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Biosecurity in the equine setting

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01 March 2015, at 12:00am

PHILIP IVENS discusses the importance of biosecurity and the need for detailed risk assessments and plans appropriate to the particular equine establishment to keep infectious disease at bay

BIOSECURITY is the principles, actions, precautions and protocols that protect the health of horses by preventing the transmission of disease through physical barriers and hygienic practices.

Biosecurity is protecting an individual horse, a yard community and national herd/ industry against biological agents. It is a strategy of disease prevention; preventing introduction of disease and/or controlling and preventing disease circulation within a herd or community such as a yard.

Infectious disease prevention is important because there are welfare concerns and potential mortality of individual animals (e.g. strangles). Prevention of infectious disease can only be successful at herd level, for example at a yard or national level.

Infectious disease can travel quickly between groups and successful biosecurity can contain the disease within a group and prevent it from spreading between groups.

It is important to see the individual horse from an infectious disease standpoint as part of multi-layered hierarchical herd structure (Figure 1).

Equine infectious diseases use direct contact, aerosols of mucus and sneezing droplets, fomites (inanimate objects that carry organisms on their surface) and vectors (living entities that may carry the organism).

Horses spreading disease are not always sick: for example, a horse carrying Streptococcus equi subspecies equi within the guttural pouch will shed the bacteria for many months to years. A healthy horse thus intermittently sheds infectious bacteria posing a risk to naive animals.

A generic circle of infection can be used to illustrate to owners the complexity of infectious disease – see Figure 2. Fomites are inanimate objects that can carry infectious diseases between horses.

Examples of fomites are brushes, head collars, buckets/troughs, horse trailers, numnah and stable doors. Examples of vectors include people, dogs, cats and other horses and wildlife. Without appropriate biosecurity measures, the cycle continues to spread disease.

How to develop an effective biosecurity programme

A biosecurity plan is no use if it is impractical and then cannot be adhered to by the people using the yard. The first step is a risk assessment for the individual horse/yard.

The aim is to clearly identify what particular concerns and disease transmission risks exist for an individual animal, herd and premises. This is best done by a questionnaire or a meeting.

Risk assessments

Animal risk factors to be considered are the age of the animal, with foals, youngstock (1-5 years old), and brood mares being of higher risk than adult horses (>5 years old).

The business of the yard should be considered with horse dealer yard being highest risk followed by public stud, breaking yard, competition yard, livery yard, riding school with private stud and private leisure yards being the lowest risk. The number of horses on yard is also important with the larger the yard the higher the risk. Average frequency of new arrivals influences risk with frequent arrivals (e.g. more than once a month) posing much higher risk than arrivals once a year or less.

The level of horses attending shows or visiting the yard for training also affects the yard’s particular risk level. If horses on the premises can physically touch horses on neighbouring yards this is obviously risky.

We have devised a temperature gauge of risk which helps guide owners to assess their own risk (Figure 3). An overall risk profile should be made ideally at a yard level and advice should be based on areas identified. A questionnaire-based approach is a good way of achieving this.

Identifying protocols for implementation

Practical and sensible recommendations then have to be made. In the real world few yards can implement all potential biosecurity measures but even a few targeted measures based on the risk profile of that yard can make a big improvement in the biosecurity for that yard.

A key step which is still unusual within the UK general horse population is the use of a quarantine/ isolation facility. If I only could make one recommendation it would be to set-up this facility.

This can be as simple as a field remote from the main yard in good weather. Ideally, the isolation area should include stables that should be in a separate building.

Equip the facility with separate feeding, mucking out and grooming equipment if at all possible. Ideally, separate drains for emptying water buckets and separate muck heap for disposing of bedding. If possible the facility should be downwind (prevailing) of the main stable block. Access should be restricted to only essential personnel and all dogs, cats and other horses should be kept away.

Protocol for new arrivals

The introduction of new horses is a common way of spreading unwanted infectious disease. Isolate all new arrivals for a minimum of 21 days. All new horses should have up-to-date equine influenza vaccination protocols (e.g. BHA or FEI).

Horses who have lapsed in the influenza vaccination status or who have not been protected before should complete the primary course (first two vaccines) and a further week elapsed prior to moving onto the main yard. Ideally, this should be completed before moving to the isolation field/ unit.

A strangles blood test should be carried out at 14 days or greater into the isolation period as it takes this long for a horse to seroconvert to Streptococcus equi subspecies equi. If the test result is negative (≤0.2 OD on A and C antigen) then the horse can leave isolation at 21 days after a clinical check to ensure the horse has no clinical signs.

If the strangles serology is equivocal (0.3 OD or 0.4 OD on either A or C antigen) then a paired sample needs to be taken in 10-14 days’ time to see if it is a rising or falling titre.

If time is of the essence then you can proceed straight to guttural pouch wash to rule out a carrier state. If the titre is equal to or above 0.5 OD, then a guttural pouch wash needs to be performed to rule in or out strangles carrier state.

I would recommend an appropriate PCR and culture. Ideally, an additional serology sample should be taken on day 1 but this increases the cost of the screening programme and most people in my experience go for the one sample at day 14 or more of isolation.

Ideally, each horse should have dedicated equipment to prevent spread between horses within the isolation facility.

Additional measures for studs and/ or yards with internationally travelling horses

New arrivals should have a negative swab result for contagious equine metritis (CEM) and a negative serology for equine viral arteritis (EVA) and equine infectious anaemia (EIA).

Ensure stallions standing at stud or being used for AI are negative for all three diseases before breeding and check that they remain free of infection by repeated swabs and blood samples.

Ensure strict hygiene measures when handling horses for breeding: for example, wearing disposable gloves and using disposable equipment.

Visitors to the yard

Ideally, there should be only one entrance/exit into the yard marked as the main entrance. Parking should be away from the horses. In high health yards such as studs, a record of visitors should be kept.

Horses travelling to events and shows

Horses should avoid sharing transport with horses from other yards. Buckets and water if possible should belong to the individual horse. Avoid noseto-nose contact between horses. Wash hands after other horses are handled. Clean and disinfect boots and outer clothing after each show.

If horses have been stabled at the show, depending on risk assessment it may be prudent to keep the horses in the yard’s isolation field/facility on returning.

Conclusion

Infectious disease is becoming more common with the increase in density and movement of horses. Therefore, biosecurity measures are increasingly important to stop an increase in infectious disease prevalence.

The British Equine Veterinary Association, in the wake of the equine herpes myeloencephalopathy (EHM) outbreak(s) in the west of the country in 2013, put out a checklist for owners for the horse’s health. This very useful document can be found at www.beva.org.uk/news-and-events/news/view/371.