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Background: Giardia is a protozoan parasite of public health relevance that causes gastroenteritis in a wide range of hosts. Two genetically distinct lineages (assemblages A and B) are responsible for the human disease. Although it is clear that differences in virulence occur, the pathogenesis and virulence of Giardia remain poorly understood., Results: The genome of Giardia is believed to contain open reading frames that could encode as many as 6000 proteins. By successfully applying quantitative proteomic analyses to the whole parasite and to the supernatants derived from parasite culture of assemblages A and B, we confirm expression of ∼1600 proteins from each assemblage, the vast majority of which are common to both lineages. To look for signature enrichment of secreted proteins, we considered the ratio of proteins in the supernatant compared with the pellet, which defined a small group of enriched proteins, putatively secreted at a steady state by cultured growing trophozoites of both assemblages. This secretome is enriched with proteins annotated to have N-terminal signal peptide. The most abundant secreted proteins include known virulence factors such as cathepsin B cysteine proteases and members of a Giardia superfamily of cysteine-rich proteins that comprise variant surface proteins, high-cysteine membrane proteins, and a new class of virulence factors, the Giardia tenascins. We demonstrate that physiological function of human enteric epithelial cells is disrupted by such soluble factors even in the absence of the trophozoites., Conclusions: We are able to propose a straightforward model of Giardia pathogenesis incorporating key roles for the major Giardia-derived soluble mediators.

Background: Acute gastroenteritis (AGE) remains a common cause of clinic visits and hospitalizations in the United States, but the etiology is rarely determined., Methods: We performed a prospective, multicenter emergency department-based study of adults with AGE. Subjects were interviewed on presentation and 3-4 weeks later. Serum samples, rectal swab specimens, and/or whole stool specimens were collected at presentation, and serum was collected 3-4 weeks later. Fecal specimens were tested for a comprehensive panel of viral, bacterial, and parasitic pathogens; serum was tested for calicivirus antibodies., Results: Pathogens were detected in 25% of 364 subjects, including 49% who provided a whole stool specimen. The most commonly detected pathogens were norovirus (26%), rotavirus (18%), and Salmonella species (5.3%). Pathogens were detected significantly more often from whole stool samples versus a rectal swab specimen alone. Nine percent of subjects who provided whole stool samples had >1 pathogen identified., Conclusions: Viruses, especially noroviruses, play a major role as agents of severe diarrhea in adults. Further studies to confirm the unexpectedly high prevalence of rotaviruses and to explore the causes of illness among patients from whom a pathogen cannot be determined are needed. Studies of enteric pathogens should require the collection of whole stool samples.

Data from a general practice-based, case-control study on gastroenteritis and the pathogens related to this disease were used to study the association between specific pathogens and the infected patients' ages and symptoms. For comparison, the occurrence of these pathogens in control patients, stratified by age, also is presented. In children with gastroenteritis who were <5 years of age, rotavirus (in 21% of patients) and Norwalk-like virus (NLV; in 15%) were the most common pathogens. Among patients who were 5-14 years of age, Campylobacter species (in 16% of patients) and Giardia lamblia (in 10%) were the most common pathogens. In the older patients, Campylobacter species was also the most common pathogen (8% to 15% of patients). In addition, several symptoms in case patients were associated with specific pathogens. Blood in the stool was associated with infection with Campylobacter species. In patients with fever, Salmonella species, Campylobacter species, and rotavirus were detected relatively often. Vomiting was associated with NLV and rotavirus. This is the first study in The Netherlands and one of the first studies in the world that has investigated a broad range of pathogens recovered from an unselected population of patients who had consulted general practitioners because of gastroenteritis.

A major gastroenteritis outbreak among >400,000 residents of Milwaukee, Wisconsin, in April 1993 was attributed to Cryptosporidium parvum oocysts in drinking water. Plasma specimens obtained from children (6 months to 12 years old) for routine blood lead level surveillance March-May 1993 were assayed by ELISA for levels of IgG antibody against the immunodominant Triton-17 and 27-kDa C. parvum antigens. Over a 5-week period, the seroprevalence for antibodies to the 2 antigens increased from 15% to 82% and from 17% to 87%, respectively, in samples from children living in southern ZIP code areas (n=218), whereas smaller increases (20% to 43% and 22% to 46%, respectively) were noted among samples from children living in northern ZIP code areas (n=335; P<.0001). The results demonstrate that C. parvum infection was much more widespread than previously appreciated and confirm that infection was associated with residence in the area served by the southern water treatment plant.

The etiology of gastroenteritis was determined in children and adults with diarrhea seen at a district hospital and three government health clinics in Suan Phung, western Thailand, in 1991. Enteric viruses (rotavirus and astrovirus) were identified in 40%, shigellae in 18%, attaching and effacing Escherichia coli in 13%, Campylobacter jejuni in 9%, and enterotoxigenic E. coli in 7% of children < 5 years old with diarrhea seen at the hospital. Enteric viruses were detected in 15% (24/156) of patients with diarrhea > or = 5 years old and were the only enteric pathogens identified in 12 patients ages 7-79 years (2 astrovirus, 10 rotavirus infections). Attaching and effacing E. coli, rotavirus, and astrovirus were potential causes of diarrhea in children and adults in this population.

An outbreak of foodborne gastroenteritis affected 648 United States Air Force personnel stationed in Jeddah, Saudi Arabia during Operation Desert Storm. The implicated food source was a locally catered meal. Despite the presence of an aggressive Air Force public health program, foodborne illness had a major impact on manpower and medical resources during a critical phase of military operations. It is the recommendation of the authors that the Air Force not rely on local caterers during future deployments.

An outbreak of Giardia lamblia gastroenteritis occurred in Reno, Nevada, in 1982, during which 324 laboratory-confirmed infections were reported. During the outbreak, Reno was supplied in part by surface water that was chemically coagulated, settled, and chlorinated, but was not filtered. Giardia cysts were recovered from the water supply, and a beaver infected with Giardia was found in one of the reservoirs. A case-control study indicated that, during the outbreak but not afterwards, persons with giardiasis drank more municipal water than did controls. Corrective measures, which included removing the infected beaver and increasing the chlorine concentration, were followed by a rapid decrease in reports of giardiasis.