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Biosecurity For Horse Farms

Introduction
    Horse owners occasionally complain about bringing home “the cough” from the racetrack or a horse show. You can prevent this disease from spreading throughout your barn. It pays (in dollars saved) to be conscientious about preventing and controlling infectious diseases. Pay particular attention to the brood mares. Bringing home an infected horse to a farm with brood mares can result in a costly abortion storm and the loss of a year’s production.
 
    Vaccination is the essential first step in controlling infectious diseases. But it only works when vaccines are administered properly. Even when used properly, vaccines have limitations. You need to do more than vaccinate. You must protect your horses from contact with infectious diseases. This concept is known as biosecurity.
 
    Biosecurity refers to management practices that reduce:
  • the chances infectious diseases will be carried onto the farm by animals or people; and 
  • the spread of infectious disease on farms.
 
Animal + Infectious Agent + Environment = Disease
     All infectious diseases of horses result from the interplay between the animal and its ability to resist disease (its immunity), an infectious agent (bacteria, viruses, and parasites), and the environment. This relationship points out the opportunities for preventing infectious diseases. For example, you can prevent some diseases by vaccinating to increase immunity. You can also prevent disease by keeping infectious agents from coming onto your farm.
 
 
Table 1. Major Infectious Diseases of Horses in Ontario and their Means of Spread
 

 Disease

 Agent

 Means of Spread

 Equine infectious anemia (EIA) (Swamp fever)
 
 virus (lenti-retrovirus)
- biting insects (bloodsucking horse flies, deer flies (Tabanids), stable flies (Stomoxys spp.), mosquitoes, and possibly midges)
- contaminated needles
 Equine protozoal myeloencephalitis (EPM)
 protozoa
(Sarcocystis neurona) 
- contamination of feed with opossum feces
  Equine viral arteritis (EVA)  virus - direct contact or contamination of utensils, water, etc. with infected secretion (a stallion can shed virus in semen)
 Equine viral encephalitides
    - Eastern (EEE)
    - Western (WEE)
    - Venezuelan equine encephalomyelitis(VEE)
    - Japanese B
    - St. Louis
    - West Nile (WNV)
    - Powassan
    - Murray Valley
 virus - biting insects especially mosquitoes
 Influenza subtype 1: H7N7 (AE-1) (now extinct)
               subtype 2: H3N8 (AE-2)
 virus - direct contact or contamination of utensils, water, etc. with infected secretion
 Potomac horse fever (PHF)
(Neorickettsia risticii -formerly known as Ehrlichia risticii) 
 rickettsia - N. risticii is maintained in nature in a complex aquatic ecosystem.  Immature and adult forms of caddisflies, mayflies, damselflies, dragonflies, and stoneflies were found to contain metacercariae (the intermediary form of trematode parasites), which were infected with N. risticii.  These flies spend part of their life cycle in water and then hatch and fly onto pastures.  Horses fed infected caddisflies developed PHF.
 Rabies
 virus (Lyssavirus)
- bite from an infected animal
 Rhinopneumonitis abortion (EHV-1)
 Rhinopneumonitis neurological (nEHV-1)
 Rhinopneumonitis respiratory (EHV-4)
 herpes virus - direct contact or contamination of utensils, water, etc. with infected secretion
 Strangles (Streptococcus equi)
 bacteria (Streptococcus equi)
 
- direct contact or environmental contamination (individual horses can be carriers, maintaining the bacteria in the guttural pouches)
 Tetanus (Clostidium tetani)
 bacteria (Clostidium tetani)
 
- contamination of a wound with spores
 Vesicular stomatitis  virus - biting insects, contaminated needles
 
Strategic Vaccination
    Vaccination is an essential component of every disease prevention plan. Vaccination is most effective when it is planned to meet the particular needs of a farm. Setting up a strategic vaccination program means:
    • determining what diseases to vaccinate against,
    • identifying who will most benefit from vaccination, and
    • finding out when they will most need the protection that vaccines provide.
 
    Depending on your geographical area there will be core vaccines and optional vaccines which your veterinarian can advise you on. For more information on planning your vaccination program contact your local veterinarian.
 
    It is important to vaccinate horses in Ontario for rabies and tetanus. For pregnant animals, consider giving the equine herpes virus 1 (EHV-1) (e.g., Pneumobort) vaccine to prevent abortions. Protect performance horses, which are continually being exposed to different stable mates at race barns and shows, with influenza and rhinopneumonitis (EHV-4) vaccines.
 
    Your veterinarian may recommend protection against other diseases. These recommendations are based on the special needs of your horse farm and knowledge of what diseases occur locally.
 
Preventing the Introduction and Spread of Infectious Diseases
    Keeping a closed herd is one way to protect horses from infectious disease. In a closed herd, no horses enter the farm either by purchase or re-entry (including horses that have left the farm for breeding, show, or racing purposes). A herd is not closed if:
    • horses are purchased or boarded,
    • horses return to the herd after going to shows, races, or breeding facilities,
    • horses use a pasture that shares a fence line with horses in pastures on a different farm,
    • mares are taken to a stallion for breeding, or 
    • horses are transported by someone else or in someone else's vehicle.
 
    It is good practice to keep the herd as closed as possible. Unfortunately, horse farms are often a hive of activity. Therefore, it may be necessary to create zones that are closed. For example, separate the brood mare band from the show horse group that are continually coming and going. Impose a minimum 30-day quarantine on animals entering or re-entering the brood mare band. Ensure that these horses do not come in contact with, or share the same air space, as resident horses for at least 30 days.
Keeping a closed herd should not be your only protection against introducing infectious disease. You also need a plan to reduce the chances that a serious infectious disease will come onto the farm.
  
Shed row type housing can reduce disease transmission because horses are not sharing the same air space
 
Purchasing New Horses - Eventually, most owners bring horses into their herds. It is important to plan the introduction to minimize the risk that an infectious disease will be brought in at the same time. Three factors are important to reducing the risk from infectious disease when you purchase new horses:
 
    1. the protection you have given the resident horses by proper vaccination; 
    2. the source of purchased horses, including how they are transported to the farm; and
    3. the method you will use to actually introduce the new horses to the rest of the herd.
 
Resident Horses - Make certain your own horses are vaccinated before bringing new horses into the herd. Even if you have vaccinated, review vaccination records to ensure horses were vaccinated at least as often as stated on the vaccine label. Vaccinate any foals over 6 months old that haven't been vaccinated. Consider vaccinating foals less than 6 months old too, even though you will have to vaccinate again when they reach 6 months.
 
Source of Purchased Horses 
  • Bring in only animals from herds where you know the health status.
  • Bring in only animals from herds with a known effective vaccination program. Get specific information about the vaccination history, such as what vaccine was used and when it was given. If killed vaccines were used, make sure that a primary series (2 doses given a few weeks apart) was given.
  • Avoid purchasing animals from unknown sources or that have mixed with many other horses before sale.
  • Ensure all horses have a negative Coggins test prior to finalizing the purchase.
  • Transport purchased horses or show animals in your own vehicle. Start with a clean truck or trailer and clean it out after transporting newly purchased horses. If someone else transports for you, make sure they start with a clean vehicle.
Introducing New Arrivals
  • Quarantine new animals for 30 days before allowing contact with animals on-farm. 
  • Designate a quarantine area, well separated from other horses on your farm. The degree of isolation determines your success in preventing disease transmission. To prevent spread of respiratory diseases, do not let quarantined horses share the same airspace with resident horses. To prevent spread of strangles and respiratory viruses, do not allow quarantined horses to touch resident horses. Ensure personnel change coveralls and boots before moving between barns.
  • Do not allow quarantined horses to share feeders, waterers, halters or grooming equipment with resident horses.
  • Check the isolated animal's temperature every day, or at least every second day, to see if it develops a fever. If it does, call your veterinarian. Don't assume it's something routine.
  • Vaccinate horses while they are in quarantine to make sure they are integrated into your farm's vaccination program.
  • Test all purchased horses for infection with equine infectious anemia.
  • It can take 1–2 weeks or more to get test results, so collect and submit the samples as soon as the animal arrives.

    It helps to know the previous health history of the horse(s) and the herd you plan to purchase from. Horses coming from outside North America go through an inspection and quarantine period dependent on the country of origin. For horses from the USA, pay special attention to diseases such as vesicular stomatitis, potomac horse fever, and equine encephalitis. The equine viral encephalitis diseases include Eastern, Western and Venezuelan equine encephalomyelitis. West Nile encephalitis is new to North America and has infected people and horses in 1999 and 2000. (These occurred in some regions of the USA more than others.)

    People and equipment can carry infectious diseases too. Some diseases are spread on clothing and boots. Some can even be carried on a person's body. If you borrow equipment from other farms, make sure it is cleaned before using on your farm. Animals other than horses can even carry a few horse diseases. Be mindful about controlling the movement of people and animals on the farm as well.
 
Summary
Some steps to reduce the risk of introducing infectious diseases:
  • Limit people's access to your brood mare and foaling barn(s).
  • Limit people’s access to barns housing horses returning from major shows or events where respiratory coughs are commonly present.
  • Have a separate area for horses that are continually moving to and from the farm to shows, races and competitions.
  • Use new sterile needles and syringes for all medications.
  • Use separate halters and lead shanks for each horse or, at least, limit their use to one group of horses.
  • Keep horses coming to the farm for short periods of time separate from the resident horses.
 
    It is difficult to control all traffic on the farm but you can identify the traffic that represents the most risk. These include people who do not pay attention to control of infectious diseases, people who frequently visit other farms and people who have already visited farms on the day they visit your farm.
 

 
Updated July 2011
(This information sheet was originally created by the author and published as a factsheet with the Ontario Ministry of Agriculture, Food and Rural Affairs )
Dr. Bob Wright, Consultant - Equine Disease Prevention and Equine Industry
6958 Wellington Rd. #16
RR#1 Belwood, Ontario Canada
N0B 1J0
519-843-1783, Fax: 519-843-3628
Click on the link to send an email .
 

 
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