P. Bryon Backenson

Dead crow density and West Nile virus monitoring, New York.

Persons in counties with high dead crow densities had elevated risk for disease.

Molecular Epidemiology of Eastern Equine Encephalitis Virus, New York

Southern strains are undergoing amplification, perpetuation, and overwintering in New York.

Babesia microti, upstate New York.

Five cases of human babesiosis were reported in the Lower Hudson Valley Region of New York State in 2001. An investigation to determine if Babesia microti was present in local Ixodes scapularis ticks yielded 5 positive pools in 123 pools tested, the first detection of B. microti from field-collected I. scapularis in upstate New York.

A Mouse Model of Borrelia Meningitis after Intradermal Injection

Both young and adult C3H/HeN mice developed meningitis within 3 weeks of intradermal inoculation with a newly identified uncultivable Borrelia species, an agent of human relapsing fever. Meningoencephalitis with perivascular infiltrates and plexitis developed at approximately 25 days after inoculation. Infiltrates were composed of B and plasma cells and monocytes. This model recreated the meningitis associated with spirochetal infections through an intradermal route of infection.

Geographical and environmental factors driving the increase in the Lyme disease vector Ixodes scapularis

The population densities of many organisms have changed dramatically in recent history. Increases in the population density of medically relevant organisms are of particular importance to public health as they are often correlated with the emergence of infectious diseases in human populations. Our aim is to delineate increases in density of a common disease vector in North America, the blacklegged tick, and to identify the environmental factors correlated with these population dynamics. Empirical data that capture the growth of a population are often necessary to identify environmental factors associated with these dynamics. We analyzed temporally- and spatially-structured field collected data in a geographical information systems framework to describe the population growth of blacklegged ticks (Ixodes scapularis) and to identify environmental and climatic factors correlated with these dynamics. The density of the ticks increased throughout the studys temporal and spatial ranges. Tick density increases were positively correlated with mild temperatures, low precipitation, low forest cover, and high urbanization. Importantly, models that accounted for these environmental factors accurately forecast future tick densities across the region. Tick density increased annually along the south-to-north gradient. These trends parallel the increases in human incidences of diseases commonly vectored by I. scapularis. For example, I. scapularis densities are correlated with human Lyme disease incidence, albeit in a non-linear manner that disappears at low tick densities, potentially indicating that a threshold tick density is needed to support epidemiologically-relevant levels of the Lyme disease bacterium. Our results demonstrate a connection between the biogeography of this species and public health.

Habitat Structure Associated with Borrelia burgdorferi Prevalence in Small Mammals in New York State

Abstract The relationship between habitat structural composition, presence of Ixodes scapularis Say (I. dammini Spielman, Clifford, Piesman, and Corwin), and the prevalence of Borrelia burgdorferi infection in small mammal populations was studied at 12 4-ha study sites selected within two perpendicular transects spanning New York State. Species-adjusted small mammal infection rates (SARs) were calculated to enable comparison of B. burgdorferi infection rates among sites with differing small mammal species composition and were used as the outcome variable in a predictive model. Sites with high SARs were characterized by lower overstory tree canopy height and basal area, increased understory coverage, substantial understory shrub coverage, decreased presence of surface water or saturated soil, high dominance values for I. scapularis, and higher tick burdens on small mammals. These differences were statistically significant from sites with moderate or low SAR values. Understory foliage height profiles were created for each study site, and significant differences in vegetation structural composition between high SAR sites and those with low or moderate SAR were documented. High SAR sites had increased density of herbaceous foliage at 0 and 25 cm, and higher shrub density at 0, 25, and 50 cm measurements above the ground, associated with I. scapularis questing success, and lower densities of sapling trees at 25, 50, and 75 cm. The structural composition of understory vegetation may dictate vector density and predict B. burgdorferi infection rates in small mammals in New York State.

Effectiveness of Residential Acaricides to Prevent Lyme and Other Tick-borne Diseases in Humans

BACKGROUND In the northeastern United States, tick-borne diseases are a major public health concern. In controlled studies, a single springtime application of acaricide has been shown to kill 68%-100% of ticks. Although public health authorities recommend use of acaricides to control tick populations in yards, the effectiveness of these pesticides to prevent tick bites or human tick-borne diseases is unknown. METHODS We conducted a 2-year, randomized, double-blinded, placebo-controlled trial among 2727 households in 3 northeastern states. Households received a single springtime barrier application of bifenthrin or water according to recommended practices. Tick drags were conducted 3-4 weeks after treatment on 10% of properties. Information on human-tick encounters and tick-borne diseases was collected through monthly surveys; reports of illness were validated by medical record review. RESULTS Although the abundance of questing ticks was significantly lower (63%) on acaricide-treated properties, there was no difference between treatment groups in human-tick encounters, self-reported tick-borne diseases, or medical-record-validated tick-borne diseases. CONCLUSIONS Used as recommended, acaricide barrier sprays do not significantly reduce the household risk of tick exposure or incidence of tick-borne disease. Measures for preventing tick-borne diseases should be evaluated against human outcomes to confirm effectiveness.

Impact of Trap Elevation on Estimates of Abundance, Parity Rates, and Body Size of Culex pipiens and Culex restuans (Diptera: Culicidae)

Abstract Trapping success, abundance, parity rate, and body size indices of Culex pipiens (L.) and Culex restuans Theobald, important vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), were determined for specimens captured from both ground level (≈1-m) and elevated (≈6- to 7-m) CO2-baited CDC miniature light traps. Mosquitoes were collected from six study sites in Albany County, New York, from mid-May to mid-October 2004. There was no significant difference in abundance or mean parity for either Cx. pipiens or Cx. restuans between the elevated and the ground-level traps. Mosquitoes collected in elevated traps tended to be larger than mosquitoes collected at ground level. Elevated traps captured significantly fewer mosquitoes per trap-night than did ground traps, but a greater proportion of those captured were Culex spp. Therefore, elevated traps more efficiently captured Cx. pipiens and Cx. restuans with similar reproductive status and body size and reduced the time necessary to sort and identify collections. These findings may be beneficial to researchers or surveillance programs focusing on Cx. pipiens or Cx. restuans.

Isolation of Bunyamwera serogroup viruses (Bunyaviridae, Orthobunyavirus) in New York state.

Abstract During routine arbovirus surveillance from 2000 to 2004 in New York state (NYS), 14,788 mosquito pools making up 36 species and nine genera were inoculated onto Vero cell cultures to test for a broad spectrum of viruses. Forty-six percent of viruses isolated in cell culture from species, excluding Culex pipiens L. and Culex restuans Theobald, were identified as Bunyamwera serogroup viruses. Here, we report the distribution and level of Bunyamwera activity in NYS detected during this period. We developed specific primers for Cache Valley virus (family Bunyaviridae, genus Orthobunyavirus, CVV) and Potosi virus (family Bunyaviridae, genus Orthobunyavirus, POTV), to facilitate rapid molecular identification of these viruses. Viral RNA was detected in 12 mosquito species by reverse transcription-polymerase chain reaction, with the majority isolated from Aedes trivittatus (Coquillet). We report the first POTV isolation in NYS and describe the development of specific primers to identify both POTV and CVV.

Zika Virus Testing Considerations: Lessons Learned from the First 80 Real-Time Reverse Transcription-PCR-Positive Cases Diagnosed in New York State.

ABSTRACT The performance and interpretation of laboratory tests for Zika virus (ZKV) continue to be evaluated. Serology is cross-reactive, laborious, and frequently difficult to interpret, and serum was initially solely recommended for molecular diagnosis. ZKV testing was initiated in January 2016 in New York State for symptomatic patients, pregnant women, their infants, and patients with Guillain-Barré syndrome who had traveled to areas with ZKV transmission. Subsequently, eligibility was expanded to pregnant women with sexual partners with similar travel histories. Serum and urine collected within 4 weeks of symptom onset or within 6 weeks of travel were tested with real-time reverse transcription-PCR (RT-PCR) assays targeting the ZKV envelope and NS2B genes. In this review of lessons learned from the first 80 positive cases in NYS, ZKV RNA was detected in urine only in 50 patients, in serum only in 19 patients, and in both samples concurrently in 11 patients, with average viral loads in urine a log higher than those in serum. Among 93 positive samples from the 80 patients, 41 were positive on both gene assays, 52 were positive on the envelope only, and none were positive on the NS2B only. Of the 80 infected patients, test results for 74 (93%) would have defined their infection status as not detected or equivocal if the requirement for positive results from two assay targets (two-target-positive requirement) in the initial federal guidance to public health laboratories was enforced, if urine was not tested, or if the extended eligibility time for molecular testing was not implemented. These changes facilitated more extensive molecular diagnosis of ZKV, reducing reliance on time-consuming and potentially inconclusive serology.