Effect of Temperature on Feeding Period of Larval Blacklegged Ticks (Acari: Ixodidae) on Eastern Fence Lizards

Ambient temperature can influence tick development time, and can potentially affect tick interactions with pathogens and with vertebrate hosts. We studied the effect of ambient temperature on duration of attachment of larval blacklegged ticks, Ixodes scapularis Say, to eastern fence lizards, Sceloporus undulatus (Bosc & Daudin). Feeding periods of larvae that attached to lizards under preferred temperature conditions for the lizards (WARM treatment: temperatures averaged 36.6°C at the top of the cage and 25.8°C at the bottom, allowing behavioral thermoregulation) were shorter than for larvae on lizards held under cool conditions (COOL treatment temperatures averaged 28.4°C at top of cage and 24.9°C at the bottom). The lizards were infested with larvae four times at roughly monthly intervals. Larval numbers successfully engorging and dropping declined and feeding period was longer after the first infestation

Comparison of Survival Patterns of Northern and Southern Genotypes of the North American Tick \u3cem\u3eIxodes scapularis\u3c/em\u3e (Acari: Ixodidae) under Northern and Southern Conditions

Background: Several investigators have reported genetic differences between northern and southern populations of Ixodes scapularis in North America, as well as differences in patterns of disease transmission. Ecological and behavioral correlates of these genetic differences, which might have implications for disease transmission, have not been reported. We compared survival of northern with that of southern genotypes under both northern and southern environmental conditions in laboratory trials. Methods: Subadult I. scapularis from laboratory colonies that originated from adults collected from deer from several sites in the northeastern, north central, and southern U.S. were exposed to controlled conditions in environmental chambers. Northern and southern genotypes were exposed to light:dark and temperature conditions of northern and southern sites with controlled relative humidities, and mortality through time was recorded. Results: Ticks from different geographical locations differed in survival patterns, with larvae from Wisconsin surviving longer than larvae from Massachusetts, South Carolina or Georgia, when held under the same conditions. In another experiment, larvae from Florida survived longer than larvae from Michigan. Therefore, survival patterns of regional genotypes did not follow a simple north–south gradient. The most consistent result was that larvae from all locations generally survived longer under northern conditions than under southern conditions. Conclusions: Our results suggest that conditions in southern North America are less hospitable than in the north to populations of I. scapularis. Southern conditions might have resulted in ecological or behavioral adaptations that contribute to the relative rarity of I. scapularis borne diseases, such as Lyme borreliosis, in the southern compared to the northern United States

Why Lyme Disease is Common in the Northern US, but Rare in the South: The Roles of Host Choice, Host-seeking Behavior, and Tick Density

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick–vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick–host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US

Spotted turtle use of a culvert under relocated Route 44 in Carver, Massachusetts

A new highway alignment for relocated Route 44 in Carver, Massachusetts, resulted in the direct alteration of 2.5 acres and indirect alteration of 3.9 acres of habitat for three statelisted turtle species: the wood turtle (Clemmys insculpta), spotted turtle (Clemmys guttata), and eastern box turtle (Terrapene c. carolina). As part of the mitigation requirements for impacts to rare species habitat, the Massachusetts Highway Department (MassHighway) conducted a two year preconstruction study to determine the habitat preferences and seasonal movements of the statelisted species. The study determined that no wood turtles were present in the study area, that there was a large but declining population of box turtles, and that two highly used spotted turtle habitats would be bisected by the proposed highway entrance ramp. An intermittent stream channel proposed to be piped under the new entrance ramp was identified as a primary travel corridor between the two habitats. Based on the findings of the preconstruction study, MassHighway identified a simple solution to allow the stream channel to continue to provide a migratory corridor for spotted turtles. To achieve this goal, MassHighway increased the proposed culvert size from a 24inch pipe to a 6foot by 6foot box culvert. In the spring and summer of 2004, postconstruction monitoring was conducted to determine the effectiveness of the culvert as a spotted turtle crossing structure. Nine turtles were fitted with radio transmitters and thread bobbins and followed three times per week in the spring and early summer, and once per week in the late summer to determine culvert effectiveness. Direct evidence (thread trails, visual observation) was documented for seven turtles, and indirect evidence (radio telemetry points on both sides of the culvert, visual observation) was documented for 13 turtles, confirming the use of the culvert as a crossing structure. A future study is recommended to document potential effects of traffic and noise on the spotted turtle population, continued use of the culvert, and potential changes to rare species habitat from the highway construction

Spotted turtle use of a culvert under relocated Route 44 in Carver, Massachusetts

A new highway alignment for relocated Route 44 in Carver, Massachusetts, resulted in the direct alteration of 2.5 acres and indirect alteration of 3.9 acres of habitat for three statelisted turtle species: the wood turtle (Clemmys insculpta), spotted turtle (Clemmys guttata), and eastern box turtle (Terrapene c. carolina). As part of the mitigation requirements for impacts to rare species habitat, the Massachusetts Highway Department (MassHighway) conducted a two year preconstruction study to determine the habitat preferences and seasonal movements of the statelisted species. The study determined that no wood turtles were present in the study area, that there was a large but declining population of box turtles, and that two highly used spotted turtle habitats would be bisected by the proposed highway entrance ramp. An intermittent stream channel proposed to be piped under the new entrance ramp was identified as a primary travel corridor between the two habitats. Based on the findings of the preconstruction study, MassHighway identified a simple solution to allow the stream channel to continue to provide a migratory corridor for spotted turtles. To achieve this goal, MassHighway increased the proposed culvert size from a 24inch pipe to a 6foot by 6foot box culvert. In the spring and summer of 2004, postconstruction monitoring was conducted to determine the effectiveness of the culvert as a spotted turtle crossing structure. Nine turtles were fitted with radio transmitters and thread bobbins and followed three times per week in the spring and early summer, and once per week in the late summer to determine culvert effectiveness. Direct evidence (thread trails, visual observation) was documented for seven turtles, and indirect evidence (radio telemetry points on both sides of the culvert, visual observation) was documented for 13 turtles, confirming the use of the culvert as a crossing structure. A future study is recommended to document potential effects of traffic and noise on the spotted turtle population, continued use of the culvert, and potential changes to rare species habitat from the highway construction

Flagging versus dragging as sampling methods for nymphal Ixodes scapularis (Acari: Ixodidae)

The nymphal stage of the blacklegged tick, Ixodes scapularis (Acari: Ixodidae), is responsible for most transmission of Borrelia burgdorferi, the etiologic agent of Lyme disease, to humans in North America. From 2010 to fall of 2012, we compared two commonly used techniques, flagging and dragging, as sampling methods for nymphal I. scapularis at three sites, each with multiple sampling arrays (grids), in the eastern and central United States. Flagging and dragging collected comparable numbers of nymphs, with no consistent differences between methods. Dragging collected more nymphs than flagging in some samples, but these differences were not consistent among sites or sampling years. The ratio of nymphs collected by flagging vs dragging was not significantly related to shrub density, so habitat type did not have a strong effect on the relative efficacy of these methods. Therefore, although dragging collected more ticks in a few cases, the numbers collected by each method were so variable that neither technique had a clear advantage for sampling nymphal I. scapularis. © 2013 The Society for Vector Ecology

Selective Host Attachment by Ixodes scapularis (Acari: Ixodidae): Tick-Lizard Associations in the Southeastern United States

Questing behavior and host associations of immature blacklegged ticks, Ixodes scapularis Say, from the southeastern United States are known to differ from those in the north. To elucidate these relationships we describe host associations of larval and nymphal I. scapularis from 8 lizard species sampled from 5 sites in the southeastern U.S. Larvae and nymphs attached in greater numbers to larger lizards than to smaller lizards, with differential levels of attachment to different lizard species. Blacklegged ticks are generally attached to skinks of the genus Plestiodon in greater numbers per unit lizard weight than to anoles (Anolis) or fence lizards (Sceloporus). The broad-headed skink, Plestiodon laticeps (Schneider), was a particularly important host for immature I. scapularis in our study and in several previous studies of tick-host associations in the southeast. Blacklegged ticks show selective attachment to Plestiodon lizard hosts in the southeast, but whether this results from behavioral host preferences or from ecological factors such as timing or microhabitat distributions of tick questing and host activity remains to be determined

Minimal role of eastern fence lizards in borrelia burgdorferi transmission in Central New Jersey Oak/Pine Woodlands

The eastern fence lizard, Sceloporus undulatus, is widely distributed in eastern and central North America, ranging through areas with high levels of Lyme disease, as well as areas where Lyme disease is rare or absent. We studied the potential role of S. undulatus in transmission dynamics of Lyme spirochetes by sampling ticks from a variety of natural hosts at field sites in central New Jersey, and by testing the reservoir competence of S. undulatus for Borrelia burgdorferi in the laboratory. The infestation rate of ticks on fence lizards was extremely low (prevalence = 0.087, n = 23) compared to that on white-footed mice and other small mammals (prevalence = 0.53, n = 140). Of 159 nymphs that had fed as larvae on lizards that had previously been exposed to infected nymphs, none was infected with B. burgdorferi, compared with 79.9% of 209 nymphs that had fed as larvae on infected control mice. Simulations suggest that changes in the numbers of fence lizards in a natural habitat would have little effect on the infection rate of nymphal ticks with Lyme spirochetes. We conclude that in central New Jersey, S. undulatus plays a minimal role in the enzootic transmission cycle of Lyme spirochetes

Seasonality of acarological risk of exposure to Borrelia miyamotoi from questing life stages of Ixodes scapularis collected from Wisconsin and Massachusetts, USA

Measures of acarological risk of exposure to Ixodes scapularis-borne disease agents typically focus on nymphs; however, the relapsing fever group spirochete Borrelia miyamotoi can be passed transovarially, and I. scapularis larvae are capable of transmitting B. miyamotoi to their hosts. To quantify the larval contribution to acarological risk, relative to nymphs and adults, we collected questing I. scapularis for 3 yr at Fort McCoy, Wisconsin (WI, n = 23,367 ticks), and Cape Cod, Massachusetts (MA, n = 4190) in the United States. Borrelia miyamotoi infection prevalence was estimated for I. scapularis larvae, nymphs, females, and males, respectively, as 0.88, 2.05, 0.63, and 1.22 % from the WI site and 0.33, 2.32, 2.83, and 2.11 % from the MA site. Densities of B. miyamotoi-infected ticks (DIT, per 1000 m2) were estimated for larvae, nymphs, females, and males, respectively, as 0.36, 0.14, 0.01, and 0.03 from the WI site and 0.05, 0.06, 0.03, and 0.02 from the MA site. Thus, although larval infection prevalence with B. miyamotoi was significantly lower than that of nymphs and similar to that of adults, because of their higher abundance, the larval contribution to the overall DIT was similar to that of nymphs and trended towards a greater contribution than adults. Assuming homogenous contact rates with humans, these results suggest that eco-epidemiological investigations of B. miyamotoi disease in North America should include larvae. A fuller appreciation of the epidemiological implications of these results, therefore, requires an examination of the heterogeneity in contact rates with humans among life stages