Outbreak of Cryptosporidiosis Associated with a Private Lake

Tarrant County, 2008

Anita Kurian, MBBS, DrPHChief Epidemiologist & Epidemiology Division Manager

Tarrant County Public Health

June 02, 2009

Detection of Outbreak and TimelineJuly 8, 2008 Initial notification of potential food-borne illness

among several persons who attended a church picnic at the privately-owned, chlorinated Lake A

July 9, 2008 A second group of Lake A attendees reported

similar illnesses

Detailed history shifted the focus from food borne to water borne illness

July 10, 2008 ~ 200+ calls with similar history 1st lab confirmed case reported

Timeline (continued)

July 11, 2008 5 lab-confirmed cases Five different groups had been identified with

similar illness/history An Epi-Aid was requested Lake A was visited by TCPH officials

Aerial View of Lake A

Lake A

Lake A

Updated Equipment

Timeline (continued)

July 16, 2008 Different exposure dates

emerge Approximately 500 + calls TCPH recommended Lake A

closure

8 Lab-confirmed cases of Cryptosporidiosis identified

Cryptosporidiosis Etiologic agent – Chlorine resistant

protozoa of the genus Cryptosporidium

Cryptosporidium is spread through the fecal-oral routewater

Has been associated with more than two-thirds of reported recreational water illness (RWI) outbreaks in the United States

Background (cont’d) Nationally reported crypto outbreaks associated

with treated recreational water venues:– 7 in 2004– 19 in 2005– 26 in 2007

Number of crypto casesin Tarrant County:

– 6 in 2006– 6 in 2007– 7 from Jan 2008 – June 2008

Epidemiological Investigation

Descriptive and Hypothesis Generating Study

Matched Case-Control Study

Confirmed cases - persons who developed gastrointestinal illness following a visit to Lake A after June 20, 2008 and whose stool tested positive for Cryptosporidium

Probable cases - persons who developed diarrhea, defined as at least 3 watery stools per day, lasting at least 3 days within 2-10 days of visiting Lake A after June 20, 2008.

Case Definitions

The purpose of the environmental study was 3-fold:

1) To determine if there was evidence of Cryptosporidium contamination of Lake A

2) To determine if a possible source of the contamination could be identified on the property surrounding Lake A

3) To determine the feasibility of remediating or hyperchlorinating Lake A.

Environmental Study

Laboratory Results

Microbiology

Well #1 Total coliform - 23.1/100ml sample

Negative for fecal coliform

Well #2 Negative for total coliform & fecal coliform

Well #3

Sample 1 feeding the lake Total coliform - 6.3/100ml sample

Negative for fecal coliform

Sample 2 from the restrooms sink Negative for total coliform & fecal coliform

Well #4 Negative for total coliform & fecal coliform

Well #5

Sample 1 from the well Negative for total coliform & fecal coliform

Sample 2 at the snack bar Negative for total coliform & fecal coliform

Composite sample from the lake Cryptosporidium- ~0.5 to 1 oocyst per 10 L of lake water

Backwash from 2 sand filters Cryptosporidium- ~0.5 to 1 oocyst per 10 L of lake water

Wells feeding Lake A

*1 parts per million (ppm) or mg/L free chlorine at ph 7.5 or less and a temperature of 77oF (25oC) or higher.

Germ Inactivation Time for Chlorinated Water

CT

E. coli O157:H7 Bacterium

Less than 1 minute 1

Hepatitis A Virus About 16 minutes 16

Giardia Parasite

About 45 minutes 45

Crypto Parasite

About 15,300 minutes 15,300

Germ Time

Parts per million free chlorine

x Minutes = CT

20 x 765 = 15,300

10 x 1,530 = 15,300

Use the formula below to calculate contact time (CT)

Crypto Inactivation Time for aDiarrheal Fecal Incident

Hyperchlorination – July 24, 2008

Hyperchlorination

Lake A was reopened on July 27, 2008

~1,400 called in sick after swimming in Lake A 113 confirmed cases 142 probable cases, and 182 persons with gastrointestinal illness

epidemiologically linked to a confirmed or probable case and the lake.    

Results

The median age of cases was 12 years (range: 3 months – 62 years),

52% were male 92% were white C. hominis identified by RT-PCR in stool

samples from cases 2 genotypes identified - IaA28R4 (56.1%)

and IaA15R3.

Results (cont’d)

Lake A Crypto Cases – Visit Dates

0

10

20

30

40

50

60

70

6/6/

08

6/11

/08

6/16

/08

6/21

/08

6/26

/08

7/1/

08

7/6/

08

7/11

/08

7/16

/08

7/21

/08

7/26

/08

7/31

/08

8/5/

08

8/10

/08

8/15

/08

Visit Date

Confirmed (n=113)*

Probable (n=135)*

06/28/08

07/05/08

Nu

mb

er

of

Cry

pto

Cases

*Cases for Tarrant County and Non-Tarrant County Residents

0

5

10

15

20

25

30

35

40

6/15

/08

6/19

/08

6/23

/08

6/27

/08

7/1/

08

7/5/

08

7/9/

08

7/13

/08

7/17

/08

7/21

/08

7/25

/08

7/29

/08

8/2/

08

8/6/

08

8/10

/08

8/14

/08

8/18

/08

8/22

/08

8/26

/08

8/30

/08

Onset of Illness Date

Nu

mb

er

of

Cry

pto

Cases

Confirmed (n=113)*

Probable (n=135)*

07/04/08

07/11/08

Lake A Crypto Cases – Onset of Illness

*Cases for Tarrant County and Non-Tarrant County Residents

Frequency of Symptoms

Percent

Diarrhea 98.8

Abdominal Cramps 88.3

Vomiting 62.1

Fever 51.2 (99.0 - 104.0)

Weight Loss 46.1

Fatigue 7.0

Headache 5.1

Bloody Diarrhea 3.5

Univariate Analysis for Factors Associated with Cryptosporidium Infection

Variable OR* Wald 95% CI

Age in years (continuous) 0.95 0.92 – 0.98

Male gender 2.67 1.24 – 5.74

Went into water** 8.17 1.18 – Infinity

Put head under water** 21.14 3.59 – Infinity

Swallowed water** 39.90 7.10 – Infinity

Brought own food ‡

Ate at concession stand 5.00 0.58 – 42.8

Ate sno-cone** 1.00 0 – 39.0

Drink from water fountain ‡‡

Contact with pet 3.00 0.31 – 28.8

* Odds ratios are matched odds ratios.** Exact matched odds ratios and confidence intervals.‡ No odds ratio possible as there are no discordant pairs.‡‡ No one drank from the water fountain.

Multivariate Logistic Regression Analysis for Factors Associated with Cryptosporidium Infection

Variable Exact OR* Exact 95% CI

Went into water 4.11 0.46 – Infinity

Put head under water 16.5 2.44 – Infinity

Swallowed water 29.5 4.75 – Infinity

*All OR’s are matched OR’s.

Crypto Case Timeline

0

2

4

6

8

10

12

14

16

18

5/13

/200

8

5/20

/200

8

5/27

/200

8

6/3/

2008

6/10

/200

8

6/17

/200

8

6/24

/200

8

7/1/

2008

7/8/

2008

7/15

/200

8

7/22

/200

8

7/29

/200

8

8/5/

2008

8/12

/200

8

8/19

/200

8

8/26

/200

8

9/2/

2008

9/9/

2008

9/16

/200

8

9/23

/200

8

9/30

/200

8

10/7

/200

8

10/1

4/20

08

10/2

1/20

08

Onset of Illness Date

Nu

mb

er

of

Cry

pto

Cases

Outbreak detected by TCPH

TCPH Visits Lake A

Initial Press Release (AM) & Lake A Closed (PM)

Recommend Hyper-Chlorination of Lake A

Lake A Hyper-Chlorinated

Lake A Re-Opened

2nd Alert Sent to Day Cares

Recommend Weekly Hyper-Chlorination of All Rec-Water Facilities

Press Conference & Alert to Health Care Providers, Day Cares, Public Pool Owners

Lake A (n=83)*

Non-Lake A (n=356)*07/10/0807/11/0807/16/0807/17/0807/22/0807/23/0807/27/0808/01/0808/13/08

*Cases for Tarrant County Residents Only

In Conclusion

First documented outbreak of cryptosporidiosis associated with

a chlorinated lake

First documentedhyperchlorination of a lake

Multi-disciplinary investigation

Multi-disciplinary approach isneeded to reduce the risk offuture RWI outbreaks.

Paul Cantey, MD, MPH Jimee Hwang, MD, MPH Rebecca Hall, MPH Michele Hlavsa, RN, MPH Vince Hill, PhD Charles Otto, MPA Jeff Taylor, MPH Rita Espinoza, MPH Jade Dukes, MPH Jawaid Asghar, MBBS TCPH staff

Acknowledgments