Type testing of a head band dosemeter for measuring eye lens dose in terms of H(P)(3).

A new head band dosemeter, for the measurement of eye lens dose in terms of Hp(3), has been type tested by Public Health England's Centre for Radiation, Environmental and Chemical Hazards [formerly part of the UK Health Protection Agency (HPA)]. The type tests were based on the International Standard ISO 12794, drawing also upon earlier work at HPA. The results show that, unlike many existing dosemeters, the new head band dosemeter correctly measures Hp(3) for beta radiations as well as photons.

Type testing of a new TLD for the UK Health Protection Agency.

The UK Health Protection Agency is currently commissioning a new personal dosimetry system based on the use of Harshaw two-element thermoluminescent dosemeter cards using LiF:Mg,Cu,P. Results of extensive type testing carried out with reference to IEC 61066, "Thermoluminescence Dosimetry Systems for Personal and Environmental Monitoring", have been presented.

West Nile virus isolates from mosquitoes in New York and New Jersey, 1999.

An outbreak of encephalitis due to West Nile (WN) virus occurred in New York City and the surrounding areas during 1999. Mosquitoes were collected as part of a comprehensive surveillance program implemented to monitor the outbreak. More than 32,000 mosquitoes representing 24 species were tested, and 15 WN virus isolates were obtained. Molecular techniques were used to identify the species represented in the WN virus-positive mosquito pools. Most isolates were from pools containing Culex pipiens mosquitoes, but several pools contained two or more Culex species.

Estimating population size and drag sampling efficiency for the blacklegged tick (Acari: Ixodidae).

Estimates of absolute density were determined over a 5-yr period (1990-1994) for a population of Ixodes scapularis Say located in Westchester County, NY, by mark-release-recapture (nymphs and adults) and removal (larvae) methods. Density estimates for larvae ranged from 5.2 to 16.5/m2 and averaged 11.5/m2. Values for nymphs varied as much as fourfold among successive years, ranging from 0.5 to 2.3/m2 and averaging 1.2/m2, whereas adult density ranged from 0.3 to 0.4/m2, averaging 0.33/m2. Natural mortality of nymphs and adults was measured in experimental cages during population estimation periods, and indicated that survival declined linearly over the short-term and did not significantly influence estimates. Drag sampling efficiency, the proportion of the estimated population obtained in a single sample, averaged 6.3% among all stages. Efficiency was not significantly different among stages and was independent of tick density within a given life stage. The population estimation techniques employed in this study are well suited for use with I. scapularis and can provide data that offer insights into mortality patterns in individual populations.

Temporal relation between Ixodes scapularis abundance and risk for Lyme disease associated with erythema migrans.

Understanding the role that nymphal and female ticks, Ixodes scapularis, have in the epidemiology of Lyme disease is essential to the development of successful prevention programs. In this study, the authors sought to evaluate the seasonal and annual relations between tick densities and patients > or = 16 years of age diagnosed with erythema migrans (EM), the rash associated with early Lyme disease. Ticks were collected weekly by drag sampling throughout most of the year from 1991 to 1996 in Westchester County, New York. The number of EM cases was based on patients diagnosed at the Westchester County Medical Center using Centers for Disease Control and Prevention (CDC) criteria. No patients with EM were diagnosed from January through April, when only adult ticks were active. Correlation analysis between monthly tick densities and EM incidence was significant for nymphs (r = 0.87, p < 0.01), but not for adult ticks (r = -0.57, p > 0.05). There was a strong, although not significant, correlation between peak annual number of patients with EM and peak nymphal tick abundance (r = 0.76, p = 0.08). These data indicate that bites from adult I. scapularis only rarely result in Lyme disease, and that annual nymphal tick abundance determines exposure. This suggests that annual fluctuations in Lyme disease case numbers are largely due to natural changes in tick abundance and, therefore, that control of nymphal I. scapularis should be a major component of Lyme disease prevention efforts.

Geographic risk for lyme disease and human granulocytic ehrlichiosis in southern New York state.

Ixodes scapularis, the tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE), is prevalent in much of southern New York state. The distribution of this species has increased, as have reported cases of both Lyme disease and HGE. The unreliability of case reports, however, demonstrates the need for tick and pathogen surveillance in order to accurately define areas of high risk. In this study, a total of 89,550 m2 at 34 study sites was drag sampled in 1995 and a total of 51,540 m2 at 40 sites was sampled in 1996 to determine tick and pathogen distribution in southern New York state. I. scapularis was collected from 90% of the sites sampled, and regionally, a 2.5-fold increase in nymphal abundance occurred from 1995 to 1996. I. scapularis individuals from all sites were infected with Borrelia burgdorferi in 1995, while an examination of ticks for both B. burgdorferi and the agent of HGE in 1996 confirmed that these organisms were present in all counties; the average coinfection rate was 1.9%. No correlation was found between estimated risk and reported cases of Lyme disease. The geographic disparity of risk observed among sites in this study underscores the need for vector and pathogen surveillance on a regional level. An entomologic risk index can help identify sites for targeted tick control efforts.

Detection of Borrelia burgdorferi OspA in Ixodes scapularis larvae by an antigen-capture enzyme-linked immunosorbent assay.

The Borrelia burgdorferi outer surface protein A (OspA) was quantified by an antigen-capture ELISA. The test detected 0.156 ng OspA/B, using purified rabbit IgG as a detection system. Dose-response relationship was described by a three-parameter equation and second degree polynomials. The estimated amount of OspA in host-attached Ixodes scapularis larvae was positively correlated with the tick's engorgement status, whereas the presence of blood in OspA-negative larvae reduced test absorbance. The antigen-capture ELISA can be effectively used in the ecology and epidemiology of Lyme borreliosis. However, host attached larvae should be matched by engorgement level to remove the effect of this variable on test results.

Deer ticks (Ixodes scapularis) and the agents of Lyme disease and human granulocytic ehrlichiosis in a New York City park.

Rodent trapping and drag sampling in Van Cortlandt Park, New York City, yielded all stages of Ixodes scapularis, the deer tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE). Polymerase chain reaction analyses of the ticks showed Borrelia burgdorferi and the Ehrlichia sp. that causes HGE.

Timing of Ixodes scapularis (Acari: Ixodidae) oviposition and larval activity in southern New York.

Timing of oviposition and larval eclosion for fall- and spring-fed female blacklegged tick, Ixodes scapularis Say, and effect of temperature on those events in southern New York state, where Lyme disease is endemic, were determined in the field. We also examined seasonal pattern of larval host-seeking activity, as well as rate of survival for overwintering, unfed larvae. Totals of 9 and 8 replete female I. scapularis were released in fall 1988 and spring 1989, respectively. For the 10 females that oviposited, egg laying began in mid-to-late May, regardless of when ticks had fed. Likewise, larval eclosion was synchronized in July for all egg masses. Microhabitat temperatures experienced by females were not reliable indicators of female reproductive success, in terms of either presence or absence of eggs, or numbers of larvae recovered. However, average body size was significantly greater for females that oviposited successfully than for those that did not. The percentage of unfed larvae surviving the 8-mo overwintering period from late August to early May ranged from 1.9 to 31.4, with a mean survival rate of 10.4%. Concurrent drag sampling through the year indicated a bimodal pattern of larval abundance marked by a relatively small early peak of activity in late May that extended into early July. Because the first peak of larval activity occurred during the period of oviposition, 8 wk before onset of larval eclosion, it appears that bimodality represents activity of 2 consecutive cohorts, with the early peak composed of overwintering survivors. These data imply variation in timing of reproduction and larval activity from 1 geographic area to another. Efforts to devise a comprehensive scheme for the life cycle of I. scapularis must consider that population differences may exist.

Increase in abundance of immature Ixodes scapularis (Acari: Ixodidae) in an emergent Lyme disease endemic area.

Changes in the abundance of immature Ixodes scapularis Say, the primary vector of Lyme disease, were assessed over a 7-yr period in Westchester County, New York, where the disease is endemic. In total, 4,000 m2 were drag sampled at each of 6 study sites in June and July of 1984 and 1991. The abundance of nymphs collected from all sites was 2.6-fold greater in 1991 than in 1984. Four of the 6 sites had significantly more nymphs in 1991, with increases ranging from 1.1- to 46.5-fold. The abundance of larvae collected from all sites was 34.2-fold higher in 1991 than in 1984. Five of the sites sampled had significantly more larvae in 1991, with increases ranging from 2.7- to 681-fold. These data demonstrate that populations of immature I. scapularis in Westchester County have, overall, increased during the 7-yr period from 1984 to 1991. However, the magnitude of increase is not uniform from site to site.

Effect of deer exclusion on the abundance of immature Ixodes scapularis (Acari: Ixodidae) parasitizing small and medium-sized mammals.

Effects of deer exclusion on abundance of immature Ixodes scapularis Say parasitizing small and medium-sized mammals, and the role mammals have in introducing ticks to exclosure areas, were examined at two sites in Westchester County, New York. In total, 686 mammal captures representing nine species were obtained, with white-footed mice, Peromyscus leucopus Rafinesque, composing > 80% of all captures, followed by raccoons, Procyon lotor (L.); opossums, Didelphis virginiana (Kerr); and striped skunks, Mephitis mephitis Schreber. At the Near Archives site, 14% of 81 individual mice, 46% of raccoons, and 33% of opossums captured were found to cross the exclosure fence, as did 12% of 50 mice and 38% of raccoons at the Hudson Pines site. Skunks apparently did not cross the fence at either site. Mice captured exclusively outside the Near Archives exclosure hosted significantly more larvae than mice captured inside only, with fence crossers hosting an intermediate number of larvae. At Hudson Pines, numbers of larvae on fence-crossing mice and those captured solely inside the exclosure were equivalent, with tick loads on mice captured outside the exclosure significantly greater. The number of larvae per raccoon did not differ significantly with capture location (inside, outside, or both sides of exclosure fence) at either site. Densities of host-seeking larvae and nymphs were significantly higher outside the exclosure than inside at Near Archives, though not at Hudson Pines. Differences in tick density inside and outside exclosures declined with each successive developmental stage so that adult density inside exclosures tended to converge with that outside at both sites. Although deer exclosures can have a significant impact on nymphal I. scapularis abundance, they may not reduce the risk of encountering infected adults. Mice, raccoons, and opossums have a role in introducing potentially infective ticks to areas where deer have been excluded, though the level of immigration of ticks into the area will likely depend on the density of ticks outside the exclosure.

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) and Lyme disease risk by deer exclusion.

The effect of deer exclosures upon the numbers of immature Ixodes scapularis Say, the vector of Lyme disease in the eastern United States, was examined at five sites in Westchester County, NY. Study areas ranged in size from 6 to 101 ha where deer had been excluded for a period of 25 yr by > 2.4-m-high fencing that surrounded each site. A total area of 40,506 m2 was drag-sampled during the study to measure tick abundance. Nymphal densities (ticks per 1,000 m2) averaged 4.6 (range, 1.3-9.6) inside exclosures and 27.7 (range, 7.3-79.4) outside. Larval densities averaged 36.7 (range, 1.2-132.1) inside exclosures and 354.4 (range, 7.5-914.5) outside. Comparisons between exclosure sites and outside areas immediately adjacent to the exclosure fence, where deer had unrestricted access, revealed that exclosures had 83% fewer host-seeking nymphs and 90% fewer host-seeking larvae. Tick numbers inside exclosures did not always decline with increasing distance from the fence. There was no significant difference in the rate of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner infection for host-seeking ticks collected inside (20%, n = 50) exclosures compared with ticks collected outside (26%, n = 50) exclosures. Deer fencing may provide a means of significantly reducing the abundance of I. scapularis and the risk of Lyme disease in relatively large areas without the need to reduce or eliminate the deer population.

Canine exposure to Borrelia burgdorferi and prevalence of Ixodes dammini (Acari: Ixodidae) on deer as a measure of Lyme disease risk in the northeastern United States.

Surveillance programs that identify areas where both the vector (Ixodes dammini) and etiologic agent (Borrelia burgdorferi) are present may identify the risk of Lyme disease and its spread earlier and more accurately than do programs relying on any single method, particularly human case reports. Hunter-killed deer (n = 1,204) from 22 counties in Maryland, Massachusetts, New Hampshire, New York, and Pennsylvania were examined in fall 1989 and all ectoparasites were identified. The following spring, canine sera (n = 884) were obtained from these sites, which included known endemic areas and those where Lyme disease is uncommon, and tested by enzyme-linked immunosorbent assay. Regression analysis of canine seroprevalence versus tick prevalence on deer from the same counties demonstrate a significant positive linear relationship. Sites were designated as low-, moderate-, or high-risk counties based upon their position on the regression curve. The geographic distribution of the sites correlated well with the distribution of known Lyme disease endemic and nonendemic areas. Locations were also identified where Lyme disease may be emerging. The positive relationship between measures of vector and pathogen abundance determined in this study permits public health workers to identify endemic and potentially endemic areas independently of human case reports.

Evaluation of host-targeted acaricide for reducing risk of Lyme disease in southern New York state.

A 2-yr evaluation of a commercial product designed to reduce the risk of Lyme disease by delivering permethrin-treated cotton to white-footed mice (Peromyscus leucopus) was conducted at three sites in Westchester County, N.Y., an area where Lyme disease is endemic. We examined the numbers of host-seeking nymphal Ixodes dammini Spielman, Clifford, Piesman & Corwin, the numbers of larval I. dammini infesting mice, and the proportion of nymphs infected with Borrelia burgdorferi, the causative agent of Lyme disease. The density of nymphs collected by drag sampling did not differ between treatment and control areas in the first year for either a woodland or recreational site. In the second year, no significant decrease in the density of nymphs was observed in the treatment areas compared with the control areas. Numbers of larvae on 67 mice captured on treatment and control grids did not differ for woodland and recreational sites, but significantly fewer larvae were found on mice captured at the residential treatment site. The percentage of host-seeking ticks infected with spirochetes did not differ between treatment and control sites in any habitat for either year. The use of permethrin-treated cotton did not measurably reduce the numbers of I. dammini or the proportion of ticks infected with spirochetes at our study sites.

The role of medium-sized mammals as reservoirs of Borrelia burgdorferi in southern New York.

The ability of raccoons (Procyon lotor), striped skunks (Mephitis mephitis) and opossums (Didelphis virginiana) to serve as reservoirs of Borrelia burgdorferi, the spirochetal agent of Lyme disease, was compared with that of white-footed mice (Peromyscus leucopus). Twenty-eight (28) medium-sized mammals and 34 white-footed mice were captured in Westchester County, New York (USA) in summer 1986. Animals were caged over pans of water for 1 to 2 days to recover engorged tick larvae (Ixodes dammini) that detached from the hosts after feeding. With the exception of mice, numbers of engorged tick larvae recovered exceeded those counted during initial examinations of the hosts by 30% (opossums) to nearly 90% (raccoons). Newly-molted nymphal ticks derived from the engorged larvae were examined for the presence of spirochetes by darkfield microscopy. Percentage infection was 5% (n = 22) for ticks from skunks and 14% (n = 191) for ticks from raccoons. None of 24 nymphs from larvae that fed on opossums survived long enough for spirochete examination. By comparison, 40% (n = 72) of nymphs from larvae which fed on white-footed mice were infected. Of the individual hosts from which molted nymphs had fed as larvae, 67% of mice, 33% of skunks, and 55% of raccoons produced spirochete-positive ticks.

Seasonal activity and survival of adult Ixodes dammini (Acari: Ixodidae) in southern New York State.

Mark-recapture studies demonstrated that adult Ixodes dammini Spielman, Clifford, Piesman, and Corwin in southern New York successfully overwinter and resume active host-seeking in the spring. Thus, the resulting bimodal peak in autumn and spring appears to reflect temperature-induced activity of the same cohort and not different generations. Adult tick abundance in the field was monitored by counting the number of ticks collected by a domestic dog on routine walks and correcting for the effects of temperature on tick activity. It is suggested that adult abundance, measured independently of ambient temperature, may be an accurate indicator of survival. The field tick abundance curve was negatively exponential (y = e(4.26-0.12x] and significantly different from the survival curve for ticks maintained in the laboratory, which displayed a constant mortality rate (y = -3.7x + 105.5). Body size influenced male survival during the winter, whereas female survival was independent of body size. Greater male mortality in fall and winter resulted in a lower sex ratio in spring.

Feralization: The making of wild domestic animals.

The widely accepted viewpoint that feralization is the reverse of domestication requires that the feralization process be restricted to populations of animals and, therefore, cannot occur in individuals. An alternative, ontogenetic approach is presented in which feralization is defined as the process by which individual domestic animals either become desocialized from humans, or never become socialized, and thus behave as untamed, non-domestic animals. Feralization will vary among species and, intraspecifically, will depend upon an individual's age and history of socialization to humans. Because feralization is not equated with morphological change resulting from evolutionary processes, species formation is not an accurate indicator of feral condition.

A study of dog bites on the Navajo reservation.

Reservation-wide dog-bite statistics indicate a bite rate on the Navajo Reservation that is comparable to that of a large city. Detailed analysis of 772 bite reports was made to determine the characteristics of biters and their victims. This included an assessment of the behavioral antecedents leading up to the bite incident; 98.4 percent of all cases for which a possible cause could be ascertained were provoked in some way. Both dog control and public education measures need to be taken to reduce the frequency of dog bites.