LYME DISEASE RISK ASSESSMENT, CAMP RIPLEY, MINNESOTA, 21-27 JUNE 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) 25 August 1992 LYME DISEASE RISK ASSESSMENT NO. 16-66-AF29-92 CAMP RIPLEY, MINNESOTA 21-27 JUNE 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, Minnesota National Guard, 9 April 1992. 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 Ripley personnel. See Appendix B for other assistance that can be obtained from the U.S. Army Environmental Hygiene Activity-West (USAEHA-W). 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 dammini) 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 CPT Michael Quintana, the Survey Officers, discussed major findings and recommendations with Camp Ripley personnel. A list of personnel contacted and personnel assisting the Survey Officers during the risk assessment is found in Appendix C. c. The field survey portion of the Lyme Disease study was conducted at Camp Ripley on 21-27 June 1992. d. This study also provided training for Camp Ripley Environmental personnel. On-the-job training conducted during the field survey portion of the assessment included: vector surveillance procedures, tick surveillance methods, small mammal trapping, and ear biopsy procedures. Camp Ripley personnel were exceptionally receptive to information on Lyme disease and personal protective measures for prevention of tick bites. e. Laboratory analyses of ticks and rodent ear tissue biopsies were conducted between 29 April-7 August 1992. 5. BACKGROUND. a. Camp Ripley is a State owned National Guard training site located about 100 miles northwest of Minneapolis/St. Paul. The City of Little Falls is 7 miles south of Camp Ripley. The installation is in Morrison County and encompasses 53,000 acres of diversified terrain. The actual maneuver/training areas are approximately 51,000 acres. Ground cover consists mainly of coniferous and mixed deciduous forests, lowland grass bordering willows, and open grassland. Camp Ripley's east boundary is the Mississippi River and the north boundary is the Crow Wing River. Camp Ripley is a year-round training post and has a training capacity for 12,000 personnel. Camp Ripley provides training for over 60,000 troops per year. Approximately 530 personnel work full-time on the installation. b. 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. c. According to the Centers for Disease Control (CDC), Fort Collins, Colorado (reference 1, Appendix A), there were 85 cases of Lyme disease occurring in Minnesota during 1991. There was one case of Lyme disease reported from Morrison County in 1990. The Camp Ripley Environmental Specialist stated that physicians at the St. Gabriels Hospital, Little Falls, Minnesota, diagnosed three people with Lyme disease during 1990, two during 1991, and two during 1992. d. This Activity collected deer ticks from rodents and from tick drags at Camp Ripley in the spring of 1989 (reference 2, Appendix A). The ticks collected in 1989 were examined by immunofluorescent staining and by darkfield microscopy. All ticks examined were found to be negative for spirochetes. Laboratory analysis performed by this Activity on ticks collected at Camp Ripley during the 1991 fall deer hunt showed that all the I. dammini and Dermacentor albipictus ticks examined by immunofluorescent staining were negative for spirochetes (reference 3, Appendix A). 6. METHODS. a. Field Survey Procedures. (1) Tick Surveys. The tick collecting methods included tick drag cloths and/or tick flags, and carbon dioxide traps. Ticks were also removed from the ears of trapped rodents on Camp Ripley. All ticks were kept alive by placing them in water-moistened vials as described in the USAEHA-W, Entomological Sciences Division (ESD) Standing Operating Procedures (SOP) No. 6 and No. 8. At each collection site, all collected ticks were identified, counted, and placed into a marked vial. Ticks collected at different sites were kep segregated and placed into separate labelled 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 being examined for attached ticks. At each collection site, attached ticks were removed from the cloth and placed in a vial labelled for that specific site. Approximately 10,000 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. At each collection site, attached ticks were removed from the cloth and placed in a labelled vial. Approximately 3,400 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 checked for ticks after 3 to 4 hours. (2) Rodent Surveys. Small rodents were captured to determine the presence of potential Lyme disease reservoir animals on Camp Ripley, and to remove ticks and take a small ear biopsy to determine the presence of spirochetes in the rodents. Rodents trapped at Camp Ripley were identified using "A Field Guide to the Mammals, North America, north of Mexico" (reference 6, Appendix A). 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. (a) Small mammals were captured in live traps (3x3x10 inches) set at several sites on the installation. At each site several trapping locations were selected, each containing two or more trap lines. The traps were usually placed near rivers, stream beds, ponds, or on hillsides, with the traps approximately 10 meters apart. At least 25 traps were set for one night at each site. (b) Each rodent was anesthetized before removing any ticks or taking an ear biopsy. Each ear biopsy was placed in a labelled vial containing a phosphate buffer solution and then frozen on dry ice. All biopsies were kept frozen until assayed for Lyme disease. (3) Specimen Handling Procedures. The ticks collected from rodents and from dragging/flagging vegetation during 21-23 June, were shipped via overnight mail to the USAEHA-W, ESD Laboratory and maintained at 18 degrees C until assayed for Lyme disease. All the ear tissue biopsies and those ticks collected from 24-27 June were hand-carried to the USAEHA-W, ESD Laboratory for Lyme disease bioassay. b. Laboratory Assay Procedures. (1) The midguts of 47 deer ticks, I. dammini and 148 American dog ticks, Dermacentor variabilis, were dissected and examined for spirochetes using immunofluorescent microscopy. In addition, four deer ticks and two American dog ticks were dissected and examined for spirochetes using darkfield microscopy. (2) Four tick pools consisting of one to five deer ticks per pool were cultured in BSK II media for spirochetes. (3) Sixty- eight rodent ear biopsies were cultured in BSK II media at the ESD laboratory. Each inoculated culture was examined under the darkfield microscope every 7 days for 21 days for spirochete growth. If no spirochetes were found during this period, the samples were considered to be negative for B. burgdorferi. (4) Spirochete positive BSK II media cultures were taken to the CDC Lyme disease laboratory, at their request, for confirmation as B. burgdorferi. The genomic deoxyribonucleic acid (DNA) was extracted from the spirochetes, amplified, and then assayed for B. burgdorferi using the Polymerase Chain Reaction (PCR) technique. 7. FINDINGS AND DISCUSSION. a. Tick Collections. Ticks were collected from humid habitats around streams, rivers, ponds, and hillsides. Table 1 shows the sites, map coordinates, species, and number of adult I. dammini and D. variabilis collected by the various methods at Camp Ripley. There were 11 I. dammini and 932 D. variabilis collected by dragging and flagging. Table 2 shows the number of nymphs and larvae of I. dammini and D. variabilis removed from the rodents. b. Rodent Collections. Six species of rodents were captured at eight sites on Camp Ripley (Table 2). The eastern chipmunk was the most common rodent captured. c. Laboratory Results. Detailed information on the sites, species of ticks and rodents, and laboratory results are given in Appendix D. (1) Ticks. Seventeen of 47 (36 percent) deer ticks examined by immunofluorescent microscopy were positive for spirochetes. However, 10 positive ticks were removed from one rodent. Two pools of deer ticks (all from the same eastern chipmunk) cultured in BSK II media for spirochetes were positive for B. burgdorferi. The spirochetes sent to CDC were confirmed as B. burgdorferi. The deer ticks which tested positive had been removed from five different animals representing three species of rodents (three eastern chipmunks, one deer mouse and one boreal redback vole). All American dog ticks were negative for this spirochete. TABLE 1. Number of adult Ixodes dammini and Dermacentor variabilis collected from drags/flags and from carbon dioxide traps at Camp Ripley, Minnesota. NUMBER OF TICKS -------------------------------------------- SITE I. dammini D. variabilis Total --------------------------------------------------------------------------- Blue Barn Training Area 0 44 44 (868,249)* East Boundary Road 2 36 38 (935,095) Picnic Area 5 3 70 73 (937,286) Pipe Island Training Area 2 87 89 (933,108) Sidi Nsir Road 1 95 96 (944,147) Minshaw Trail Site 0 101 101 (923,172) East Boundary and Chorwan Road 0 84 84 (957,249) Pusan Road and Inchon Trail 0 29 29 (905,296) Wonsan and Chorwan Training Area 1 49 50 952,266) North of Goose Pond 0 110 110 (897,087) M-5 Range 0 10 10 (916,135) D-Park 0 19 19 (966,035) Biathlon Course 1 89 90 (908,089) Toul Road 1 109 110 (948,075) ---------------------------------------------------- TOTAL TICKS COLLECTED 11 932 943 * Map coordinates given as longitude and latitude; based on Camp Ripley & Vicinity, Series V772S, Edition 1-TPC (Scale 1:50,000), Published by the U.S. Army Topographic Command, Washington, D. C., dated 1969. -------------------------------------------------------------------------- (2) Rodent Ear Biopsies. Sixty-eight ear biopsies were cultured in BSK II media for spirochetes (Table 2). Two eastern chipmunks, one from M-5 Range and the other from Toul Road, were positive for B. burgdorferi, suggesting that the spirochete had circulated within the population sampled at Camp Ripley. The spirochetes sent to CDC were confirmed as B. burgdorferi. TABLE 2. Number of Ixodes dammini and Dermacentor variabilis removed from rodents at Camp Ripley, Minnesota. RODENTS ------------------- I. D. SITE No. Species dammini variabilis --------------------------------------------------------------------------- Luzon and Normandy Roads 2 Peromyscus maniculatus 0 1N,5L (856,124)* (deer mouse) Blue Barn Training Area 2 Napaeozapus insignis 0 7L (woodland jumping mouse) 4 Tamias striatus 1N 1L (eastern chipmunk) Normandy Road 3 Clethrionomys gapperi 0 6N,12L (846,133) (boreal redback vole) 1 Peromyscus leucopus 0 0 (white-footed mouse) 3 P. maniculatus 1L 7L 7 Tamias striatus 0 1L Pusan Road and Inchon Trail 1 P. leucopus 0 3L 7 P. maniculatus 0 5N,30L Wonsan and Choran Training 1 C. gapperi 0 3N Area 3 P. maniculatus 0 1N,27L 5 Zapus hudsonius 1N 1N,1L (meadow jumping mouse) 1 T. striatus 0 0 Broken Bow Creek 5 C. gapperi 2L 4N,5L (938,091) 3 Z. hudsonius 1N 1L 1 T. striatus 2L 0 M-5 Range 1 C. gapperi 0 0 1 P. maniculatus 1N,5L 1L 12 T. striatus 8N,41L 1L Toul Road 2 C. gapperi 1L 4N,38L 1 P. maniculatus 0 0 1 Z. hudsonius 0 0 1 T. striatus 0 0 ----- ---------------- TOTALS 68 12N,52L 25N,140L * Map coordinates. See Table 1 for details. L - Larva, N - Nymph, --------------------------------------------------------------------------- d. 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 the comments from installation personnel that people find ticks on themselves when outdoors on Camp Ripley. No ticks were collected using the carbon dioxide traps. (2) Eleven adult deer ticks were collected form seven different sites during dragging/flagging operations. There were 64 deer ticks removed from 4 species of rodents at 8 different sites on Camp Ripley. The deer tick is a known vector of Lyme disease. Many American dog ticks were collected from dragging/flagging and from captured rodents at Camp Ripley; however, this tick has not been implicated as a vector of Lyme disease. (3) Lyme disease spirochetes were recovered from the deer ticks and from the ear tissue samples from rodents collected during this study. (4) To determine the human health risk from Lyme disease at Camp Ripley, the Risk Definition as listed in paragraph 4a, this report was used. The data collected during this assessment indicated that all the criteria for a High risk for acquiring Lyme disease were present. Although no human case has been documented as originating on the installation, cases have been diagnosed by physicians in Little Falls, which is located 7 miles from the installation. There may be two possible reasons why no human cases have originated on Camp Ripley. The first is the low number of I. dammini found in the field during this and prior studies. Another reason is that, until this year, no spirochetes were found on the installation. Personal protective measures to guard against tick bites must be emphasized. 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 E for repellent products available in the Defense General Supply Center or Self Service System). General Lyme disease reduction measures can be found in Appendix F. (5) Camp Ripley had implemented the following Lyme disease prevention program: (a) The Environmental Specialist was appointed as the Lyme Disease coordinator for the installation. (b) A good Lyme disease awareness program had been developed for personnel and troops assigned to Camp Ripley. Active duty, National Guard, and Reserve Troop commanders, advance party personnel, and other personnel working or training on the installation received a briefing on Lyme disease and were given educational material such as tick cards and Lyme disease fact sheets. The video entitled "Lyme Disease, a Growing Threat" was also shown. (c) The Troop Medical Clinic personnel have been following a Lyme disease protocol for treating soldiers and other personnel who have attached ticks or have been bitten by a tick. (d) Insect repellents and a permethrin arthropod repellent were available for purchase at the Army and Air Force Exchange Services prior to this assessment when Lyme disease was considered to be a Low risk. Since Camp Ripley personnel were notified telephonically that Lyme disease spirochetes were found in deer ticks and rodent ear biopsies during this assessment, permethrin repellent is being issued to the troops. (e) Since 1989, environmental personnel conducted tick surveillance each year to determine if the population of deer ticks was increasing. The Lyme Disease Coordinator stated that personnel from the Environmental Office will continue to conduct tick surveillance on the installation. (6) This Activity had coordinated collection of ticks from Camp Ripley during the fall 1991 deer hunt. Ticks sent to our USAEHA-W, ESD Laboratory were identified and analyzed for Lyme disease. This Activity will continue to conduct further Lyme disease studies to define the distribution patterns and host reservoirs of Lyme disease on Camp Ripley. 8. CONCLUSIONS. The deer tick, I. dammini, the vector for Lyme disease in Minnesota, was collected at Camp Ripley. Borrelia burgdorferi, the causative agent for Lyme disease, was found in the tick and small mammal populations sampled. According to the U.S. Army Environmental Hygiene Agency Lyme disease risk criteria, personnel training, working, or residing on Camp Ripley are in the High risk category for acquiring Lyme disease. Camp Ripley personnel were exceptionally receptive to information on Lyme disease and had a good personal protection program for the prevention of tick bites on the installation. [signature] LESTER D. HALE Entomologist [signature] MICHAEL QUINTANA CPT, MS Entomologist APPROVED BY: [signature - unreadable] for THOMAS P. GARGAN II MAJ, 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, this Activity, HSHB-AW-P, 11 September 1989, subject: Pest Profile No. 16-66-0534-89, Lyme Disease Survey, Camp Ripley, Camp Ripley, Minnesota, 5-9 June 1989. 3. Memorandum, this Activity, HSHB-AW-P, 21 January 1992, subject: Lyme Disease Risk Assessment, Project No. 16-66-AC56-92, Camp Ripley, Minnesota. 4. USAEHA-W, ESD SOP No. 6, 24 April 1991, Tick Collection Procedures. 5. USAEHA-W, ESD SOP No. 8, 25 April 1991, Small Mammal Tick and Ear Tissue Collections. 6. 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. 7. 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. 8. USAEHA-W, ESD SOP No. 7, 25 April 1991, Procedures for Trapping and Handling Small Mammals. APPENDIX B TECHNICAL ASSISTANCE Technical advice and/or consultation on pest management problems, to include on-site assistance, may be obtained by telephone from our Activity, DSN 943-8090. Please inform your Major Command Pest Management Consultant if you desire to request on-site assistance from our Activity. Technical services that we can assist you with are as follows: 1. Entomological laboratory support 2. Environmental laboratory support 3. Hazardous waste management 4. Industrial hygiene management 5. Medical systems safety and health 6. Sanitation and hygiene 7. Wastewater management 8. Water supply management 9. Worksite hazards management 10. Cholinesterase testing management For assistance in any of the above listed programs, please call: Environmental Health and Engineering Division - DSN 943-8100 Field sanitation and hygiene; potable, recreational and wastewater quality; hazardous waste management; document/design reviews. Industrial Hygiene Division - DSN 943-8881 Industrial hygiene; hazard communication; protective equipment programs; document/design reviews. Environmental Laboratory Division - DSN 943-3293 Routine and emergency analysis of water, soil, and occupational health- related samples. Cholinesterase Laboratory Division - DSN 943-4838 Testing of red blood cell-cholinesterase (RBC-ChE) specimens and quality assurance consultations and training for RBC-ChE labs. During non-duty hours calls will be recorded by an answering machine and returned the next day. Many additional services are available from our parent organization, the U.S. Army Environmental Hygiene Agency, and are described in AEHA Pamphlet 40-2, Directory of Services (published annually). We will gladly coordinate any additional services you request and that we cannot provide, with our parent organization. APPENDIX C PERSONNEL CONTACTED 1. Mr. Ben Bertsch (H) Environmental Intern DSN 871-7201 2. MAJ Martin Breaker (H) Environmental Officer DSN 871-7201 3. COL Benton D. Murdock (*) Post Commander DSN 871-7321 4. SFC Dennis F. Myers (H) Environmental Protection Specialist DSN 871-7201 5. Mr. Martin J. Skoglund (*H) Environmental Specialist DSN 871-7201 6. Mr. Trevor Swenson (H) Environmental Intern DSN 871-7201 7. Ms. Debra Yliniemi (H) Environmental Intern DSN 871-7201 ----------- * Individual received an inbriefing. H Individual assisted with the field portion of the Lyme disease risk assessment. APPENDIX D [untitled tick log] [Data omitted - data summarized in above report] APPENDIX E 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: a. Insect/Arthropod Repellent Lotion (cream, 2 fluid ounces). 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 through six normal launderings. 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 50 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. 3. The U.S. Army Medical Department Tick-Borne Disease Card (7189) is available from the USAEHA-W, ESD. APPENDIX F Lyme Disease Risk Reduction Measures 1. Emphasize public awareness programs to educate troops, dependents, civilian employees and visitors on personal protective measures and Lyme disease. Methods should include, but are not 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 (April-September). c. Making available, for viewing, video and 35mm slide format presentations on Lyme disease that are available from this Avtivity. 2. Submit any collected tick specimens (both field-collected or ticks that have been removed from individuals) for identification and immunofluorescent staining or darkfield microscopy testing to the Entomological Sciences Division, U.S. Army Environmental Hygiene Activity-West, Fitzsimons Army Medical Center, Aurora, CO 80045-5001. 3. Stock Permethrin Arthropod Repellent (NSN 6840-01-278-1336, 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 and the 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 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 Borrelia burgdorferi. Sampling should be performed in early summer when I. dammini nymphs (the life stage responsible for most human Lyme disease infections) are active. Post DA Poster 40-5, and thereby identify high risk areas. DA Poster 40-5 can be obtained by writing to the Commander, U.S. Environmental Hygiene Agency, ATTN: HSHB-MR-E, Aberdeen Proving Ground, MD 21010-5422 or by telephone: DSN 584-3613 or Commercial (410) 671-3613. 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. dammini. 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., November - 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