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Title: Invasive Potential of Cattle Fever Ticks in the Southern United States

Author
item GILES, JOHN - Northern Arizona University
item PETERSON, A - University Of Kansas
item BUSCH, JOSEPH - Northern Arizona University
item Olafson, Pia
item Scoles, Glen
item DAVEY, RONALD - Former ARS Employee
item POUND, JOE - Former ARS Employee
item Kammlah, Diane
item Lohmeyer, Kimberly - Kim
item WAGNER, DAVID - Northern Arizona University

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2014
Publication Date: 4/17/2014
Citation: Giles, J.R., Peterson, A.T., Busch, J.D., Olafson, P.U., Scoles, G.A., Davey, R.B., Pound, J.M., Kammlah, D.M., Lohmeyer, K.H., Wagner, D.M. 2014. Invasive potential of cattle fever ticks in the southern United States. Parasites & Vectors. 7:189.

Interpretive Summary: For >100 years cattle production in the southern United States has been threatened by cattle fever. It is caused by an invasive parasite-vector complex that includes the protozoan hemoparasites Babesia bovis and B. bigemina, which are transmitted among domestic cattle via cattle fever ticks (Rhipicephalus (Boophilus microplus and R. (B.) annulatus). In 1906 an eradication effort was begun and by 1943 cattle fever ticks had been confined to a narrow tick eradication quarantine area (TEQA) along the Texas-Mexico border. However, a dramatic increase in tick infestations in areas outside the TEQA over the last decade suggests these tick vectors may be poised to reinvade the southern United States. We investigated historical and potential future distributions of climatic habitat of cattle fever ticks to assess potential for a range expansion. We used spatial prediction of habitat suitability of cattle fever ticks across the southern United States for three time periods: 1906, present day (2012), and 2050. We used analysis of molecular variance to identify persistent tick occurrences and analysis of bias in the climate proximate to these occurrences to identify key environmental parameters associated with the ecology of both species. We then used ecological niche modeling algorithms to construct models that related known occurrences of ticks in the TEQA during 2001-2011 with geospatial data layers that summarized important climate parameters at all three time periods. Overall, we identified persistent tick infestations and specific climate parameters that appear to be drivers of ecological niches of the two tick species. Spatial models projected onto climate data representative of climate in 1906 reproduced historical pre-eradication tick distributions. Presentday predictions, although constrained to areas near the TEQA, extrapolated well onto climate projections for 2050. Most importantly, our models indicate the potential for range expansion of climate suitable for survival of cattle fever ticks in the southern United States by mid-century, which increases the risk of reintroduction of these ticks and cattle tick fever into major cattle producing areas.

Technical Abstract: For >100 years cattle production in the southern United States has been threatened by cattle fever. It is caused by an invasive parasite-vector complex that includes the protozoan hemoparasites Babesia bovis and B. bigemina, which are transmitted among domestic cattle via Rhipicephalus tick vectors of the subgenus Boophilus. In 1906 an eradication effort was begun and by 1943 Boophilus ticks had been confined to a narrow tick eradication quarantine area (TEQA) along the Texas-Mexico border. However, a dramatic increase in tick infestations in areas outside the TEQA over the last decade suggests these tick vectors may be poised to reinvade the southern United States. We investigated historical and potential future distributions of climatic habitat of cattle fever ticks to assess potential for a range expansion. We built robust spatial predictions of habitat suitability for the vector species Rhipicephalus (Boophilus) microplus and R. (B.) annulatus across the southern United States for three time periods: 1906, present day (2012), and 2050. We used analysis of molecular variance (AMOVA) to identify persistent tick occurrences and analysis of bias in the climate proximate to these occurrences to identified key environmental parameters associated with the ecology of both species. We then used ecological niche modeling algorithms GARP and Maxent to construct models that related known occurrences of ticks in the TEQA during 2001-2011 with geospatial data layers that summarized important climate parameters at all three time periods. We identified persistent tick infestations and specific climate parameters that appear to be drivers of ecological niches of the two tick species. Spatial models projected onto climate data representative of climate in 1906 reproduced historical pre-eradication tick distributions. Presentday predictions, although constrained to areas near the TEQA, extrapolated well onto climate projections for 2050. Our models indicate the potential for range expansion of climate suitable for survival of R. microplus and R. annulatus in the southern United States by mid-century, which increases the risk of reintroduction of these ticks and cattle tick fever into major cattle producing areas.