Herbert L. DuPont

The Infectivity of Cryptosporidium parvum in Healthy Volunteers

BACKGROUND Small numbers of Cryptosporidium parvum oocysts can contaminate even treated drinking water, and ingestion of oocysts can cause diarrheal disease in normal as well as immunocompromised hosts. Since the number of organisms necessary to cause infection in humans is unknown, we performed a study to determine the infective dose of the parasite in healthy adults. METHODS After providing informed consent, 29 healthy volunteers without evidence of previous C. parvum infection, as determined by the absence of anti-cryptosporidium-specific antibodies, were given a single dose of 30 to 1 million C. parvum oocysts obtained from a calf. They were then monitored for oocyst excretion and clinical illness for eight weeks. Household contacts were monitored for secondary spread. RESULTS Of the 16 subjects who received an intended dose of 300 or more oocysts, 14 (88 percent) became infected. After a dose of 30 oocysts, one of five subjects (20 percent) became infected, whereas at a dose of 1000 or more oocysts, seven of seven became infected. The median infective dose, calculated by linear regression, was 132 oocysts. Of the 18 subjects who excreted oocysts after the challenge dose, 11 had enteric symptoms and 7 (39 percent) had clinical cryptosporidiosis, consisting of diarrhea plus at least one other enteric symptom. All recovered, and there were no secondary cases of diarrhea among household contacts. CONCLUSIONS In healthy adults with no serologic evidence of past infection with C. parvum, a low dose of C. parvum oocysts is sufficient to cause infection.

Infections of the Gastrointestinal Tract

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Practice Guidelines for the Management of Infectious Diarrhea

The widening array of recognized enteric pathogens and the increasing demand for cost-containment sharpen the need for careful clinical and public health guidelines based on the best evidence currently available. Adequate fluid and electrolyte replacement and maintenance are key to managing diarrheal illnesses. Thorough clinical and epidemiological evaluation must define the severity and type of illness (e.g., febrile, hemorrhagic, nosocomial, persistent, or inflammatory), exposures (e.g., travel, ingestion of raw or undercooked meat, seafood, or milk products, contacts who are ill, day care or institutional exposure, recent antibiotic use), and whether the patient is immunocompromised, in order to direct the performance of selective diagnostic cultures, toxin testing, parasite studies, and the administration of antimicrobial therapy (the latter as for travelers diarrhea, shigellosis, and possibly Campylobacter jejuni enteritis). Increasing numbers of isolates resistant to antimicrobial agents and the risk of worsened illness (such as hemolytic uremic syndrome with Shiga toxin-producing Escherichia coli O157:H7) further complicate antimicrobial and antimotility drug use. Thus, prevention by avoidance of undercooked meat or seafood, avoidance of unpasteurized milk or soft cheese, and selected use of available typhoid vaccines for travelers to areas where typhoid is endemic are key to the control of infectious diarrhea.

Virulence of Three Distinct Cryptosporidium parvum Isolates for Healthy Adults

The infectivity of three Cryptosporidium parvum isolates (Iowa [calf], UCP [calf], and TAMU [horse]) of the C genotype was investigated in healthy adults. After exposure, volunteers recorded the number and form of stools passed and symptoms experienced. Oocyst excretion was assessed by immunofluorescence. The ID50 differed among isolates: Iowa, 87 (SE, 19; 95% confidence interval [CI], 48.67-126); UCP, 1042 (SE, 1000; 95% CI, 0-3004); and TAMU, 9 oocysts (SE, 2.34; 95% CI, 4.46-13.65); TAMU versus Iowa, P=.002 or UCP, P=.019. Isolates also differed significantly (P=.045) in attack rate between TAMU (86%) and Iowa (52%) or UCP (59%). A trend toward a longer duration of diarrhea was seen for the TAMU (94.5 h) versus UCP (81.6 h) and Iowa (64.2 h) isolates. C. parvum isolates of the C genotype differ in their infectivity for humans.

Economic healthcare costs of Clostridium difficile infection: a systematic review.

Clostridium difficile infection (CDI) is the leading cause of infectious diarrhoea in hospitalised patients. CDI increases patient healthcare costs due to extended hospitalisation, re-hospitalisation, laboratory tests and medications. However, the economic costs of CDI on healthcare systems remain uncertain. The purpose of this study was to perform a systematic review to summarise available studies aimed at defining the economic healthcare costs of CDI. We conducted a literature search for peer-reviewed studies that investigated costs associated with CDI (1980 to present). Thirteen studies met inclusion and exclusion criteria. CDI costs in 2008 US dollars were calculated using the consumer price index. The total and incremental costs for primary and recurrent CDI were estimated. Of the 13, 10 were from the USA and one each from Canada, UK, and Ireland. In US-based studies incremental cost estimates ranged from

Prevalence of enteric pathogens among international travelers with diarrhea acquired in Kenya (Mombasa), India (Goa), or Jamaica (Montego Bay)

2,871 to

Nitazoxanide for the Treatment of Clostridium difficile Colitis

4,846 per case for primary CDI and from

Fecal Leukocytes in Diarrheal Illness

13,655 to

Enteroaggregative Escherichia coli as a Major Etiologic Agent in Traveler's Diarrhea in 3 Regions of the World

18,067 per case for recurrent CDI. US-based studies in special populations (subjects with irritable bowel disease, surgical inpatients, and patients treated in the intensive care unit) showed an incremental cost range from

Post-Diarrhea Chronic Intestinal Symptoms and Irritable Bowel Syndrome in North American Travelers to Mexico

6,242 to