Case-control studies of sporadic cryptosporidiosis in Melbourne and Adelaide, Australia

Abstract

Few studies have assessed risk factors for sporadic cryptosporidiosis in industrialized countries, even though it may be numerically more common than outbreaks of disease. We carried out case-control studies assessing risk factors for sporadic disease in Melbourne and Adelaide, which have water supplies from different ends of the raw water spectrum. In addition to examining drinking water, we assessed several other exposures. 201 cases and 795 controls were recruited for Melbourne and 134 cases and 536 controls were recruited for Adelaide. Risk factors were similar for the two cities, with swimming in public pools and contact with a person with diarrhoea being most important. The consumption of plain tap water was not found to be associated with disease. This study emphasizes the need for regular public health messages to the public and swimming pool managers in an attempt to prevent sporadic cryptosporidiosis, as well as outbreaks of disease.

Is drinking water a risk factor for endemic cryptosporidiosis? A case-control study in the immunocompetent general population of the San Francisco Bay Area

“…rain and spring water consumption, were significantly associated with cryptosporidiosis [55]. But more powerful, recent studies in the same country found no elevated risk for plain tap water consumption [53]. Given our difficulties in recruitment and sometimes conflicting data, such studies must be done in multiple communities simultaneously to obtain an accurate picture of the local situation.…”

“…Other routes of exposure to Cryptosporidium may be responsible for sporadic disease in the general population such as specific sexual contact with an infected individual [44-46], travel to endemic countries [47-50], and contact with animals, both domestic and livestock [1,2,51,52]. Recent studies in Australia have demonstrated that exposure to persons with diarrhea and swimming in public pools rather than consumption of untreated tap water are the sources of community-acquired cryptosporidiosis in that country [53]. The relative contribution for each of these modes of transmission to the total burden of sporadic cryptosporidiosis among immunocompetent persons continues to be unknown in the U.S.…”

Estimation of the consumption of cold tap water for microbiological risk assessment: an overview of studies and statistical analysis of data

“…To assess the volume of water consumed most studies use the number of cups or glasses as a measure (DWI 1996;Robertson et al 2000aRobertson et al , 2002Gofti-Laroche et al 2001;Dangendorf 2003;Hunter 2003 personal communication;Sinclair 2003 personal communication;Westrell et al 2004). This is a very easy way of estimating the water consumption and it is close to the everyday habits of the consumer.…”

Enteric illness risks before and after water treatment improvements

“…The importance of non-waterborne exposures was suggested by findings that people with high levels of raw vegetable consumption have half the risk of people who do not (odds ratio of 0.5; 95% CI 0.3-0.7) (Roy et al 2004). Two other studies have found similar protective effects from consuming fresh fruit and vegetables (Casemore et al 1997;Robertson et al 2002).…”

“…In this study, the enhanced water Exposure to Cryptosporidium oocysts and other enteric pathogens can also occur from sources other than drinking water, and these exposures may help explain the increased risks. Water recreation can be an important source of exposure as are some foods, and exposures to these and other sources may have affected illness rates among the study population (Robertson et al 2002;Roy et al 2004;Craun et al 2005;Dziuban et al 2006). The importance of non-waterborne exposures was suggested by findings that people with high levels of raw vegetable consumption have half the risk of people who do not (odds ratio of 0.5; 95% CI 0.3-0.7) (Roy et al 2004).…”