Description of the egg of Ochlerotatus japonicus japonicus (Diptera: Culicidae) using variable pressure scanning electron microscopy.

The egg of Ochlerotatus japonicus japonicus (Theobald) is described with the aid of variable pressure scanning electron micrographs. The egg is black, cigar shaped, and tapers ventrally. The length is approximately 591 microm and the width is approximately 172 microm. The outer chorionic cells are irregular in shape, either hexagonal or pentagonal, and decrease in size toward the anterior and posterior poles. Ventral tubercles typically range from three to six and contact the chorionic reticulum. Dorsal tubercles contain two large tubercles with small oval-shaped tubercles grouped around them. A large thread-shaped tubercle extends from this grouping either as a single tubercle or as a series of connected tubercles. The micropylar collar is low and discontinuous and is seldom complete. This description will aid researchers in the identification of this invasive vector species.

Ectoparasites of cattle and small ruminants.

Arthropod ectoparasites are the most ubiquitous life forms affecting ruminant animals and commonly affect the daily activity and health status of ruminants. This article describes the phenology of several important ectoparasites of livestock and small ruminants, and delineates some general control and management strategies for protecting domestic ruminants.

First collection of Ochlerotatus japonicus japonicus in the state of Tennessee.

This is the 1st report of Ochlerotatus japonicus japonicus in the state of Tennessee, USA. Adults were collected at 5 sites in northwestern Knox County from June 9 through November 3, 2003, and from 1 site in both 2003 and 2004.

Molecular identification of Ehrlichia species and host bloodmeal source in Amblyomma americanum L. from two locations in Tennessee, United States.

The current status of tick-borne diseases in the southeastern United States is challenging to define due to emerging pathogens, uncertain tick/host relationships, and changing disease case definitions. A golf-oriented retirement community on the Cumberland Plateau in Tennessee experienced an ehrlichiosis outbreak in 1993, prompting efforts to reduce the local tick population using '4-Poster' acaricide devices targeting white-tailed deer (Odocoileus virginianus). In 2009, the prevalence of Ehrlichia spp. in questing ticks was surveyed in the area and compared to a Tennessee state park where acaricide had not been applied. The range of wildlife hosts that immature Amblyomma americanum fed upon and the role that these hosts may play in pathogen dynamics were investigated using a reverse line blot (RLB) bloodmeal analysis technique. Amblyomma americanum was by far the most common tick species in both study areas (>99% of ticks collected). Of 303 adult and nymphal A. americanum tested at the retirement community, six were positive for Ehrlichia chaffeensis (2.0%), 16 were positive for E. ewingii (5.3%), and six were positive for Panola Mountain Ehrlichia (2.0%). This is the first confirmation of Panola Mountain Ehrlichia in A. americanum from the state of Tennessee. The 9.3% prevalence of Ehrlichia spp. in ticks from the retirement community was similar to that detected at the state park site (5.5%), suggesting that the 4-Poster treatment had not been sufficient to reduce Ehrlichia spp. cycling in the tick population. At both study sites, A. americanum fed on a wide range of mammal and bird species, with a minority of detectable bloodmeals coming from deer. Of the Ehrlichia-infected nymphs with positive bloodmeal identification, none fed on deer, indicating that multiple vertebrate species are contributing to sylvatic maintenance of Ehrlichia spp. at these sites. This highlights the difficulty of attempting to reduce the risk of tick-borne disease through host-targeted interventions alone.

Assessment of parasitism of house fly and stable fly (Diptera: Muscidae) pupae by pteromalid (Hymenoptera: Pteromalidae) parasitoids using a polymerase chain reaction assay.

The internal transcribed spacer (ITS) regions of the ribosomal DNA of house flies, Musca domestica L., the stable flies, Stomoxys calcitrans (L.), and four parasitoid species in the genus Muscidifurax (Hymenoptera: Pteromalidae) were characterized to develop a method based on the polymerase chain reaction (PCR) to better define the role of pteromalid parasitism of pupae of the house fly and stable fly. Two parasitoid-specific primers were designed to anneal to the 5' end of the 5.8S rRNA gene in the parasitoid species. When paired with a universal primer at the 3' end of the 18S rRNA, the primers amplified the target ITS1 region in 10 pteromalid species. PCR allowed detection of parasitoid DNA within 24 h after females of Spalangia endius Walker oviposited into house fly puparia. PCR failed to amplify parasitoid DNA or detect parasitism in puparia that were exposed to parasitoid oviposition, allowed to develop 7 d, then killed by freezing and held at 20-24 degrees C for 4 d to allow DNA degradation. Digestion of the PCR products with restriction enzymes produced restriction fragment length polymorphisms that allowed identification of individual parasitoid species. Significantly greater levels of parasitism (P < 0.05) were detected by PCR for two of the five field collection dates in 1997. On the dates when PCR detected higher levels of parasitism than estimates provided by emergence of adult insects from samples taken at Feedlot M in 1997, more than 65% of all puparia in the emergence samples failed to produce an adult insect. Three puparia collected in 1997 produced double PCR bands that corresponded to PCR band sizes of Muscidifurax spp. and Spalangia sp., possibly indicating multiple parasitism or hyperparasitism.

Distribution of Salmonella in swine production ecosystems.

The objective of this 2-year field survey was to sample multiple ecological compartments within swine production systems to identify potential sources of Salmonella infection for swine. Twelve single-site production systems within Illinois were identified by slaughter sampling to have detectable Salmonella in swine and therefore selected for study. There were four visits to each farm during a 5-month period. Fecal samples were obtained from swine and other wild and domestic mammals. Arthropods and environmental samples of feed, water, pen floors, boots, and bird feces were also collected. All 8,066 samples obtained were cultured to detect Salmonella. Salmonella was detected on 11 of the 12 farms. There were 206 positive cultures, including samples from swine (83), pen floors (54), boots (32), flies (16), mice (9), cats (3), and birds (3). Swine shedding Salmonella in feces were detected on 9 of the 12 farms. The more Salmonella-abundant ecological compartments were cats (12% of samples positive), boots (11%), bird feces (8%), flies (6%), and mice (5%); 2.1% of 4,024 swine samples were positive. All 221 feed samples were negative for Salmonella. There was a correlation between a farm having a high prevalence of shedding Salmonella in pigs and a high abundance on pen floors, flies, and boots. The most common serotypes detected were Derby, Agona, Worthington, and Uganda, which were distributed throughout the ecosystem, suggesting widespread transmission across ecological compartments. The ubiquitous distribution of Salmonella suggests that an effective control strategy must target multiple compartments of the swine production ecosystem.

Evaluation of 4-poster acaricide applicators to manage tick populations associated with disease risk in a Tennessee retirement community.

In 1993, four residents of a retirement community in middle Tennessee were hospitalized with symptoms of ehrlichiosis causing community managers to implement mitigation methods to reduce tick numbers. For the past four years, managers have utilized 4-poster acaricide applicators that aim to reduce disease risk to residents by killing ticks that feed on deer. To determine the efficacy of this technique, we assessed Amblyomma americanum abundance in the vicinity of the devices by dragging 400 m vegetation transects once per month while ticks were active. In 2009, adult tick activity peaked in May, nymphal tick activity peaked in June, and larval activity peaked in September. Close to 4-poster devices, larval, nymphal, and adult tick abundances were reduced by 91%, 68%, and 49%, respectively (larval and nymphal p<0.001, adult p=0.005), relative to nearby untreated areas. No significant reduction in nymphal or adult A. americanum ticks was evident >300 m from 4-poster devices, however a ∼90% reduction in larvae was observed to our sampling limit (400 m). At the low density at which these devices are currently being used (average distance between devices = 6.6 km), we conclude that they will have little large-scale effect on the health risk posed by ticks in this community.

Assessing risk in focal arboviral infections: are we missing the big or little picture?

BACKGROUND: Focal arboviral infections affecting a subset of the overall population present an often overlooked set of challenges in the assessment and reporting of risk and the detection of spatial patterns. Our objective was to assess the variation in risk when using different at-risk populations and geographic scales for the calculation of incidence risk and the detection of geographic hot-spots of infection. We explored these variations using a pediatric arbovirus, La Crosse virus (LACV), as our model. METHODS AND FINDINGS: Descriptive and cluster analyses were performed on probable and confirmed cases of LACV infections reported to the Tennessee Department of Health from 1997 to 2006, using three at-risk populations (the total population, the population 18 years and younger, and the population 15 years and younger) and at two geographic levels (county and census tract) to assess the variation in incidence risk and to investigate evidence of clustering using both global and local spatial statistics. We determined that the most appropriate at-risk population to calculate incidence risk and to assess the evidence of clustering was the population 15 years and younger. Based on our findings, the most appropriate geographical level to conduct spatial analyses and report incidence risk is the census tract level. The incidence risk in the population 15 years and younger at the county level ranged from 0 to 226.5 per 100,000 persons (median 41.5) in those counties reporting cases (n = 14) and at the census tract level it ranged from 50.9 to 673.9 per 100,000 persons (median 126.7) in those census tracts reporting cases (n = 51). To our knowledge, this is the highest reported incidence risk for this population at the county level for Tennessee and at the census tract level nationally. CONCLUSION: The results of this study indicate the possibility of missing disease clusters resulting from performing incidence risk investigations of focal diseases using inappropriate at-risk populations and/or at large geographic scales. Improved disease surveillance and health planning will result through the use of well defined at-risk populations and the use of appropriate geographic scales for the analysis and reporting of diseases. The finding of a high incidence risk of LACV infections in eastern Tennessee demonstrates that the vast majority of these infections continue to be under-diagnosed and/or underreported in this region. Persistent prevention and surveillance efforts will be required to reduce exposure to infectious vectors and to detect new cases of infection in this region. Application of this study's observations in future investigations will enhance the quantification of incidence risk and the identification of high-risk groups within the population.

The mosquitoes of eastern Tennessee: studies on abundance, habitat preferences, and host-seeking behaviors.

A significant increase in the number of reported cases of La Crosse virus (LACV) infections in eastern Tennessee has occurred in the last ten years. The objective of this study was to determine the abundance and habitat preferences of the potential vectors of LACV in this region. Adult host-seeking mosquitoes were collected using CO(2)-baited CDC light traps and a series of human-landing catches in eastern Tennessee from 2004 to 2006. A total of 4,200 female mosquitoes of 23 species was collected by CO(2)-baited CDC trapping at ten sites during the study period. Aedes albopictus (Skuse) was the most abundant mosquito collected at all sites and vegetation types, with the ratios of total Ae. albopictus to Ae. triseriatus (Say) females collected being 2.1:1 in 2004, 3.8:1 in 2005, and 4.9:1 in 2006. Ten species were collected during a series of human-landing catches made at four different sites; one probable and three confirmed case sites of LACV infections, totaling 528 female mosquitoes. Aedes albopictus was the most abundant species collected, with a 4:1 ratio of Ae. albopictus to Ae. triseriatus females. Aedes albopictus exhibited two clear peaks of "landing" activity, one in the early morning and one in the late afternoon or early evening. Simple and multiple regression analyses of the predictors of the number of mosquitoes collected showed that populations of Ae. albopictus were three times more likely to be collected overall than Ae. triseriatus. Species (Ae. albopictus), vegetation (residential), and the previous cumulative precipitation for the four weeks prior to collection were significantly (P < 0.05) associated with the number of mosquitoes collected by CO(2)-baited CDC trapping. Aedes albopictus was also more likely to be collected than Ae. triseriatus at confirmed cases of LACV infections.

Detection, characterization, and prediction of tick-borne disease foci.

Tick-borne disease (TBD) transmission foci need to be characterized in space and time, and are often discontinuous on both scales. An active TBD focus is dependent on the fulfillment of three conditions: tick survival, pathogen survival and opportunities for human exposure. The essentials for tick survival include food sources, reproduction, and protection from environmental extremes. The pathogen survival kit includes sufficient densities of ticks and suitable reservoir hosts, and opportunities for transmission between them in order to maintain infection. Opportunities for human exposure depend on sufficient number of encounters between ticks and humans. Because tick foci need to be described on a range of spatial and temporal resolutions, data for such characterization include a variety of surveillance data, field and laboratory experimental data, as well as results of statistical and mathematical analysis and modeling. The application of new tools from molecular biology, geographic information systems (GIS), and satellite imagery, in conjunction with appropriate analytical methods allow for detection of unknown foci and prediction of new ones. A long-term multi-scale study of Ixodes scapularis and Lyme disease in the north-central U. S. is reviewed. Diverse surveillance methods of ticks, rodents, deer, canids and humans were coupled with environmental characterization in situ to create a habitat profile for Lyme disease ticks. Incorporating various digitized databases, a statistical model was used to develop a risk map for tick distribution in the region. The process of introduction and establishment of new tick foci along the Illinois River is described in relation to the known tick distribution and predictions of invasion based on the risk model.