Installation Pest Management Consultation, Camp Roberts, California, 17-20 January 1989 DEPARTMENT OF THE ARMY U.S. Army Environmental Hygiene Agency Aberdeen Proving Ground, Maryland 21010-5422 [Seal of Department of Defense, United States of America] REPLY TO ATTENTION OF: HSHB-MR-EMG 22 January 1990 MEMORANDUM FOR Commander, U.S. Army Health Services Command, ATTN; HSCL-P, Fort Sam Houston, TX 78234-6000 SUBJECT: Installation Pest Management Consultation No. 16-44-0512-90, Camp Roberts, California, 17-20 January 1989 1. REFERENCES. a. AR 40-5, Preventive Medicine, 1 June 1985. b. AR 420-76, Pest Management, 3 June 1986. 2. AUTHORITY. a. Memorandum, HSC, HSCL-P, 10 February 1988, subject: Lyme Disease on Army Installations, Project No. 16-44-0520-88. b. Telephone conversation between MAJ Mary Wiseman, Environmental Coordinating Officer, California Army National Guard Bureau, and CPT George W. Korch, Jr., U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, MD. 3. PURPOSE. a. To characterize the spatial distribution and relative frequency of the California black legged tick, Ixodes pacificus, on Camp Roberts as determined by drag cloth survey and infestation on small mammals. b. To determine the prevalence of infection of indigenous tick species with the Lyme disease (LD) agent, Borrelia burgdorferi. c. To assess the prevalence of specific antibody to B. burgdorferi in the small mammal population. d. To evaluate the existing risk of LD exposure to personnel at Camp Roberts, and offer recommendations on tick surveillance, tick control, and reduction of human exposure to LD. e. To gather information on possible human cases of Lyme disease acquired on the installation. f. To present information concerning the epidemiology, and symptomatology of this disease to installation medical and civilian personnel, and to discuss protective measures to reduce the risk of exposure to the vector species. 4. GENERAL. a. Personnel Contacted. See Appendix A for a list of personnel contacted and/or briefed. b. Survey Conduct. The survey was conducted by CPT George W. Korch, Entomologist, Entomological Sciences Division, U.S. Army Environmental Hygiene Agency, APG, MD, and Dr. Darrell Hale, Entomologist, and MAJ Thomas Gargan, U.S. Army Environmental Hygiene Activity - West (USAEHA-W), Fitzsimons Army Medical Center, Aurora, CO, 17-20 January 1989. c. Background. (1) Camp Roberts Military Training Site is a California National Guard operated facility located approximately 10 miles north of Paso Robles, California, within the San Joaquin Valley and overlaps the borders of Monterey and San Luis Obispo Counties. The installation comprises 34,700 acres of land. (2) The installation is bordered on the west by the Pacific Coastal Mountain range, and on the east by high rolling hillsides leading to a flat alluvial plain. The Nacimiento River runs from the southwest to the northeast through the installation separating the impact area (8700 acres) to the northwest of the river from the operational training area to the southeast. The Salinas River also passes through the installation on the east, separating the East Garrison area from the remainder of the facility. (3) The terrain in the center and southeastern sections includes flat plains and moderate relief. This area is primarily used by combined arms maneuver units, and contains most of the firing points for artillery. The vegetation in this area is mainly grassland with some stands of oak. The terrain along the southwestern boundary is mountainous with denser oak cover, and is reserved for infantry maneuver. The East Garrison Maneuver Area is used for armored infantry training, and by MATES for storage and maintenance of vehicles. The vegetation growth along the rivers is much denser, and more varied, while chaparral predominates on the upland areas on the higher slopes of the southwest. (4) Camp Roberts is used approximately 300 days of the year by units from all branches of the military. The number of troops using this facility vary from year to year, with a troop strength of 34,912 (259,936 man days) in 1981 to a high of 82,141 troops (655,608 man days) in 1986. During this peak year the active duty component (primarily 7th Division, Fort Ord) accounted for 43% of the training population, the National Guard for 49%, and the Reserve for 7%. (5) The proportion of active duty troops has declined steadily to 10% in 1988, while the proportion of National Guard and Reserve populations now represent 70% and 19.5% of the trainees, respectively. Peak training activity occurs on the installation from April through June. (6) There are no medical assets permanently assigned to this installation. All visiting battalion-sized or larger unit must provide personnel to staff the Troop Medical Clinic. No medical support is available for company-size or smaller units. Range control provides medical evacuation coverage from Ft. Hunter-Liggett, as needed. No Preventive Medicine personnel are assigned to this installation either, however, Fort Ord has provided limited support in the past. (7) This installation serves as a natural sanctuary for the endangered San Joaquin kit fox. The presence of this species on the installation has prompted tremendous conservation efforts and resulted in strict environmental management practices, leading to conservation efforts for prey species as well as the target species. The pressure to maintain a pristine habitat for this species would likely have an impact on possible tick control methods. Sizable populations of black-tailed deer (Odocoileus hemionus) and Tule elk (Cervus nannodes) are reportedly present especially on the impact area. (8) Lyme disease is a bacterial disease transmitted to man and animals via the bite of an infective tick. A synopsis of this disease is presented in Appendix B with regard to the transmission cycle found in California. This information can be abstracted by the California National Guard Bureau, as they see fit, to produce Lyme disease fact sheets for personnel. (9) Four human cases of Lyme disease were reported to the California State Department of Health between 1983-1987 from the two counties which include Camp Roberts. No infected ticks have been identified by the Health Department in these counties to date. 5. FINDINGS AND DISCUSSION. a. LD surveillance, occurrence, and practices to date. (1) No human cases of Lyme disease have been reportedly acquired on Camp Roberts, according to the Office of the Army Surgeon General and the California State Department of Health. No anecdotal cases, or unreported cases were noted. (2) Reportedly, no surveillance for either the presence of the etiologic agent of disease or the distribution of tick vectors has occurred on the installation to our knowledge. b. Lyme Disease Briefings. The survey officer presented a one hour seminar on Lyme disease symptoms, ecology, epidemiology, and personal protective measures to the Installation Commander, and management personnel from the Safety Office, Facilities Engineering Division, and Training and Operations Office. c. Tick and Serum Collection Activities. (1) Two trapping areas were established to sample small mammals from the installation in order to obtain tick specimens and serum samples. The first site was located in Sherwood Forest, Training Site P (Map coordinate OF 002,630) and the second was located along Boy Scout Road, Training Site R (Map coordinates OF 960,585). Twenty five traps were placed per site, along 3 different transects. Intertrap distance was 15 m. Six National live traps of sufficient size to capture ground squirrels were also set in Sherwood Forest. (2) Trapping was performed for two consecutive nights. Observed ticks were removed, and a blood specimen was taken from each animal for serologic assay by immunofluorescent antibody test (See Appendix D). Animals were identified to species, weighed, sexed, measured, and released at point of capture. (3) Host questing ticks were collected from vegetation by dragging a 1 m square white flannel cloth along 10 consecutive 10 m transects per person. A total of 1200 m square per site were thus sampled (unless otherwise noted). Seven sites were evaluated. A description of these sites is provided in Appendix E. (4) A total of 35 small mammals, representing 7 species were collected between the two sites (Table 2, App. F). Thirty-three ticks were removed from five of these animals. None of these mammals were seropositive (titer less than 1:32) for Borrelia burgdorferi by immunofluorescent antibody testing. (5) We collected 70 ticks on drags, 49 Ixodes pacificus adults and 21 Dermacentor occidentalis adults ( Table 3, App. F) over 7.5 km of dragging. Twenty-five Ixodes specimens were sent to the Connecticut Agricultural Experiment Station, New Haven, CT for spirochete isolation attempts. Only 4 of the remaining I. pacificus and eight of the D. occidentalis survived sufficiently long for analysis of spirochete infection by IFA. No spirochetes were found in any of these ticks, nor were spirochetes isolated from any of the tick tissues. (6) Adult ticks of the two species sampled were infrequently found on drags. While site 3 yielded approximately 33 black-legged ticks per km, and 12 D. occidentalis per km, the other sample sites provided only 1 to 3 ticks per km. The high concentration of ticks at site 3 resulted from a dense cluster of ticks encountered within an area on the site. The area from which these ticks were sampled was a steep north facing slope along the Nacimiento River. (7) These data indicate that soldiers would encounter a low number of adult ticks during general field exercises. The results also suggest that spirochetal infection in these ticks is either quite low, or has not yet been introduced into the tick population on the installation. We cannot, however, comment on the likelihood of acquiring nymphal state ticks since none were active at the time of this survey. Nymphs would presumably be at peak activity however during the period of highest troop utilization (April through June). (8) Units at greater risk would be those required to traverse through underbrush and along slopes. The occurrence of the Pacific black-legged tick does indicate that the proper vector species is present, and that an endemic focus for Lyme disease spirochetes could become generally established on the installation, especially in cooler, moister habitats. Small mammal serologic findings suggest that the spirochete had not circulated within the limited population sampled. (9) An ongoing effort to study the ecology and prey base of the San Joaquin kit fox, Vulpes macrotis mutica, is being carried out on Camp Roberts by Edgerton, Grier & Gurdhausen, Inc. While Lyme disease assessment is not an aspect of the contracted services provided by this organization, the collection of additional sera and/or tissues from mammals on the installation during the normal sampling process would be very valuable in further defining the scope of B. burgdorferi activity. 6. CONCLUSIONS. The tick vector species (I. pacificus) for Lyme disease in California is present on Camp Roberts. We found no evidence of activity of Borrelia burgdorferi in the tick and small mammal populations sampled. The prevalence of B. burgdorferi infection in ticks in California foci is generally lower (1-2%) than that found in the eastern U.S. foci (15-40%), and this, combined with our relatively small sample size of ticks, may have accounted for our inability to detect infection on this installation. Current epidemiologic data also support the findings of low level human involvement, although further surveillance is needed to elucidate risk to personnel. 7. RECOMMENDATIONS. a. Safety Office, Camp Roberts. (1) Select a Lyme disease coordinator who will oversee the training of installation personnel concerning Lyme disease prevention. (2) Conduct annual safety briefings in the spring for installation personnel concerning Lyme disease prevention using personal protective measures. (3) Provide Lyme disease information or briefing to unit commanders for subsequent training and protection of unit personnel. b. Environmental Safety Office, California Army National Guard Bureau. (1) Coordinate with this Agency to perform additional Lyme disease surveillance to evaluate the risk of Lyme disease transmission to soldiers during period of peak subadult activity. (2) Monitor State of California Health Department reports for evidence of local cases of Lyme disease in counties surrounding the installation. (3) Provide timely notification to the Office of the Army Surgeon General of human Lyme disease acquired on Camp Roberts via Report of Selected Condition (MED 16 (R4)) as required by AR 40-5, para 3-1. 8. TECHNICAL ASSISTANCE. Sources for technical assistance are provided in Appendix C. FOR THE COMMANDER: [signature] EDWARD S. EVANS, JR. Acting Chief Entomological Sciences Division APPENDIX A PERSONNEL CONTACTED 1. COL Baird, Commander, Camp Roberts Military Training Site, California Army National Guard. 2. COL Scully, Chief, Training & Operations, Camp Roberts Military Training Site. 3. MAJ E. Marzden, Chief, Safety Office, Camp Roberts Military Training Site. 4. LTC Madison, Chief, Facilities Engineers, Camp Roberts Military Training Site. 5. Mr. Chris Wilde, Pest Management Office, Camp Roberts Military Training Site. 6. Mr. Brian Duke, Environmental Officer, Camp Roberts Military Training Site. 7. Mr. William Berry, Chief Biologist, Edgerton, Grier & Gurdhausen, Inc., Government Contractor, Camp Roberts Military Training Site. 8. Mr. James Clover, Entomologist, California State Department of Health, Santa Rosa, CA. APENDIX B GENERAL LYME DISEASE INFORMATION AND PERSONAL PROTECTIVE MEASURES Lyme disease is a multi-systemic bacterial disease which is transmitted to man generally via the bite of an infected tick. The disease progresses from an early stage involving a rash, malaise, fever and several other general symptoms to a secondary stage characterized by neurologic, or cardiologic abnormalities. Intermittent or transient arthritis and chronic debilitating neurologic disturbance are typically seen in the third stage of illness and can last months to years in duration. Not all patients present the entire range of symptoms. Many individuals apparently become asymptomatic, although it is not clear whether this necessarily indicates elimination of the causative organism from the patient. Serological findings are used to corrobarate clinical evidence of disease but should not be relied upon as diagnostic of Lyme disease. Early antibiotic therapy is effective in reducing likelihood of further symptoms, although failures to alleviate symptoms with antibiotic therapy have been reported. Tetracycline and its derivatives are the current drugs of choice in treatment. In California, the tick species primarily responsible for Lyme disease transmission to humans is the California Black-legged tick, Ixodes pacificus. The spirochete resides in the midgut of the tick, and is transmitted to a mammal (or avian) host via the tick's salivary secretions during ingestion of a blood meal. Mice of the genus Peromyscus (deer mice) are particularly important hosts for the subadult tick stages (larvae and nymphs), and participates in the natural transmission cycle of the spirochete. This tick, however, feeds on a wide variety of birds, mammals, and reptiles. Other tick species have been found naturally infected with B. burgdorferi in California, including Ixodes neotomae, and hemaphysalis leporispalustris(1). These species were recovered from black tailed jack rabbits (Lepus californicus) which also demonstrated high serum antibody prevalence rates (79%) to spirochetal infection. Black tailed deer (Odocoileus hemionus) also yielded high recovery rates of spirochetes from blood (15%). -------------- (1)Lane, R.S. and W. Burgdorferi. 1988. Spirochetes in mammals and ticks (Acari: Ixodidae) from a focus of Lyme borreliosis in California. J. Wildlife Diseases, 24(1):1-9. The life history of the California black-legged begins with the larvae which are active from mid-spring to early summer. Successfully fed larvae molt to become the second stage, or nymphal ticks, which feed slightly later in the spring season. They then complete their life cycle feeding on deer and other large mammals. The ticks become infected either while feeding on their small mammal hosts, or acquire spirochetes congenitally (transovarial transmission). While deer support the adult tick population, and provide an opportunity for mating, and dispersal of gravid females they probably do not play an important role as far as transmitting infection to the ticks. The black-legged tick is most likely to be encountered in cooler, wooded settings along ravine, and streams. North facing slopes yield the highest number of ticks which seek hosts while waiting on low lying vegetation. The nymph measures only 1.2 mm in length and is dark brown to black in color, making it difficult to see on military field uniforms. Frequent inspection of the garments for ticks while in the field is necessary to prevent later tick attachment. Attached ticks must be removed as soon as possible, using tweezers to grasp the tick at the skin surface and gently pull away from the skin. Use of repellents such as DEET provide only limited protection against tick attachment. The clothing based permethrin repellents administered as a 0.5 percent aerosol spray provide a very high level of repellency (due to toxic effect against ticks) however are not available for use under current law in the State of California. Use of permethrin spray would be possible only after State application for a local use permit under section 24 (c) of the Federal Insecticide Fungicide and Rodenticide Act (FIFRA), or under national or military registration for this particular application route. APPENDIX C TECHNICAL ASSISTANCE 1. Technical advice or consultation regarding issues concerning pest management may be obtained from your Major Command Pest Management Consultant, Mr. John Halisak, at the following address and telephone number: Commander ARNG Operating Activity Center Environmental Resource Branch/NGB-ARI-E Building E-6810 APG, MD 21010-5422 AUTOVON: 584-6806 COMMERCIAL: (301) 671-6806 2. Technical advice concerning the findings and recommendations forwarded in this report may be obtained from Entomological Sciences Division (ESD), USAEHA, Aberdeen Proving Ground, MD at the following address and telephone number: Commander U.S. Army Environmental Hygiene Agency ATTN: HSHB-MR-EMG APG, MD 21010-5422 AUTOVON: 584-3613/3015 COMMERCIAL: (301) 671-3613/3015 3. Technical information regarding Lyme disease surveillance may be acquired either from ESD (address provided in para 2) or from USAEHA-W at the following address and phone number: Commander U.S. Army Environmental Hygiene Activity - West ATTN: HSHB-AW-P Fitzsimons Army Medical Center, CO AUTOVON: 943-8090 COMMERCIAL: (303) 361-8090 4. Medical reporting of human cases of Lyme disease must be transmitted via Report of Selected Condition (MED 16(R4)) through the Preventive Medicine Svcs, MEDDAC, Fort Ord, CA at the following address and telephone number: Commander MEDDAC ATTN: PVNTMED Svc Fort Ord, CA 92394-5800 AUTOVON: 929-0365 COMMERCIAL: (408) 242-0365/5722 5. Requests for USAEHA services should be directed through command channels of the requesting activity to the address listed in para 2 above. 6. An information copy of any request for USAEHA services should be sent to: Commander U.S. Army Health Services Command ATTN: HSCL-P Fort Sam Houston, TX 78234-6000 APPENDIX D LYME DISEASE DETECTION METHODS Immunofluorescent antibody assay methods Infection status was determined by dissecting the midgut from the tick in phosphate buffered saline (PBS); triturating the tissues, and air drying on 10 well teflon coated spot slides (Cel-line, Inc.). These slides were fixed in acetone at -20 degrees C for 7 minutes and stored at -70 degrees C until assayed. The B. burgdorferi were observed using an immunofluorescent antibody (IFA) technique. The primary antibody used to detect the spirochete was a monoclonal antibody directed against the outer surface A protein (H 5332), the secondary detection antibody was Fluorescein isothiocyanate (FITC) conjugated Goat anti-mouse IgG (Heavy and Light chain, Kirkegaard & Perry Labs, Inc.). An immunofluorescent antibody test was used to determine the prevalence of infection with Borrelia burgdorferi in rodents. Sera were initially screened for antibody response at a 1:32 dilution in PBS. Any samples yielding positive reaction at this dilution level were further titrated by four fold dilution to 1:512. Serum samples were overlain in replicate on to B. burgdorferi-coated antigen spot slides (Cel-line, inc.) for 1 hour at room temperature in a humidified chamber. Slides were washed twice with PBS, and a detector antibody, FITC conjugated Goat anti-mouse IgG (Heavy and Light chain, Kirkegaard & Perry Labs, Inc.), was added to each well of the spot slides. Following a 30-minute incubation at room temperature, slides were washed twice with PBS, and coverslipped. Slides were read under ultra violet light at 400X magnification and response was graded as either strong (+), weak (+/-) or negative. Final antibody titer category for a sample was assigned based on the highest dilution yielding at least one strong response. APPENDIX E DESCRIPTION OF DRAGGING SITES Site 1 - Map coordinate OF 974,585. Deeply cut canyon running approximately North to South, well shaded. Grass was very low and sparse due to grazing by sheep. Sampled along east facing slope and canyon bottom. Total distance dragged was 1200 m. Site 2 - Map coordinate OF 963,581. Northeastern facing slope. Grasses with moderate tree cover, but grasses very short due to sheep grazing. Total distance sampled was 1200 m. Site 3 - Map coordinate OF 956,586. Grassy flat area and very steeply cut, north facing embankment (approximately 120 foot drop) along southern bank of Nacimiento River. Flat area with well developed grass layer and sparse but mature tree canopy. Embankment with grass and shrub cover. Deer trails were evident. Total distance sampled was 1200 m. Site 4 - Map coordinate OF 952,593. Steep northeast facing slope and adjacent steep canyon. Good grass cover with few trees on slope and more dense tree cover in canyon. Deer trails along slope. Total distance covered 1200 m. Site 5 - Map coordinate OF 006,637. Sherwood forest along river embankment and floodplain. Dense vegetation with woody forbs, grasses and shrubs. Thick tree canopy to open along floodplain. Total distance sampled was 900 m. Site 6 - Map coordinate OF 978,566. Northeast facing slope, and north / south canyon along deer trail Road. Moderate tree cover, and well developed grass cover. Canyon moist and cool. Total distance covered 1200 m. Site 7 - Map coordinate OF 974,562. North facing slope along Deer trail road. Densely covered with oak trees and thin grasses. Very loamy, sandy soils. Total of 600 m surveyed. APPENDIX F TABLE 1. Capture record for small mammal trapping at Camp Roberts, Jan 1989. Sherwood Forest Boy Scout Road ------------------------------------------------------------------------ Opossum 1 - (Didelphis virginianus) Desert woodrat 2 - (Nectoma lepida) Pinyon mouse 4 - (Peromyscus truei) Brush mouse 3 9 (15)* (Peromyscus boylei) Deer mouse 7 2 (Peromyscus maniculatus) California mouse 1 2 (18) (Peromyscus californicus) Western harvest mouse - 4 (Reithrodonomys megalotis) Total 18 17 ------------------------------------------------------------------------ a. Total ticks removed per animal species TABLE 2. Adult ticks taken on drags per site Ixodes Dermacentor Site pacificus occidentalis Total --------- ------------ N (ticks/m) N (ticks/m) 1 1 (0.001) 3 (0.003) 4 2 1 (0.001) 1 (0.001) 2 3 40 (0.033) 14 (0.012) 54 4 3 (0.003) 2 (0.002) 5 5 0 (-----) 0 (-----) 0 6 4 (0.003) 1 (0.001) 5 7 0 (-----) 0 (-----) 0 Total 49 (0.007) 21 (0.003) 70