Widespread movement of invasive cattle fever ticks (Rhipicephalus microplus) in southern Texas leads to shared local infestations on cattle and deer

Busch, Joseph D. and Stone, Nathan E. and Nottingham, Roxanne and Araya-Anchetta, Ana and Lewis, Jillian and Hochhalter, Christian and Giles, John R. and Gruendike, Jeffrey and Freeman, Jeanne and Buckmeier, Greta and Bodine, Deanna and Duhaime, Roberta and Miller, Robert J. and Davey, Ronald B. and Olafson, Pia U. and Scoles, Glen A. and Wagner, David M. (2014) Widespread movement of invasive cattle fever ticks (Rhipicephalus microplus) in southern Texas leads to shared local infestations on cattle and deer. Parasites & Vectors, 7 (188). ISSN 1756-3305

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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 (F-ST 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 (F-ST 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 (F-ST = 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.

Item Type:	Article
ID number or DOI:	10.1186/1756-3305-7-188
Keywords:	Bovine babesiosis; Cattle fever ticks; Eradication; Population genetics; Rhipicephalus (Boophilus) microplus;
Subjects:	Q Science > QH Natural history > QH426 Genetics Q Science > QL Zoology
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	Research Centers > Center for Microbial Genetics and Genomics
Date Deposited:	21 Oct 2015 23:08
URI:	http://openknowledge.nau.edu/id/eprint/1799

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