Horse unhappy about needles? A topical painkiller might help, study finds

Share
A recent survey of equine veterinarians in Britain reported that 92% of respondents encountered injection-shy horses at least a few times each month, with nearly half indicating they saw them at least a few times each week.
A recent survey of equine veterinarians in Britain reported that 92% of respondents encountered injection-shy horses at least a few times each month, with nearly half indicating they saw them at least a few times each week. File image.

Horses can easily become averse to injections, sometimes showing dangerous behaviors in their efforts to avoid a jab.

“A considerable proportion of horses react to these procedures, particularly as a needle pierces the skin,” Catherine Torcivia and Sue McDonnell noted in the journal Animals. Many progress to become “needle shy”, with avoidance behaviors often escalating quickly.

This can be a problem because vaccinations and blood sampling are now part of routine preventative health care for most horses.

A recent survey of equine veterinarians in Britain reported that 92% of respondents encountered injection-shy horses at least a few times each month, with nearly half indicating they saw them at least a few times each week.

“In addition to affecting the quality of veterinary care that horses will safely tolerate, injection shyness poses a danger to handlers and veterinarians if horses display animated avoidance responses.”

Despite the brief discomfort caused by injections, the behavioral consequences for horses and their impact on welfare may be long-lasting, Torcivia and McDonnell said.

“Our experience indicates that horses can begin to develop an injection aversion after only one uncomfortable experience. From that point forward, the typical progression for many horses involves increasingly aggressive handling techniques to attempt to restrain or punish increasingly animated avoidance behavior.

“This experience can quickly lead to conditioned fear that may generalize beyond injections, making those horses dangerously challenging to handle for other health care procedures.

“If we can reduce the discomfort of injections, we may be able to avoid development of aversions to injections and other health care procedures, thereby improving welfare both at the time of vaccinations and lifelong.”

A topical anesthetic may provide a relatively simple way to accomplish this, they said.

“Our clinical experience suggests that topical numbing solutions shown to reduce needle discomfort in other species also help horses better tolerate needles,” said the pair, with the New Bolton Center at the University of Pennsylvania School of Veterinary Medicine.

For their study, they divided 78 ponies, all of whom were to receive two vaccine injections into muscle, into three groups.

Two minutes before injections, one group had a 5% lidocaine solution applied to the intended jab site, another group had a 10% lidocaine solution applied (both were commercially available preparations), and the third group had sterile water applied, which served as the control.

Lidocaine can be used as a topical anesthetic, causing numbness of the skin.

Those handling the ponies, performing the injections, scoring the behavioral reactions, and analyzing the data were unaware of the treatment assignments.

For both lidocaine treatments, behavioral reactions were lower than the control treatment. The results from the two concentrations of lidocaine were not significantly different from one another, the researchers reported.

Fewer than 15% of the lidocaine-treated ponies (7 of 51) showed anything more than a slight flinch reaction, compared to more than half (55%) of the control group ponies (15 of 27).

This, they said, clearly demonstrates that a topical anesthetic can effectively reduce the behavior reaction of horses to intramuscular injections, providing convincing support for its routine use to improve animal welfare and staff safety.

The authors also discussed the size of needles used.

“As was performed for this study, our routine practice and recommendation for least-stress health care for horses is to use 22-gauge (G) needles whenever possible for administering intramuscular or intravenous injection of aqueous preparations.”

In equine practice, it is more typical to use 20 G or 21 G, or even 18 G needles.

They noted that most single-dose equine vaccines marketed in North America are packaged with 20 G needles.

“In our experience, the finer 22 G needles appear to be conspicuously less uncomfortable for most horses. Nonetheless, even when using 22 G needles in this study, topical lidocaine added benefit.

“Also of note,” they continued,  “we used 1-inch-long needles.” It is quite common for 1.5-inch-long needles to be used with horses and to be provided with single-dose vaccines, the pair noted.

“Further work to address the relative contribution of topical anesthetic and needle gauge and length may be indicated to inform health care providers of the individual and combined benefits of these relatively simple and inexpensive methods that may improve equine patient comfort and tolerance.”

Torcivia, C.; McDonnell, S. Efficacy of Lidocaine Topical Solution in Reducing Discomfort Reaction of Horses to Intramuscular Vaccination. Animals 2022, 12, 1659. https://doi.org/10.3390/ani12131659

The study, published under a Creative Commons License, can be read here.

Horsetalk.co.nz

Latest research and information from the horse world.

Leave a Reply

Your email address will not be published.