Haemaphysalis longicornis: Measuring tick burdens on pasture and on sheep.

Abstract

This research project includes a comparison of two methods to estimate tick burdens of the tick Haemaphysalis longicornis. H.longicornis is the only tick which has considerable importance in New Zealand. It is the only exotic tick which causes production losses in cattle, deer, sheep and other livestock. Furthermore, in New Zealand H. longicornis has been shown to be a competent vector of bovine theileriosis (Theileria orientalis). This gives rise to the need for proper methods to evaluate ticks burdens. The first experiment was to measure tick burdens with two different methods. One by measuring the number ticks on pasture, by using the towelling method. Secondly, ticks were counted on sheep which were on the same paddocks. The correlation between the towelling method and the number ticks on sheep was tested, resulting in one significant formula to predict the numbers adults on sheep. Based on the high number of ticks found on the ears of the sheep the relationship between ticks on the ears and total number of ticks on sheep was tested. This resulted in significant formulas to predict the total number of ticks, nymphs and larvae on sheep, based on counts of ticks, nymphs and larvae on their ears. Furthermore the use of two different colour towels, a blue and white one are compared. No difference in number ticks on the different towels was found, whatever the weather conditions were. Nevertheless, the data did show a significant lower chance to find larvae on the towels when it is windy. Furthermore the time H. longicornis larvae take to engorge was investigated. Unfortually the experiment did not provide enough data to provide an answer. This research project did provide an insight on the life cycle of H. longicornis in New Zealand and could be a start for providing validated methods to monitor the presence of these ticks.