Location: Tick and Biting Fly Research
Title: High resolution predictive mapping of Rhipicephalus microplus and R. annulatus in south Texas after vaccination with the anti-tick vaccine Gavac Authors
Submitted to: Agricultural Research International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: July 23, 2010
Publication Date: August 23, 2010
Citation: Estrada-Pena, A., Miller, R., Perez De Leon, A.A. 2010. High resolution predictive mapping of Rhipicephalus microplus and R. annulatus in south Texas after vaccination with the anti-tick vaccine Gavac [abstract]. Agricultural Research International Conference Proceedings. 1:298. Interpretive Summary: The Cattle Fever Tick Eradication Program (CFTEP) has successfully prevented the permanent re-introduction of the cattle fever tick (CFT) into the U.S since 1943. Eradication is maintained through continuous, systematic inspection of cattle within the quarantine zone for ticks. The detection of one tick initiates biweekly acaricide dips of all cattle every 7-14 days. Because the current CFT eradication strategy is based primarily on the use of acaricides, the integrity of the CFTEP is vulnerable to the development of acaricide resistance in the CFT. In this study we used computer modeling of tick habitat and cattle density to predict the usefulness of an anti-tick vaccine within the CFTEP. The modeling results predicted that a control of 95% of the cattle tick would eradicate, whereas control of 60-80% of the southern cattle tick would drastically reduce the numbers of ticks present, but would not eradicate. The impact of this work is that computer modeling predicts that the use of anti-tick vaccines within the CFTEP will eradicate cattle ticks (present in the northern part of the eradication zone) and will greatly decrease the habitat suitability for the southern cattle tick (present in the southern part of the eradication zone).
Technical Abstract: Conventional anti-tick vaccines based on the tick gut antigen Bm86 exist commercially (TickGARD (TM) and Gavac (R)) and could serve as an alternative to the use of acaricides to eradicate ticks, but their level of efficacy against R. microplus is too low for eradication if used alone. Therefore, the current anti-tick vaccine technology would need to be used as part of an integrated eradication program to be beneficial. Using Gavac with ticks found in Cuba and Northern Mexico, control of R. microplus ranges from 60 to 80%. However, for reasons that remain to be fully understood, Gavac is more efficacious against R. annulatus. Recent experiments achieved 99.6 and 100.0% control of R. annulatus infested cattle in two different studies (Canales et al. 2009; Almazan et al. 2010). Interestingly, vaccination in combination with macrocylic lactone (ML) treatment has been shown to be synergistic (Willadsen, personal communication). This is an indication that anti-tick vaccination could be useful in an integrated eradication program. In order to investigate the potential benefit of anti-tick vaccines within south Texas, the effect of tick vaccination on habitat suitability was modeled based on technology developed previously for the prediction of habitat suitability along the Rio Grande/Rio Bravo Valley. Estrada-Pena et al. (2006) used high-resolution satellite imagery to map habitat suitability for both R. annulatus and R. microplus over an area covering parts of southeastern Texas and northeastern Mexico. Results from the computation were compared to actual data on tick outbreaks at the Texas–Mexico border, and it was able to predict with high accuracy areas of high habitat quality and correlate this with actual numbers of outbreak ticks found in Texas. Presently, we used the model, updated with current climate and cattle abundance data, to predict habitat suitability along south Texas border counties, assuming all cattle were vaccinated with Gavac and including control levels previously reported from recent literature. The results of this analysis are discussed.