Abstract
BackgroundThe cattle tick, Rhipicephalus (Boophilus) microplus, affects livestock production in many regions of the world. Up to now, the widespread use of chemical acaricides has led to the selection of acaricide-resistant ticks and to environmental contamination. Gavacplus is a subunit vaccine based on the recombinant Bm86 tick antigen expressed in yeast, capable to control infestations of R. microplus under controlled and production conditions. The vaccine constitutes the core element of broad control programs against this ectoparasite, in which acquired immunity in cattle to Bm86 is combined with a rational use of acaricides. At present, the conventional vaccine scheme consists of three doses that should be administered at weeks 0, 4 and 7, followed by a booster every six months.ResultsIn this study we assayed a reduction in the number of the initial doses of Gavacplus, evaluated the time course and the level of bovine anti-Bm86 antibodies elicited, and analyzed the vaccine effect on ticks engorging on immunized cattle under production conditions. Following three different immunization schemes, the bovines developed a strong and specific immune response characterized by elevated anti-Bm86 IgG titers. A reduction in the weight of engorging female ticks, in the weight of the eggs laid and also in R. microplus viable eggs percentage was obtained by using only two doses of Gavacplus administered at weeks 0 and 4, followed by a booster six months later. This reduction did not differ from the results obtained on ticks engorging on cattle immunized at weeks 0, 4 and 7. It was also demonstrated that anti-Bm86 antibody titers over 1:640, measured in bovines immunized at weeks 0 and 4, were sufficient to affect weight and reproductive potential of female ticks as compared with ticks engorging on unvaccinated animals. In addition, no statistically significant differences were detected in the average weight of eggs laid by ticks engorged on immunized cattle that showed anti-Bm86 specific titers in the range of 1:640 to 1:81920.ConclusionThe administration of two initial doses of Gavacplus containing 100 μg of Bm86 antigen to non-immunized cattle under production conditions is sufficient to affect the weight and the reproductive capacity of R. microplus engorging females. According to these results, cattle herds' manipulation and vaccine costs could be potentially reduced with a positive impact on the implementation of integrated control programs against R. microplus.
Highlights
The cattle tick, Rhipicephalus (Boophilus) microplus, affects livestock production in many regions of the world
It is known that using Bm86 for cattle immunization turns into a highly effective control method if it is used as part of an integrated control program in which acaricides are simultaneously applied according to the infestation index detected [21,22]
We demonstrated that the generation of specific antibodies and the physical damage caused to female ticks engorging on cattle immunized under production conditions remained invariable after reducing in one dose the number of initial administrations of the Gavacplus vaccine
Summary
The cattle tick, Rhipicephalus (Boophilus) microplus, affects livestock production in many regions of the world. A reduction in the weight of engorging female ticks, in the weight of the eggs laid and in R. microplus viable eggs percentage was obtained by using only two doses of Gavacplus administered at weeks 0 and 4, followed by a booster six months later. Conclusion: The administration of two initial doses of Gavacplus containing 100 μg of Bm86 antigen to nonimmunized cattle under production conditions is sufficient to affect the weight and the reproductive capacity of R. microplus engorging females. According to these results, cattle herds’ manipulation and vaccine costs could be potentially reduced with a positive impact on the implementation of integrated control programs against R. microplus. The most remarkable benefits regarding the use of Bm86-derived vaccines are the reduction in reproductive capacity of engorging females and in the frequency of acaricide treatments
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