title: Widespread movement of invasive cattle fever ticks (Rhipicephalus microplus) in southern Texas leads to shared local infestations on cattle and deer.
abstract: BACKGROUND
  Rhipicephalus (Boophilus) microplus is a highly-invasive tick that transmits the cattle parasites (Babesia bovis and B. bigemina) that cause cattle fever. R. microplus and Babesia are endemic in Mexico and ticks persist in the United States inside a narrow tick eradication quarantine area (TEQA) along the Rio Grande. This containment area is threatened by unregulated movements of illegal cattle and wildlife like white-tailed deer (WTD; Odocoileus virginianus).
  
  
  METHODS
  Using 11 microsatellite loci we genotyped 1,247 R. microplus from 63 Texas collections, including outbreak infestations from outside the TEQA. We used population genetic analyses to test hypotheses about ecological persistence, tick movement, and impacts of the eradication program in southern Texas. We tested acaricide resistance with larval packet tests (LPTs) on 47 collections.
  
  
  RESULTS
  LPTs revealed acaricide resistance in 15/47 collections (32%); 11 were outside the TEQA and three were resistant to multiple acaricides. Some collections highly resistant to permethrin were found on cattle and WTD. Analysis of genetic differentiation over time at seven properties revealed local gene pools with very low levels of differentiation (FST 0.00-0.05), indicating persistence over timespans of up to 29 months. However, in one neighborhood differentiation varied greatly over a 12-month period (FST 0.03-0.13), suggesting recurring immigration from distinct sources as another persistence mechanism. Ticks collected from cattle and WTD at the same location are not differentiated (FST = 0), implicating ticks from WTD as a source of ticks on cattle (and vice versa) and emphasizing the importance of WTD to tick control strategies. We identified four major genetic groups (K = 4) using Bayesian population assignment, suggesting multiple introductions to Texas.
  
  
  CONCLUSIONS
  Two dispersal mechanisms give rise to new tick infestations: 1) frequent short-distance dispersal from the TEQA; and 2) rare long-distance, human-mediated dispersal from populations outside our study area, probably Mexico. The threat of cattle fever tick transport into Texas is increased by acaricide resistance and the ability of R. microplus to utilize WTD as an alternate host. Population genetic analyses may provide a powerful tool for tracking invasions in other parts of the world where these ticks are established.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Busch
authors.forename: Nathan E
authors.initials: NE
authors.lastname: Stone
authors.forename: Roxanne
authors.initials: R
authors.lastname: Nottingham
authors.forename: Ana
authors.initials: A
authors.lastname: Araya-Anchetta
authors.forename: Jillian
authors.initials: J
authors.lastname: Lewis
authors.forename: Christian
authors.initials: C
authors.lastname: Hochhalter
authors.forename: John R
authors.initials: JR
authors.lastname: Giles
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Gruendike
authors.forename: Jeanne
authors.initials: J
authors.lastname: Freeman
authors.forename: Greta
authors.initials: G
authors.lastname: Buckmeier
authors.forename: Deanna
authors.initials: D
authors.lastname: Bodine
authors.forename: Roberta
authors.initials: R
authors.lastname: Duhaime
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Miller
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Davey
authors.forename: Pia U
authors.initials: PU
authors.lastname: Olafson
authors.forename: Glen A
authors.initials: GA
authors.lastname: Scoles
authors.affiliation: Center for Microbial Genetics and Genomics, Northern Arizona University, 1298 S Knoles Drive, PO Box 4073, Flagstaff, AZ 86011, USA. Dave.Wagner@nau.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: Wagner
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology*; D003670:Deer / Q000469:parasitology*; D058865:Introduced Species; D048494:Rhipicephalus / Q000502:physiology*; D013781:Texas / Q000453:epidemiology; D013984:Tick Infestations / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*
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