Joanne Oliver

Antibody Response of Wild Birds to Natural Infection with Alphaviruses

Abstract From 1986 to 1990, we conducted our second longitudinal study in the central (upstate) New York (CNY) area on the wild avian hosts of eastern equine encephalomyelitis (EEE) virus. Field-collecting methods mirrored a study conducted from 1978 to 1980 at the same endemic focus. Over the 5-yr study period, we captured 6,296 birds representing 99 species and took 4,174 blood samples from representatives of 83 species. Gray catbirds, song sparrows, and veerys were the three dominant species captured and bled, accounting for 40 and 55% of birds captured and bled. Blood clots were assayed for virus and sera tested for hemagglutination-inhibition (HI) antibodies to EEE and Highlands J virus. Virus isolations from birds defined two epiornitics of EEE virus in 1988 and 1990, and an epiornitic of HJ virus in 1986. Infected birds responded with the production of HI antibodies with titers indicative of recent infection (HI ≥ 1:160), and titers of sera positive during the epiornitics were significantly higher than positive sera during nonepiornitics. The 1990 EEE epiornitic extended from mid-July to the end of September, providing data to compare infection rates among species, habitats, and combinations of species with habitats. Few significant differences were found. The HJ epiornitic was only the second time this virus has occurred in CNY. Song sparrows were identified as the primary amplifying avian host of both viruses, although our capture and serological data would suggest a role for gray catbirds as the species most likely involved in yearly virus reintroduction. However, the cryptic nature of enzootic virus maintenance remains unresolved for the CNY virus foci. The appearances of HJ and EEE viruses were not epidemiologically linked, and there were no virus isolations from adults returning on site or virus isolations without concurrent isolations from mosquito vectors. Whether EEE and/or HJ virus are consistently present in or sporadically introduced into the inland foci of CNY area still has not been determined.

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.

Identification of bloodmeals in Anopheles quadrimaculatus and Anopheles punctipennis from eastern equine encephalitis virus foci in northeastern U.S.A.

The host‐feeding patterns of Anopheles quadrimaculatus Say and Anopheles punctipennis (Say) were examined in order to evaluate their potential contributions to the transmission of eastern equine encephalitis virus (EEEv) and other arboviruses in the northeastern U.S.A. Engorged mosquitoes of the two species were collected from EEEv foci in central New York (NY) and throughout New Jersey (NJ), and their bloodmeals were identified using a polymerase chain reaction (PCR)‐based assay and sequencing portions of the mitochondrial cytochrome b gene. Analysis of 131 An. quadrimaculatus and 107 An. punctipennis from NY revealed that 97.7% and 97.2%, respectively, had acquired blood solely from mammalian hosts. Similarly, examination of 288 An. quadrimaculatus and 127 An. punctipennis from NJ showed 100% and 96.0%, respectively, contained mammalian‐derived bloodmeals. Mosquitoes containing mixed bloodmeals from both avian and mammalian hosts were detected in 1.6% of An. quadrimaculatus from NY, and 2.8% and 4.0% of An. punctipennis from NY and NJ, respectively. White‐tailed deer (Odocoileus virginianus) constituted the most common vertebrate host for these anopheline mosquitoes, accounting for 85.8–97.7% of all bloodmeals identified. The predominance of white‐tailed deer as a source of bloodmeals supports enzootic amplification of deer‐associated arboviruses in this region, including Jamestown Canyon, Cache Valley and Potosi viruses. One horse‐ and two human‐derived bloodmeals were also detected in An. quadrimaculatus collected in NJ. Limited avian‐derived bloodmeals were detected from mourning dove (Zenaida macroura), sharp‐shinned hawk (Accipiter striatus) and house finch (Carpodacus mexicanus), mostly in mixed bloodmeals. Occasional feeding on avian hosts suggests that these mosquitoes may participate as epizootic–epidemic bridge vectors of EEEv from viraemic birds to mammalian hosts of concern, including horses and humans. An isolate of EEEv was recovered from the head and thorax of an An. punctipennis mosquito collected in NY.

Prevalence of Borrelia burgdorferi in Small Mammals in New York State

Abstract Intensive small mammal trapping was conducted in 12 counties in New York state during 1998–2000 to investigate the prevalence and site specificity of the Lyme disease spirochete, Borrelia burgdorferi in, and presence of the blacklegged tick, Ixodes scapularis Say on, the wild mice Peromyscus leucopus Rafinesque and Peromyscus maniculatus Wagner and other small mammal species. Previously captured mice (1992–1997) from throughout New York state also were recruited into the study, providing a total of 3,664 Peromyscus from 107 sites in 31 counties. Infection with B. burgdorferi was determined by polymerase chain reaction testing of ear tissue, and rates were determined by species, counties, and regions of the state. B. burgdorferi was detected in 10 small mammal species captured during 1998–2000. Peromyscus captured from Dutchess County in the lower Hudson Valley had the highest infection rate of 21%. The next highest infection rates were in counties within the Capital District: Albany (18%), Rensselaer (17%), and Columbia (13%). From 4,792 small animals examined, we recovered 2,073 ticks representing six species from 414 individuals of 12 mammal species, including 1,839 I. scapularis collected from 315 Peromyscus trapped in five counties. I. scapularis were most often collected from animals trapped in Albany, Rensselear, and Dutchess counties. We used protein electrophoresis of salivary amylase to distinguish between P. leucopus and P. maniculatus species. I. scapularis burdens were 5.7 ticks per P. leucopus and 14.3 ticks per P. maniculatus.

Fecundity of Naturally Blood-Fed Ochlerotatus japonicus

Abstract Ochlerotatus japonicus (Theobald) collected in gravid traps were held individually in modified BioQuip breeders in a darkened room under ambient conditions and readily oviposited on Styrofoam blocks. Counts were made of eggs laid on Styrofoam blocks, container sides, and water surface, and dissections allowed for counts of retained eggs to determine the fecundity of this species. In total, 32,970 eggs were oviposited by 289 females with a range of 3–249 eggs per female. The mean ± SD number of eggs oviposited per female, 114.08 ± 51.08, was significantly less than the mean number of eggs produced per female, 125.85 ± 47.89. Wing lengths ranged from 2.8 to 4.7 mm with a mean of 3.81 ± 0.38 mm. Wing length was positively correlated with total eggs formed (r2 = 0.3481); wing = 3.22054 + 0.0047 total eggs formed. There was no monthly size difference although females collected during October produced significantly fewer eggs than females collected from June to September. A low egg viability of 40% was attributed to improper storage of the Styrofoam blocks on which eggs were oviposited.

A GYNANDROMORPH OF CULISETA MORSITANS

ABSTRACT A gynandromorph of Culiseta morsitans was found in a collection made from resting shelters located near the village of Central Square, Oswego County, New York in June of 2004. This is the 1st report of a gynandromorph of this species. The polar (anterior–posterior) gynandromorph possessed a head and legs with male characteristics, and an abdomen with female characteristics. The specimen is further described and compared to a normal male and female of this species.

Assessing the use of diurnal resting shelters by Culiseta melanura (Diptera: Culicidae).

ABSTRACT Twenty resting shelters were set on the edge of a known Culiseta breeding habitat in four groups of five to support a 4 × 4 Latin square field experiment. Collection times were 0900, 1100, 1300, and 1500 hours and systematically rotated for the order by which each group of five boxes was collected. Mosquitoes were collected from resting shelters by chloroform anesthetization. Collections were identified to species, sex, and physiological status of the females (nonblooded or blood-fed and gravid). More than 77% of the mosquitoes collected were Culiseta melanura (Coquillett). Analyses included means and SE for total collections and shelter-day (number collected per units) and means comparison by t-test and general linear model with Student—Newman—Keuls or least significant differences means tests for replicate, group, time, and interactions of time and group. There were few significant differences among or between shelter-day means but more blood-fed and gravid female Cs. melanura were collected at 1300 hours than any other time. Results confirm the effectiveness of resting shelters in a surveillance program for Cs. melanura, demonstrate the flexibility of resting shelters as a surveillance tool, and suggest that Cs. melanura will move to more acceptable resting sites during daylight.

Fecundity of Wild-Caught Gravid Culiseta morsitans (Diptera: Culicidae)

ABSTRACT Culiseta morsitans (Theobald) is a mosquito vector of eastern equine encephalitis virus. Gravid Cs. morsitans were collected from resting shelters during June–September of 2004 and 2005 associated with a natural breeding area known as Toad Harbor-Big Bay Wildlife Management Unit in Oswego County, New York. Specimens were held individually in water-filled containers to encourage egg laying. Conditions in captivity provided three site options for oviposition, as follows: on a paper filter above the water line, on the filter at the water line, or on the water surface. Oviposited eggs were counted, as were eggs found retained in abdomens of dissected females. Fecundity for 181 female Cs. morsitans was based on the total egg count for each female. There were 89 females that oviposited ≥ 1 egg and produced an average of 158.4 eggs ± 4.9 eggs with a range of 51–318 eggs. Of the 89, there were 63 captive females that oviposited all their eggs, producing a mean of 160.4 ± 4.9 eggs, range 81–254 eggs. There were 62 egg masses oviposited above the water line within a range of 2–68 mm (average = 24 mm), 12 egg rafts or oviposition of scattered eggs directly on the water surface, and no rafts oviposited on filter paper directly at the water line. Wing length was used as a measure of mosquito size. The mean wing length for 154 females was 4.37 ± 0.02 mm (range, 3.8–4.9 mm).