ARS | Publication request: Research update on the potential use of anti-tick vaccines to support the USDA Cattle Fever Tick Eradication Program

Submitted to: Livestock Insect Worker's Conference Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 13, 2011
Publication Date: N/A

Technical Abstract: The USDA APHIS VS Cattle Fever Tick Eradication program (CFTEP) was established in 1906 to eliminate populations of the cattle fever ticks (CFT) Rhipicephalus (Boophilus) annulatus and R. microplus as a way to eradicate bovine babesiosis from the continental United States, which is a high-impact disease of cattle. The main eradication effort was completed in 1943. A permanent quarantine zone is maintained along the Rio Grande (Rio Bravo) from Del Rio to Brownsville, TX, to monitor the movement of CFT along the border with Mexico where the ticks and bovine babesiosis are endemic. The success of the CFTEP is based largely on human inspection of cattle for the presence of ticks, the quarantine of infected cattle herds, and eradication of ticks with the use of acaricides. However, the existence of high levels of acaricide resistance in Mexican CFT populations and the great amount of labor involved in the re-eradication of ticks found in US cattle has driven the need to integrate new tick control technologies into the CFTEP in order to maintain the success of the program. Anti-tick vaccines based on the Bm86 antigen have been shown to be effective in the control of CFT in Australia, Cuba, and Mexico. The level of control seems to be dependent on specific tick populations found in discrete regions of the world. For example, the reported efficacy of Bm86-based anti-tick vaccines is lower in Argentina and Brazil in relationship to Australia, Cuba, and Mexico. An evaluation of the Bm86-based vaccine, Gavac®, was completed at the USDA, ARS, Cattle Fever Tick Research Laboratory in order to determine its efficacy on CFT strains from outbreaks in Texas. Efficacy against R. annulatus was high (99.7%) whereas the control of R. microplus was statistically insignificant. A computerized model of habitat suitability taking into account the climate, vegetation, and cattle density of the Texas eradication zone showed that a level of sustained control through vaccination of greater than 40 and 80% was required for R. annulatus and R. microplus, respectively, to maintain eradication. Based on these results, it is theorized that the use of Bm86-based anti-tick vaccines in all cattle within the eradication zone would maintain the eradication of R. annulatus in the northern sector, but would not eradicate R. microplus in the southern part of the permanent quarantine zone. Novel candidate antigens have shown efficacy greater than 75% against R. microplus in cattle stall tests. Confirmation of this level of efficacy against CFT strains from outbreaks in Texas offers the opportunity to develop effective tools for integrated eradication approaches. This science-based strategy will allow the CFTEP to achieve its mission in a sustainable manner.