Easing intramuscular injections

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Applying topical anaesthetic to the skin a couple of minutes before vaccinating horses can reduce signs of discomfort recent research has shown.

Puncturing the skin for Intramuscular injections and collecting blood samples are common procedures in equine medicine. However, many horses show signs of discomfort, and may become “needle shy”.

Catherine Torcivia  and Sue McDonnell at the University of Pennsylvania School of Veterinary Medicine’s New Bolton Center,  conducted a study to see if  applying topical anaesthetic before inserting the needle reduced the signs of discomfort..

They explain: “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.”

The study involved semi-feral ponies from the University’s herd. They were restrained in a holding pen while various management procedures were carried out – such as measuring height and weight with a girth tape, body condition scoring, palpating and estimating the size of testicles, and administering oral anthelmintic - as well as administering two intramuscular vaccinations.

Torcivia and McDonnell applied topical anaesthetic (5% an 10% lidocaine) or a  placebo to the injection site two minutes before injecting the ponies.  Each pony was given two vaccinations – one on either side of the neck, and the researchers, blinded to which concentration of ointment had been used, recorded the ponies’ responses at the moment of each injection

They found that reaction scores for both the 5% and 10% lidocaine groups were significantly lower ( ie showed less reaction) than for the control group. The difference between the 5% and 10% lidocaine groups was not significant. 

They conclude that applying topical anaesthetic can reduce the reaction of horses to intramuscular injection.

“Both the 5% and 10% lidocaine products commercially available for numbing human skin were effective when applied only two minutes before vaccination, making the procedure practical for routine use.”

They suggest that further work should be helpful in optimizing benefit from these and other topical numbing preparations.

For more details, see:

Efficacy of Lidocaine Topical Solution in Reducing Discomfort Reaction of Horses to Intramuscular Vaccination
Catherine Torcivia , Sue McDonnell 
Animals (Basel) (2022) 28;12(13):1659.
https://doi.org/10.3390/ani12131659