LYME DISEASE RISK ASSESSMENT, FORT RILEY, KANSAS, 11-15 JUNE 1993 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) 16 August 1993 LYME DISEASE RISK ASSESSMENT NO. 16-66-A12H-93 FORT RILEY, KANSAS 11-15 JUNE 1993 1. REFERENCE. 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, U.S. Army Health Services Command, 7 July 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 Fort Riley 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, the black-legged tick, Ixodes scapularis, and the mammalian host population needed to sustain a viable population of the vectors. (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. The criteria for risk categorization are: Low risk - Some element of the Lyme disease cycle identified in nearby areas but not on the installation. Moderate risk - Some 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. c. Mr. William E. Irwin, the Survey Officer, discussed the findings and recommendations with Fort Riley personnel. A list of personnel contacted and personnel assisting the Survey Officer during the risk assessment is found in Appendix C. d. The field survey portion of the Lyme Disease Risk Assessment was conducted at Fort Riley on 11-15 June 1993. The laboratory analyses of ticks and rodent ear biopsies were conducted between 14 June - 9 July 1993. 5. BACKGROUND. a. Fort Riley is located in eastern Kansas in three counties (Riley, Clay, and Geary) 130 miles west of Kansas City, Kansas. The major portion of the installation is the firing range fan and impact area. The Republican and Kansas Rivers border the installation on the West and South, respectively. Variation of habitat is considerable with old growth forests, woodlands, grasslands, shrub-lands, and previously farmed land returning to natural prairie. The terrain is mostly a gently rolling plateau between 1000 and 1400 feet with a number of creeks and canyons draining into the bordering rivers. b. There have been a number of cases of Lyme disease reported from Fort Riley between 1988 and 1989. However, these soldiers were probably infected while at summer camp at Fort McCoy, Wisconsin (Reference 1). There were 18 confirmed cases of Lyme disease reported for 1992 in the state of Kansas (Reference 2). 6. METHODS. a. Field Survey Procedures. (1) Rodent Surveys. Small rodents were captured to determine if they were reservoirs for Lyme disease by taking a small ear biopsy for culture. Each rodent was also screened for ticks which were removed for additional analysis. Rodents trapped at Fort Riley were identified using "A Field Guide to the Mammals, North America, north of Mexico" (Reference 5). 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, Entomological Sciences Division (ESD) Standing Operating Procedure (SOP) No. 7. (2) Tick Surveys. Ticks were collected by removing them from the ears of rodents trapped on Fort Riley. In addition, ticks were collected by contract personnel and picked up by this Activity during the survey (Table 2). Ticks were also collected from approximately 2000 meters of drags/walks. Most ticks were kept alive by placing them in water-moistened vials, as described in the USAEHA-W, ESD SOPs NO. 6 and No. 8. Ticks collected at different sites or off individual rodents were kept segregated, placed into separately labeled vials, and subsequently sent to the USAEHA-W, ESD Laboratory for identification and bioassay. b. Laboratory Assay Procedures. (1) All rodent ear biopsies were surface decontaminated, cut into small pieces, and placed in BSK II, a liquid culture medium specially developed to promote the growth of B. burgdorferi. If any of the trapped rodents were serving as the reservoir hosts for Lyme disease, the spirochetes should grow in the medium. (2) All ticks collected from the survey were processed by using either darkfield or immunofluorescent microscopy, culturing, or by using the Polymerase Chain Reaction (PCR) technique. 7. FINDINGS AND DISCUSSION. a. Tick Collections. Two groups of people (contracted wildlife biologists and USAEHA-W personnel) collected ticks from rodents at Fort Riley during the months of May and June 1993. The wildlife biologists collected 193 ticks from 30 rodents between 7-28 May (Table 1). The USAEHA-W personnel collected 33 ticks from 38 trapped mammals between 11-14 June (Table 2). In addition five ticks were collected from drags/walks. This information suggests that ticks are more abundant in May rather than in June. b. Rodent Collections. Three species of rodents from 19 transects were trapped by contractors on Fort Riley (see Table 1). The White-footed mouse was the most common rodent captured in both collections. Seven species of mammals were captured from six sites by USAEHA-W personnel (see Table 2). c. Laboratory Results. Detailed information on the laboratory results, the trapping sites, and the species of ticks and rodents collected are given in Appendix D. (1) Ticks. All of the ticks examined by darkfield microscopy, immunofluorescent microscopy, and PCR were negative for B. burgdorferi. (2) Rodent Ear Biopsies. Thirty-seven rodent ear biopsies were cultured in BSK II media for spirochetes. All samples were negative for B. burgdorferi, suggesting that the spirochete had not circulated within the small number of rodents sampled at Fort Riley. Ear biopsies were not collected from rodents listed in Table 2. d. Lyme Disease Risk. (1) No Lyme disease spirochetes were recovered from either the ticks or from the rodent ear biopsies collected during this assessment. (2) The categorization defined in paragraph 4a were used to describe the human health risk from Lyme disease at Fort Riley. The data collected during this assessment indicated that only one criterion for acquiring Lyme disease was present; the tick vector. One specimen of I. scapularis has been found in Riley County (collected from a white-tailed deer on Fort Riley); however, the collection of this species was an isolated incident. No further specimens of this species have been collected, and it appears that I. scapularis, while found, has not become established in this part of Kansas. Even though human cases have been diagnosed at Fort Riley, no human cases have been documented as originating on the installation according to the Lyme disease coordinator at Fort Riley (see paragraph 5b). While the risk definition criteria suggest a Moderate risk, based on the one Table 1. Ixodes, Dermacentor, and Amblyomma spp. Ticks Removed from Mammals at Fort Riley, Kansas during 7-28 May 1993 by Contract Wildlife Biologists --------------------------------------------------------------------------- Mammals ---------------------------- Ixodes Dermacentor Amblyomma Site No. Species spp. variabilis americanum --------------------------------------------------------------------------- Transect 6 2 Peromyscus leucopus 0 6N, 14L 0 (White-footed mouse) Transect 8 2 Peromyscus leucopus 0 18L 0 (White-footed mouse) Transect 11 1 Peromyscus leucopus 0 10L 0 (White-footed mouse) Transect 15 1 Peromyscus leucopus 0 1N, 1L 0 (White-footed mouse) Transect 23 1 Peromyscus leucopus 0 6N 0 (White-footed mouse) Transect 24 3 Peromyscus leucopus 1L 2L, 5N 0 (White-footed mouse) Transect 26 1 Reithrodonomys 0 1L 0 megalotis (Western harvest mouse) Transect 36 1 Peromyscus leucopus 0 1N, 9L 0 (White-footed mouse) 1 Peromyscus maniculatus 0 13N 0 (Deer mouse) Transect 43 1 Peromyscus leucopus 0 14N 0 (White-footed mouse) Transect 52 1 Peromyscus leucopus 0 1A, 2N 0 (White-footed mouse) Transect 55 2 Peromyscus leucopus 0 4N, 25L 0 (White-footed mouse) 1 Peromyscus maniculatus 0 6N, 1L 0 (Deer mouse) Transect 59 1 Peromyscus leucopus 0 3L 0 (White-footed mouse) Transect 62 1 Peromyscus leucopus 0 1L 1L (White-footed mouse) Transect 75 1 Peromyscus leucopus 0 8N 1N, 4L (White-footed mouse) 1 Reithrodonomys 0 2N 0 megalotis (Western harvest mouse) Transect 77 1 Peromyscus leucopus 1L 0 0 (White-footed mouse) Transect 78 1 Peromyscus leucopus 0 1L 0 (White-footed mouse) Transect 121 1 Peromyscus leucopus 0 3N 0 (White-footed mouse) Transect 127 1 Peromyscus leucopus 0 3N, 2L 0 (White-footed mouse) 1 Peromyscus maniculatus 0 1L 0 (Deer mouse) 1 Reithrodonomys 0 1L 0 megalotis (Western harvest mouse) Transect 132 2 Peromyscus maniculatus 0 8N, 12L 0 (Deer mouse) ----- ---------------------------- TOTAL 30 2L 1A, 84N, 1N, 5L 100L --------------------------------------------------------------------------- A - Adult, N - Nymph, L - Larva. --------------------------------------------------------------------------- Table 2. Dermacentor spp. Ticks Removed from Mammals at Fort Riley, Kansas During 11-14 June 1993 by USAEHA-W Personnel --------------------------------------------------------------------------- Mammals ---------------------------- Dermacentor Site No. Species variabilis --------------------------------------------------------------------------- Creek and 2 Neotoma floridana 0 Kansas River (Eastern woodrat) 2 Peromyscus leucopus 3L (White-footed mouse) 1 Peromyscus maniculatus 0 (Deer mouse) 1 Sigmodon hispidus 5N (Hispid cotton rat) East of Sand 1 Didelphis marsupialis 2A Storage Area (Oposum) 2 Peromyscus leucopus 0 (White-footed mouse) Wildcat Creek 1 Blarina brevicauda 0 (Short-tailed shrew) 6 Peromyscus leucopus 2N, 1L (White-footed mouse) 1 Peromyscus maniculatus 0 (Deer mouse) Bivouac Area 1 Microtus ochrogaster 0 (Prairie vole) 4 Neotoma floridana 0 (Eastern woodrat) 3 Peromyscus leucopus 9N (White-footed mouse) 1 Peromyscus maniculatus 0 (Deer mouse) 1 Sigmodon hispidus 0 (Hispid cotton rat) Obstacle Course 1 Microtus ochrogaster 0 (Prairie vole) 1 Neotoma floridana 0 (Eastern woodrat) 2 Peromyscus leucopus 0 (White-footed mouse) Above Breakneck Canyon 3 Peromyscus leucopus 0 (White-footed mouse) 3 Peromyscus maniculatus 2N (Deer mouse) 1 Sigmodon hispidus 0 (Hispid cotton rat) ----- ------------- TOTALS 38 2A, 18N, 4L --------------------------------------------------------------------------- A - Adult, N - Nymph, L - Larva. --------------------------------------------------------------------------- collection of I. scapularis, the actual risk to personnel residing and training is probably Low based on the virtual absence of a known vector tick species on the installation. (3) Although no human cases of Lyme disease have been diagnosed as originating on Fort Riley, personal protective measures to guard against tick bites would be prudent. Risk of contracting any tick-borne disease can be minimized by the proper wearing of clothing, 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 Supply System). General Lyme disease reduction measures can be found in Appendix F. (4) Ticks may be sent to our USAEHA-W, ESD Laboratory at any time; we will identify and analyze submitted specimens for Lyme disease. Continuing surveillance should further define the presence and distribution of ticks and the risk of acquiring Lyme disease on Fort Riley. Additional collections of ticks should be made from deer during the hunting season in the fall of 1993, and from rodents trapped throughout the year. Any ticks collected should be identified to genus at the installation and only suspected vector species should be sent to USAEHA-W for analysis. Collection kits will be sent to the Preventive Medicine Service upon request. 8. CONCLUSIONS. Amblyomma americanum, the Lone Star tick, a suspected vector of Lyme disease, was collected at Fort Riley. The black-legged tick, Ixodes scapularis, another suspected vector species for Lyme disease in the state of Kansas, was not collected at Fort Riley during this survey but had been collected in the past. A third tick, in the genus Ixodes, was collected but could not be identified to species. This subgenus, Ixodes (Pholeoixodes), has some species that are believed to transmit Lyme disease, but ticks in this group are not considered important vectors as they rarely bite humans. Borrelia burgdorferi, the causative agent for Lyme disease, was not found on the installation. Personnel training, working or residing on Fort Riley are at Low risk for acquiring Lyme disease; however, implementation of personal protective measures for all military, civilians, and dependents using Fort Riley for outdoor training or recreation is recommended as a good preventive medicine practice. 9. RECOMMENDATIONS. a. Use personal protective measures to protect individuals potentially exposed to ticks as discussed in paragraph 7d(3), this report. b. Collect ticks at Fort Riley during different times of the year as discussed in paragraph 7d(4), this report. [signature] WILLIAM E. IRWIN Lyme Disease Investigator APPROVED BY: [signature] THOMAS P. GARGAN II MAJ, MS Chief, Entomological Sciences Division APPENDIX A REFERENCES 1. Memorandum, this Activity, HSHB-AW-P, 23 February 1990, subject: Lyme Disease Consultation No. 16-66-0502, Fort Riley, Kansas, 24-27 November 1989. 2. Morbidity and Mortality Weekly Report, Volume 42, No. 18, May 1993, Massachusetts Medical Society. 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. 8. Mock, D. E., D. B. Brillhart, and S. J. Upton, Field Ecology of Lyme Disease in Kansas, Kansas Medicine, September 1992. 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 at 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 943-3318 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 environmental 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. William Wildman Environmental Technician U.S. Army Medical Department Activity (USA MEDDAC) Preventive Medicine Service (PVNTMED Svc) Fort Riley, KS 66442-5037 DSN 856-7471 2. 1LT Robert A. Donovan Environmental Science Officer USA MEDDAC, PVNTMED Svc Fort Riley, KS 66442-5037 DSN 856-7471 3. Mr. Herb Ables Chief, Natural Resource Branch Department of Engineering and Housing (DEH) Fort Riley, KS 66442-5037 DSN 856-6211 Commercial (913) 239-6211 4. Mr. Craig Phillips Range Conservationist Natural Resource Branch, DEH Fort Riley, KS 66442-5037 DSN 856-6211 Commercial (913) 239-6211 5. Mr. Jim Brethour Range Control Safety Officer Fort Riley, KS 66442-5037 DSN 856-4281 Commercial (913) 239-4281 APPENDIX D FORT RILEY TICK LOG 1993 [Data omitted - data summarized in above report] APPENDIX E REPELLENTS 1. Several repellent products are available through the Defense General Supply Center (DGSC) or Self-Service Supply System. When used in accordance with label directions and in conjunction with the proper wearing of the uniform, 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 for: a. Insect/Arthropod Repellent Lotion (cream, 2 fluid ounces), NSN 6840-01-0284-3982. The lotion 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, 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, especially prior to the high-risk months (April to September). c. Making available video and 35mm slide format presentations on Lyme disease; both are available from this Activity. 2. Forward any collected live tick specimens (either field-collected ticks or those 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, 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 spring when Ixodes scapularis nymphs (the life stage responsible for most human Lyme disease infections) are active. 6. 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 telephone DSN 584-3613 or Commercial (410) 671-3613. 7. Avoid high tick population areas for troop training or recreation. Such areas can be identified by dragging or flagging for ticks prior to use. Case-by-case surveillance is necessary due to the patchy distribution of I. scapularis and A. americanum. 8. 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 to February). 9. 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