Location: Aquatic Animal Health ResearchTitle: Salivary Gland Thrombostasin Isoforms Differentially Regulate Blood Uptake of Horn Flies Fed on Control- and Thrombostasin-Vaccinated Cattle Author
Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2010
Publication Date: 5/1/2010
Publication URL: http://handle.nal.usda.gov/10113/55872
Citation: Cupp, M.S., Cupp, E.W., Navarre, C., Zhang, D., Yue, X., Todd, L., Panangala, V. 2010. Salivary Gland Thrombostasin Isoforms Differentially Regulate Blood Uptake of Horn Flies Fed on Control- and Thrombostasin-Vaccinated Cattle. Journal of Medical Entomology. 47(4): 610-617. Interpretive Summary: Horn flies (Haematobia irritans) are blood sucking parasites that feed on cattle. In addition to the parasitism (blood feeding), the flies are also a hindrance to the normal activities such as feeding, resting and rumination in cattle. As a result Horn flies could interfere both directly and indirectly in the normal growth and well being of cattle. Parasitism of Horn flies is a world wide problem and the economic impact is estimated to approach $1 billion in North America alone. Our studies on Horn fly parasitism, identified an important salivary protein (Thrombostasin) of the fly that interacts with the blood of the cattle host leading to successful parasitism. Studies testing blood uptake of horn flies feeding on cattle confirmed the association of thrombostasin (ts) genotype isoforms with blood uptake and that the interaction was host-species specific. Based on our initial studies, we developed a vaccine incorporating a recombinant form of the most dominant isoforms of thrombostasin. Immunization of Alabama dairy cattle with this vaccine resulted in a significant decrease in blood uptake by the flies. Our studies show that vaccination of cattle with a recombinant vaccine would be the most successful for control of this economically important ectoparasite rather than chemical control strategies that lead to selection for insecticide resistance in the fly population.
Technical Abstract: Thrombostasin (TS) is an anticlotting protein found in saliva of Haematobia irritans (horn flies). The polymorphic nature of the ts gene was first associated with success of horn flies blood feeding on a laboratory host, New Zealand White rabbits. In this study, we report results of similar studies testing blood uptake of horn flies feeding on a natural hosts, cattle. These studies confirmed the association of ts genotype with blood uptake of horn flies and showed that it was host species specific. In contrast to rabbits, blood uptake volumes of homozygous ts10 horn flies were lower than those of other ts genotypes when fed on control (ovalbumin-vaccinated) cattle. Cattle vaccinated with recombinant protein isoforms, rTS9 or rTB8, resisted horn fly feeding by yielding lower blood volumes compared with flies feeding on control cattle. The specific impact of vaccination, however, varied by ts genotype of flies. Cattle vaccinated with isoform rTS9 resisted flies of ts2, ts9, and tb8 genotype. Vaccination with isoform rTB8 produced resistance to ts8, ts9, and tb8 genotype flies. Horn flies of genotype ts10 were not affected by vaccination with either TS isoform and fed as well on rTS9- and rTB8-vaccinated as on control-vaccinated cattle. These experimental results confirm the efficacy of vaccines targeting horn fly salivary proteins and provide new insight into the dynamics of horn fly-cattle interactions in nature.