Ask the expert

FIGHTING FLU WITH SCIENCE

EQUINE INFLUENZA CAN HAVE A SERIOUS IMPACT ON HORSE HEALTH, AND AN OUTBREAK CAN CAUSE DISRUPTION TO COMPETITION PLANS AS WE HAVE SEEN IN RECENT YEARS. DR ESTHER RAWLINSON MRCVS TALKS ABOUT WHY THIS DISEASE IS SUCH A CAUSE FOR CONCERN AND HOW TO TACKLE IT WITH IMPROVED BIOSECURITY AND VACCINATION.

QWhat is equine infl uenza? E uine in uen a u is a viral respiratory infection whose signs include a high temperature, cough, nasal discharge, depression and loss of appetite. econdary bacterial infections are common and prolong the disease, re uiring further treatment. s well as aff ecting performance, in rare cases u can cause serious complications and even death. he eff ects can be more severe in foals, elderly horses and those suff ering from other health problems. ecuperation from the disease can take several weeks and often re uires the whole yard to go into isolation. lu spreads very rapidly between horses when an infected horse coughs or snee es, the virus can spread through the air up to several kilometres1. It can also be transmitted on ob ects such as tack, feed bowls, water troughs or clothes, so horses are at risk even if an infected horse is no longer present.

QWhy do fl u outbreaks occur? lu is endemic in the which means it is always circulating in our horse population. he more horses are vaccinated against u, the less the chance of a serious outbreak occurring, however only about of horses in the are vaccinated, leaving a large vulnerable population which increases the risk of a ma or u outbreak, as happened in .

Biosecurity is also important to reduce the risk of outbreaks. horse can be shedding virus and infecting others before showing any signs of ill health so we should minimise contact with horses from other yards, for e ample at competitions avoiding nose to nose contact, sharing of e uipment, or gra ing communal areas. ew arrivals to a yard should be uarantined, especially if they are unvaccinated this was a common source of spread in the outbreak. t all times good stable ventilation is of paramount importance.

QHow do vaccines work? imilar to ovid vaccination in people, u vaccination does not prevent horses getting infected, but the aim is to protect the vaccinated horse from becoming seriously ill, and to reduce the amount of virus it sheds, which reduces the risk of infecting other horses. accination stimulates the immune system so that it is primed to recognise the u virus and ready to uickly protect the horse if it becomes infected in the future. o comply with British ressage rules as shown in the handbook an initial course of two in ections for primary vaccination, not less than days and not more than days apart, is re uired before being eligible to compete.

Immunity declines over time so regular boosters are needed to “remind the immune system. Boosters don’t ust protect the individual horse, they also reduce the risk of spreading infection to others. ompetition governing bodies continually review the risk of an outbreak and may change vaccination re uirements depending on current risk levels.

British ressage re uires that the fi rst booster in ection must be given between and days after the second in ection of primary vaccination. ubse uent booster in ections must be given at regular intervals of not more than months, commencing after the fi rst booster in ection.

British Dressage rules require that the most recent booster injection must have been given within six calendar months +21 days prior to the horse competing, and the full course or booster must have been administered at least seven days before arriving at the competition.

Qre a fl u vaccines the sa e? ust like ovid, the e uine in uen a virus mutates over time and new strains can appear, which means that vaccines must keep up to date as the closer the strain in the vaccine matches the strain circulating in the fi eld, the longer and more eff ective protection the vaccine is likely to provide.

The circulating strains are continually monitored by the World Organisation for Animal Health (OIE) whose experts advise which strains should be in vaccines. One

JUST LIKE COVID, THE EQUINE INFLUENZA VIRUS MUTATES OVER TIME AND NEW STRAINS CAN APPEAR.

e uine u vaccine complies with the current OIE and FEI recommendation that vaccines should contain Clade 1 and Clade 2 strains. Ask your veterinary surgeon for more details to help ensure your horses are adequately covered.

QWhat side e ects ay occur and

how can revent these?

It is important to remember that vaccination stimulates an immune response – that’s what we want it to do. This means that, while unfavourable, in rare cases (less than 1 in a a slight temperature, muscle stiff ness or mild swelling, pain or heat at the injection site may occur after vaccination, and a very small number of horses react more strongly.

If your horse seems unwell after vaccination, please contact your veterinary surgeon for advice and so that they can inform the vaccine manufacturer. The manufacturers record all suspected adverse events and report them to the regulatory authorities, which helps to ensure that product labels stay up to date.

You can reduce the risk of a reaction by ensuring your horse is clean and dry where they are going to be injected (eg putting a rug on or keeping them stabled), many people also give their horses a couple of easy, low stress days after vaccination, avoiding heavy exercise.

QWhich horses shou d be

vaccinated?

The more horses mix with others from a diff erent yard, the higher the risk that they will encounter u, therefore it is very important that competition horses are vaccinated. However it is equally important that all the horses at home are protected too as often these are the most vulnerable – the young, the elderly or those with health problems such as Cushing’s disease whose immune systems may not be working eff ectively and are therefore more at risk of becoming very unwell if infected.

There is plenty we can do to protect our horses from infectious diseases and keep them healthy and performing at their best. Do ask your veterinary team for advice so we can stamp on u together.

For more information visit: equitop.co.uk/vet-article-17.html

References: 1. Davis, J. et al. (2009) Transboundary & Emerging

Diseases 56, 31-38

An educational service from the makers of ProteqFlu® suspension for injection for horses. Further information available in the SPC or from Boehringer Ingelheim Animal Health UK Ltd., RG12 8YS, UK. ProteqFlu® is a registered trademark of Boehringer Ingelheim Animal Health France SCS. ©2022 Boehringer Ingelheim Animal Health UK Ltd. All rights reserved. Date of preparation: February 2022. UI-EQU-0018-2022. Use Medicines Responsibly.