688 Modern Food Microbiology
(from vertebrate animals to humans) is most likely where infected animals (such as calves) deposit
fecal matter to which humans are exposed. The disease may be contracted by drinking untreated water.
Oocysts at levels of 2–112 per liter were found in 11 samples of water from four rivers in Washington
and California.
74 Although the minimum infectious dose for humans is not known, two of two primates
became infected after the ingestion of 10 oocysts.
2 The organism has been shown to be an etiological
agent of travelers’ diarrhea.
102
Symptoms, Diagnosis, and Treatment
The clinical course of cryptosporidiosis in humans depends on the immune state, with the most severe
cases occurring in the immunocompromised. In immunocompetent individuals, the organism primarily
parasitizes the intestinal epithelium and causes diarrhea. The disease is self-limiting, with an incubation
period of 6–14 days, and symptoms typically last 9–23 days. In the immunocompromised, diarrhea is
profuse and watery, with as many as 71 stools per day and up to 17 l per day reported.
32 Diarrhea is
sometimes accompanied by mucus but rarely blood. Abdominal pain, nausea, vomiting and low-grade
(<39
◦ C) fever are less frequent than diarrhea, and symptoms may last for more than 30 days in the
immunocompromised but generally less than 20 days (range: 4–21 days) in the immunocompetent.
From the Milwaukee outbreak (see below), symptoms revealed by 285 of the victims were as follows:
watery diarrhea, 93%; abdominal cramps, 84%; fever, 57%; and vomiting, 48%.
67 The median duration
of illness was 9 days (range: 1–55), and the median maximal number of stools per day was 12 (range:
1–90). In an outbreak associated with a swimming pool in California in 1988, the following symptoms
(and percentages affected) were given by the 44 of 60 victims: watery diarrhea (88%), abdominal
cramps (86%), and fever (60%).
17 The organism was identified from stool cultures of some patients
by a modified acid-fast stain. Oocysts generally persist beyond the diarrheal stage.
Diagnosis of cryptosporidiosis requires the identification of oocysts in stools of victims. Staining
methods are used, including modified acid-fast procedures, negative staining, and sugar flotation.
Another diagnostic method is a direct immunofluorescence test used for the detection of oocysts in
feces.
101 The latter method employs a monoclonal antibody against an oocyst wall antigen.
Over 100 chemotherapeutic regimens have been tested and found to be ineffective,
25 although
spiramycin, fluconazole, and amphotericin B show some promise. More recently, the aminoglycoside
antibiotics paromomycin and geneticin were found to inhibit the growth of intracellular C. parvum in
Caco-2 cells.
41
Waterborne and Foodborne Outbreaks
The first demonstrated waterborne outbreak of cryptosporidiosis occurred in Braun Station, Texas,
in 1984 following the consumption of artesian well water. There were actually two outbreaks—
one in May and the other in July, with 79 victims.
26 A second outbreak with 13,000 victims occurred
in Carrollton, Georgia, in 1987 and oocysts were found in the stools of 58 of 147 victims.
43 Three
separate outbreaks occurred in the United Kingdom in 1988–1989. In one, there were 500 confirmed
cases that resulted from the consumption of treated water, and as many as 5000 persons may have been
affected.
97 In another outbreak, 62 cases were traced to contaminated swimming pool water. Early in
1990, there was an outbreak in Scotland.
Although foodborne cryptosporidiosis was suspected in the 1980s, only relatively recently have
clear-cut outbreaks been documented, and some are summarized in Table 29–2. The 1993 apple cider
outbreak occurred among at least 759 students and staff who attended a 1-day school fair.
70 The median
incubation period was 6 days (range of 10 hours to 13 days). In the chicken salad outbreak, the food
(from vertebrate animals to humans) is most likely where infected animals (such as calves) deposit
fecal matter to which humans are exposed. The disease may be contracted by drinking untreated water.
Oocysts at levels of 2–112 per liter were found in 11 samples of water from four rivers in Washington
and California.
74 Although the minimum infectious dose for humans is not known, two of two primates
became infected after the ingestion of 10 oocysts.
2 The organism has been shown to be an etiological
agent of travelers’ diarrhea.
102
Symptoms, Diagnosis, and Treatment
The clinical course of cryptosporidiosis in humans depends on the immune state, with the most severe
cases occurring in the immunocompromised. In immunocompetent individuals, the organism primarily
parasitizes the intestinal epithelium and causes diarrhea. The disease is self-limiting, with an incubation
period of 6–14 days, and symptoms typically last 9–23 days. In the immunocompromised, diarrhea is
profuse and watery, with as many as 71 stools per day and up to 17 l per day reported.
32 Diarrhea is
sometimes accompanied by mucus but rarely blood. Abdominal pain, nausea, vomiting and low-grade
(<39
◦ C) fever are less frequent than diarrhea, and symptoms may last for more than 30 days in the
immunocompromised but generally less than 20 days (range: 4–21 days) in the immunocompetent.
From the Milwaukee outbreak (see below), symptoms revealed by 285 of the victims were as follows:
watery diarrhea, 93%; abdominal cramps, 84%; fever, 57%; and vomiting, 48%.
67 The median duration
of illness was 9 days (range: 1–55), and the median maximal number of stools per day was 12 (range:
1–90). In an outbreak associated with a swimming pool in California in 1988, the following symptoms
(and percentages affected) were given by the 44 of 60 victims: watery diarrhea (88%), abdominal
cramps (86%), and fever (60%).
17 The organism was identified from stool cultures of some patients
by a modified acid-fast stain. Oocysts generally persist beyond the diarrheal stage.
Diagnosis of cryptosporidiosis requires the identification of oocysts in stools of victims. Staining
methods are used, including modified acid-fast procedures, negative staining, and sugar flotation.
Another diagnostic method is a direct immunofluorescence test used for the detection of oocysts in
feces.
101 The latter method employs a monoclonal antibody against an oocyst wall antigen.
Over 100 chemotherapeutic regimens have been tested and found to be ineffective,
25 although
spiramycin, fluconazole, and amphotericin B show some promise. More recently, the aminoglycoside
antibiotics paromomycin and geneticin were found to inhibit the growth of intracellular C. parvum in
Caco-2 cells.
41
Waterborne and Foodborne Outbreaks
The first demonstrated waterborne outbreak of cryptosporidiosis occurred in Braun Station, Texas,
in 1984 following the consumption of artesian well water. There were actually two outbreaks—
one in May and the other in July, with 79 victims.
26 A second outbreak with 13,000 victims occurred
in Carrollton, Georgia, in 1987 and oocysts were found in the stools of 58 of 147 victims.
43 Three
separate outbreaks occurred in the United Kingdom in 1988–1989. In one, there were 500 confirmed
cases that resulted from the consumption of treated water, and as many as 5000 persons may have been
affected.
97 In another outbreak, 62 cases were traced to contaminated swimming pool water. Early in
1990, there was an outbreak in Scotland.
Although foodborne cryptosporidiosis was suspected in the 1980s, only relatively recently have
clear-cut outbreaks been documented, and some are summarized in Table 29–2. The 1993 apple cider
outbreak occurred among at least 759 students and staff who attended a 1-day school fair.
70 The median
incubation period was 6 days (range of 10 hours to 13 days). In the chicken salad outbreak, the food