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.

Prevalence and direct costs of emergency department visits and hospitalizations for selected diseases that can be transmitted by water, United States.

National emergency department (ED) visit prevalence and costs for selected diseases that can be transmitted by water were estimated using large healthcare databases (acute otitis externa, campylobacteriosis, cryptosporidiosis, Escherichia coli infection, free-living ameba infection, giardiasis, hepatitis A virus (HAV) infection, Legionnaires' disease, nontuberculous mycobacterial (NTM) infection, Pseudomonas-related pneumonia or septicemia, salmonellosis, shigellosis, and vibriosis or cholera). An estimated 477,000 annual ED visits (95% CI: 459,000-494,000) were documented, with 21% (n = 101,000, 95% CI: 97,000-105,000) resulting in immediate hospital admission. The remaining 376,000 annual treat-and-release ED visits (95% CI: 361,000-390,000) resulted in $194 million in annual direct costs. Most treat-and-release ED visits (97%) and costs ($178 million/year) were associated with acute otitis externa. HAV ($5.5 million), NTM ($2.3 million), and salmonellosis ($2.2 million) were associated with next highest total costs. Cryptosporidiosis ($2,035), campylobacteriosis ($1,783), and NTM ($1,709) had the highest mean costs per treat-and-release ED visit. Overall, the annual hospitalization and treat-and-release ED visit costs associated with the selected diseases totaled $3.8 billion. As most of these diseases are not solely transmitted by water, an attribution process is needed as a next step to determine the proportion of these visits and costs attributable to waterborne transmission.

Mortality from selected diseases that can be transmitted by water - United States, 2003-2009.

Diseases spread by water are caused by fecal-oral, contact, inhalation, or other routes, resulting in illnesses affecting multiple body systems. We selected 13 pathogens or syndromes implicated in waterborne disease outbreaks or other well-documented waterborne transmission (acute otitis externa, Campylobacter, Cryptosporidium, Escherichia coli (E. coli), free-living ameba, Giardia, Hepatitis A virus, Legionella (Legionnaires' disease), nontuberculous mycobacteria (NTM), Pseudomonas-related pneumonia or septicemia, Salmonella, Shigella, and Vibrio). We documented annual numbers of deaths in the United States associated with these infections using a combination of death certificate data, nationally representative hospital discharge data, and disease-specific surveillance systems (2003-2009). We documented 6,939 annual total deaths associated with the 13 infections; of these, 493 (7%) were caused by seven pathogens transmitted by the fecal-oral route. A total of 6,301 deaths (91%) were associated with infections from Pseudomonas, NTM, and Legionella, environmental pathogens that grow in water system biofilms. Biofilm-associated pathogens can cause illness following inhalation of aerosols or contact with contaminated water. These findings suggest that most mortality from these 13 selected infections in the United States does not result from classical fecal-oral transmission but rather from other transmission routes.

Direct healthcare costs of selected diseases primarily or partially transmitted by water.

Despite US sanitation advancements, millions of waterborne disease cases occur annually, although the precise burden of disease is not well quantified. Estimating the direct healthcare cost of specific infections would be useful in prioritizing waterborne disease prevention activities. Hospitalization and outpatient visit costs per case and total US hospitalization costs for ten waterborne diseases were calculated using large healthcare claims and hospital discharge databases. The five primarily waterborne diseases in this analysis (giardiasis, cryptosporidiosis, Legionnaires' disease, otitis externa, and non-tuberculous mycobacterial infection) were responsible for over 40 000 hospitalizations at a cost of $970 million per year, including at least $430 million in hospitalization costs for Medicaid and Medicare patients. An additional 50 000 hospitalizations for campylobacteriosis, salmonellosis, shigellosis, haemolytic uraemic syndrome, and toxoplasmosis cost $860 million annually ($390 million in payments for Medicaid and Medicare patients), a portion of which can be assumed to be due to waterborne transmission.

The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008.

Naegleria fowleri, a free-living, thermophilic amoeba ubiquitous in the environment, causes primary amoebic meningoencephalitis (PAM), a rare but nearly always fatal disease of the central nervous system. While case reports of PAM have been documented worldwide, very few individuals have been diagnosed with PAM despite the vast number of people who have contact with fresh water where N. fowleri may be present. In the USA, 111 PAM case-patients have been prospectively diagnosed, reported, and verified by state health officials since 1962. Consistent with the literature, case reports reveal that N. fowleri infections occur primarily in previously healthy young males exposed to warm recreational waters, especially lakes and ponds, in warm-weather locations during summer months. The annual number of PAM case reports varied, but does not appear to be increasing over time. Because PAM is a rare disease, it is challenging to understand the environmental and host-specific factors associated with infection in order to develop science-based, risk reduction messages for swimmers.

Multiple risk factors associated with a large statewide increase in cryptosporidiosis.

Cryptosporidium species have emerged as a major cause of outbreaks of diarrhoea and have been associated with consumption of contaminated recreational and drinking water and food as well as contact with infected attendees of child-care programmes. In August 2007, the Colorado Department of Public Health and Environment detected an increase in cryptosporidiosis cases over baseline values. We conducted a case-control study to assess risk factors for infection and collected stool specimens from ill persons for microscopy and molecular analysis. Laboratory-confirmed cases (n=47) were more likely to have swallowed untreated water from a lake, river, or stream [adjusted matched odds ratio (aOR) 8.0, 95% confidence interval (CI) 1.3-48.1], have had exposure to recreational water (aOR 4.6, 95% CI 1.4-14.6), or have had contact with a child in a child-care programme or in diapers (aOR 3.8, 95% CI 1.5-9.6). Although exposure to recreational water is commonly implicated in summertime cryptosporidiosis outbreaks, this study demonstrates that investigations of increased incidence of cases in summer should also examine other potential risk factors. This study emphasizes the need for public health education efforts that address the multiple transmission routes for Cryptosporidium and appropriate prevention measures to avoid future transmission.

Outbreak of cryptosporidiosis at a California waterpark: employee and patron roles and the long road towards prevention.

In August-September 2004, a cryptosporidiosis outbreak affected >250 persons who visited a California waterpark. Employees and patrons of the waterpark were affected, and three employees and 16 patrons admitted to going into recreational water while ill with diarrhoea. The median illness onset date for waterpark employees was 8 days earlier than that for patrons. A case-control study determined that getting water in one's mouth on the waterpark's waterslides was associated with illness (adjusted odds ratio 7.4, 95% confidence interval 1.7-32.2). Laboratory studies identified Cryptosporidium oocysts in sand and backwash from the waterslides' filter, and environmental investigations uncovered inadequate water-quality record keeping and a design flaw in one of the filtration systems. Occurring more than a decade after the first reported outbreaks of cryptosporidiosis in swimming pools, this outbreak demonstrates that messages about healthy swimming practices have not been adopted by pool operators and the public.

Outbreak of norovirus illness associated with a swimming pool.

On 3 February 2004, the Vermont Department of Health received reports of acute gastroenteritis in persons who had recently visited a swimming facility. A retrospective cohort study was conducted among persons attending the facility between 30 January and 2 February. Fifty-three of 189 (28%) persons interviewed developed vomiting or diarrhoea within 72 h after visiting the facility. Five specimens tested positive for norovirus and three specimen sequences were identical. Entering the smaller of the two pools at the facility was significantly associated with illness (RR 5.67, 95% CI 1.5-22.0, P=0.012). The investigation identified several maintenance system failures: chlorine equipment failure, poorly trained operators, inadequate maintenance checks, failure to alert management, and insufficient record keeping. This study demonstrates the vulnerability of recreational water to norovirus contamination, even in the absence of any obvious vomiting or faecal accident. Our findings also suggest that norovirus is not as resistant to chlorine as previously reported in experimental studies. Appropriate regulations and enforcement, with adequate staff training, are necessary to ensure recreational water safety.

An outbreak of Cryptosporidium hominis infection at an Illinois recreational waterpark.

Cryptosporidium has become increasingly recognized as a pathogen responsible for outbreaks of diarrhoeal illness in both immunocompetent and immunocompromised persons. In August 2001, an Illinois hospital reported a cryptosporidiosis cluster potentially linked to a local waterpark. There were 358 case-patients identified. We conducted community-based and waterpark-based case-control studies to examine potential sources of the outbreak. We collected stool specimens from ill persons and pool water samples for microscopy and molecular analysis. Laboratory-confirmed case-patients (n=77) were more likely to have attended the waterpark [odds ratio (OR) 16.0, 95% confidence interval (CI) 3.8-66.8], had pool water in the mouth (OR 6.0, 95% CI 1.3-26.8), and swallowed pool water (OR 4.5, 95% CI 1.5-13.3) than age-matched controls. Cryptosporidium was found in stool specimens and pool water samples. The chlorine resistance of oocysts, frequent swimming exposures, high bather densities, heavy usage by diaper-aged children, and increased recognition and reporting of outbreaks are likely to have contributed to the increasing trend in number of swimming pool-associated outbreaks of cryptosporidiosis. Recommendations for disease prevention include alteration of pool design to separate toddler pool filtration systems from other pools. Implementation of education programmes could reduce the risk of faecal contamination and disease transmission.

Factors associated with participation in a campaign of mass treatment against lymphatic filariasis, in Leogane, Haiti.

In October 2000, to interrupt transmission of Wuchereria bancrofti, an intense health-education campaign followed by a mass drug administration (MDA) with diethylcarbamazine and albendazole was undertaken in Leogane, Haiti. Three months after the MDA, which was the first in the study area, a knowledge-attitude-practice (KAP) survey, with a cluster-sample design and probability sampling, was undertaken, to determine the existing knowledge of the local residents, their attitudes toward the MDA, and the possible reasons for non-compliance. Questionnaire-based interviews were used to explore the KAP of 304 subjects (one randomly chosen resident aged > 14 years from each selected household) in 33 communities. Most (93%) of the interviewees were aware of filariasis and 72% knew at least one clinical sign of the disease. Awareness of the MDA was high (91%). The most frequently mentioned sources of information were other people (56%) and radio announcements (33%). More than 80% of the respondents encouraged other people to take the drugs distributed in the MDA and 63% had been treated. The primary reasons given for failing to take the drugs were absenteeism during the distribution (17%), use of contraceptive drugs (12%) and pregnancy (11%). In a multivariate analysis, being male [odds ratio (OR) = 3.3; 95% confidence interval (CI) = 1.5-7.4], knowing that a mosquito transmits the disease (OR = 2.6; CI = 1.2-5.4), and having learned about the MDA through posters and banners (OR = 2.9; CI = 1.2-7.5) were found to be positively associated with taking the drugs. Information from such post-treatment surveys should be useful in developing better health communication for subsequent MDA.

Short report: documentation of iodine deficiency in Haitian schoolchildren: implication for lymphatic filariasis elimination in Haiti.

In this study we documented unexpected moderate-to-severe iodine deficiency in Haitian schoolchildren although they live in a coastal community where presumably they have access to iodine-containing seafood. This fact combined with the lack of an iodized salt supply and endemic lymphatic filariasis makes community distribution of diethylcarbamazine-fortified, iodized salt an attractive strategy for elimination of lymphatic filariasis and iodine deficiency disorders in this area of Haiti. Combining lymphatic filariasis elimination with other public health interventions is one strategy to increase its public health benefit and maximize the impact of limited public health resources.

Giardiasis surveillance--United States, 1992-1997.

PROBLEM/CONDITION: Giardia intestinalis, the organism that causes the gastrointestinal illness giardiasis, is the most commonly diagnosed intestinal parasite in public health laboratories in the United States. In 1992, the Council of State and Territorial Epidemiologists assigned giardiasis an event code that enabled states to begin voluntarily reporting surveillance data on giardiasis to CDC. REPORTING PERIOD: This report includes data that were reported from January 1992 through December 1997. DESCRIPTION OF THE SYSTEM: The National Giardiasis Surveillance System includes data about reported cases of giardiasis from participating states. Because most states were already collecting data on occurrence of giardiasis, the assignment of an event code to giardiasis has allowed voluntary reporting of these data to CDC via the National Electronic Telecommunications System for Surveillance. RESULTS: Since 1992, the number of states reporting cases of giardiasis to CDC has risen from 23 to 43. The annual number of giardiasis cases reported has ranged from 12,793 in 1992 to 27,778 in 1996. In 1997, cases per 100,000 state population ranged from 0.9 to 42.3, with 10 states reporting >20.0 cases per 100,000 population and a national average of 9.5 cases per 100,000 population. In 1997, New York State, including New York City, reported the highest number of cases (3,673, or 20.3 cases per 100,000 population), accounting for 14.5% of cases nationally; however, Vermont reported the highest incidence rate in 1997 (42.3 cases per 100,000 population). Both states have active surveillance systems in place for giardiasis. Cases have an approximately equal sex distribution. Nationally, rates were the highest among children aged 0-5 years, followed closely by persons aged 31-40 years. In these two age groups, most cases were reported during late summer and early fall--an indication that transmission occurred during the summer. INTERPRETATION: This report documents the first nationwide look at epidemiologic parameters and disease burden estimates for giardiasis in the United States. Transmission occurs in all major geographic areas of the country. The seasonal peak in age-specific case reports coincides with the summer recreational water season and might reflect the heavy use by young children of communal swimming venues (e.g., lakes, rivers, swimming pools, and water parks)--a finding consistent with Giardia's low infectious dose, the high prevalence of diaper-aged children in swimming venues, the extended periods of cyst shedding that can occur, and Giardia's environmental resistance. Estimates based on state surveillance data indicate that as many as 2.5 million cases of giardiasis occur annually in the United States. PUBLIC HEALTH ACTION: Giardiasis surveillance provides data to educate public health practitioners and health-care providers about the scope and magnitude of giardiasis in the United States. These data can be used to establish research priorities and to plan future prevention efforts.

Surveillance for waterborne-disease outbreaks--United States, 1997-1998.

PROBLEM/CONDITION: Since 1971, CDC and the U.S. Environmental Protection Agency (EPA) have maintained a collaborative surveillance system for collecting and periodically reporting data relating to occurrences and causes of waterborne-disease outbreaks (WBDOs). REPORTING PERIOD COVERED: This summary includes data from January 1997 through December 1998 and a previously unreported outbreak in 1996. DESCRIPTION OF THE SYSTEM: The surveillance system includes data regarding outbreaks associated with drinking water and recreational water. State, territorial, and local public health departments are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC on a standard form. RESULTS: During 1997-1998, a total of 13 states reported 17 outbreaks associated with drinking water. These outbreaks caused an estimated 2,038 persons to become ill. No deaths were reported. The microbe or chemical that caused the outbreak was identified for 12 (70.6%) of the 17 outbreaks; 15 (88.2%) were linked to groundwater sources. Thirty-two outbreaks from 18 states were attributed to recreational water exposure and affected an estimated 2,128 persons. Eighteen (56.3%) of the 32 were outbreaks of gastroenteritis, and 4 (12.5%) were single cases of primary amebic meningoencephalitis caused by Naegleria fowleri, all of which were fatal. The etiologic agent was identified for 29 (90.6%) of the 32 outbreaks, with one death associated with an Escherichia coli O157:H7 outbreak. Ten (55.6%) of the 18 gastroenteritis outbreaks were associated with treated pools or ornamental fountains. Of the eight outbreaks of dermatitis, seven (87.5%) were associated with hot tubs, pools, or springs. INTERPRETATION: Drinking water outbreaks associated with surface water decreased from 31.8% during 1995-1996 to 11.8% during 1997-1998. This reduction could be caused by efforts by the drinking water industry (e.g., Partnership for Safe Water), efforts by public health officials to improve drinking water quality, and improved water treatment after the implementation of EPA's Surface Water Treatment Rule. In contrast, the proportion of outbreaks associated with systems supplied by a groundwater source increased from 59.1% (i.e., 13) during 1995-1996 to 88.2% (i.e., 15) during 1997-1998. Outbreaks caused by parasites increased for both drinking and recreational water. All outbreaks of gastroenteritis attributed to parasites in recreational water were caused by Cryptosporidium, 90% occurred in treated water venues (e.g., swimming pools and decorative fountains), and fecal accidents were usually suspected. The data in this surveillance summary probably underestimate the true incidence of WBDOs because not all WBDOs are recognized, investigated, and reported to CDC or EPA. ACTIONS TAKEN: To estimate the national prevalence of waterborne disease associated with drinking water, CDC and EPA are conducting a series of epidemiologic studies to better quantify the level of waterborne disease associated with drinking water in nonoutbreak conditions. The Information Collection Rule implemented by EPA in collaboration with the drinking water industry helped quantifythe level of pathogens in surface water. Efforts by CDC to address recreational water outbreaks have included meetings with the recreational water industry, focus groups to educate parents on prevention of waterborne disease transmission in recreational water settings, and publications with guidelines for parents and pool operators.

An analysis of the safety of the single dose, two drug regimens used in programmes to eliminate lymphatic filariasis.

This review of the safety of the co-administration regimens to be used in programmes to eliminate lymphatic filariasis (albendazole + ivermectin or albendazole + diethylcarbamazine [DEC]) is based on 17 studies conducted in Sri Lanka, India, Haiti, Ghana, Tanzania, Kenya, Ecuador, the Philippines, Gabon, Papua New Guinea, and Bangladesh. The total data set comprises 90,635 subject exposures and includes individuals of all ages and both genders. Results are presented for hospital-based studies, laboratory studies, active surveillance of microfilaria-positive and microfilaria-negative individuals, and passive monitoring in both community-based studies and mass treatment programmes of individuals treated with albendazole (n = 1538), ivermectin (9822), DEC (576), albendazole + ivermectin (7470), albendazole + DEC (69,020), or placebo (1144). The most rigorous monitoring, which includes haematological and biochemical laboratory parameters pre- and post-treatment, provides no evidence that consistent changes are induced by any treatment; the majority of abnormalities appear to be sporadic, and the addition of albendazole to either ivermectin or DEC does not increase the frequency of abnormalities. Both DEC and ivermectin show, as expected, an adverse event profile compatible with the destruction of microfilariae. The addition of albendazole to either single-drug treatment regimen does not appear to increase the frequency or intensity of events seen with these microfilaricidal drugs when used alone. Direct observations indicated that the level of adverse events, both frequency and intensity, was correlated with the level of microfilaraemia. In non microfilaraemic individuals, who form 80-90% of the 'at risk' populations to be treated in most national public health programmes to eliminate lymphatic filariasis (LF), the event profile with the compounds alone or in combination does not differ significantly from that of placebo. Data on the use of ivermectin + albendazole in areas either of double infection (onchocerciasis and LF), or of loiais (with or without concurrent LF) are still inadequate and further studies are needed. Additional data are also recommended for populations infected with Brugia malayi, since most data thus far derive from populations infected with Wuchereria bancrofti.

Assessment of combined ivermectin and albendazole for treatment of intestinal helminth and Wuchereria bancrofti infections in Haitian schoolchildren.

This randomized, placebo-controlled trial investigated the efficacy and nutritional benefit of combining chemotherapeutic treatment for intestinal helminths (albendazole) and lymphatic filariasis (ivermectin). Children were infected with Ascaris (29.2%), Trichuris (42.2%), and hookworm (6.9%), with 54.7% of children having one or more of these parasites. Wuchereria bancrofti microfilaria were found in 13.3% of the children. Children were randomly assigned to treatment with placebo, albendazole, ivermectin, or combined therapy. Combination treatment reduced the prevalence of Trichuris infections significantly more than either drug alone. Combination therapy also significantly reduced the prevalence and density of W. bancrofti microfilaremia compared with placebo or ivermectin alone. Only combination therapy resulted in significantly greater gains in height (hookworm-infected children) or weight (Trichuris-infected children) compared with the placebo group. Combined albendazole and ivermectin was a more efficacious treatment for intestinal helminth and W. bancrofti infections in children and resulted in nutritional benefits not found with either drug alone.

Chlorine disinfection of recreational water for Cryptosporidium parvum.

We examined the effects of chlorine on oocyst viability, under the conditions of controlled pH and elevated calcium concentrations required for most community swimming pools. We found that fecal material may alter the Ct values (chlorine concentration in mg/L, multiplied by time in minutes) needed to disinfect swimming pools or other recreational water for Cryptosporidium parvum.

The return of Cyclospora in 1997: another outbreak of cyclosporiasis in North America associated with imported raspberries. Cyclospora Working Group.

BACKGROUND: In the spring of 1996, an outbreak of cyclosporiasis associated with fresh Guatemalan raspberries occurred in the United States and Canada. Another multistate outbreak of cyclosporiasis occurred in North America in the spring of 1997. OBJECTIVE: To identify the vehicle of the outbreak that occurred in the spring of 1997. DESIGN: Retrospective cohort studies of clusters of cases associated with events (such as banquets) and traceback investigations of sources of implicated produce. SETTING: United States and Canada. PATIENTS: Persons who attended events associated with clusters of cases of cyclosporiasis. MEASUREMENTS: Identification of clinically defined or laboratory-confirmed cases of cyclosporiasis and risk factors for infection. RESULTS: 41 clusters of cases were reported in association with events held from 1 April through 26 May in 13 U.S. states, the District of Columbia, and 1 Canadian province. The clusters comprised 762 cases of cyclosporiasis, 192 (25.2%) of which were laboratory confirmed. In addition, 250 laboratory-confirmed sporadic cases were reported in persons who developed gastrointestinal symptoms from April through 15 June, for a total of 1012 cases. Fresh raspberries were the only food common to all 41 events and were the only type of berry served at 9 events (22.0%). Statistically significant associations between consumption of raspberry-containing items and cyclosporiasis were documented for 15 events (40.5% of 37). For 31 of the 33 events with well-documented traceback data, the raspberries either definitely came from Guatemala (8 events) or could have come from Guatemala (23 events). The mode of contamination of the raspberries remains unknown. The outbreak ended shortly after the exportation of fresh raspberries from Guatemala was voluntarily suspended at the end of May 1997. CONCLUSIONS: Similar multistate, multicluster outbreaks of cyclosporiasis associated with consumption of Guatemalan raspberries have occurred in consecutive years. These outbreaks highlight the need for better understanding of the biology and epidemiology of Cyclospora cayetanensis and for stronger prevention and control measures to ensure the safety of produce eaten raw.