Molecular screening for rickettsial bacteria and piroplasms in ixodid ticks surveyed from white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) in southern Texas.

A survey of ixodid ticks parasitizing white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) was completed during the 2018-2019 public hunt season on the Laguna Atascosa National Wildlife Refuge (Cameron County, Texas) and the East Foundation's El Sauz Ranch in nearby Willacy County (Texas). Anocenter nitens was the predominant tick species identified with 5% of these ticks collected from nilgai. All life stages were encountered in high numbers on white-tailed deer, indicating that deer may be a primary host in this region. Amblyomma maculatum and Amblyomma inornatum were identified from both hosts, while Ixodes scapularis was encountered only on white-tailed deer. This is the first published record of A. inornatum on nilgai. A subset of ticks was used in PCR assays to detect Rickettsia spp., family Anaplasmataceae, Borrelia spp., and Theileria-Babesia spp. Borrelia spp. were not detected in any of the ticks analyzed. Rickettsia parkeri was detected in three A. maculatum adult ticks from deer, Rickettsia sp. endosymbiont sequences were present in all I. scapularis ticks, and Rickettsia amblyommatis was detected in three A. inornatum adult ticks from deer. Sequence analysis of Anaplasmataceae-positive amplicons from A. nitens and A. maculatum had low percent identity to published Anaplasma spp. sequences, suggesting a unique Anaplasma sp. may be circulating in the population. Anaplasma platys was detected from A. nitens larvae and an Ehrlichia sp. Delta strain was present in A. maculatum, both of unknown pathogenicity towards deer. Theileria cervi was detected in all stages of A. nitens ticks, and positive ticks originated from 27 of 31 deer and a single nilgai sampled from throughout the survey site. The primary vector for T. cervi is absent from this region, suggesting T. cervi is possibly maintained by a different tick species.

TICK VECTOR AND DISEASE PATHOGEN SURVEILLANCE OF NILGAI ANTELOPE ( BOSELAPHUS TRAGOCAMELUS) IN SOUTHEASTERN TEXAS, USA.

Nilgai ( Boselaphus tragocamelus) are nonnative bovines that were originally introduced as game animals to one large, south Texas, US ranch but that are now present throughout southeastern Texas from Baffin Bay to Harlingen and in northern Mexico at least as far west as Durango. Between October 2014 and January 2017, nilgai ( n=517) were examined for the presence of tick ectoparasites, with particular interest in the cattle fever tick, Rhipicephalus ( Boophilus) microplus. These animals were either hunter killed or they were culled as part of federal cooperative harvesting from Cameron and Willacy counties in southeastern Texas. The proportion of fever tick-infested animals differed in a N-to-S pattern, and this was at least partly attributed to differences in habitat. The southern area is a lowland floodplain predominated by halophytes, whereas the northerly area is upland thorn scrub, the latter of which provides a vegetative canopy that is more conducive to tick survival and persistence. A subset of nilgai, all from the Texas-Mexico border area, were screened for livestock pathogens using molecular and serological assays. All nilgai were seronegative for Babesia ( Theileria) equi and Babesia cabalii. Although 11 animals were seropositive for Anaplasma marginale by competitive enzyme-linked immunosorbent assay (cELISA), these were interpreted with caution because of the lack of concordance between cELISA and molecular detection assays. All animals were PCR negative for presence of Babesia spp. DNA, and a single nilgai was seropositive for Babesia bovis and Babesia bigemina by complement fixation. It remains unknown whether cattle Babesia spp. can establish an infection in nilgai.

Implication of Nilgai Antelope (Artiodactyla: Bovidae) in Reinfestations of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in South Texas: A Review and Update.

The Cattle Fever Tick Eradication Program was the first parasite eradication program of veterinary importance in the United States and is considered to be one of the greatest disease eradication programs of all time. The program's utilization of pasture vacation and dipping of cattle in acaricide has been extremely successful for controlling Rhipicephalus (Boophilus) microplus (Canestrini) and R. (B.) annulatus (Say), collectively known as cattle fever ticks, on cattle along the Texas border with Mexico for decades. However, the increase of white-tailed deer, Odocoileus virginianus (Zimmermann), populations in South Texas over the last 50 yr has compromised the success of the program. R. (B.) microplus and R. (B.) annulatus infestation data have confirmed that O. virginianus can support the maintenance and movement of both species of cattle fever tick within the permanent quarantine or buffer zone in South Texas along the Rio Grande, and also in the cattle fever tick-free area north and east of the buffer zone. Over the last two decades, increasing populations of exotic nilgai antelope, Boselaphus tragocamelus (Pallas), in South Texas have further complicated cattle fever tick eradication efforts. Historical cattle fever tick infestation data, host source data, and geographical data support the continued role of O. virginianus in maintaining reinfestations of R. (B.) microplus and R. (B.) annulatus in South Texas as well as the increasing role of nilgai antelope in cattle fever tick maintenance and dispersal.