Invasive potential of cattle fever ticks in the southern United States

Abstract

Abstract'BackgroundFor >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 started 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 re-invade the southern United States. We investigated historical and potential future distributions of climatic habitats of cattle fever ticks to assess the potential for a range expansion.MethodsWe 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 identify 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.ResultsWe 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. Present-day predictions, although constrained to areas near the TEQA, extrapolated well onto climate projections for 2050.ConclusionsOur 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.

Target validation of highly conserved Amblyomma americanum tick saliva serine protease inhibitor 19

“…There is evidence that deer populations were associated with human cases of TBDs in several localities around in the USA (Piesman et al, 1979, Nieto et al, 2012, Raizman et al, 2013, Wiznia et al, 2013, Mays et al, 2014). In the US livestock industry, the threat of R. microplus and R. annulatus including its vectored deadly Babesia cattle parasites have been eradicated for more than 50 years (Walker, 2011, Giles et al, 2014). Re-establishment of R. microplus and R. annulatus ticks and their associated parasites are prevalent in Mexico (Lohmeyer et al, 2011; Busch et al, 2014).…”

Quantitative models of Rhipicephalus (Boophilus) ticks: historical review and synthesis

“…Most recently, Giles et al. () correlated R. annulatus and R. microplus presence and climate data in the southern United States, while Phillips et al. () predicted south Texas habitats favorable to white‐tailed deer ( Odocoileus virginianus (Zimmerman)), a recognized host of R. microplus and R. annulatus , and habitats favorable to R. microplus larvae.…”

“…), which is predicted to expand habitat suitable for Rhipicephalus ticks to the north (Giles et al. ).…”

“…Similarly, bioclimatic envelope models calculate indices of temperature and ambient moisture, either directly, from weather data (Sutherst and Maywald ), or indirectly, from remotely sensed vegetation or geographic data (e.g., Giles et al. ).…”

Multiple mutations in the para -sodium channel gene are associated with pyrethroid resistance in Rhipicephalus microplus from the United States and Mexico

“…Following these procedures the cattle can then be transported beyond the TEQA to feedlots or slaughter facilities but are not allowed to remain within it. Despite rigorous efforts to prevent tick movements into southern Texas, new infestations are being discovered both in the TEQA and beyond it in temporary preventative quarantine areas (TPQAs) (Figure 1) [14,15].…”