Location: Livestock Arthropod Pests Research
Project Number: 3094-32000-042-44-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 15, 2019
End Date: Jun 30, 2021
Continue development of vaccine based on the P0 antigen against the southern cattle fever tick, Rhipicephalus microplus.
This study is a continuation of previous work that documented the feasibility of using a peptide derived from the P0 protein to develop a vaccine against the southern cattle fever tick, Rhipicephalus microplus. ARS Principal Investigators and the Cooperator will generate a Target Product Profile based on the results from the previous study to select three experimental P0 vaccine formulations for additional tests. The Cooperator will use the Target Product Profile to provide the P0 vaccine formulations needed for these experiments. Cattle procured by the Cooperator will be used to evaluate the anti-fever tick efficacy of the vaccine formulations in a stall test at the USDA-ARS Cattle Fever Tick Research Laboratory where they will be kept grazing until artificially infested in individual stalls. There will be five cattle in each of the three treatment groups and in the negative control group. Cattle will be immunized with the P0 vaccine formulations on days 0, 21, 36, and 60. This schedule will be followed to inject cattle in the negative control with formulated adjuvant alone. On day 75, each animal will be placed in an individual stall within the research barn to be artificially infested with approximately 5,000 tick larvae. Fully engorged females that dropped-off from each animal will be collected to weigh them and further processed to assess reproductive parameters used to calculate efficacy. Serum from blood samples collected from each animal on days 0, 14, 21, 28, 36, 60, 74, and 90 will be tested for anti-P0 antibodies by ELISA at the ARS Laboratory in Kerrville, TX. An additional sample collected according to the aforementioned schedule will be used for capillary tick feeding at the Cattle Fever Tick Research Laboratory to complement the profiling of the experimental vaccine formulations. Efficacy results from the stall and capillary tests will be used to select the lead vaccine formulation and a back-up formulation for further testing. A pilot field trial testing the lead and back-up vaccine formulations will be conducted in two premises raising cattle in south Texas that will be selected in consultation with Cattle Fever Tick Eradication Program personnel, the Cooperator, ARS Principal Investigators, and ranchers interested in participating in this trial. Forty cattle procured for the pilot field trial by the Cooperator will be vaccinated on days 0, 21, 36, and 60 while kept at the Cattle Fever Tick Research Laboratory before they are moved to the test premises. The Cooperator will establish an agreement with the owner of each premises raising cattle in south Texas to conduct the trial as per the protocol approved by the Cooperator and ARS Animal Care and Use Committees. Twenty vaccinated cattle will be used at each premises. Cattle will be moved by the Cooperator from the Cattle Fever Tick Research Laboratory to the test premises 14 days after the last vaccination. Cattle held at each premises will be inspected for ticks monthly for three months at which time the study will end. Blood samples will be collected every time the animals are inspected for ticks to run ELISA as described above.