LYME DISEASE RISK ASSESSMENT, NAVAL AIR STATION, PATUXENT RIVER, MARYLAND, 30 NOVEMBER AND 7 DECEMBER 1991 DEPARTMENT OF THE ARMY U.S. Army Environmental Hygiene Activity - North Fort George G. Meade, Maryland 20755-5225 [Seal of Department of Defense, United States of America] REPLY TO ATTENTION OF: HSHB-AN-P (40-5) 15 APR 1992 LYME DISEASE RISK ASSESSMENT NO. 16-61-0543-92 NAVAL AIR STATION PATUXENT RIVER, MARYLAND 30 NOVEMBER AND 7 DECEMBER 1991 1. REFERENCES. a. Lyme Disease Surveillance Summary, Vol. 1, No. 2, Centers for Disease Control, August 20,1990. b. Technical Information Memorandum No. 26, Lyme Disease: Vector Surveillance and Control. Armed Forces Pest Management Board, March 1990. 2. AUTHORITY. Section 335, Lyme Disease Research and Education Program, FY 92 Department of Defense Authorization Bill. 3. PURPOSE. To assess the risk of Lyme disease to Naval Air Station, Patuxent River (NASP) personnel by examining white-tailed deer for the tick vector, Ixodes spp. and to assay collected ticks for the Lyme disease etiologic agent, Borrelia burgdorferi. 4. GENERAL. a. Risk Definition. The term "risk", as used in this report, is a non-statistical evaluation of qualitative and quantitative information available to determine the potential to acquire Lyme disease. To the extent available, information evaluated includes the following elements: Past history of Lyme disease in the area, the presence or absence of the tick vector and the mammalian host population needed to sustain a viable population of the vector, the presence of B. burgdorferi in the tick population or the presence of antibodies to B. burgdorferi in the mammalian host population. Criteria for risk categorization follow: Low risk - Some elements 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 reported from the local area. High risk - All elements of the Lyme disease cycle present on the installation. b. Personnel Contacted. Mr. Kyle Rambo, Natural Resources Manager, NASP. HM1 Anne Novotny, Preventive Medicine Unit NASP. Ms. Diana McKinney, RN, Saint (St.) Mary's County health department. c. Survey Conduct. The field survey was conducted by Melissa K. Miller, Entomologist, U.S. Army Environmental Hygiene Activity - North (USAEHA-North), Fort George G. Meade (FGGM), Maryland, on 30 November 1991. Follow-up samples were collected by Mr. Kyle Rambo, Natural Resources Manager; Mr. James Sobrack, Forester; Mr. Doug Lister, Natural Resources Specialist; of the Natural Resources Branch, Public Works Department, Environmental Division, NASP on 7 December 1991 and submitted to this activity for analysis. Serum samples were assayed via Indirect Fluorescent Antibody (IFA) tests by personnel of the U.S. Army Regional Veterinary Laboratory, Fort George G. Meade, Maryland for the presence of Lyme disease antibody. Ticks were identified and assayed via Direct Fluorescent Antibody (DFA) tests by personnel of USAEHA-North, FGGM, Maryland for the presence of B. burgdorferi. d. Technical Assistance. Technical assistance or further informal advice may be obtained by contacting Chief, Entomological Sciences Division (ESD), USAEHA-North, Commercial Phone 410-677-5281/6502, (DSN 923-5281/6502). 5. METHODS. a. Tick Collection. The heads, ears, and necks of 51 hunter-shot white-tailed deer (Odocoileus virginianus) were examined immediately before or after the weigh in and tagging at the NASP deer check station. The deer hair was stroked contrary to the natural lay, using the hand to expose the skin. Ticks were removed, using fine-point (No. 5) jeweler's forceps, from the head, ears or neck of the 51 animals examined. Total examination time-per-carcass was 5 minutes. Collected ticks were placed in labeled, 20 ml humidified vials and kept cool (1.5 - 4.5 degrees C). b. Tick Testing. Ticks were assayed via DFA testing using antibody conjugate from Kirkegaard and Perry Laboratories, Inc. to determine presence of the Lyme disease spirochete, B. burgdorferi. This conjugate is affinity absorbed to minimize cross reactivity with other spirochetes. c. Blood Samples. Blood pooled in the body cavities of 21 hunter-shot deer was collected using clean plastic (4ml) disposable pipettes. Blood samples were not taken from carcasses that were rinsed with water or otherwise treated in a manner which might contaminate or invalidate the sample. Samples were placed in 7 ml labeled tubes, spun, sera were collected, and frozen (-8.5 degrees C) until IFA testing could be performed. 6. RESULTS. (See also Enclosure 1 and 2.) a. A total of 459 ticks were removed from 51 deer examined at NASP. Of the 2 sampling days, 337 ticks were removed from 22 deer, examined on 30 November 1991 and 122 ticks removed from 28 deer, examined on 7 December 1991. Forty-one (80 percent), of the deer examined, were infested with the deer tick, I. dammini. Thirty eight (15 percent) of the 257 I. dammini ticks tested were positive for the Lyme disease spirochete. b. Two (10 percent) of the 21 serum samples tested from deer examined on 30 November 1991 were positive (greater than 1:128 titer level) for B. burgdorferi antibodies. No blood samples were collected at NASP on 7 December 1991. c. Preventive Medicine at NASP reported 4 confirmed cases of Human Lyme disease on the installation in 1991 and 6 cases in 1990. Fifteen and 13 cases of human Lyme disease were reported by the county health department in St. Mary's County, the location of NASP, in 1991 and 1990, respectively. 7. DISCUSSION. This survey provides evidence that the vector and causative agent of Lyme disease are established at NASP. The potential at-risk human population (recreational and natural resources activities), availability of suitable animal hosts and environmental conditions necessary for the occurrence of Lyme disease, and past history of human Lyme disease on the installation and in the area, all make [NASP] an area warranting continued vigilance. 8. CONCLUSIONS. The presence of specimens of I. dammini on examined deer, positive DFA and IFA results from ticks and deer serum tested and information from the Preventive Medicine Unit and county health department, indicate that the present risk of contracting human Lyme disease at NASP is high. 9. RECOMMENDATIONS. The high risk category dictates immediate action. a. Implement contingency planning in accordance with guidelines in Enclosure 3. b. Conduct annual follow-up surveillance using the methods described in reference 1.b and para 5 above. Provide continued monitoring and note changes in the degree of Lyme disease threat to NASP personnel. [signature] MELISSA K. MILLER Entomologist Entomological Sciences Division APPROVED BY: [signature] JAMES T. KARDATZKE, PhD, BCE MAJ, MS Chief, Entomological Sciences Division Enclosure 1 DOD LYME DISEASE SURVEY U.S. ARMY ENVIRONMENTAL HYGIENE ACTIVITY-NORTH DATA SUMMARY - FALL/WINTER 1991 INSTALLATION Naval Air Station, Patuxent River, Maryland SURVEY DATE(S) 30 November 1991 # OF DEER EXAMINED 23 # (%) DEER EXAMINED WITH Ixodes dammini 19 (83%) # DEER SERUM SAMPLES TESTED 21 # DEER SERUM SAMPLES POSITIVE * 2 (10%) TICK SPECIMENS ----------------------------------- # COLLECTED # TESTED # POSITIVE Ixodes dammini ** 273 173 29 (17%) Dermacentor albipictus 33 33 3 (9%) Amblyomma americanum 31 26 5 (19%) --------------------------------- TOTAL TICKS 337 232 37 (16%) * positive screening titer levels greater than 1:128 ** Ixodes dammini vs. Ixodes scapularis determination in adult ticks is difficult. However, random samples of adult specimens from installations as far south as Virginia and North Carolina were all identified as I. dammini by The Curator of Ticks, U.S. National Tick Collection, at the Institute of Arthropodology and Parasitology at Georgia Southern University. Enclosure 2 DOD LYME DISEASE SURVEY U.S. ARMY ENVIRONMENTAL HYGIENE ACTIVITY-NORTH DATA SUMMARY - FALL/WINTER 1991 INSTALLATION Naval Air Station, Patuxent River, Maryland SURVEY DATE(S) 7 December 1991 # OF DEER EXAMINED 28 # (%) DEER EXAMINED WITH Ixodes dammini 22 (79%) # DEER SERUM SAMPLES TESTED 0 # DEER SERUM SAMPLES POSITIVE * 0 TICK SPECIMENS ----------------------------------- # COLLECTED # TESTED # POSITIVE Ixodes dammini ** 109 84 9 (11%) Dermacentor albipictus 3 3 1 (33%) Amblyomma americanum 11 11 3 (27%) --------------------------------- TOTAL TICKS 122 98 13 (13%) * positive screening titer levels greater than 1:128 ** Ixodes dammini vs. Ixodes scapularis determination in adult ticks is difficult. However, random samples of adult specimens from installations as far south as Virginia and North Carolina were all identified as I. dammini by The Curator of Ticks, U.S. National Tick Collection, at the Institute of Arthropodology and Parasitology at Georgia Southern University. Enclosure 3 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-7/89), 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-November). c. making available, for viewing, the video, LYME DISEASE: A growing threat (FAUPIN No. 504494DA). 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 George G. Meade, MD, 20755-5225. 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 B. 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 (or equivalent), and thereby 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. 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., 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