ARS | Publication request: Current Agricultural Research Issues on One-Host ticks and Bovine Babesiosis

Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2010
Publication Date: July 21, 2010
Citation: Perez De Leon, A.A., Knowles Jr, D.P. 2010. Current Agricultural Research Issues on One-Host ticks and Bovine Babesiosis. United States Animal Health Association Proceedings. p. 703-705.

Technical Abstract: Bovine babesiosis is a tick-borne disease caused by the apicomplexan protozoans Babesia bovis and B. bigemina, which can have devastating economic effects on the livestock industry. Estimates indicate the domestic livestock industry realizes annual savings of at least 3 billion dollars at today’s currency rate since the U.S. was declared free of the disease. Clinical bovine babesiosis is currently controlled in the U.S by control of its tick vectors, Boophilus (Rhipicephalus) annulatus and B. (R.) microplus, commonly known as cattle fever ticks (CFT). These ticks were eradicated from the continental U.S. in 1943 through the successful efforts of the Cattle Fever Tick Eradication Program (CFTEP), which is an effective and ongoing partnership between the USDA Animal and Plant Health Inspection Service, the Texas Animal Health Commission, and cattle producers. CFT have enormous economic impact on livestock production in tropical and subtropical parts of the world like Mexico and Brazil where they are endemic. The annual cost of tick infestation to the cattle industry in Brazil by the cattle tick R. (B.) microplus is estimated to be greater than two billion U.S. dollars. Post-eradication outbreaks of clinical bovine babesiosis in the U.S. due to re-emerging populations of CFT is a continual issue for the livestock industry for a number of reasons. First, there has been a considerable increase in the number of CFT infestations in South Texas during the last six years; 19 infested premises were reported in fiscal year 2003 whereas in fiscal year 2009 that number was 146. Second, increasing populations of white-tailed deer and other wild ungulates in South Texas appear to assist in maintaining CFT populations in pastures vacated of cattle. Third, there is no serologic surveillance for persistent infection in cattle and the susceptibility of the U.S. cattle herd to clinical babesiosis remains unknown. Finally and importantly, the organophosphate compound coumaphos is the only acaricide approved for official use by the CFTEP in dipping vats since 1970 and acaricide resistance is prevalent in Mexico. The USDA-ARS convened a public workshop in April 2009 where state and federal regulators, federal and academic investigators, and producers met with the goal of identifying gaps in the scientific knowledge associated with babesial disease systems. Research priorities were identified in these major areas: 1) epidemiology and surveillance; 2) ecology and biology of tick vectors and wildlife; 3) diagnosis, treatment, and prevention, 4) integrated approaches for sustainable tick eradication, and 5) anti-tick/parasite vaccines which control tick infestation and/or block pathogen transmission. One of the collaborative research projects at the USDA-ARS ADRU in Pullman, WA focuses on the development of persistent anti-tick/anti-transmission vaccines requiring one immunization. It is hypothesized that the use of attenuated and transfected Babesia parasites expressing tick antigens would elicit anti-tick immunity. Preliminary findings by USDA-ARS KBUSLIRL scientists indicate that the application of satellite image analysis using normalized difference vegetation index times series data in South Texas can identify habitat preferences of white-tailed deer and therefore predict the distribution of CFT in the landscape. Additional field data is being gathered to enhance the predictability of CFT infestations associated with white-tailed deer. Practical applications of satellite imaging in support of the CFTEP include the ability to assess the risk of restocking with livestock pastures that include preferred white-tailed deer, which had been vacated of cattle for 9 months or longer. Additionally, satellite images could also be used to make evidence-based decisions for the deployment in South Texas of technologies to control CFT infesting white-tailed deer. In collaboration with Northern Arizona University scientists, USDA-ARS investigators from Pullman, WA and Kerrville, TX are researching the population structure of CFT and prevalence of Babesia spp. in South Texas. This research is expected to generate science-based information that the CFTEP can use to enhance the decision-making process regarding quarantined premises and strategies preventing the re-emergence of CFT and bovine babesiosis in the U.S. A collaborative research project between Texas A&M-Kingsville and USDA-ARS KBUSLIRL scientists, and USDA APHIS-VS personnel will integrate ecologically-based approaches to re-eradicate cattle fever ticks from the U.S. This project will specifically address the impediment of ungulate wildlife species with re-eradication efforts. It is concluded that: - Maintaining CFT eradication in the U.S. and thus keeping the national cattle herd free of bovine babesiosis is a current and critical agricultural biosecurity issue of national relevance. - The eradication of bovine babesiosis from the U.S. represents a very successful campaign in the history of disease control efforts, but global environmental variation combined with changing domestic and wildlife animal populations, is impacting the ability of state and federal agencies to keep the national cattle herd CFT-free. - The level of CFT infestation in the U.S. has increased to alarming levels during the last six years. - In the absence of cattle as the preferred host, white-tailed deer and some species of non-native wild ungulates appear to fill in the ecological niche as hosts for CFT in South Texas rangeland and pastures. - More research on epidemiology and surveillance, ecology and biology of tick vectors and wildlife, diagnosis, treatment, and prevention of bovine babesiosis, integrated approaches for tick eradication, and anti-tick vaccines is required to develop technologies that will keep the U.S. free of CFT in a sustainable manner. - The CFT Eradication Strategic Plan developed by APHIS- VS, which was originally proposed for implementation between fiscal years 2006 and 2011, requires financial attention; full funding for the Strategic Plan is critical so the new challenges the U.S. faces to eradicate CFT can be addressed.