Rhythm of engorgement and detachment of Anocentor nitens females feeding on horses.

This research paper presents a study on the feeding patterns and detachment rhythms of Anocentor nitens females (a type of tick) on horses. The study was successful in developing a new tracking method without significant interference with the ticks’ feeding rate and capacity, and had notable findings about the ticks’ behavior in varying conditions and different parts of the horse’s body.

Methodology

• The researchers observed the ticks’ drop-off rhythm at 6-hour intervals on horses in stalls or on a pasturing field. They aimed to monitor the ticks’ feeding (engorgement) and detachment activity during different times in a 24-hour period.
• To track ticks in a pasture setting, the team developed a new method known as the “bowknot technique” to mark feeding female ticks. The research confirmed that this methodology did not significantly disrupt the ticks’ engorgement rate nor affect their final weight, length, or reproductive capabilities.

Findings

• The study found only 28.2% of ticks disconnected from the horses during daylight hours in the summer (between 06:00 and 18:00). In contrast, more than half (53.4%) of the ticks detached during the same period in winter, likely due to a longer period of darkness (scotoperiod) in winter.
• Drop-off rhythms varied depending on the anatomical location of the tick on the horse’s body. Ticks connected to the ears, perineum, and tail exhibited similar detachment patterns that differed from those on the mane, rump, and other body parts.
• The study also recorded the body length, or idiosoma, of the female ticks every six hours until their natural detachment post-feed. This provided insights into the engorgement rate during the last 96 hours of parasitism.

Conclusion

• The highest engorgement rates were noted during the final 24 hours of parasitism (around 0.16 mm/h), a four-fold increase compared to the previous three days. This variance illustrated the slow and rapid feeding phases reported in other research.
• Using the derived data, the study estimated that a 6mm idiosoma length would correspond to the start point of rapid feeding in ticks (24 hours before detachment).
• The accuracy in estimating the number of fully engorged females detaching from horses over a 24-hour period, based on this 6mm length, was between 58.5 to 97.7%, with a mean accuracy of 73.3% .