Download - Outbreak of Cryptosporidiosis Among Veterinary Students in a Bovine Obstetrics Laboratory
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Outbreak of Cryptosporidiosis Among Veterinary Students in a
Bovine Obstetrics Laboratory
Carrie Klumb1,2, Jeff Bender3,Kirk Smith1, Elizabeth Cebelinski1, Joni Scheftel1
1Minnesota Department of Health 2CSTE/CDC Applied Epidemiology Fellowship
3University of Minnesota Veterinary Population Medicine
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Background - Cryptosporidiosis• Acute gastrointestinal illness caused by
the protozoan parasite Cryptosporidium• Estimated 748,000 cases and 46 deaths
per year in the United States• Incubation period 1-12 days, mean 7 days• Profuse watery diarrhea, and cramping
over days to weeks. Fever and vomiting also may occur
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Background - Cryptosporidiosis (cont.)• 19 species of Cryptosporidium
– C. hominis – human primary reservoir– C. parvum – cattle primary reservoir
• Oocysts (infective stage) are shed in the feces of infected hosts
• In cattle, primarily disease of calves – Shed up to 1010 oocysts per day in
feces • C. parvum is present on 90% of dairy
farms in the United States
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Background - Cryptosporidiosis (cont.)• Transmission occurs through water and
food, from person-to-person and through direct animal contact
• 1983: Published report of cryptosporidiosis outbreak due to direct cattle contact among veterinary researchers
• Numerous outbreaks of cryptosporidiosis have been reported among veterinary students
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Outbreak Detection• On April 22, 2010 gastrointestinal illness
among second year veterinary students at a college of veterinary medicine (CVM) was reported to the Minnesota Department of Health (MDH)
• Students had participated in a 2-day bovine obstetrics (OB) laboratory prior to becoming ill
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Outbreak Detection (cont.)
• Four, 2-day OB laboratory sessions were scheduled at the CVM on:
Lab 1: April 1 and 2Lab 2: April 8 and 9Lab 3: April 15 and 16Lab 4: April 29 and 30
• The first three sessions had already occurred
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Methods - Epidemiologic Investigation
• Obtained contact list of all students registered for any of four OB laboratory sessions
• Spoke to professor and employees about laboratory set-up and specific activities
• Developed a questionnaire regarding symptoms and risk factors both in and outside of the laboratory setting
• Interviewed students by phone or in person
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Methods - Epidemiologic Investigation (cont.)
• Risk factors assessed– Tracking in small, mixed or large animal
practice– Dates of laboratory attendance – Eating or drinking in the laboratory – Use of personal protective equipment
(PPE)
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Methods - Epidemiologic Investigation (cont.)
• Risk factors assessed– Hand hygiene– Being splashed in the face during the
laboratory session– Events or meals in common with other
students• Analyses were performed using Epi-Info
software, version 6.04d and SAS, version 9.2
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Methods - Case Definition
A student who attended an OB laboratory session and subsequently had either:
a) A stool sample test positive for Cryptosporidium spp.
ORb) 3 or more days of diarrhea
(≥3 loose stools in 24 hours)
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Methods - Laboratory Investigation• Testing was performed on stool samples
– Students and employees with symptoms
– Calves from Dairy Farm A, where animals for class were obtained
• Fecal samples from the calves actually used in the laboratories were unavailable
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Methods - Laboratory Investigation (cont.)
• The MDH Public Health Laboratory conducted routine testing for Salmonella, Shigella, Campylobacter, Yersinia and E. coli O157:H7
• PCR for Shiga toxin-producing E. coli virulence factor genes (stx1, stx2, eae and hlyA) performed
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Methods - Laboratory Investigation (cont.)
• Testing for Giardia and Cryptosporidium spp. performed using acid fast staining, direct fluorescent antibody tests
• Positive Cryptosporidium specimens identified to species by PCR fragment length polymorphism (PCR-RFLP) – Further identified to subtype by DNA
sequence analysis of the 60-kDa glycoprotein (gp60) gene
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• Laboratory gives students hands-on experience assisting cows with difficult labors
• Course is highly physical and occurs in a small room
• Approximately 12 students working in pairs under the supervision of professor or lab technician
Results - OB Laboratory Description
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• Mock cows consisting of a wooden box, plastic bag, and cow pelvic bones
• Dead calves are placed inside mock cow• Calves used are generally healthy, 48-hour
old bull calves euthanized by captive bolt
Results - OB Laboratory Description
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Mock Cow
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Mock Cow
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Mock Cow
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Mock Cow
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• Day 1: practiced re-positioning abnormal fetal presentations and manual assistance of difficult births
Results - OB Laboratory Description
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• Day 2: Students practiced re-positioning abnormal presentations and performed a fetotomy– Used when calf has died in utero and too
large to be delivered naturally– Calf is cut up in utero, removed in pieces
• Often results in laceration of the dead calf’s bowels
• Introduces fecal material into the classroom
Results - OB Laboratory Description
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• Clean-up procedures– Students hosed down the inside of the
boxes, the plastic linings, and the floor with a garden hose
– No facial protection used
Results - OB Laboratory Description
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OB Laboratory
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OB Laboratory
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Results - OB Laboratory Description
• Calves from Dairy Farm A used during outbreak were:– Mix of male and female – Several weeks old– Some had died of diarrheal illness
• Calves stored together between day 1 and 2 and not labeled– Could not tell who was exposed to which
calves
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Results (cont.)
• 42 students had completed a lab at the time of the investigation
• 38 (91%) interviewed• 8 (21%) met the case definition• 22 (58%) reported no symptoms• 8 (21%) reported gastrointestinal symptoms
but did not meet case definition
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Results (cont.)
• 8 of 8 (100%) and 4 of 22 (18%) controls attended Lab 2 on April 8 and 9 – Fisher’s exact p < 0.001
• There were no cases among Lab 1 or Lab 3 attendees
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Case Symptoms (n = 8)
Symptom No. (%)Diarrhea 8 (100)Cramps 8 (100)Gas 7 (88)Weight Loss 4 (50)Fever 3 (38)Vomiting 1 (13)Bloody Diarrhea 1 (13)
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Results (cont.)
• Median incubation period from Lab 2 was 7 days (range, 5 to 12 days)
• Median duration of illness for the 6 cases that had recovered at the time of the interview was 8.5 days (range, 7 to 14 days)
• 1 case was seen by their physician and 1 case was seen in an Emergency Department
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Results (cont.)
• A CVM employee also became ill with bloody diarrhea, gas and cramps with illness onset on April 23
• Employee still ill at time of interview• Set up and cleaned up the OB laboratories on
several different dates• Incubation period calculated from the date of
Lab 2 was 15 days
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• 4 of 8 human samples (3 student cases and CVM employee) positive for C. parvum of the same gp60 subtype (IIaA15G2R2)
• All human stool samples negative for Salmonella, Shigella, Campylobacter, Yersinia, E. coli O157:H7, Shiga toxin-producing E. coli virulence factors, and Giardia
Results - Human Testing
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No.
of C
ases
16 17 18 19 20 21 2212 13 14 153129 30
March
1
4
23
1 1110987
April
62 43
First Obstetrics Lab
5
Second Obstetrics Lab
Third Obstetrics Lab
23 24 25 2628
Second Obstetrics Lab Attendee
Laboratory-confirmedVeterinary School Employee
Onset Date
Cryptosporidium parvum Cases Associated with a Veterinary School Bovine Obstetrics Laboratory by
Illness Onset Date, Minnesota, 2010
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Results (cont.)• Among the Lab 2 attendees, the only risk
factor that approached significance was being splashed in the face at any point during day 2 of the lab– 7 of 7 cases vs. 1 of 3 controls*– Fisher’s exact p = 0.07
*1 case and 1 control were not able to recall and could not answer the question
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Results (cont.)
• Students in Lab 2 were significantly more likely to have been splashed in the face at any point during the lab session than students in Labs 1 and 3– Odds ratio, 13.0– 95% confidence interval, 1.44 to 117.20 – p = 0.01
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Self-Reported Personal Protective Equipment (PPE) Use Among Students
PPE No. (%) PPE No. (%)
Day 1 Day 2Sleeves 42 (100) Sleeves 42 (100)
Coveralls 28 ( 93) Coveralls 27 ( 96)
Boots 29 ( 97) Boots 29 (100)Rubber Apron 0 ( 0) Rubber
Apron 0 ( 0)
Mask/Face Shield 0 ( 0) Mask/Face
Shield 0 ( 0)
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• 3 of 9 calf fecal samples collected at Dairy Farm A positive for C. parvum gp60 subtype (IIaA15G2R2)– Matched C. parvum in human samples– Subtype commonly found in Minnesota
• 3 fecal samples were positive for the E. coli virulence factor gene stx1
• Calf fecal samples negative for Salmonella, Shigella, Campylobacter, Yersinia, E. coli O157:H7 and Giardia
Results - Calf Testing
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Conclusion• This was an outbreak of cryptosporidiosis
among veterinary students in an OB laboratory
• Calves that had died of a diarrheal illness and then used in the laboratories were the source of infection
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Conclusion (cont.)
• Not surprising that stool samples from calves at Dairy Farm A tested positive for C. parvum
– C. parvum is present on 90% of dairy farms in the U.S.
– Higher prevalence in calves • Highlights the zoonotic risk inherent in
certain veterinary school activities
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RecommendationsMDH epidemiologists and infection control specialists from CVM made recommendations
• Have students read provided information about zoonoses and prevention measures
• Remind students about proper hand hygiene
• Restrict calves used to euthanized 48-hour old healthy bull calves
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Recommendations (cont.)
• Provide face shields/masks and rubber aprons to students
• Offer laundry service at school• Use an EPA-approved disinfectant to
clean laboratory
No illnesses were identified during the last laboratory on April 29 and 30
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Follow Up• Visited laboratory on May 12, 2011 to observe• Warning was added to this year’s syllabus
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Follow Up (cont.)
• Observations made– All students wore boots, coveralls,
sleeves – No face shields/masks offered or worn
by students– Laundry service not being provided by
the school– Near-term fetuses were being obtained
from slaughter facilities
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Follow Up (cont.)
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Conclusion• Cryptosporidiosis is sometimes called a
“rite of passage” in veterinary school– Serious disease– Infections should be avoided to the
extent possible
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Conclusion• Prevention of future outbreaks
– Educating students about the risks– Ensuring calves used in laboratories
are healthy– Providing face shields or a mask and
goggles• Compendium of Veterinary Standard
Precautions for Zoonotic Disease Prevention in Veterinary Personnel offers infection control guidance
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Acknowledgments
Minnesota Department of Health
Team Diarrhea
Foodborne, Vectorborne, and Zoonotic Disease Unit
University of Minnesota
Dr. Ricardo Chebel Amanda Doran
Dr. Tom Molitor Leslie Hiber