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Cryptosporidiosis -- New Mexico, 1986
Between July 1 and October 1, 1986, 78 laboratory-confirmed cases of cryptosporidiosis were reported to the Office of Epidemiology at the New Mexico Health and Environment Department. Because the source of infection in these cases was unclear, investigators conducted a case-control study to establish risk factors for infection.
For study purposes, a patient was defined as a Bernalillo County resident with laboratory-confirmed cryptosporidiosis reported to the Office of Epidemiology from July 1 through October 1, 1986. If more than one laboratory-confirmed case occurred in a household or day-care group, only the person with the earliest onset of symptoms was included in the study.
Fifty-eight (74%) of the 78 patients with cryptosporidiosis lived in Bernalillo County, which includes the city of Albuquerque. Twenty-four of these patients were included in the study. Thirty-two of the remaining patients were household or day-care contacts of these patients, and two were lost to follow-up.
The 24 patients included in the study were matched with 46 controls by age, sex, and neighborhood of residence. Using a questionnaire administered by telephone to both patients and controls, investigators gathered information on household size; day-care-center attendance, employment, or other principal sources of contact; travel; surface-water exposure; pet and domestic animal exposure; and the source of water to the home.
Patients' dates of onset of symptoms ranged from May 28 through September 2, 1986. Symptoms lasted from 5 to 60 days, with a median of 21 days. Ninety-six percent of the patients reported watery, nonbloody diarrhea; 79% reported flatulence; 67%, abdominal pain; 58%, nausea; and 54%, low-grade fever.
Patients ranged in age from 4 months to 44 years, with a median age of 3 years. Seventeen (71%) were less than 10 years of age. Seventeen (71%) of the patients were female, and seven (29%) were male. Thirteen (77%) of the patients less than 10 years of age and four (57%) of those greater than 10 were female.
Univariate analysis suggested that drinking untreated surface water and attending a day-care center where other children were ill with diarrhea were possible risk factors for this infection. There was a strong statistical association between drinking surface water and illness (odds ratio (OR) incalculable, p = 0.0016). None of the five patients who drank surface water had treated it in any way. One of these five patients attended a day-care center, the others had no other risk factors for cryptosporidiosis. None of the 46 controls had drunk surface water.
There may have been an increased risk of illness among those who had swum in surface water (OR = 3.7; 95% confidence interval (CI), 0.71 to 12.6). Exposure to surface water (either through drinking or swimming) had occurred in New Mexico, southern Colorado, and Mexico. If the two patients exposed to surface water in Mexico and their controls are eliminated from the analysis, drinking surface water is still significantly associated with illness (OR incalculable, p = 0.014). The time between exposure to surface water and illness ranged from 4 to 21 days, with a median of 7 days. The average incubation period of cryptosporidiosis is 2 to 10 days. Fourteen (82%) of the 17 household members with exposures to surface water similar to the patients' became ill with diarrhea within 2 to 7 days.
There was no statistically significant difference between patients and controls in attendance at day-care centers or in employment. However, patients were more likely than controls to attend a day-care center reported by a parent as having other children ill with diarrhea (OR = 5; 95% CI, 1.4 to 26.3). A patient was also more likely to be a household contact of a day-care-center attendee or employee, but this did not reach statistical significance (OR = 3.7, 95% CI, 0.95 to 14.2). Reported by: DJ Grabowski, MS, Albuquerque Environmental Health; KM Powers, JA Knott, MV Tanuz, LJ Nims, MS, MI Savitt-Kring, CM Lauren, BI Stevenson, HF Hull, MD, State Epidemiologist, New Mexico Health and Environment Dept. Div of Field Svcs, Epidemiology Program Office; Div of Parasitic Diseases, Center for Infectious Diseases, CDC.
Editorial Note: Cryptosporidium sp. was recognized as a human pathogen in 1976. The illness is associated with significant morbidity, including diarrhea, which is often prolonged and which can be accompanied by severe weight loss. In immunodeficient persons, cryptosporidiosis can cause life-threatening dehydration. There is no known effective therapy.
Previous outbreaks of cryptosporidiosis have occurred among animal handlers, through direct contact with animal feces (1), and in day-care centers, through person-to-person contact (2,3). An outbreak has also been reported from a Texas community where a common water well became contaminated (4).
Although surface water has not been previously recognized as a source of infection with Cryptosporidium, this study demonstrates that it may be. Further evidence was provided in January 1987 when a major waterborne outbreak of cryptosporidiosis in Georgia was traced to a river serving as the municipal water supply (CDC, unpublished data). Cryptosporidium sp. has been isolated from a broad variety of animals, including cattle, sheep, dogs, cats, deer, mice, rabbits, and snakes. Cryptosporidium sp. found in cattle have been shown to be transmitted to humans (1). Surface water might become contaminated through direct deposit of feces into water or by surface runoff that washes feces into water. The seasonal distribution of cryptosporidiosis, which occurs primarily in the summer and early fall (1,5), could be partially explained by the increased outdoor activity during that time of year.
Cryptosporidium species are known to be resistant to most chemical disinfectants, such as chlorine and iodine. Physicians should consider cryptosporidiosis in the differential diagnosis of persons with diarrhea who have a history of drinking surface water that is untreated or treated by chemical means alone.
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