INSTALLATION PEST MANAGEMENT CONSULTATION, FORT ORD, CALIFORNIA, 24-26 JANUARY 1989 DEPARTMENT OF THE ARMY U.S. Army Environmental Hygiene Agency Aberdeen Proving Ground, Maryland 21010-6422 [Seal of Department of Defense, United States of America] EXECUTIVE SUMMARY INSTALLATION PEST MANAGEMENT CONSULTATION NO. 16-44-0520-90 FORT ORD, CALIFORNIA 24-26 JANUARY 1989 1. PURPOSE. To characterize the spatial distribution and relative frequency of the western black-legged tick, Ixodes pacificus, on Fort Ord and to evaluate the risk of Lyme disease (LD) exposure to personnel on the installation; to offer recommendations on tick surveillance, tick control, and control of human exposure to LD. 2. CONCLUSIONS. Borrelia burgdorferi infected ticks were found on Fort Ord and present a possible health risk to personnel using the facility. The level of exposure to infected ticks is probably minimal due to low frequency of encounter with black-legged ticks, and to the low prevalence (1-2 percent of infection of this species in California, in general. Epidemiologic data also support the findings of a low level of human involvement, although further surveillance is needed to greater elucidate risk to personnel. 3. RECOMMENDATIONS. Select a LD coordinator who will oversee training of installation personnel concerning LD prevention and conduct annual safety briefings concerning LD prevention using personal protective measures. Provide LD information or briefing to unit commanders for subsequent training and protection of unit personnel. Coordinate with this Agency to perform additional LD surveillance to evaluate the risk of LD transmission to soldiers during period of peak subadult activity, as well as possible serologic and tick survey from hunter-killed deer. Monitor State of California Health Department reports for evidence of local cases of LD in counties surrounding the installation. Provide timely notification to the Office of the Surgeon General concerning human LD acquired on Fort Ord in a Report of Selected Condition (MED 16 (R4)) as required by AR 40-5, Preventive Medicine, paragraph 3-1. DEPARTMENT OF THE ARMY U.S. Army Environmental Hygiene Agency Aberdeen Proving Ground, Maryland 21010-6422 [Seal of Department of Defense, United States of America] REPLY TO ATTENTION OF: HSHB-MR-EMG 1 AUG 1990 INSTALLATION PEST MANAGEMENT CONSULTATION NO. 16-44-0520-90 FORT ORD, CALIFORNIA 24-26 JANUARY 1989 1. REFERENCES. a. AR 40-5, 30 August 1986, Preventive Medicine. b. AR 420-76, 3 June 1986, Pest Management. 2. AUTHORITY. a. Memorandum, HSC, HSCL-P, 10 February 1988, subject: Lyme Disease on Army Installations, Project No. 16-44-0520-90. b. Telephone conversation between CPT Richard Johnson, Entomologist, Preventive Medicine Services, Fort Ord, California and CPT George W. Korch, Jr., U.S. Army Environmental Hygiene Agency. 3. PURPOSE. a. To characterize the spatial distribution and relative frequency of the western black-legged tick, Ixodes pacificus, on Fort Ord as determined by tick surveys of ground vegetation and 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 Lyme disease exposure to personnel at Fort Ord, and offer recommendations on tick surveillance, tick control, and control of human exposure to LD. e. To gather information on possible human cases of LD 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 Personnel. The survey was conducted by CPT George W. Korch, Entomologist, who has since transferred from this Agency, and by Dr. Darrell Hale, Entomologist, and Mr. Jim Harrison, both from U.S. Army Environmental Hygiene Activity - West (USAEHA-W), Fitzsimons Army Medical Center, Aurora, Colorado, 24-26 January 1989. Additional assistance was provided to the survey team by personnel from the Preventive Medicine Service, Fort Ord, California. c. Background. (1) Fort Ord is a Forces Command (FORSCOM) facility which serves as the headquarters for the 7th Army. It is located in Monterey County, California, approximately 2.4 km from the City of Monterey. The installation measures roughly 11,700 hectares in area. It is bounded to the northeast by agricultural areas and the city of Salinas, on the east and southeast by California route 68, and on the west by Monterey Bay. (2) The topography ranges from coastal dunes on the west to hilly chaparral on the east, with moderately cut canyons and elevations up to 290 m. The central area of the installation is generally characterized by mixed chaparral, scrub, and open grassland. The predominant tree cover is oak with manzanita and some sparse eucalyptus, and pine. The western area is composed of dune and low dune vegetation, predominated by ice plant, thick scrub, and oak vegetation with interspersed grassland. There are no major bodies of water (rivers or lakes) on the installation; however, numerous small streams drain the installation. Vegetation along these streams and in the canyons is more complex and dense due to the more mesic conditions. (3) The cantonment area occupies the entire western border of the installation. A firing range is located in the south central portion of the site. The central 22 km square area is the primary field training area for light infantry exercises. This area is characterized by low rolling terrain with vegetation ranging from very thick scrub to fairly opened grassy areas with interspersed tree cover. The northern end of the installation contains much of the family housing area and is otherwise similar to the training areas in vegetative cover. There is a recreation area located on the far eastern end of the installation. (4) Medical services are provided through the Silas B. Hayes U.S. Army Community Hospital. This unit has organic Preventive Medicine services which service both Fort Ord, as well as Fort Hunter Liggett, and Camp Roberts, as necessary. (5) State Health Department reports indicate that a total of three cases of LD were reported from Monterey County during the period 1986-1988. To date, no ticks in this area have been found to be infected with Borrelia burgdorferi, according to investigation by the California State Department of Health. (6) Lyme disease is a bacterial disease transmitted to man and animals via the bite of an infective tick. A synopsis of this disease and its transmission cycle in California is presented in Appendix B. 5. FINDINGS AND DISCUSSION. a. Lyme Disease surviellance, Occurrence, and Practices To Date. (1) No human cases of Lyme disease had been reported from Fort Ord, according to the Office of the Army Surgeon General and the California State Department of Health. A physician attending a 1-hour briefing conducted by the survey officer (see paragraph 5.b.) suggested that one unsubstantiated case of LD may have occurred on Fort Ord; however, no specifics on the case were remembered. (2) No surveillance for either the presence of the etiologic agent of disease or the distribution of tick vectors has previously occurred on the installation to our knowledge. b. Lyme Disease Briefings. The survey officer presented a 1-hour seminar on LD symptoms, ecology, epidemiology, and personal protective measures to the Preventive Medicine staff and other physicians and physicians assistants from the U.S. Army Medical Department Activity (MEDDAC). Approximately 25 individuals attended this presentation. During a question period following the presentation, physicians indicated that they received very little complaint by patients of tick bite. 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 (see Appendix C for description) was located at artillery firing point 28 (FR083487), and the second site was Watkins gate canyon (FR137565). These locations correspond to our tick dragging sites 1 and 4, respectively. (2) A total of 25 traps were placed per site, along 5 different transects. Intertrap distance was 15 m. Six National live traps of sufficient size to capture ground squirrels were set at site 4. (3) 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 and measured, and released at point of capture. (4) Host questing ticks were collected from vegetation by dragging a 1 m square white flannel cloth along 10 consecutive 10 m transects per replicate. A total of 500 m square (5 replicates) per site were sampled (unless otherwise noted). Nine sites were evaluated. A description of these sites is provided in Appendix C. (5) A total of 39 small mammals, representing 3 species were collected between the two sites (Appendix E). A total of 14 ticks were found on these animals. None of these mammals were seropositive for Borrelia burgdorferi by immunofluorescent antibody testing. (6) We collected 73 ticks on drags, 22 Ixodes pacificus adults and 51 Dermacentor occidentalis adults (Table 3, Appendix E) over a combined dragging distance of 4.3 km. Forty ticks, 9 I. pacificus and 31 D. occidentalis, were analyzed for spirochete infection by immunoflourescent antibody (IFA). Spirochetes were found in 1 (11 percent) I. pacificus collected at site 9, and in 2 (6 percent) of the D. occidentalis collected at site 1. The latter tick species is not usually considered to be an important vector species for LD spirochetes. This event likely represents a spillover of spirochetes into an atypical species. While D. occidentalis does attack man, it is unknown whether the species represents a threat of LD transmission to humans. (7) Adult ticks of the two species sampled were infrequently found on drags. A maximum of nine black-legged ticks per 500 m square was found at sites 4 and 9, while the other sites ranged from no ticks to three ticks per 500 m square. (8) The data suggest that soldiers engaged in field exercises would be exposed to a low number of black-legged ticks at this time of the year. It is also possible that these personnel may be at low risk of Lyme disease exposure based on finding Borrelia burgdorferi in ticks from two sites. Additional surveillance is necessary to further elucidate the prevalence of infection in these tick species and to evaluate the population density of nymphal black-legged ticks during their spring activity period. (9) The black-legged tick is more commonly found in cool, moist habitats such as along stream beds and canyons. The coastal climatic conditions generally found on Fort Ord are suited to this tick species; thus, the tick may enjoy a wider distribution on the installation than is found for instance further inland on Fort Hunter Liggett. 6. CONCLUSIONS. Borrelia burgdorferi infected ticks were found on Fort Ord and present a possible health risk to personnel utilizing the facility. The level of exposure to infected ticks is probably minimal due to low frequency of encounter with black-legged ticks and to the low prevalence (1-2 percent) of infection of this species in California, in general. Epidemiologic data also support the findings of low level human involvement, although further surveillance is needed to greater elucidate risk to personnel. 7. RECOMMENDATIONS. Ensure the MEDDAC, Fort Ord, does the following: a. Select a LD coordinator who will oversee training of installation personnel concerning LD prevention. b. Conduct annual safety briefings, concerning LD prevention using personnel protective measures, in the spring for installation personnel. c. Provide LD information or briefings to unit commanders to encourage subsequent training and protection of unit personnel. d. Coordinate with this Agency to perform additional LD surveillance to evaluate the risk of LD transmission to soldiers during periods of peak subadult activity, as well as possible serologic and tick survey from hunter-killed deer. e. Monitor State of California Health Department reports for evidence of local cases of LD in counties surrounding the installation. f. Provide timely notification to the Office of the Army Surgeon General, concerning human Lyme disease acquired on Fort Ord, in a Report of Selected Condition (MED 16 (R4)) as required by AR 40-5, paragraph 3-1. [signature] ALFRED L. HOCH MAJ, MS Chief, Pest Management Branch Entomological Sciences Division APPENDIX A PERSONNEL CONTACTED 1. COL Manmohan Ranadive, Commander, Silas B. Hayes U.S. Army Community Hospital, Fort Ord, California, FORSCOM *. 2. CPT Richard Johnson, Entomologist, Preventive Medicine Services, Silas B. Hayes U.S. Army Community Hospital, Fort Ord, California, FORSCOM *. 3. MAJ D. Inouye, Preventive Medicine Officer, Preventive Medicine Services, Silas B. Hayes U.S. Army Community Hospital, Fort Ord, California. 4. Mr. Franklin Ennik, Biologist, California State Department of Health. 5. Mr. Richard Yescott, Biologist, California State Department of Health. ------------ * Personnel present at outbriefing APPENDIX B GENERAL LYME DISEASE INFORMATION AND PERSONAL PROTECTIVE MEASURES 1. Lyme disease (LD) is a multisystemic 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. 2. 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. Serologic findings are used to corroborate clinical evidence of disease but should not be relied upon as diagnostic of LD. 3. 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. 4. In California, the tick species primarily responsible for LD transmission to humans is the western 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 participate in the natural transmission cycle of the spirochete. This tick, however, feeds on a wide variety of birds, mammals, and reptiles. 5. Other tick species have been found naturally infected with B. burgdorferi in California, including Ixodes noetomas, and Hemaphysalis leporispalustris*. These species were recovered from black-tailed jack rabbits (Lepus californicus) which also demonstrated high serum antibody prevalence rates (79 percent) to spirochetal infection. Black-tailed deer (Odocoileus hemionus) also yielded high recovery rates of spirochetes from blood (15 percent). 6. The life history of the western black-legged tick 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 animals. 7. 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. 8. The black-legged tick is most likely to be encountered in cooler, wooded settings along ravines and streams. North facing slopes yield the highest number of ticks seeking hosts while waiting on low-lying vegetation. Within the State of California, higher prevalence rates of infection in ticks are found within the northern counties, Humboldt, Sonoma, and Marin Counties, although infected ticks have been found in a number of other counties as well. 9. 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. 10. Skin repellents, such as DEET, provide limited protection against ticks when used alone. However, when used in combination with currently available clothing repellents containing permethrin, protection is greatly enhanced. Insect/Arthropod Repellent, Personal Application (NSN 6840-01-284-3982) and Insect repellent, Clothing Application, (Permethrin Arthropod Repellent) (NSN 6840-01-278-1336) are available through the federal stock system. -------- * Lane, R.S. and W. Burgdorfer. 1988. Spirochetes in mammals and ticks (Acari: Ixodidae) from a focus of Lyme borreliosis in California. J. Wildlife Diseases, 24(1):1-9. APPENDIX C DESCRIPTION OF TICK SURVEILLANCE SITES FORT ORD, CALIFORNIA 24-26 JANUARY 1989 --------------------------------------------------------------------------- Map Site Coordinates* Description --------------------------------------------------------------------------- 1 FR083487 Scrub, moderate to low height (1-2 m); densely vegetated with 'Pampas' grass, ice plant, manzanita; adjacent to Boundary Road; deer trails evident. 2 FR108496 Scrub, moderate to low height (1-2 m), manzanita and ice plant predominant, little grass. 3 FR082553 Mixed deciduous woodland and open grass, fairly level. 4 FR137565 Well shaded, moist, north-south canyon with mixed deciduous woodland, grassland, and herbaceous cover. Blackberry and poison oak common to western slope. 5 FR133566 Level open area with grassland and deciduous woodland mix. 6 FR126572 Deciduous woodland with widely-spaced oaks and thick ground cover consisting mostly of ferns and grasses. 7 FR143529 Deeply-cut stream bed running through grassland, scrub habitat. Moderately-thick tree cover along stream bed. 8 FR133515 Slope with grasses and tree cover 9 FR052497 Chaparral --------------------------------------------------------------------------- * Map coordinates based on Defense Mapping Agency Topographic Center map, Fort Ord and vicinity (1:25,000) Edition 5-DMATC, Series V895S, 1972. APPENDIX D LYME DISEASE DETECTION METHODS (immunofluorescent antibody assay methods) 1. 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 [registered]-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 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.). 2. An IFA 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 fourfold dilution to 1:512. Serum samples were overlain in replicate onto 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 cover-slipped. Slides were read under ultraviolet 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. --------- [Registered] Teflon is a registered trademark of E.I. DuPont de Nemours & Co., Inc., Wilmington, Delaware. APPENDIX E TICKS TAKEN ON DRAGS PER SITE FORT ORD, CALIFORNIA 24-26 JANUARY 1989 --------------------------------------------------------------------------- Ixodes Dermacentor Site pacificus occidentalis Total --------------------------------------------------------------------------- 1 2 15 17 2 - 6 6 3 1 1 2 4 9 16 25 5 0 0 0 6 0 4 4 7 0 0 0 8 1 5 6 9 9 4 13 Total 22 51 73 --------------------------------------------------------------------------- APPENDIX F CAPTURE RECORD FOR SMALL MAMMAL TRAPPING FORT ORD, CALIFORNIA JANUARY 1989 --------------------------------------------------------------------------- Site 1 Site 4 --------------------------------------------------------------------------- Brush mouse 6 14 (3)* (Peromyscus boylei) Deer mouse 3 - (Peromyscus maniculatus) California mouse 10 (5) 6 (6) (Peromyscus californicus) Total 19 20 --------------------------------------------------------------------------- * Total ticks removed from animals APPENDIX G TECHNICAL ASSISTANCE Request for services should be directed through appropriate command channels of the requesting activity to Commander, U.S. Army Environmental Hygiene Agency, ATTN: HSHB-MR-EMG, Aberdeen Proving Ground, MD 21010-5422, with an information copy furnished the Commander, U.S. Army Health Services Command, ATTN: HSCL-P, Fort Sam Houston, TX 78234-6000.