Since the introduction of the mosquito-borne West Nile Virus (WNV) into New York City (NYC) in 1999, it has expanded westward across the North American continent in an unprecedented fashion, taking in its wake hundreds of thousands and possibly millions of native and exotic birds. Corvid species, particularly the American crow, are particularly susceptible to this virulent strain of virus and have died dramatically during the summer virus transmission season. Experimental studies have shown that the fatality rate from WNV infection in American crows is nearly 100%. This mortality in crows and other corvids was used as a sensitive sentinel system to detect the presence and movement of the virus through a public reporting and laboratory testing national surveillance program. Crows were also the earliest indicator of virus activity in the majority of locations and were a useful predictor of human cases. Bird mortality from WNV peaks during August-September at the height of the mosquito-transmission period but extends from April to November each year in some states. An impact of WNV on local populations of crows was observed in some localities such as the NYC area, but no significant declines have been detected yet by the regional population trend data. The geographical distribution of WNV activity is not continuous across local landscapes and unexposed crows can then serve as a source to repopulate affected areas when overall populations are high. If WNV transmission continues for years with regular mortality, the resiliency of the regional crow populations to sustain this high mortality rate will diminish.

Since the invasion of the mosquito-borne, West Nile virus (WNv) into North America in New York City (NYC) in 1999, the distribution of the virus has expanded throughout most of the continent during the ensuing years, causing mortality in hundreds of thousands of native and exotic birds and producing tens of thousands of equine and human cases. The initial outbreaks in the NYC area in 1999 were intense in local bird populations, with small outbreaks in humans and equines. Then, WNv spread north and south from this focal area during the next 2 years. The northward and southward sequence of dissemination continued as WNv began to encompass the remainder of the continent. Migrating birds are thought to be the one of the major contributors to the rapid dissemination of this mosquito-borne virus. The temporal and spatial pattern and rapidity of the continental spread of WNv, as detected by the national surveillance system, match the semi-annual migratory movements of hundreds of millions of North American birds. The subsequent dissemination of the virus to Canada, the Caribbean, Mexico, Central America, and now South America fits this method of spread as well. The strain of WNv introduced into the U.S. had increased virulence for North American birds, which quickly became apparent after its introduction and from the subsequent avian epizootics it caused. More than 200 species of birds experienced mortality, especially corvid species such as the American crow, blue jay, and several species of magpies, and recently the greater sage grouse. These species were particularly susceptible to this virulent strain of virus, as demonstrated in experimental studies and from dramatic die-offs during the summer virus transmission seasons. Bird mortality from WNv peaks during August-September at the height of the mosquito-transmission period but extends from April to November each year in some states. This mortality in crows and other corvid species was used as a sensitive sentinel system to detect the presence and movement of the virus through a public health reporting and laboratory testing national surveillance program. Mammal species were frequently infected, and some suffered mortality. The nationwide bird mortality from WNv infections was dramatic in North America during the last 7 years, but the actual impact of the mortality on bird populations is not known because of the insensitivity of national population data available on birds. Few regional declines in bird populations have been detected; however, the impact of WNv on local populations of crows and sage grouse has been observed in some localities. The geographical distribution of WNv activity is not continuous across local landscapes, and unexposed birds can then serve as a source to repopulate local impacted areas when overall populations are high. West Nile virus persists through the winter periods and reappears annually in the spring in temperate regions of the continent. The mechanisms responsible for this recrudescence are unique and largely unknown. Focusing on these overwintering locations with targeted mosquito control could suppress early season initiation of virus transmission and possibly prevent subsequent summer amplification. Integrated pest management aimed at controlling mosquito populations is currently the only effective approach to control this disease.

Bovine tuberculosis (bTB) is a contagious disease of livestock, wildlife, and humans. Typically, it is transmitted through inhalation of aerosolized bacilli and direct or indirect contact between animals. In northeastern Michigan, bTB is endemic in white-tailed deer, and evidence suggests deer have spread the disease to domestic cattle. Previous research indicates bTB transmission likely occurs through contamination of cattle feeding sources by infected deer and subsequent use by cattle. We are investigating deer movements in relation to farm management practices such as feeding schedules as well as locations of cattle feeding areas, hay storage sites, barns, and water sources. All locations are plotted using ArcMap software. Regular communication with cooperators allows for updates in feeding schedules and locations. We are capturing free-ranging whitetailed deer and fitting them with radio collars equipped with a global positioning system (GPS). As of 15 February 2008, we have retrieved GPS collars from 7 of 16 deer collared in 2007, and 7 new collars have been deployed since 1 January 2008. Each retrieved collar has recorded over 2,500 data points, and preliminary results suggest individual deer are staying within 1.5 km of their capture site. Spatial analysis on deer locations relative to livestock management practices and farm structures will take place when all data is retrieved in late 2008 and early 2009. Once complete, we hope this information will allow us to recommend mitigating measures for livestock producers to reduce the risk of transmission of bTB from free ranging whitetailed deer to domestic cattle.

The raccoon variant of rabies is distributed throughout the eastern and southeastern United States. Historically, the westward spread of raccoon variant rabies has been prevented by geographical barriers and the distribution of oral rabies vaccines (ORV). In 2004, raccoons positive for raccoon variant rabies were discovered beyond the vaccination zone in northeastern Ohio, suggesting the potential westward spread of the disease. To evaluate the potential westward spread of rabies across Ohio, we are employing two strategies: telemetry, and genetics. We are radio-tracking raccoons to determine which factors, if any, may be considered barriers or corridors to raccoon movement. In addition, we are collecting genetic samples from raccoons in urban and rural areas in 9 distinct regions of northeastern Ohio. These samples will be used to evaluate relatedness between raccoon populations. We hypothesize that the degree of genetic relatedness will be proportional to the distance separating populations. Populations showing less or more relatedness may be indicative of barriers or corridors to movement, respectively. Preliminary movement data suggest that raccoons are remaining within their home ranges in greenbelt areas, although some have traveled over 2.0 km into urban and suburban areas before returning. Genetic sampling is 45% complete, and analysis will be performed once all samples have been collected. The results from this study will provide a more thorough understanding of raccoon movement in northeastern Ohio. This information will allow researchers to recommend ORV bait distribution strategies to more effectively stem the westward spread of raccoon variant rabies.

A study was initiated in 2005 to examine the ecology of gray fox in Texas, to assist the oral rabies vaccination program. The study’s objectives are to examine space use and long-distance movements of radio-collared foxes, and to provide landscape-level ecological assessment of fox dispersal and the factors that influence it. Concurrently, GIS habitat layers being built will assist in understanding fox movement and gene flow.