, Giardia intestinalis, is widely distributed throughout the world with a high prevalence in developing countries in the tropics and subtropics, including Malaysia. Approximately 200 million people are infected with the parasite globally, with 500,000 new cases reported annually. This cross-sectional study was conducted among three tribes of Orang Asli communities in Selangor, Perak and Pahang states of Malaysia. The main objective was to determine the prevalence of and risk factors for giardiasis. Stool samples were collected from 500 individuals aged between 2 and 74 years (males=219, females=281). The samples were examined with formalin-ether sedimentation and trichrome staining techniques. Socioeconomic data were collected through a pre-tested questionnaire. The overall prevalence of giardiasis was 20.0% with the highest prevalence in the Proto-Malays (33.3%) followed by Negritos (20.1%) and Senois (10.4%). The positive cases showed a decrease with increasing age and most of the positive cases were observed in individuals less than 24 years old. Males had significantly higher prevalence than females (χ(2)=5.283, P=0.022). Logistic regression analysis of the overall population studied and the Senoi tribe confirmed that being a child aged less than 15 years, being male, the consumption of raw vegetables and the presence of other family members infected with G. intestinalis were the main risk factors for giardiasis. The presence of other family members infected with G. intestinalis was the only risk factor highlighted in the Proto-Malay and Negrito tribes. Diarrhoea was significantly associated with giardiasis. However, the cause and effect relationship has yet to be determined. Thus, screening family members and treating the infected individuals are the main strategies that should be adopted by the public health authority in combating this infection in Orang Asli communities as well as health education regarding good personal and food hygiene practises.

Outbreak of giardiasis associated with a community drinking-water source

Giardiasis is a common waterborne gastrointestinal illness. In 2007, a community giardiasis outbreak occurred in New Hampshire, USA. We conducted a cohort study to identify risk factors for giardiasis, and stool and environmental samples were analysed. Consuming tap water was significantly associated with illness (risk ratio 4·7, 95% confidence interval 1·5–14·4). Drinking-water samples were coliform-contaminated and a suspectGiardiacyst was identified in a home water filter. One well was coliform-contaminated, and testing indicated that it was potentially under the influence of surface water. The well was located 12·5 m from aGiardia-contaminated brook, although the genotype differed from clinical specimens. Local water regulations require well placement at least 15 m from surface water. This outbreak, which caused illness in 31 persons, represents the largest community drinking-water-associated giardiasis outbreak in the USA in 10 years. Adherence to well placement regulations might have prevented this outbreak.

Risk of giardiasis associated with water supply in an endemic context

Consumption of untreated, inadequately treated or simply chlorinated water has been the source of a number of giardiasis epidemics. The aim of this study was to verify if water supply is associated with giardiasis in an endemic context. We conducted a case-control study that included 139 cases and 417 control subjects. To assess risk associated to water consumption, we calculated odds ratios (OR) using "source of water" and "presence and type of filtration" as criteria. A logistic regression model was used to control other risk factors. In children aged 1 - 13, the only significant risk factor was the consumption of at-risk tap water (i.e., filtered or unfiltered surface water or unfiltered shallow well water; OR = 6.13). In people aged 14 - 64, the consumption of this water was not a risk factor for the disease. The divergence in results between age groups could be explained by acquired immunity.

The impact of the Catholic Jubilee in 2000 on infectious diseases. A case-control study of giardiasis, Rome, Italy 2000-2001

Mass gatherings are believed to increase the transmission of infectious diseases although surveillance systems have shown a low impact. The Catholic Jubilee was held in Rome, Italy in 2000. We conducted a case-control study to analyse the risk factors of giardiasis among residents. All diseases reported to the laboratory surveillance system from January 2000 to May 2001 were compared with hospital controls concurrently selected in the same season as cases and frequency-matched for age and birth country. Fifty-two cases (44.1%) and 72 controls were enrolled. In the multivariable analysis factors associated with giardiasis among adults were: travelling abroad (OR 24.2, P>0.01), exposure to surface water (OR 4.80, P=0.05), high educational level (OR 3.8, P=0.03). Having a maid from a high-prevalence country was independently associated (OR 2.3) although not statistically significant. This is the only exposure that changed during the Jubilee.

Does dog or cat ownership lead to increased gastroenteritis in young children in South Australia?

The aim of this study was to investigate the relationship between dog and cat ownership and gastroenteritis in young children. A diary study of 965 children aged 4-6 years living in rural or semi-rural South Australia was undertaken. Data were collected on pet ownership, drinking water and other risk factors for gastroenteritis. Overall 89% of households had pets and dog ownership was more common than cat ownership. The multivariable models for gastroenteritis and pet ownership indicated that living in a household with a dog or cat was associated with a reduced risk of gastroenteritis (adj. OR 0.71, 95% CI 0.55-0.92; OR 0.70, % CI 0.51-0.97 respectively). This paper adds to the evidence that pets are not a major source of gastroenteritis in the home and lends support to the health benefits of pet ownership. However, this must be weighed against the potential negative consequences, such as dog bites, particularly for this age group.

Prevalence of Giardiasis due to wastewater reuse for agriculture in the suburbs of Asmara City, Eritrea

A study was undertaken to assess the health impact of utilization of the raw domestic sewage for vegetable cultivation in the suburbs of the capital city of Asmara, Eritrea. Standard techniques were adopted for the analysis of the samples. Results showed heavy contamination of vegetables by faecal coliforms as well as with Giardia cysts. Stool samples of 75 farmers who were occupationally exposed revealed that 45% of them were harbouring giardia cysts. The dietary intake of raw salads (lettuce, cabbage) grown on the raw sewage appear to be a causative factor of Giardiasis in the farming community as well as in the town of Tsadachristian located on the suburbs of the capital city of Asmara. The hospital data of the affected town is compared with other towns of Eritrea. The result indicates agriculture reuse of untreated wastewater is a major cause for the increase in Giardasis.

Public health effects of inadequately managed stormwater runoff

OBJECTIVES

This study investigated the scale of the public health risk from stormwater runoff caused by urbanization.

METHODS

We compiled turbidity data for municipal treated drinking water as an indication of potential risk in selected US cities and compared estimated costs of waterborne disease and preventive measures.

RESULTS

Turbidity levels in other US cities were similar to those linked to illnesses in Milwaukee, Wis, and Philadelphia, Pa. The estimated annual cost of waterborne illness is comparable to the long-term capital investment needed for improved drinking water treatment and stormwater management.

CONCLUSIONS

Although additional data on cost and effectiveness are needed, stormwater management to minimize runoff and associated pollution appears to make sense for protecting public health at the least cost.

Risk factors for sporadic giardiasis: a case-control study in southwestern England

To investigate risk factors for sporadic infection with Giardia lamblia acquired in the United Kingdom, we conducted a matched case-control study in southwest England in 1998 and 1999. Response rates to a postal questionnaire were 84% (232/276) for cases and 69% (574/828) for controls. In multivariable analysis, swallowing water while swimming (p<0.0001, odds ratio [OR] 6.2, 95% confidence intervals [CI] 2.3 to 16.6), recreational fresh water contact (p=0.001, OR 5.5, 95% CI 1.9 to 15.9), drinking treated tap water (p<0.0001, OR 1.3, 95% CI 1.1 to 1.5 for each additional glass per day), and eating lettuce (pç=0.01, OR 2.2, 95% CI 1.2 to 4.3) had positive and independent associations with infection. Although case-control studies are prone to bias and the risk of Giardia infection is minimized by water treatment processes, the possibility that treated tap water is a source of sporadic giardiasis warrants further investigation.

Environmental sanitation conditions and health impact: a case-control study

This epidemiological investigation examines the impact of several environmental sanitation conditions and hygiene practices on diarrhea occurrence among children under five years of age living in an urban area. The case-control design was employed; 997 cases and 999 controls were included in the investigation. Cases were defined as children with diarrhea and controls were randomly selected among children under five years of age. After logistic regression adjustment, the following variables were found to be significantly associated with diarrhea: washing and purifying fruit and vegetables; presence of wastewater in the street; refuse storage, collection and disposal; domestic water reservoir conditions; feces disposal from swaddles; presence of vectors in the house and flooding in the lot. The estimates of the relative risks reached values up to 2.87. The present study revealed the feasibility of developing and implementing an adequate model to establish intervention priorities in the field of environmental sanitation.

Gastrointestinal infections

Advances in public health have reduced the risk of contracting certain enteric diseases, but many remain, and new pathogens have emerged and/or recently have been discovered. The pathogenic agents are varied and consist of a variety of bacteria and select viruses and parasites. Selected use of microbiologic assays to detect these pathogens is encouraged. When tests are ordered non-judiciously, costs rapidly accrue. The age of the patient, time of year, travel history, and clinical presentation all provide clues to the etiologic agent. Microbiologic assays should be used judiciously to confirm or exclude the likely infectious agents.

Parasitic infections of the gastrointestinal tract

This article updates recent advances in the body of knowledge of diagnosis and treatment of intestinal parasites. The articles focus on the manifestations of disease in the immunocompetent adult host from developed countries. Specific pathogens discussed are Giardia lamblia and Dientamoeba fragilis, Entamoeba histolytica, Entamoeba dipar, Blastocystis hominis, Cyclospora cayetanensis, and Cryptosporidium parvum.

A longitudinal study of Giardia lamblia infection in north-east Brazilian children

OBJECTIVE

To evaluate the epidemiology of Giardia lamblia infection, investigate factors which might be associated with clinical manifestations and recurrence, and examine the role of copathogens in disease course.

METHODS

Prospective 4-year cohort study of children born in an urban slum in north-eastern Brazil.

RESULTS

Of 157 children followed for > or = 3 months, 43 (27.4%) were infected with Giardia. The organism was identified in 8.8% of all stool specimens, and although found with similar frequency in non-diarrhoeal (7.4%) and diarrhoeal stools (9.7%), was more common in children with persistent (20.6%) than acute diarrhoea (7.6%, P=0.002). Recurrent or relapsing infections were common (46%). Children with symptomatic infections had significantly lower weight-for-age and height-for-age than asymptomatic children. Copathogens were not associated with disease course. CONCLUSION With its protean clinical manifestations, Giardia may be associated with substantial morbidity amongst children in Brazil.

Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data

OBJECTIVES

A meta-analytic study was conducted to test the hypothesis that consumption of water from North American backcountry sources poses a statistically significant risk for acquisition of giardiasis.

METHODS

The biomedical literature was surveyed by accessing Medline, and identified studies were supplemented with references in current reviews, published dissertations, and prior communications with state health departments. Studies were classified by methodologic design and subjected to predetermined inclusion criteria. Odds ratios with 95% confidence intervals, chi-squares, and P-values for epidemiologic surveys were either computed from raw data or abstracted directly from the included studies.

RESULTS

Of 104 articles identified in the initial screening, nine met the inclusion criteria. Neither of two case reports met the criteria of the Centers for Disease Control and Prevention (CDC) for waterborne disease outbreak. Two prospective studies were identified, but neither showed a significant association. Of four case-control studies providing data, three reported an odds ratio of greater than one.

CONCLUSIONS

Published reports of confirmed giardiasis among outdoor recreationalists clearly demonstrate a high incidence among this population. However, the evidence for an association between drinking backcountry water and acquiring giardiasis is minimal. Education efforts aimed at outdoor recreationalists should place more emphasis on handwashing than on water purification. Further studies should attempt to separate the specific risk factor of drinking water from backcountry sources from other behaviors among this group that may contribute to the risk.

Intestinal parasite carriage in workers exposed to sewage

The presence of protozoan cysts and helminth eggs in sewage and the very low minimal infective doses of parasites suggest an occupational risk for workers exposed to sewage. The objective of this study was to assess this risk in a group of raw sewage-exposed workers. The relationship between sewage exposure and intestinal parasite carriage was estimated by a multiple cross-sectional survey comparing yearly prevalence rates in 126 employees working in sewers in Paris, France, with the prevalence rate in 363 food-handlers employed between 1988 and 1993. The incidence of intestinal parasitic infestation was estimated among sewage-exposed workers. Four parasite species were identified among sewage-exposed workers: whipworm, Giardia lamblia, Entamoeba coli and Endolimax nanus. The prevalence mean of intestinal parasite carriage was 11.8% (57/480), related to the presence of protozoa in 91% of samples. G. lamblia was present in 3.5% (17/480) of samples. The incidence of positive parasitological stool examination was 5.9/100 person-years. The incidence of G. lamblia in stool examinations was 1.7/100 person-years. Age-adjusted odds ratios were significantly higher in exposed workers in 1988 (OR: 6.5; 95% CI: 2.0-14.5), 1990 (OR: 4.4; 95% CI: 1.2-10.1) and 1991 (OR: 3.4; 95% CI: 1.0-8.2), but not during the other three years. The results of this study emphasize an occupational risk of intestinal protozoan infestation in workers exposed to sewage. The decrease of adjusted OR with time reflects the efficacy of compliance with rules of hygiene.

Protozoal agents: what are the dangers for the public water supply?

Safe and efficient treatment of drinking water has been one of the major public health advances of the twentieth century. People in developed countries generally take for granted that their water is safe to drink, a luxury the majority of the world's population does not have. The leading cause of infant mortality in the developing world is infectious diarrhea, and the prevalence of diarrheal pathogens is largely influenced by the quality and quantity of clean water available for drinking and washing. Until recently, modern water treatment had all but eliminated these concerns in developed nations. Over the past two decades, however, the safety of our water supply has been threatened by the emergence of Cryptosporidium parvum, a protozoal pathogen. The hearty oocysts of this organism survive chlorination and filtration to cause a diarrheal illness that, while unpleasant enough in healthy people, is devastating in immunocompromised individuals. The 1993 Milwaukee outbreak, in which 403,000 people developed diarrhea from drinking water that met all the updated federal safety standards, demonstrated the tremendous public health importance of this organism. While earlier attention had focused on Giardia and amebic infections, the other "emerging" protozoan besides Cryptosporidium is Cyclospora. This review discusses the protozoal pathogens, including Cryptosporidium parvum, Giardia lamblia, Entamoeba histolytica, and Cyclospora cayetanensis, that cause waterborne diarrheal outbreaks and the threats they pose to the public.

Risk factors for giardiasis: a case-control study in Avon and Somerset

Giardia lamblia is a common and increasing cause of gastrointestinal illness in the UK. We report a case-control study that examined risk factors for giardiasis. Patients with giardiasis were identified from reports to the Consultants in Communicable Disease in Avon and Somerset, and age-sex matched controls were obtained from their general practitioners' lists. Details of travel history, water consumption and recreational water use were collected by postal questionnaire. Over the period July 1992 to May 1993, 74 cases and 108 matched controls were obtained. The data were analysed using conditional logistic regression. Swimming appeared to be an independent risk factor for giardiasis (odds ratio 2.4, 95% CI 1.0 to 6.1, P = 0.050). Travel (P = 0.001), particularly to developing countries, and type of travel (P = 0.004)--that is, camping, caravanning or staying in holiday chalets--were also observed to be significant risk factors. Other recreational water use and drinking potentially contaminated water were found to be not statistically significant after adjustment for other factors.

Giardia--diagnosis, clinical course and epidemiology. A review

Infection with giardia may be associated with significant ill-health and while the reported incidence of infection is increasing in the United Kingdom, the true prevalence of infection and extent of morbidity due to this organism is unknown. Diagnosis is made difficult by non-specificity of symptoms and low sensitivity of traditional diagnostic techniques. Immunological methods of diagnosis hold promise for the future, but in the meantime, more routine testing by laboratories and multiple faecal testing by clinicians may prevent unnecessary morbidity. The late summer/autumn peak in reported infection is difficult to explain while the age distribution is typical of an organism which is spread faeco-orally. The importance of potable water supplies as a source of infection in this country is not clear, nor is the role of zoonotic spread. The apparent susceptibility to infection of certain population groups requires further exploration as does the role of the asymptomatically infected in transmission.

Giardiasis

Giardiasis is one of the most common pathogenic intestinal protozoal infections worldwide. Giardia lamblia is the most frequently identified etiologic agent in outbreaks associated with the ingestion of surface water, often due to ineffective filtration or pretreatment. In addition to humans, other sources of infection include beavers, perhaps muskrats, and possibly domestic animals. A low infecting dose (10 to 25 cysts) is reported to be sufficient to produce human infection. Clinical manifestations range from asymptomatic to a transient or persistent acute stage, with steatorrhea, intermittent diarrhea, and weight loss, or to a subacute or chronic stage that can mimic gallbladder or peptic ulcer disease. Diagnosis is usually based on repeated stool examinations but examination of duodenal fluid or biopsy material may also be necessary. Enzyme immunoassay or indirect immunofluorescence methods for direct detection of antigen or whole organisms in clinical specimens have also been developed. These tests are reported to be more sensitive than routine stool examination. Demonstration of serum immunoglobulin M and G antibodies may help differentiate recent from past infection or help detect recurrence in individuals who have been treated previously. Serum immunoglobulin A levels may be a useful indicator of exposure in waterborne outbreaks of diarrhea. Drugs available for treatment within the United States include metronidazole, quinacrine hydrochloride, and furazolidone.

Single-dose ornidazole versus seven-day metronidazole therapy of giardiasis in Kibbutzim children in Israel

The efficacy of single-dose ornidazole versus seven days metronidazole in the treatment of giardiasis was tested in a randomized study of 75 Kibbutzim children in Israel. All the children treated were clinically cured, and the parasites disappeared from stool examinations after the first follow-up. By the end of the study (21 days after the beginning of treatment), all the patients remained free of symptoms, but cysts of Giardia lamblia were found in the stools of three children from the ornidazole group (p = 0.24). The possibility of treating Giardia lamblia with ornidazole in a single dose, with results similar to those obtained with a seven-day course of metronidazole, makes this drug a good alternative in the treatment of Giardia lamblia in children, especially if compliance is not assured.

The microbiologic quality of drinking water in North Carolina migrant labor camps

A two-year study of the microbiological quality of drinking water in 27 randomly selected North Carolina migrant labor camps yielded total and fecal coliform prevalences of 44 percent and 26 percent, respectively in 1988 and similar but higher prevalences in 1989. Preoccupancy testing by county sanitarians had found virtually no total coliform contamination. These findings suggest that a potential source of contamination existed and that current testing protocols which rely on preoccupancy testing may be inadequate.

Endemic giardiasis and municipal water supply

To test the hypothesis that endemic giardiasis may be transmitted by unfiltered municipal water supplies, the incidence of laboratory-confirmed giardiasis was studied in a natural experiment due to the arrangement of the public water supply of Dunedin, New Zealand. The incidence rate ratio was 3.3 (90% CI = 1.1, 10.1) for the population receiving unfiltered (microstrained) water relative to that using sand filtered water. In a parallel case-control study of incident cases, the odds ratio for giardiasis and unfiltered (microstrained) water supply was 1.8 (90% CI = 0.5, 6.9).