Movement patterns of nilgai antelope in South Texas: Implications for cattle fever tick management.

Wildlife, both native and introduced, can harbor and spread diseases of importance to the livestock industry. Describing movement patterns of such wildlife is essential to formulate effective disease management strategies. Nilgai antelope (Boselaphus tragocamelus) are a free-ranging, introduced ungulate in southern Texas known to carry cattle fever ticks (CFT, Rhipicephalus (Boophilus) microplus, R. (B.) annulatus). CFT are the vector for the etiological agent of bovine babesiosis, a lethal disease causing high mortality in susceptible Bos taurus populations and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful. However, a permanent quarantine area is maintained between Texas and Mexico to check its entry from infested areas of neighboring Mexico states on wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the permanent quarantine area in Texas. Nilgai are of interest in understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. Median annual home range sizes were highly variable in males (4665ha, range=571-20,809) and females (1606ha, range=848-29,909). Female movement patterns appeared to be seasonal with peaks during June-August; these peaks appeared to be a function of break-ups in female social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus four other types of helicopter activities. Nilgai did not cross 1.25m high cattle fences parallel to paved highways but did cross other fence types. Results indicate that females have a higher chance of spreading CFT through the landscape than males, but spread of CFT may be mitigated via maintenance of cattle fences running parallel with paved highways. Our results highlight the importance of documenting species-specific behavior in wildlife-livestock interfaces that can be used to develop effective disease management strategies in the United States and worldwide.

Pathogenic Landscape of Transboundary Zoonotic Diseases in the Mexico-US Border Along the Rio Grande.

Transboundary zoonotic diseases, several of which are vector borne, can maintain a dynamic focus and have pathogens circulating in geographic regions encircling multiple geopolitical boundaries. Global change is intensifying transboundary problems, including the spatial variation of the risk and incidence of zoonotic diseases. The complexity of these challenges can be greater in areas where rivers delineate international boundaries and encompass transitions between ecozones. The Rio Grande serves as a natural border between the US State of Texas and the Mexican States of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. Not only do millions of people live in this transboundary region, but also a substantial amount of goods and people pass through it everyday. Moreover, it occurs over a region that functions as a corridor for animal migrations, and thus links the Neotropic and Nearctic biogeographic zones, with the latter being a known foci of zoonotic diseases. However, the pathogenic landscape of important zoonotic diseases in the south Texas-Mexico transboundary region remains to be fully understood. An international perspective on the interplay between disease systems, ecosystem processes, land use, and human behaviors is applied here to analyze landscape and spatial features of Venezuelan equine encephalitis, Hantavirus disease, Lyme Borreliosis, Leptospirosis, Bartonellosis, Chagas disease, human Babesiosis, and Leishmaniasis. Surveillance systems following the One Health approach with a regional perspective will help identifying opportunities to mitigate the health burden of those diseases on human and animal populations. It is proposed that the Mexico-US border along the Rio Grande region be viewed as a continuum landscape where zoonotic pathogens circulate regardless of national borders.