Is drinking water a risk factor for endemic cryptosporidiosis? A case-control study in the immunocompetent general population of the San Francisco Bay Area.
BACKGROUND
Cryptosporidiosis, caused by Cryptosporidium, is an enteric illness that has received much attention as an infection of immunocompromised persons as well as in community outbreaks (frequently waterborne). There are, however, no studies of the risk factors for sporadic community-acquired cryptosporidiosis in the immunocompetent US population. We undertook a case-control study in the San Francisco Bay Area as part of a national study sponsored by the Centers for Disease Control and Prevention to ascertain the major routes of transmission for endemic cryptosporidiosis, with an emphasis on evaluating risk from drinking water.


METHODS
Cases were recruited from a population-based, active surveillance system and age-matched controls were recruited using sequential random-digit dialing. Cases (n = 26) and controls (n = 62) were interviewed by telephone using a standardized questionnaire that included information about the following exposures: drinking water, recreational water, food items, travel, animal contact, and person-to-person fecal contact, and (for adults) sexual practices.


RESULTS
In multivariate conditional logistic regression analyses no significant association with drinking water was detected. The major risk factor for cryptosporidiosis in the San Francisco Bay Area was travel to another country (matched odds ratio [95% confidence interval]: 24.1 [2.6, 220]).


CONCLUSIONS
The results of this study do not support the hypothesis that drinking water is an independent risk factor for cryptosporidiosis among the immunocompetent population. These findings should be used to design larger studies of endemic cryptosporidiosis to elucidate the precise mechanisms of transmission, whether waterborne or other.
Khalakdina
Asheena
A
Division of Public Health Biology and Epidemiology, Centers for Family & Community Health and Occupational & Environmental Health, School of Public Health, University of California, Berkeley, California, USA. asheena@socrates.berkeley.edu
Vugia
Duc J
DJ
Nadle
Joelle
J
Rothrock
Gretchen A
GA
Colford
John M
JM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003457:Cryptosporidiosis / Q000453:epidemiology* / Q000209:etiology / Q000635:transmission; D016785:Cryptosporidium parvum / Q000302:isolation & purification / Q000469:parasitology*; D019353:Endemic Diseases; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D016867:Immunocompromised Host; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors; D012495:San Francisco / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014867:Water / Q000469:parasitology*; D014876:Water Pollution / Q000032:analysis; D014881:Water Supply / Q000032:analysis / Q000592:standards*
D014867:Water