LYME DISEASE RISK ASSESSMENT, CAMP PENDLETON, CALIFORNIA 5-11 APRIL 1992 DEPARTMENT OF THE ARMY US Army Environmental Hygiene Activity-West Fitzsimons Army Medical Center Aurora, Colorado 80045-5001 [Seal of Department of Defense, United States of America] REPLY TO ATTENTION OF: HSHB-AW-P (40-5f) 12 June 1992 LYME DISEASE RISK ASSESSMENT NO. 16-66-AF32-92 CAMP PENDLETON, CALIFORNIA 5-11 APRIL 1992 1. REFERENCES. See Appendix A for a list of references. 2. AUTHORITY. a. Conference Report on the National Defense Authorization Act for Fiscal Years 92 and 93, House Report 102-311, 102nd Congress, 1st Session, 13 November 1991, p. 422. b. USAEHA Form 250-R, Navy Environmental Health Center, Norfolk, VA, 4 September 1991. 3. PURPOSE. The purpose in performing this risk assessment was to survey for Lyme disease vectors, to determine the prevalence of the infective agent, Borrelia burgdorferi, in rodents and ticks, and to assess the risk of Lyme disease to Camp Pendleton (CAMPEN) personnel. 4. GENERAL. a. Risk Definition. The term "risk", as used in this report, is a non- statistical determination of qualitative and quantitative information available to evaluate the potential to acquire Lyme disease. To the extent available, information evaluated includes the following elements of the Lyme disease cycle: (1) History of Lyme disease in the area. (2) The presence or absence of the tick vector (Ixodes pacificus) and the mammalian host population needed to sustain a viable population of the vector. (3) The presence of the Lyme disease-causing spirochete (B. burgdorferi) in the tick population or in the mammalian reservoir host population. (4) The presence of antibodies to B. burgdorferi in the mammalian host population. Criteria for risk categorization follow: Low risk - Some element of the Lyme disease cycle identified in nearby areas but not on the installation. Moderate risk - Elements of Lyme disease cycle identified from the installation or human cases of Lyme disease identified from the local area. High risk - All elements of the Lyme disease cycle are present on the installation. b. Dr. Lester D. Hale and Mr. William E. Irwin, the Survey Officers, discussed major findings and recommendations with CAMPEN personnel. A list of personnel contacted and personnel assisting Dr. Hale and Mr. Irwin during the risk assessment is found in Appendix B. c. The field survey portion of the Lyme Disease Risk Assessment was conducted at CAMPEN on 5-11 April 1992. d. This study also provided training for the CAMPEN Medical Entomologist, CAMPEN Preventive Medicine personnel, the Entomologist from Preventive Medicine Unit No. 5, and six personnel from the San Diego Vector Surveillance and Control Division, San Diego County Department of Health Services. On-the-job training conducted during the field survey portion of the risk assessment included: vector surveillance procedures, tick surveillance methods, small mammal trapping, and ear tissue biopsy sample methodology. e. Laboratory analyses of ticks and rodent ear tissue biopsies were conducted between April-June 1992. 5. BACKGROUND. a. Lyme disease is a multi-systemic infectious disease caused by the spirochete, B. burgdorferi, which is transmitted to humans by the bite of an infected tick. The disease is most often referred to as Lyme disease or Lyme arthritis in the United States. Lyme disease has become the most prevalent arthropod-borne illness in North America. Its geographic range is expanding and the number of reported cases continues to rise each year. The Office of the Surgeon General reported 379 cases of Lyme disease contracted on Department of Defense (DOD) installations from 1987 through 1991. During 1990, there were 78 cases of Lyme disease treated in military hospitals from all the Armed Services of which 26 of the cases were either dependents or retired members. During 1991, there were 81 cases of Lyme disease treated in military hospitals of which 31 of the cases were either dependents or retired members. There were 3 soldiers who were reported to have permanent disabilities caused by Lyme disease during 1991. The need to protect soldiers and other personnel working on DOD installations has increased with the spread of Lyme disease. b. There have been no cases of Lyme disease reported from CAMPEN. During 1991, there were 323 cases of Lyme disease occurring in California which were reported to the Centers for Disease Control (Reference 1, Appendix A). San Diego County Department of Health Services personnel stated that the following cases of Lyme disease had been reported from San Diego County: one case in 1991; two cases in 1990 (one case was considered to have been contracted outside San Diego County); and four cases in 1989. During 1991, one case of Lyme disease was reported in Orange County. c. Laboratory analysis performed by this Activity on ticks collected at CAMPEN during the 1991 fall deer hunt showed that 18 (15 percent) western black-legged ticks, I. pacificus and 1 (3 percent) Pacific Coast tick, Dermacentor occidentalis, examined by immunofluorescent staining were positive for spirochetes (Reference 2, Appendix A). In addition to the deer hunt mentioned above, 100 blood samples were taken from deer and analyzed by the Fort Meade Veterinary Service; 19 (19 percent) tested positive for the presence of antibodies to B. burgdorferi. Deer blood samples also were taken by the CAMPEN game wardens on 29 February and 1 March 1992; 14 blood samples were analyzed and 6 samples (43 percent) were positive for the presence of antibodies. The latter blood samples were taken from deer in areas where antibodies had been detected in the 1991 fall deer blood tests. d. Camp Pendelton is located along the corridor of Interstate Highway 5 and along the Southern California coast within the boundaries of San Diego County. Orange County marks the Camp's Northern boundary with the Santa Margarita Mountains along the Camp's Northeast boundary. The Marine Corps Air Station is located next to CAMPEN. The installation currently encompasses approximately 128,000 acres. The actual maneuver/training areas were approximately 47,000 acres. During 1991, CAMPEN provided training for approximately 31,000 U.S. Marine Active troops and 30,000 Reservists. 6. METHODS. a. Field Survey Procedures. (1) Tick Surveys. Ticks were collected using tick drag cloths and/or tick flags, and carbon dioxide traps. Ticks were also removed from the ears of trapped rodents on CAMPEN. All ticks were kept alive by placing them in water moistened vials as described in the U.S. Army Environmental Hygiene Activity-West (USAEHA-W), Entomological Sciences Division (ESD) Standing Operating Procedures (SOPs) No. 6 and No. 8. For each collection site, all collected ticks were identified, counted, and placed into a marked vial. Ticks collected at different sites were kept segregated and placed into separate marked vials and subsequently sent to the USAEHA-W, ESD Laboratory. (a) Tick Drag Technique. Two narrow boards (1x2x36-inch) were attached on opposite ends of a 3x3-foot white flannel cloth. A cord was fastened to the ends of one board. The cloth was then pulled slowly over vegetation for approximately 10 meters before examination for attached ticks. Ticks were then removed from the cloth and placed in a marked vial for that particular dragging operation. Approximately 11,750 linear meters were covered by team members at the different collection sites. (b) Tick Flag Technique. A 3x3-foot piece of white flannel cloth was dragged over the tops of large vegetation, i.e., sagebrush, or was used on steep slopes. Attached ticks were then removed from the cloth and placed in a marked vial for each collection site. Aproximately 8,150 linear meters were covered by team members doing the flagging. (c) Carbon Dioxide Traps. A 2x2-foot piece of white flannel cloth was placed on the ground and the edges were weighted down with stones. An aluminum-foil covered pie plate was placed upside down in the middle of the cloth. Approximately 2 pounds of dry ice were wrapped in newspaper and placed on top of the pan. The area around each trap and the cloth were examined for ticks after 3 to 4 hours. (2)Rodent Surveys. Rodents trapped at CAMPEN were identified using "A Field Guide to the Mammals, North America, north of Mexico" (Reference 5). (a) Small mammals were captured in 3x3x10-inch live traps on CAMPEN. Eight trapping locations were selected on the installation. One or more trap lines were set in each area. The traps were usually located near stream beds, springs, or creeks with traps located approximately 10 meters apart. The traps were set only one night at each location using at least 15 traps. Five 5x5x16-inch live traps were used to trap larger mammals (i.e., dusky-footed woodrats) at CAMPEN. (b) All mammals were anesthetized before removing ticks and taking ear tissue biopsies. All rodents were handled in accordance with the guidelines outlined in the National Institutes of Health Publication No. 85-23, Revised 1985, "Guide for the Care and Use of Laboratory Animals" and USAEHA-W, ESD SOP No. 7. (c) Ticks found on mammals were removed for bioassay. b. Laboratory Assay Procedures. (1) The ticks collected from rodents and from dragging/flagging vegetation during 5-7 April were shipped via overnight mail to USAEHA-W, ESD Laboratory for bioassay. All the ear tissue biopsies from CAMPEN and those ticks collected from 8-11 April were hand-carried to the USAEHA-W, ESD Laboratory for Lyme disease bioassay. (2) The midguts of 31 ticks were dissected and examined using darkfield microscopy, and 172 ticks were examined by immunofluorescent staining for spirochetes. Two pools of I. pacificus, consisting of a homogenate of 5 adult ticks for each pool, and 14 D. occidentalis pools consisting of a homogenate of 10 adult ticks for each pool, were ground in tissue grinders and cultured in modified Barbour-Stoenner-Kelley (BSK) II media for spirochetes. Ninety-four ear tissue biopsies from trapped rodents and one ear tissue biopsy from a desert cottontail also were cultured in BSK II media. Each inoculated culture was examined using the darkfield microscope every 3-7 days for 21 days for spirochete growth. If no spirochetes were found during this period, the ear tissues or tick pools were considered to be negative for B. burgdorferi. 7. FINDINGS AND DISCUSSION. a. Survey Results. (1) Ticks were collected from humid or wet sites such as stream banks, meadows, and hillsides. Table 1 shows the sites, map coordinates, species, and number of each of the life stages of ticks collected on CAMPEN during tick drags/flags. No ticks were attracted to the carbon dioxide traps. A total of 41 I. pacificus, 430 D. occidentalis, and 21 American dog ticks, Dermacentor variabilis, were collected by either dragging or flagging. One adult Pacific Coast tick was positive for B. burgdorferi from the Bravo Two site. All other species of ticks examined by darkfield and immunofluorescent microscopy in the laboratory analysis were negative for B. burgdorferi. (2) Table 2 shows the rodents captured on CAMPEN and the number of Ixodes spp., D. occidentalis, and Haemaphysalis leporispalustris (rabbit tick) removed from these mammals. All biopsies were negative for B. burgdorferi, suggesting that the spirochete had not circulated within the limited population sampled. (3) One adult I. pacificus from the Onofre site and one from the Bravo Two site were found attached to an individual on the survey team. Both ticks were examined in the laboratory and found to be negative for spirochetes. (4) In addition to those ticks analyzed microscopically, the 16 tick pools discussed in paragraph 6b(2), this report, were found to be negative for the spirochetes which cause Lyme disease. Additional detailed information on sites, rodents and laboratory analysis are given in Appendix C. TABLE 1. Number of Ixodes pacificus, Dermacentor occidentalis, and Dermacentor variabilis, collected from drags/flags at Camp Pendleton, California. NUMBER ADULT TICKS -------------------------------------------- SITE I. pacificus D. occidentalis D. variabilis Total --------------------------------------------------------------------------- San Onofre State Park 4 138 11 153 (454,965)* Alfa One 1 38 0 39 (511,959) Romeo One (Range 215) Negative (no ticks on trapped rodents; did not (577,924) drag/flag in this area) Deer Park (Romeo One) 4 20 0 24 (577,928) Echo (Case Springs) 0 36 0 36 (613,006) Foxtrot 0 10 0 10 (640,985) Bravo Two (riverbed) 31 107 10 148 (472,006) (One D. occidentalis tested positive for spirochetes) Kilo 1 0 11 0 11 (667,865) Box Canyon (Section H) 1 70 0 71 (656,778) Kilo Two Negative (did not drag/flag in this area) (673,894) ---------------------------------------------------- TOTAL TICKS COLLECTED 41 430 21 492 * Map coordinates given as longitude and latitude; based on Camp Joseph H. Pendleton (1:32,500), Sheet Camp Pendleton Special, Series V895S, Edition 2-DMA, DMA Stock No. V895SCAMPPENDLE, dated 1980. -------------------------------------------------------------------------- TABLE 2. Number of Ixodes spp., Dermacentor occidentalis, and Haemaphysalis leporispalustris ticks removed from mammals at Camp Pendleton, California. MAMMALS ------------------- I. D. H. SITE No. SPECIES spp. occidentalis leporispalustris --------------------------------------------------------------------------- San Onofre 17 Peromyscus eremicus 0 0 0 State Park (Cactus mouse) 1 Microtus californicus 1L 1L 0 (California vole) 4 Neotoma fuscipes 0 0 0 (Dusky-footed woodrat) Romeo One 10 Peromyscus californicus 0 0 0 (California mouse) 2 Mus musculus 0 0 0 (House mouse) 2 N. fuscipes 0 0 0 Alfa One 13 P. californicus 0 0 0 1 P. eremicus 0 0 0 6 Peromyscus maniculatus 2L 1L 0 (Deer mouse) 3 N. fuscipes 0 0 0 Deer Park 4 Spermophilus beecheyi 0 0 0 (California ground squirrel) Echo 1 M. californicus 0 0 0 Foxtrot 1 P. californicus 0 0 0 2 P. eremicus 0 0 0 2 Perognathus fallax 0 0 0 (San Diego pocket mouse) 1 M. californicus 0 0 0 2 N. fuscipes 1L 1L,2N 0 Bravo Two 4 P. maniculatus 3L 2L 0 3 M. californicus 0 1L 0 2 N. fuscipes 1L 0 0 Box Canyon 5 P. californicus 3L,1N 2L 0 4 P. maniculatus 19L 0 0 3 N. fuscipes 0 0 0 Kilo Two 1 Sylvilagus audobonii* 0 0 9N (Desert cottontail rabbit) --- --------------------------- TOTALS 94 30L,1N 8L,2N 9N * - roadkill L - Larva, N - Nymph --------------------------------------------------------------------------- b. Lyme Disease Risk. (1) During the field survey portion of this Lyme Disease Risk Assessment, many ticks were collected by dragging/flagging or removed from trapped rodents. This information reflected comments from installation personnel that ticks are encountered by people exposed to outdoor field environments on CAMPEN. No ticks were attracted to the carbon dioxide traps. (2) Of the ticks collected at CAMPEN, the western black-legged tick is a proven vector of Lyme disease; however, its potential to acquire and successfully transmit the disease has been reported as being less than five percent. The other species of ticks collected during this survey, the Pacific Coast tick and the American dog tick have not been implicated in Lyme disease transmission. (3) Lyme disease spirochetes were observed by immunofluorescent staining of one Pacific Coast tick. No spirochetes were found growing in the rodent ear tissue cultures. However, the presumption at this time, based on all available information, is that spirochetes may be present in the western black-legged ticks collected from deer and that deer on the installation have developed antibodies to B. burgdorferi. (4) To determine the human health risk from Lyme disease at CAMPEN, the categorization established by the Risk Definition as defined in paragraph 4a, this report, was used. The data collected during this assessment and prior studies done on ticks and deer blood at CAMPEN indicate that all the criteria for a High risk for acquiring Lyme disease are present. However, no human cases have been documented as originating on the installation. Although the criteria suggest a High risk, the actual risk to troops training in the field is probably a Moderate risk based on the relative low population density of I. pacificus encountered during the assessment and also due to the low competency of this tick vector. Although no human cases of Lyme disease have been diagnosed as originating on CAMPEN, personal protective measures to guard against tick bites would be prudent. Risk of contracting Lyme disease can be minimized by the proper wearing of clothing, by avoiding areas known to harbor high tick populations, and by the use of repellents (See Appendix D for repellent products available in the Defense General Supply Center or Self Service System). General Lyme disease reduction measures can be found in Appendix E. (5) This Activity had coordinated collection of ticks from CAMPEN during the fall, 1991 and spring 1992 deer hunts. Ticks may be sent to our USAEHA-W, ESD Laboratory at any time; we will identify and analyze submitted specimens for Lyme disease. Continuing studies such as these should further define the presence and distribution of Lyme disease on CAMPEN. 8. CONCLUSIONS. The western black-legged tick, I. pacificus, the tick vector species for Lyme disease in California, was collected at CAMPEN. Borrelia burgdorferi, the causative agent for Lyme disease, was found in one Pacific Coast tick, D. occidentalis, collected from the installation. No spirochetes were cultured from the mammal populations sampled. Personnel training, working or residing on CAMPEN may be at Moderate risk for acquiring Lyme disease. Implementation of personal protective measures for all military, civilians, and dependents using CAMPEN for outdoor training or recreation is recommended. [signature of Ronald J. Rakickas] for LESTER D. HALE Entomologist APPROVED BY: [signature] RONALD J. RAKICKAS LTC, MS Chief, Entomological Sciences Division APPENDIX A REFERENCES 1. Lyme Disease Surveillance Summary, Volume 3, No. 1, March 1992, Centers for Disease Control. 2. Memorandum, the Activity, HSHB-AW-P, 15 January 1992, subject: Lyme Disease Risk Assessment, Project No. 16-66-AF34-92, Camp Pendleton, California. 3. USAEHA-W, ESD SOP No. 6, 24 April 1991, Tick Collection Procedures. 4. USAEHA-W, ESD SOP No. 8, 25 April 1991, Small Mammal Tick and Ear Tissue Collections. 5. Burt, W. H. and R. P Grossenheider, A Field Guide to the Mammals North America north of Mexico, Third Edition, 1976, Houghton Mifflin Company, Boston, 289pp. 6. National Institutes of Health Publication No. 85-23, Revised 1985, Guide for the Care and Use of Laboratory Animals, U.S. Department of Health and Human Services. 7. USAEHA-W, ESD SOP No. 7, 25 April 1991, Procedures for Trapping and Handling Small Mammals. APPENDIX B PERSONNEL CONTACTED 1. CAPT Fredrick F. Braiand [*] Hospital Executive Officer DSN 365-1305 2. HM1 Ralph E. Clemons [H] Hospital Corpsman First Class DSN 365-3663 3. Mr. Paul Damos [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2363 4. LT Rafael J. Del Vecchio [*H] Medical Entomologist DSN 365-3663 5. Dr. Michele Ginsgerg Chief, Aids and Community Epidemiology San Diego County Department of Health Services Commercial (619) 236-3598 6. Mr. Donald Hinkel [H] Pest Control Foreman DSN 365-4709 7. LCDR William W. Kanour, Jr. [H] Head, Entomology Department Environmental and Preventive Medicine Unit No. 5 DSN 526-7077 8. Mr. James D. Lang [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2364 9. LCDR Brian P. Murphy [*H] Environmental Health Officer DSN 365-1305 10. Mr. Ronald Ramos [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2363 11. Mr. Robert J. Showmake [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2799 12. HMI Cathaleen Soderberg [*H] Hospital Corpsman First Class DSN 356-4764 13. Mr. Dung Tran [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2353 14. Mr. Chris Wickham [H] San Diego County Department of Health Services Vector Surveillance and Control Division Commercial (619) 694-2888 ----------- * Individual received an inbriefing. H Individual assisted with the field portion of the Lyme disease risk assessment. APPENDIX C TICK LOG Camp Pendleton April 92 Lyme Disease Survey [Data omitted - data summarized in above report] APPENDIX D REPELLENTS 1. Several arthropod repellents are available through the Defense General Supply Center (DGSC) or Self Service Supply System. When used in accordance with directions on the label and in conjunction with the proper wearing of clothing, they provide personal protection against a wide variety of medically important insect/arthropod pests. Availability and current pricing can be obtained by calling the DGSC at DSN 695-4865 or commercial (804) 790-4865. Repellents available for use are described below: a. Insect/Arthropod Repellent Lotion (cream, 2 fluid ounces) for application to exposed skin. The lotion, NSN 6840-01-284-3982, is not labeled for ticks, but will repel chigger mites and many biting flies. b. Permethrin Arthropod Repellent, Insect Repellent, Clothing Application (aerosol, 6 ounces) NSN 6840-01-278-1336. Seventy-five percent of the can is used to apply to the field uniform and the remainder is used to treat mosquito netting. The product provides protection from ticks and mosquitoes for a maximum of five weeks or five launderings. Apply more frequently if "buddy checks" reveal attached ticks. c. Insect Repellent Fabric Treatment (liquid, 5.1 fluid ounces) NSN 6840-01-334-2666. The contents are added to 2 gallons of water and applied with the 2-gallon sprayer from a field sanitation kit at a pressure of 55 pounds per square inch to field uniforms, mosquito netting, and tent fabric to provide protection from ticks, biting flies, and other insects. Since most sprayers are not equipped with the required pressure gauge (NSN 3740- 01-332-8746), it will be necessary to obtain a pressure gauge and filter (NSN 4330-01-332-1639), in order to complete the retrofitting. Proper application can provide protection for the normal life of the uniform (180 days in the field), six launderings of mosquito netting, and 6-9 months of treatment for tent fabric, depending on the climate. 2. Detailed directions for the use of these and other repellents can be found in the U.S. Army Environmental Hygiene Agency Technical Guide (TG) 174, Personal Protective Techniques Against Insects and Other Arthropods of Military Significance, June 1991. 3. The U.S. Army Medical Department Tick-Borne Disease Card (7189) is available from the USAEHA-W, ESD. APPENDIX E Lyme Disease Risk Reduction Measures 1. Emphasize public awareness programs to educate troops, family members, civilian employees and visitors on personal protective measures and Lyme disease. Methods should include, but not be limited to: a. Distribution of printed Lyme disease handouts, such as tick identification cards (USAMD-7189), pamphlets, and fact sheets. b. Notifications in the installation newsletter and post electronic media (e.g., closed-circuit TV), especially prior to the high-risk months (May-September). c. Making available, for viewing, videos "Lyme Disease: A growing threat" (FAUPIN No. 504494DD, Army TVT number 8-196) and "Application of the Arthropod Repellent System" (No. 708575, Army TVT number 8-232). 2. Submit any collected tick specimens (both field-collected or ticks that have been removed from individuals) alive for identification and DFA testing to USAEHA-North, Fort Meade, Maryland, 20755-5225. 3. Stock Permethrin Arthropod Repellent (NSN 6940-01-278-1336, box of 12 cans for $36.99), and 3M [Trademark] Insect Repellent (NSN 6840-01-284- 3982, box of 12 tubes, $29.30) for distribution. Emphasize tick habitat avoidance, proper wearing of clothing, and use of repellents. 4. Report all confirmed and suspected cases of Lyme disease [e.g., suspicious febrile illnesses, arthralgias, rashes, (Erythema Migrans)] by special telegraphic report [MED-16(R4)] for all soldiers and civilian medical care beneficiaries. 5. Identify high risk foci in cantonment areas via tick dragging/flagging, small mammal trapping, deer checks and the assaying of collected ticks for B. burgdorferi. Sampling should be performed in early summer when I. scapularis nymphs (the life stage responsible for most human Lyme disease infections) are active. Post DA Poster 40-5, to identify high risk areas. 6. Avoid high tick population areas for troop training or recreation. Such areas can be identified by tick dragging or flagging prior to use. Case by case surveillance is necessary due to the patchy distribution of I. scapularis. 7. Eliminate tick habitat in heavily used, infested areas (e.g., wooded recreation areas) by removing low brush and leaf litter. Tick infestations should be verified via tick flagging or dragging prior to habitat modification. Clearing should be done in low risk months (i.e., January and February). 8. Prepare, as a contingency, to treat high-use areas with pesticides to decrease tick numbers if surveillance reveals high tick numbers and if nonchemical control techniques (e.g., brush removal, mowing, raking) do not provide adequate control. --- Trademark 3M is a registered trademark of Minnesota Mining and Manufacturing Co., St. Paul, MN 55133-3053