Distribution, seasonality, and hosts of the Rocky Mountain wood tick in the United States.

Anaplasma marginale Theiler is a tick-borne pathogen that causes anaplasmosis in cattle. There are approximately 20 tick species worldwide that are implicated as vectors of this pathogen. In the United States, Dermacentor andersoni Stiles and Dermacentor variabilis (Say) are the principal vectors. The risk of transmission of anaplasmosis to cattle has been largely based on the distribution of D. andersoni in the United States. We developed a centralized geographic database that incorporates collection records for D. andersoni from two large national databases. We reviewed the geographic records in each database and postings from MEDLINE and AGRICOLA to produce a national county-level distribution map based on a total of 5,898 records. The records spanned the period from 1903 through 2001 with the majority between 1921 to 1940. Populations of D. andersoni were recorded from 267 counties in 14 states and were distinguished as either established or reported. We found 180 counties with established populations of D. andersoni and 87 counties with reported occurrences in 14 states with the majority of established populations reported from Montana, Idaho, and Oregon. D. andersoni populations in the United States currently extend from the western portions of Nebraska and the Dakotas westward to the Cascade Mountains and from the northern counties of Arizona and New Mexico northward to the Canadian border. The data will be useful for identifying regions at increased risk of acquiring anaplasmosis in the United States. Based upon the database collection records, we also present a summary of recorded hosts for D. andersoni and comments on its seasonal occurrence.

Candidate vectors and rodent hosts of Venezuelan equine encephalitis virus, Chiapas, 2006-2007.

Enzootic Venezuelan equine encephalitis virus (VEEV) has been known to occur in Mexico since the 1960s. The first natural equine epizootic was recognized in Chiapas in 1993 and since then, numerous studies have characterized the etiologic strains, including reverse genetic studies that incriminated a specific mutation that enhanced infection of epizootic mosquito vectors. The aim of this study was to determine the mosquito and rodent species involved in enzootic maintenance of subtype IE VEEV in coastal Chiapas. A longitudinal study was conducted over a year to discern which species and habitats could be associated with VEEV circulation. Antibody was rarely detected in mammals and virus was not isolated from mosquitoes. Additionally, Culex (Melanoconion) taeniopus populations were found to be spatially related to high levels of human and bovine seroprevalence. These mosquito populations were concentrated in areas that appear to represent foci of stable, enzootic VEEV circulation.

Geographic information systems: introduction.

The recent exponential growth of the science and technology of geographic information systems (GIS) has made a tremendous contribution to epidemiological analysis and has led to the development of new powerful tools for the surveillance of animal diseases. GIS, spatial analysis and remote sensing provide valuable methods to collect and manage information for epidemiological surveys. Spatial patterns and trends of disease can be correlated with climatic and environmental information, thus contributing to a better understanding of the links between disease processes and explanatory spatial variables. Until recently, these tools were underexploited in the field of veterinary public health, due to the prohibitive cost of hardware and the complexity of GIS software that required a high level of expertise. The revolutionary developments in computer performance of the last decade have not only reduced the costs of equipment but have made available easy-to-use Web-based software which in turn have meant that GIS are more widely accessible by veterinary services at all levels. At the same time, the increased awareness of the possibilities offered by these tools has created new opportunities for decision-makers to enhance their planning, analysis and monitoring capabilities. These technologies offer a new way of sharing and accessing spatial and non-spatial data across groups and institutions. The series of papers included in this compilation aim to: - define the state of the art in the use of GIS in veterinary activities - identify priority needs in the development of new GIS tools at the international level for the surveillance of animal diseases and zoonoses - define practical proposals for their implementation. The topics addressed are presented in the following order in this book: - importance of GIS for the monitoring of animal diseases and zoonoses - GIS application in surveillance activities - spatial analysis in veterinary epidemiology - data collection and remote sensing applications - Web - GIS as a tool for data and knowledge sharing. All 43 manuscripts selected for this book have been peer-reviewed. These contributions were originally commissioned for the First international conference on the use of GIS in veterinary activities organised by the Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise 'G. Caporale', Teramo, Italy, and the World Organisation for Animal Health (OIE: Office International des Epizooties) that was held in Silvi Marina, Italy, from 8 to 11 October 2006. The editors would like to thank all authors for their valuable contributions.

Geospatial field applications within United States Department of Agriculture, Veterinary Services.

Epidemiologists, veterinary medical officers and animal health technicians within Veterinary Services (VS) are actively utilising global positioning system (GPS) technology to obtain positional data on livestock and poultry operations throughout the United States. Geospatial data, if acquired for monitoring and surveillance purposes, are stored within the VS Generic Database (GDB). If the information is collected in response to an animal disease outbreak, the data are entered into the Emergency Management Response System (EMRS). The Spatial Epidemiology group within the Centers for Epidemiology and Animal Health (CEAH) has established minimum data accuracy standards for geodata acquisition. To ensure that field-collected geographic coordinates meet these minimum standards, field personnel are trained in proper data collection procedures. Positional accuracy is validated with digital atlases, aerial photographs, Web-based parcel maps, or address geocoding. Several geospatial methods and technologies are under investigation for future use within VS. These include the direct transfer of coordinates from GPS receivers to computers, GPS-enabled digital cameras, tablet PCs, and GPS receivers preloaded with custom ArcGIS maps - all with the objective of reducing transcription and data entry errors and improving the ease of data collection in the field.

Geospatial analysis and modelling in the prevention and control of animal diseases in the United States.

Geospatial analysis of disease investigation data improves data standardisation and validation and enhances pathogen detection. Grid-based surveillance systems for Newcastle disease in southern California and for bovine tuberculosis on Molokai Island, Hawaii, demonstrate the importance of this approach to operational planning. In addition, as shown by a bovine tuberculosis study in wildlife on Molokai Island, a lattice grid can be used to develop zonal strategies for disease regulatory actions. In risk mapping, disease risk distribution is compared with the distribution of risk factors to identify potential determinants of risk. This process is being applied to North American waterfowl migratory routes to identify geographic areas with high concentrations of migratory waterfowl so that a spatially targeted sampling strategy for use in surveillance operations can be designed. Finally, while farm location data are needed to model pathogen spread through susceptible animal populations, this information is generally unavailable to analysts and modellers. Recently, a farm location and animal population simulator application was developed in which agricultural census data is distributed to create a farm location dataset representative of an agricultural commodity within a specific geographic area.

A Rift Valley fever risk surveillance system for Africa using remotely sensed data: potential for use on other continents.

The authors developed a monitoring and risk mapping system using normalized difference vegetation index (NDVI) times series data derived from the advanced very high resolution radiometer (AVHRR) instrument on polar orbiting national oceanographic and atmospheric administration (NOAA) satellites to map areas with a potential for a Rift Valley fever (RVF) outbreaks in sub-Saharan Africa. This system is potentially an important tool for local, national and international organisations involved in the prevention and control of animal and human disease, permitting focused and timely implementation of disease control strategies several months before an outbreak. We are currently developing a geographic information system (GIS)-based remotely sensed early warning system for potential RVF vectors in the United States. Forecasts of the potential emergence of mosquito vectors will be disseminated throughout the United States, providing several months' warning in advance of potentially elevated mosquito populations. This would allow timely, targeted implementation of mosquito control, animal quarantine and vaccine strategies to reduce or prevent animal and human disease.

Venezuelan equine encephalitis virus, southern Mexico.

Equine epizootics of Venezuelan equine encephalitis (VEE) occurred in the southern Mexican states of Chiapas in 1993 and Oaxaca in 1996. To assess the impact of continuing circulation of VEE virus (VEEV) on human and animal populations, serologic and viral isolation studies were conducted in 2000 to 2001 in Chiapas State. Human serosurveys and risk analyses indicated that long-term endemic transmission of VEEV occurred among villages with seroprevalence levels of 18% to 75% and that medical personnel had a high risk for VEEV exposure. Seroprevalence in wild animals suggested cotton rats as possible reservoir hosts in the region. Virus isolations from sentinel animals and genetic characterizations of these strains indicated continuing circulation of a subtype IE genotype, which was isolated from equines during the recent VEE outbreaks. These data indicate long-term enzootic and endemic VEEV circulation in the region and continued risk for disease in equines and humans.