Location: Animal Disease Research Unit
Project Number: 2090-32000-040-052-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Oct 1, 2024
End Date: Jun 30, 2026
Objective:
Developing the in vitro tick feeding for multiple tick stages and assessing tick engorgement, oviposition, hatchability, and larva-to-adult development.
Approach:
Two groups of 6 calves will be used in the project. Six calves will be vaccinated and 6 additional calves will receive a control vaccination (adjuvant alone). Three 10-ml blood samples will be collected from each calf at 30, 60, 120 and 180 days post-vaccination. Samples (20 ml total) from each animal will be used to feed ticks and characterize the effect on feeding, reproduction, and development. Ticks will be allowed to feed for 5 – 14 days. This feeding system will be used in conjunction with standard methods for quantifying tick feeding (engorgement), egg laying (oviposition), egg hatching, and larval development at 30, 60, 120 and 180 days post vaccination. Engorgement will be quantified by counting and weighing the female ticks that have fed to repletion and detached from the feeding membrane. The mean tick weight per group will be used to calculate the effect of the vaccine on engorgement. Oviposition will be quantified after feeding by individually incubating 100 engorged female ticks per animal under appropriate conditions and recording the number of ticks laying eggs and the number of eggs laid. The number of eggs laid will be estimated by weighing a sample of the eggs from a cluster, counting them under a magnifying glass, weighing the cluster, and obtaining an estimate of the total egg number on this basis (i.e., [cluster weight/sample weight] × sample egg number). The mean egg number for each group will be used to calculate the effect on oviposition. Hatchability will be quantified by gently mixing the eggs from the individual ticks in each group, weighing 3 equal samples corresponding to the mean cluster weight, and incubating them under appropriate conditions to hatch. The mean number of larvae for each group will be determined along with the standard deviation and used to calculate the effect on hatchability. In addition, the effect of the vaccine on larval development will be determined through assessment of larval feeding (engorgement), percent of larvae that molt into nymphs, and larva-to-adult developmental time for each group.