Eleanor H. Lacombe

Abundance of Ixodes scapularis (Acari: Ixodidae) after the complete removal of deer from an isolated offshore island, endemic for lyme disease

Abstract Monhegan is an isolated 237-ha island lying 16 km off the coast of Maine. Introduced to the island in 1955, white-tailed deer, Odocoileus virginianus Zimmerman, reached a density of ∼37/km2 by the mid-1990s. Black-legged ticks, Ixodes scapularis Say, first noticed in the late 1980s, flourished thereafter. Norway rats (Rattus norvegicus Berkenhout) on Monhegan are highly infected with Borrelia burgdorferi Johnson, Schmidt, Hyde, Steigerwalt, and Brenner, the agent of Lyme disease. By 1996, 13% of year-round residents had contracted the disease. The community’s subsequent decision to eliminate deer from the island provided a unique opportunity to monitor the abundance of vector ticks in response to the complete and permanent removal of the primary hosts of their reproductive stage. With the exception of humans and their dogs and cats, there are no other potential hosts for adult I. scapularis on Monhegan. From November 1996 to March 1999, all deer were removed from the island. Previous annual fall flagging of vegetation from 1990 to 1998 produced 6–17 adult ticks/h, of which 24–41% were infected with the Lyme disease spirochete. During this same period, up to 18 larvae and 4 nymphs were removed per Norway rat live-trapped on the island each July. With the absence of deer in the fall of 1999, both the density of host-seeking adult ticks and infection prevalence rose substantially to 28/h and 75.0%, respectively. By the summer of 2003, however, no sub-adult ticks were found on rats, and that fall, only 0.67 adult ticks/h were flagged. Of the 68 adults collected from 2002 to 2003, 20 (29.4%) were infected. Over this same period, adult tick abundance on a deer-populated, reference island continued to gradually increase.

Deer Density and the Abundance of Ixodes scapularis (Acari: Ixodidae)

Abstract The abundance of Ixodes scapularis Say (Ixodes dammini Spielman, Clifford, Piesman & Corwin), the vector tick of the Lyme disease spirochete and other human pathogens, is related to the presence of its primary reproductive stage host, white-tailed deer (Odocoileus virginianus Zimmerman). However, this relationship has not been quantified in terms that would guide wildlife management in areas in which the public is, or is likely to become, exposed to infected ticks. In this study, deer density and tick abundance were measured in an emergent area for Lyme disease at three spatial scales using estimation methods appropriate for each. Simple linear regression was used to relate (1) the number of ticks found on deer at tagging stations in southern Maine to harvest-derived estimates of the density of deer within the towns in which they were killed, (2) tick densities estimated from fall flagging counts to deer densities estimated from pellet group counts made within multiple transects distributed through 5.2-km2 study sites, and (3) tick counts to pellet group counts within the individual transects. At the broadest scale, ticks on deer decreased with elevation and distance from the coast and increased with deer density, although deer and tick presence were only weakly related. Among the 5.2-km2 study sites and within individual transects, tick abundance related more strongly to deer pellet group counts. Few ticks were collected at deer densities <7/km2.

Anaplasma phagocytophilum, Babesia microti, and Borrelia burgdorferi in Ixodes scapularis, southern coastal Maine.

Ixodes scapularis (deer ticks) from Maine were tested for multiple infections by polymerase chain reaction and immunofluorescence. In 1995, 29.5%, 9.5%, and 1.9% of deer ticks were infected with Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti, respectively. In 1996 and 1997, the number of A. phagocytophilum-infected ticks markedly declined. In 1995 through 1996, 4 (1.3%) of 301 were co-infected.

Hemodilution, Tonicity, and Blood Viscosity *

Since the introduction of intravenous therapy, fluids containing glucose or saline in relatively isotonic concentrations have far exceeded others in use. Within the last decade new techniques in many areas of diagnosis and treatment have required that fluids of various tonicity and viscosity be introduced into the blood stream with such rapidity or in such great volume as to preclude adequate dilution with the circulating cells and plasma. Several in vivo studies (1-4) have demonstrated the effect of hypertonic solutions on blood flow. Some authors (5-7) have noted circulatory changes, especially in the pulmonary vascular bed, secondary to the injection of angiographic contrast media, which are both hypertonic and highly viscous. Others (8-11) have commented on the benefits of gross dilution of perfused blood during extracorporeal support for open-heart surgery, and some data have been presented concerning the flow properties of blood diluted with solutions of dextrose (12) or dextran (13, 14). At any given shear rate or temperature it is the concentration of red cells which primarily affects the viscosity of whole blood. Viscosity rises with an increasing hematocrit. While investigating the effects of various intravenous solutions on the hematocrit and viscosity of whole blood in vitro, we have noted that under certain conditions a drop in hematocrit has been accompanied by a rise in viscosity, whereas under other circumstances an increase in hematocrit has been accompanied by a fall in viscosity. The significance of these findings in respect to the flow of blood exposed to diluents of varying osmolality and viscosity appears to be of sufficient importance to warrant reporting at this time. Methods The principal experiments were designed to measure changes in the viscosity of blood after its in vitro dilution by solutes that alter either plasma tonicity or plasma viscosity. To study the effects of tonicity, compounds were selected that vary in their ability to permeate the red cell membrane and hence in their ability to produce cell distention or creation by osmotic gradients; all are components of common intravenous fluids. Wide ranges of dilution and concentration were explored. The parameters measured, in addition to blood and plasma viscosity, included osmolality, water content, and hematocrit. Since the initial number of red cells remained constant in each case, variations in hemato-crit from the level predicted on the basis of equivalent isotonic dilution indicated changes in cell size. Similar methods were used to study the response of blood …

Passive Surveillance in Maine, an Area Emergent for Tick-Borne Diseases

Abstract In 1989, a free-of-charge, statewide tick identification program was initiated in Maine, 1 yr after the first Ixodes scapularis Say (=I. dammini Spielman, Clifford, Piesman & Corwin) ticks were reported in the state. This article summarizes data from 18 continuous years of tick submissions during which >24,000 ticks of 14 species were identified. Data provided include tick stage, degree of engorgement, seasonal abundance, geographical location, host, and age of the person from whom the tick was removed. Maps depict the distributions of the three major species submitted. I. scapularis emerged first along the coast, and then it advanced inland up major river valleys, Dermacentor variabilis Say slowly expanded centrifugally from where it was initially reported in southwestern Maine, and the distribution of long-established Ixodes cookei Packard remained unchanged. Submissions of nymphal I. scapularis closely correlated with reported Lyme diseases cases at the county level. Annual fluctuations of nymphal submissions in Maine correlated with those of Lyme disease cases for New England, supporting the possibility of a regional influence on tick abundance. More ticks were removed from people ≤14 and ≥30 yr of age, and their degree of engorgement was greatest in people ≤20 yr of age and progressively increased in people ≥30 yr of age. This study demonstrates the usefulness and potential of tick identification programs.

Borrelia garinii in Seabird Ticks (Ixodes uriae), Atlantic Coast, North America

TOC summary: The primary agent of neurotropic Lyme disease in Eurasia was found in seabird ticks in northeastern North America.

Habitat Associations of Ixodes scapularis (Acari: Ixodidae) in Maine

Abstract The habitat associations of Ixodes scapularis Say (=I. dammini Spielman, Clifford, Piesman, and Corwin) were examined at the northern edge of its range. We assessed the association of habitat features with the abundance of ticks by flagging for questing adult I. scapularis at three sites in coastal Maine from 1998 to 2000 along 27 305-m transects. Multivariable logistic regression indicated that probability of tick abundance was greater in the presence of shrub layer, canopy closure >50%, deciduous litter, forest grasses, and moist-soil ferns. In a second model that related I. scapularis abundance to canopy- and shrub-layer species, probability of tick abundance was greater in the presence of Japanese barberry Berberis thunbergii DC, winterberry holly Ilex verticillata L. (Gray), and Eurasian honeysuckle Lonicera spp., and less with the presence of eastern hemlock saplings Tsuga canadensis L. (Carr.). These associations were true despite variation in deer abundance as indicated by deer pellet group counts. Natural resource managers should be aware that landscape changes, including the invasion by exotic vegetation, might create favorable tick habitat. These findings could prove helpful in assessing local risk of exposure to this vector tick.

Deer Browse Resistant Exotic-Invasive Understory: An Indicator of Elevated Human Risk of Exposure to Ixodes scapularis (Acari: Ixodidae) in Southern Coastal Maine Woodlands

Abstract We evaluated the relationships between forest understory structure and the abundance of questing adult and nymphal blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), in three Maine towns endemic for Lyme disease, 2001–2003. In fragmented New England woodlands, overabundant white-tailed deer, Odocoileus virginianus Zimmerman, overbrowse palatable species, allowing browse-resistant exotic-invasive species to replace native forest understory structures. We predicted there would be more ticks in plots dominated by exotic-invasive shrubs (such as Japanese barberry, Berberis thunbergii DC) than in plots dominated by native shrubs, ferns, or open understory. We assessed canopy composition and closure, tree basal area, litter composition, percentage of coverage and stem density of understory species, litter depth, soil moisture, and abundance of small mammals and white-tailed deer pellet groups. We used generalized linear mixed model analysis of covariance to determine the effect of understory structure on tick counts, controlling for continuous habitat and host covariates and adjusting for random spatial effects. There were twice as many adults and nearly twice as many nymphs in plots dominated by exotic-invasives than in plots dominated by native shrubs. Both adult and nymphal counts were lowest in open understory with coniferous litter. Adults were positively associated with increasing litter depth, medium soil moisture, and increasing abundance of white-footed deer mice, Peromyscus leucopus Rafinesque, and deer pellet group counts. Nymphs were positively associated with increasing litter depth, moderately wet soil, and mice. We concluded that deer browse-resistant exotic-invasive understory vegetation presented an elevated risk of human exposure to the vector tick of Lyme disease.

Effects of angiocardiographic injections on blood viscosity.

THE RESULTS of a number of recent studies (1–5) indicate that modern angiographic contrast media may be employed with safety provided certain criteria of dosage and patient selection are observed. Their rapid and widespread clinical acceptance has fortified this opinion. It is not surprising, however, that serious complications continue to arise as a result of both the greater application of these agents in relatively poor-risk patients and the ever-present temptation to improve radiographic clarity by increasing the volume or rapidity of injection. While some of the reactions can be explained on the basis of sensitization, this mechanism does not appear to account for the majority of cardiovascular catastrophes which have occurred. Within the last few years emphasis has been focused on the marked hemodynamic effects which these severely hypertonic and viscid angiographic media produce, apparently a result of red cell crenation and agglutination (6–10). In a recent study involving the in vitro measurement...

Attempt to Control Ticks (Acari: Ixodidae) on Deer on an Isolated Island Using Ivermectin-Treated Corn

Abstract We report an attempt by an offshore island community to control the vector tick of Lyme disease by providing ivermectin-treated corn to an isolated herd of free-ranging white-tailed deer, 0docoileus virginianus Zimmerman. Medicated corn was supplied in troughs within the island village and from automatic feeders at remote sites during 5 consecutive fall and spring adult tick questing seasons. Acaricide consumption was monitored by assaying its presence in fresh deer pellets and its concentration in deer sera. Its effectiveness was evaluated by recording the number of adult ticks collected from the hides of deer, the number of females becoming sufficiently engorged to oviposit, and the success of subsequent oviposition and eclosion. Entomologic risk was monitored by collecting immature ticks from hosts and adult ticks from vegetation. Estimates based on a subsequent deer reduction program indicated that up to twice as many deer had been present during the project as originally presumed. For this and other reasons related to deer behavior, target levels of serum ivermectin were achieved in a minority of deer. Nevertheless, >90% control of female tick infestation, subsequent oviposition, and larval eclosion was obtained in those 8 of 16 sampled deer with serum ivermectin levels of ≥15 ng/ml. In addition, the ratio of females to males, the numbers of females engorging >10 mg body weight, and the numbers of those eventually hatching, were all significantly less among ticks from island deer in comparison with ticks from untreated deer. No consistent changes in the numbers of ticks found on immature-stage hosts or removed from vegetation were noted within 3 yr of the cessation of treatment.