Public Healt Briefs
Leptospirosis on Kauai: Investigation of a Common Source Waterborne Outbreak -
mm
Alan R Katz, MD, MPH, Sally Jo Manea, BSN, and David M. Sasaki; DVM, MPH
Introdon Since the Hawaii State Department of Health (DOH) began collecting detailed statistics on leptospirosis in the early 1970s, Hawaii has consistently had the highest national annual incidence rate.' In 1987, the DOH reported a rate of 2.5 per 100 000 population2 compared with the national rate of 0.02 per 100 000 population.3 The following report describes a common source outbreak of leptospirosis from recreational exposure to a fresh water source.
Alan R. Katz is with the University of Hawaii School of Public Health. Sally Jo Manea and David M. Sasaki are with the Hawaii State Department of Health. Request for reprints should be sent to Alan R. Katz, MD, MPH, Department of Public Health Sciences, University of Hawaii School of Public Health, 1960 East-West Road, Honolulu, HI 96822. This paper was submitted to the journal October 10, 1990, and accepted with revisions May 6, 1991.
October 1991, Vol. 81, No. 10
Public Health Briefs The
OWbreak
On July 14, 1987, the DOH was notified of three youths hospitalized with suspected leptospirosis. All had repeated exposures to the Waimea River via swimming. The river runs within the lush Waimea Valley on southwestern Kauai. The valley and hills above the river contain cattle, feral goats, pigs, mongooses, and other rodents. In April 1987, several spontaneous abortions occurred among a herd of 50 cattle pastured adjacent to the swimmig area. Sera from the affected animals (9/9) tested positive for Leptospira interragans serovar hardjo (Sejroe serogroup), with micoscopic agglutination test (MAT) titers of 1:800 or greater (personal communication Dr. Craig Nishimoto, 1988, oral).
Me ods Case Finding The three case-patients and their parents were interviewed in an attempt to identify others with recent river exposure.
Sixteen males were identified and sampled, including the three hospitalized youths, who swam at this site almost daily between June 14 and July 4, 1987. Sera were sent to the Leptospirosis Reference Laboratory at the US Centers for Disease Control for MAT evaluation. A "confirmed" case was defined as an individual with recreational exposure to the Waimea River during the abovementioned dates, and positive leptospiral culture or serologic evidence of recent leptospiral infection manifested by a minimal fourfold increase in MAT titers in paired acute and convalescent sera.
Environmental Investigation Rodents were trapped at and above the exposure site. Water and mud samples downstream from the swimming spot were cultured for pathogenic leptospires. Seroprevalence data from an island-wide leptospirosis cattle survey conducted in late 1987 by the Hawaii State Department of Agriculture (DOA) were evaluated. Ongoing US Geological Survey measurements on the Waimea River near the exposure site were also evaluated.
Result Eight individuals reported a flu-like illness with onset between July 8 and July 21, 1987. Symptoms included headache 100o (8/8), fever 100% (8/8), chills 87.5%
October 1991, Vol. 81, No. 10
(7/8), nausea 87.5% (7/8), vomiting 75% (6/8), myalgia 62.5% (5/8), diarrhea 50% (4/8), and jaundice 12.5% (1/8). Five of the eight were hospitalized (62.5%), two were treated as outpatients, and one did not seek medical consultation. Initial MAT paired sera were positive for only two of the eight symptomatic individuals: one demonstrated L. intenmgans serovar bataviae (Bataviae serogroup), and one demonstrated L. inten'ogans serovarfon bnzgg (Autumnalis serogroup). After blood cultures from an individual with a negative MAT grew L ntrir)gans serovarbangkok (Australis serogroup), all sera were retested with a new battery of antigens including serovar australis (Australis serogroup), which had been missing from the initial antigen battery. The six with initial negative MAT results demonstrated L. interrogans serovar australs in the retest (Table 1). Two cases demonstrated positive blood cultures: one with serovar bangkok (as noted above) and one with serovarbataviae. The eight asymptomatic males were negative serologically for leptospirosis.
Cases ranged in age from 10 to 24 years (median age=14). The duration of symptoms ranged from 2 to 7 days, with a median of 6 days. Kidney cultures from 14 rodents trapped near the exposure site as well as water and mud samples from the Waimea River were all culture negative for patho-
genic leptospires. The median river flow rate near the exposure site during the outbreak exposure period was 0.31 m3/second. The 1987 annual mean flow rate at this site was 1.73 m3/second. On the two dates most closely bracketing the exposure period, the water
temperatures were 22°C and 249C and the pH measurements were 7.10 and 8.20.4 The island-wide DOA cattle seroprevalence survey revealed 89 (64%) of 139 cattle positive for Leptospira as manifested by MAT titers of 1:100 or greater against one or more serovars. Of 19 cattle bled on the ranch adjacent to the swimming site, 9 were positive: 8 demonstrated serovar hardjo, and 1 demonstrated serovarbataviae. Four animals geographically removed from the outbreak demonstrated serovar australis (personal communication DOA laboratory report, 1988, writ-
ten).
Intervention The local radio station, news media, and press reported the outbreak and warned ofthe potential danger from swimming in the Waimea River. DOH personnel were on site July 15 and 16 to post warning signs and inform swimmers ofthe potential danger. In addition individuals obtaining camping or conservation permits were given information on leptospirosis. No subsequent leptospirosis cases were reported from the Waimea River, and only one additional case was reported from the entire island of Kauai during the remainder of 1987.
Diwsion The majority of reported leptospirosis cases both nationally and in Hawaii have been sporadic and unrelated.56 However, cluster outbreaks are reported
infrequently*7-10 The antecedent epizootic of leptospirosis and the high cattle seroprevalence rate would appear to incriminate cattle as the source of this outbreak. However, be-
American Journal of Public Health 1311
Public Healt Briefs
cause serovar australis was not identified in cattle pastured adjacent to the exposure site and because the area contains many potential animal reservoirs, this outbreak may be unrelated to cattle. The small number of feral rodents sampled does not justify exclusion from the analysis. Optimal water conditions for the survivability of waterbome leptospires-a neutral or slightly alkaline pH"1"2 and temperature of 22°C or higher'3-were documented in the Waimea River around the outbreak exposure period. Decreased flow rates may have allowed concentration of waterborne Leptospira.1014 Although river water and mud samples were culture negative, the isolation of pathogenic Leptospira by direct culture from soil and natural waters is not routinely done and is generally unsuccessful.15.16 Although the MAT is considered a reference test for serological diagnosis of leptospirosis,17 a negative result does not rule out infection because the patient may be infected with a serotype absent from the battery of testing antigens.17 This phenomenon was responsible for the initial false negative results on six of eight cases in the present outbreak because serovar australis was absent from the testing battery. In addition, the MAT is only partially serovar specific. Cross-reactivity is well documented between serovars in the same serogroup as well as related serovars from different serogroups.17 This explains the confirmed case with positive blood cultures for serovar bangkok but MAT results showing the presumptive presence of serovar australs.
1312 American Journal of Public Health
Through this experience, we learned that sera from individuals infected with serovar australs may not cross-react with antigens from the other serogroups and serovars routinely used in the MAT. To optimize the MAT as a diagnostic tool, the testing battery should include antigens from all leptospiral serovars known to be geographically enzootic. [1
Acknowledgments Grateful acknowledgment is given to Hal Eichelberger, State of Hawaii Department of Health (Kauai), and Dr. Henri Minette, State of Hawaii Department of Health, for their valuable assistance in the investigation and reporting of this outbreak.
References 1. Lewin J. From the Director of Health: leptospirosis in Hawaii. Hawaii Med J.
1987;46:330. 2. Hawaii State Dept. of Health, Research and Statistics Office. Statistical Report, 198& Honolulu, HI: 1989. 3. Centers for Disease Control. Summary of notifiable diseases, United States, 1988. Atlanta, GA: 1988. US Dept of Health and Human Services publication (CDC) 908017. 4. US Geological Survey, Water Resources Division. Water Resources Data for Hawaii and Other PacicAreas, Water Year 1987. VoL 1, Hawaii Springfield, Va: NationalTechnical Information Service, 1988. Report No. USGS/WRD/HD-89/204. 5. Centers for Disease Control. Leptospirosis Swveillance, Anual Swmnmary 1977. Atlanta, GA: 1979. US Dept of Health, Education, and Welfare publication (CDC) 798260. 6. Anderson BS, Minette HP. Leptospirosis
in Hawaii: shifting trends in exposure, 1907-1984. Int JZoonoses. 1986;13:76-88. 7. Havens WP, Bucher CJ, Reimann HA. Leptospirosis: a public health hazardreport of a small outbreak of Weil's disease in bathers. JAMA. 1941;116:289-291. 8. Kaufmann AF. Epidemiology trends of leptospirosis in the United States, 19651974. In: Johnson RC, ed. The Biology of Parasitic Spirochetes. New York: Academic Press; 1976;177-189. 9. Martone WJ, Kaufmann AF. From the Centerfor Disease Control: leptospirosis in the United States, 1974-1978. JInfect Dis. 1979;140:1020-1022. 10. Anderson DC, Follard DS, Fox MD, Patton CM, Kaufmann AF. Leptospirosis: a common-source outbreak due to leptospires ofthe Grippotyphosa serogroup.Am JEpidemioL 1978;107:538-544. 11. Jacobs R. Leptospirosis-medical staff conference. University of California, San Francisco. WestJMed. 1980;132:440-450. 12. Hanson LE. Leptospirosis in domestic animals: the public health perspective. JAm Vet Med Assoc. 1982;181:1505-1509. 13. Edwards GA, Domm BM. Human leptospirosis. Medicine. 1960;39:117-156. 14. Diesch SL, McCulloch WF. Isolation of pathogenic leptospires from water used for recreation. Public Health Rep. 1966;81:299-304. 15. Henry RA, Johnson RC. Distribution of leptospira in soil and water. Appl Environ MicrobioL 1978;35:492-499. 16. Baker MF, Baker HJ. Pathogenic Leptospira in Malaysian surface waters: I. A method of survey for Leptospira in natural waters and soils.AmJ Trop Med Hyg. 1970;19:485-492. 17. Sulzer CR, Jones WL, eds. Leptospiroisi: Methods in Laboratory Diagnosis, Rev. Atlanta, Ga: 1982. Centers for Disease Control; US Dept of Health and Human Services publication (CDC)82-8275.
October 1991, Vol. 81, No. 10
Leptospirosis on Kauai: Investigation of a Common Source Waterborne Outbreak -
mm
Alan R Katz, MD, MPH, Sally Jo Manea, BSN, and David M. Sasaki; DVM, MPH
Introdon Since the Hawaii State Department of Health (DOH) began collecting detailed statistics on leptospirosis in the early 1970s, Hawaii has consistently had the highest national annual incidence rate.' In 1987, the DOH reported a rate of 2.5 per 100 000 population2 compared with the national rate of 0.02 per 100 000 population.3 The following report describes a common source outbreak of leptospirosis from recreational exposure to a fresh water source.
Alan R. Katz is with the University of Hawaii School of Public Health. Sally Jo Manea and David M. Sasaki are with the Hawaii State Department of Health. Request for reprints should be sent to Alan R. Katz, MD, MPH, Department of Public Health Sciences, University of Hawaii School of Public Health, 1960 East-West Road, Honolulu, HI 96822. This paper was submitted to the journal October 10, 1990, and accepted with revisions May 6, 1991.
October 1991, Vol. 81, No. 10
Public Health Briefs The
OWbreak
On July 14, 1987, the DOH was notified of three youths hospitalized with suspected leptospirosis. All had repeated exposures to the Waimea River via swimming. The river runs within the lush Waimea Valley on southwestern Kauai. The valley and hills above the river contain cattle, feral goats, pigs, mongooses, and other rodents. In April 1987, several spontaneous abortions occurred among a herd of 50 cattle pastured adjacent to the swimmig area. Sera from the affected animals (9/9) tested positive for Leptospira interragans serovar hardjo (Sejroe serogroup), with micoscopic agglutination test (MAT) titers of 1:800 or greater (personal communication Dr. Craig Nishimoto, 1988, oral).
Me ods Case Finding The three case-patients and their parents were interviewed in an attempt to identify others with recent river exposure.
Sixteen males were identified and sampled, including the three hospitalized youths, who swam at this site almost daily between June 14 and July 4, 1987. Sera were sent to the Leptospirosis Reference Laboratory at the US Centers for Disease Control for MAT evaluation. A "confirmed" case was defined as an individual with recreational exposure to the Waimea River during the abovementioned dates, and positive leptospiral culture or serologic evidence of recent leptospiral infection manifested by a minimal fourfold increase in MAT titers in paired acute and convalescent sera.
Environmental Investigation Rodents were trapped at and above the exposure site. Water and mud samples downstream from the swimming spot were cultured for pathogenic leptospires. Seroprevalence data from an island-wide leptospirosis cattle survey conducted in late 1987 by the Hawaii State Department of Agriculture (DOA) were evaluated. Ongoing US Geological Survey measurements on the Waimea River near the exposure site were also evaluated.
Result Eight individuals reported a flu-like illness with onset between July 8 and July 21, 1987. Symptoms included headache 100o (8/8), fever 100% (8/8), chills 87.5%
October 1991, Vol. 81, No. 10
(7/8), nausea 87.5% (7/8), vomiting 75% (6/8), myalgia 62.5% (5/8), diarrhea 50% (4/8), and jaundice 12.5% (1/8). Five of the eight were hospitalized (62.5%), two were treated as outpatients, and one did not seek medical consultation. Initial MAT paired sera were positive for only two of the eight symptomatic individuals: one demonstrated L. intenmgans serovar bataviae (Bataviae serogroup), and one demonstrated L. inten'ogans serovarfon bnzgg (Autumnalis serogroup). After blood cultures from an individual with a negative MAT grew L ntrir)gans serovarbangkok (Australis serogroup), all sera were retested with a new battery of antigens including serovar australis (Australis serogroup), which had been missing from the initial antigen battery. The six with initial negative MAT results demonstrated L. interrogans serovar australs in the retest (Table 1). Two cases demonstrated positive blood cultures: one with serovar bangkok (as noted above) and one with serovarbataviae. The eight asymptomatic males were negative serologically for leptospirosis.
Cases ranged in age from 10 to 24 years (median age=14). The duration of symptoms ranged from 2 to 7 days, with a median of 6 days. Kidney cultures from 14 rodents trapped near the exposure site as well as water and mud samples from the Waimea River were all culture negative for patho-
genic leptospires. The median river flow rate near the exposure site during the outbreak exposure period was 0.31 m3/second. The 1987 annual mean flow rate at this site was 1.73 m3/second. On the two dates most closely bracketing the exposure period, the water
temperatures were 22°C and 249C and the pH measurements were 7.10 and 8.20.4 The island-wide DOA cattle seroprevalence survey revealed 89 (64%) of 139 cattle positive for Leptospira as manifested by MAT titers of 1:100 or greater against one or more serovars. Of 19 cattle bled on the ranch adjacent to the swimming site, 9 were positive: 8 demonstrated serovar hardjo, and 1 demonstrated serovarbataviae. Four animals geographically removed from the outbreak demonstrated serovar australis (personal communication DOA laboratory report, 1988, writ-
ten).
Intervention The local radio station, news media, and press reported the outbreak and warned ofthe potential danger from swimming in the Waimea River. DOH personnel were on site July 15 and 16 to post warning signs and inform swimmers ofthe potential danger. In addition individuals obtaining camping or conservation permits were given information on leptospirosis. No subsequent leptospirosis cases were reported from the Waimea River, and only one additional case was reported from the entire island of Kauai during the remainder of 1987.
Diwsion The majority of reported leptospirosis cases both nationally and in Hawaii have been sporadic and unrelated.56 However, cluster outbreaks are reported
infrequently*7-10 The antecedent epizootic of leptospirosis and the high cattle seroprevalence rate would appear to incriminate cattle as the source of this outbreak. However, be-
American Journal of Public Health 1311
Public Healt Briefs
cause serovar australis was not identified in cattle pastured adjacent to the exposure site and because the area contains many potential animal reservoirs, this outbreak may be unrelated to cattle. The small number of feral rodents sampled does not justify exclusion from the analysis. Optimal water conditions for the survivability of waterbome leptospires-a neutral or slightly alkaline pH"1"2 and temperature of 22°C or higher'3-were documented in the Waimea River around the outbreak exposure period. Decreased flow rates may have allowed concentration of waterborne Leptospira.1014 Although river water and mud samples were culture negative, the isolation of pathogenic Leptospira by direct culture from soil and natural waters is not routinely done and is generally unsuccessful.15.16 Although the MAT is considered a reference test for serological diagnosis of leptospirosis,17 a negative result does not rule out infection because the patient may be infected with a serotype absent from the battery of testing antigens.17 This phenomenon was responsible for the initial false negative results on six of eight cases in the present outbreak because serovar australis was absent from the testing battery. In addition, the MAT is only partially serovar specific. Cross-reactivity is well documented between serovars in the same serogroup as well as related serovars from different serogroups.17 This explains the confirmed case with positive blood cultures for serovar bangkok but MAT results showing the presumptive presence of serovar australs.
1312 American Journal of Public Health
Through this experience, we learned that sera from individuals infected with serovar australs may not cross-react with antigens from the other serogroups and serovars routinely used in the MAT. To optimize the MAT as a diagnostic tool, the testing battery should include antigens from all leptospiral serovars known to be geographically enzootic. [1
Acknowledgments Grateful acknowledgment is given to Hal Eichelberger, State of Hawaii Department of Health (Kauai), and Dr. Henri Minette, State of Hawaii Department of Health, for their valuable assistance in the investigation and reporting of this outbreak.
References 1. Lewin J. From the Director of Health: leptospirosis in Hawaii. Hawaii Med J.
1987;46:330. 2. Hawaii State Dept. of Health, Research and Statistics Office. Statistical Report, 198& Honolulu, HI: 1989. 3. Centers for Disease Control. Summary of notifiable diseases, United States, 1988. Atlanta, GA: 1988. US Dept of Health and Human Services publication (CDC) 908017. 4. US Geological Survey, Water Resources Division. Water Resources Data for Hawaii and Other PacicAreas, Water Year 1987. VoL 1, Hawaii Springfield, Va: NationalTechnical Information Service, 1988. Report No. USGS/WRD/HD-89/204. 5. Centers for Disease Control. Leptospirosis Swveillance, Anual Swmnmary 1977. Atlanta, GA: 1979. US Dept of Health, Education, and Welfare publication (CDC) 798260. 6. Anderson BS, Minette HP. Leptospirosis
in Hawaii: shifting trends in exposure, 1907-1984. Int JZoonoses. 1986;13:76-88. 7. Havens WP, Bucher CJ, Reimann HA. Leptospirosis: a public health hazardreport of a small outbreak of Weil's disease in bathers. JAMA. 1941;116:289-291. 8. Kaufmann AF. Epidemiology trends of leptospirosis in the United States, 19651974. In: Johnson RC, ed. The Biology of Parasitic Spirochetes. New York: Academic Press; 1976;177-189. 9. Martone WJ, Kaufmann AF. From the Centerfor Disease Control: leptospirosis in the United States, 1974-1978. JInfect Dis. 1979;140:1020-1022. 10. Anderson DC, Follard DS, Fox MD, Patton CM, Kaufmann AF. Leptospirosis: a common-source outbreak due to leptospires ofthe Grippotyphosa serogroup.Am JEpidemioL 1978;107:538-544. 11. Jacobs R. Leptospirosis-medical staff conference. University of California, San Francisco. WestJMed. 1980;132:440-450. 12. Hanson LE. Leptospirosis in domestic animals: the public health perspective. JAm Vet Med Assoc. 1982;181:1505-1509. 13. Edwards GA, Domm BM. Human leptospirosis. Medicine. 1960;39:117-156. 14. Diesch SL, McCulloch WF. Isolation of pathogenic leptospires from water used for recreation. Public Health Rep. 1966;81:299-304. 15. Henry RA, Johnson RC. Distribution of leptospira in soil and water. Appl Environ MicrobioL 1978;35:492-499. 16. Baker MF, Baker HJ. Pathogenic Leptospira in Malaysian surface waters: I. A method of survey for Leptospira in natural waters and soils.AmJ Trop Med Hyg. 1970;19:485-492. 17. Sulzer CR, Jones WL, eds. Leptospiroisi: Methods in Laboratory Diagnosis, Rev. Atlanta, Ga: 1982. Centers for Disease Control; US Dept of Health and Human Services publication (CDC)82-8275.
October 1991, Vol. 81, No. 10
