Kirsten Voigt, VMD

September 2006

Everyone has heard of quarantining an animal.  It is usually associated with the negative feeling of spending extra time and money.  Having the facilities to do it can be an issue, as well as having the supplies.  But what exactly does it mean to quarantine?  The veterinary definition is “restrictions placed upon entering or leaving a premise where a case of communicable (contagious) disease exists".  I would extend that definition to “places where a disease may exist” in order to include such places as a sale barn where there is a potential for a disease to be even if the animals do not yet appear ill.

Why do we quarantine?  The whole point of a quarantine is prevention.  We want to prevent other animals from becoming sick.  This is for their health and well being as well as for their owner’s economic sake.  The money spent on quarantining is a fraction of what it costs to treat a whole barn full of sick horses that need vet care and medication.  The time spent quarantining is also minimal compared to how long it takes to do daily treatments for multiple horses and the weeks of riding, training or showing lost - not to mention the emotional drain of worrying and the implications an outbreak may have on a boarding or training facility.

When to Quarantine

Now that we have good reason for doing it, when is a quarantine indicated?  Not all new horses need to be quarantined.  If the horse is not coming from far and you are sure of the medical history, such as its vaccination and de-worming schedule, it is probably not necessary.  Indications for quarantine are:

• Any time a horse comes from an unknown source.

• Any time a horse has an unknown medical history.

• If the horse has recently been mixed with other unknown horses such as at a sale barn          or horse show.

• If the horse has been transported a long distance, which is stressful to the body and may depress the immune system.

• Any horse with clinical signs such as a cough, runny nose, swollen lymph nodes, fever or diarrhea.

So how do you quarantine?  There are several important factors to an effective quarantine. 

Length of time.  This is based on the incubation time of the disease you’re trying to prevent which is the time it takes from when the horse is exposed to when it becomes ill and shows clinical signs. By quarantining for a few days to a week longer than the incubation time, we ensure that if the horse was exposed to a disease the day he was acquired, there would be enough time for him to become sick and show signs of illness before he is okayed to be released with other horses and infect them.

 Distance from other horses.  This is determined by the mode of transmission, or how the disease is spread. Unless there is a solid (no cracks) physical barrier between the horses, there needs to be a greater distance of separation for disease that can be transmitted by nose blowing or a cough, versus one that is transmitted by manure. A minimum distance still requires that they are not able to touch noses over a fence and are not in direct contact in any other way.  The confinement can be as simple as a temporary electric fence or panels set up at a distance from the other horses.  Be sure that if it rains, water flow will not go from the quarantined area to the non-quarantined area.  Also take into account the direction of a strong wind or air flow in the barn that may carry particles produced by coughing or nose blowing. In this case they should be housed downwind or at a greater distance from others.  It is important that you provide the quarantined horse with some means of dealing with the elements if the weather is not ideal, as it quite often is not in Minnesota.

Avoiding fomites.  What is a fomite?  Fomites are objects such as buckets, grooming tools or even your boots that may be contaminated with a disease from a sick animal and then moved to another area where it infects a healthy horse even if it is miles away.  So never share equipment, even wheel barrows and stall cleaning tools, between quarantined and non-quarantined horses until it has been properly disinfected.  It works well to have an extra set of equipment that can be dedicated to the quarantined horse and disinfected after the quarantine is over. Also, the quarantined horse should always be handled last.  In other words, finish all the chores with the other horses before starting with him.  This prevents you from becoming a fomite.  Alternatively there could be one person dedicated to caring for the quarantined horse that does not deal with the others.

Know What To Look For

It is important to know a little about the diseases you are trying to prevent because the incubation time and mode of transmission can be different for each disease.  The most common contagious diseases of general concern are equine influenza, rhinopneumonitis (equine herpes virus), and strangles.

Equine influenza is a viral respiratory disease of horses characterized by runny nose, cough, fever, depressed attitude, and loss of appetite.  It is transmitted by aerosolized droplets produced by nose blowing or coughing and by fomites.  The incubation period is one to three days.  Horses remain sick for two to three weeks and can be contagious for up to ten days after getting well.

Strangles is a bacterial disease characterized by a runny nose, fever, depressed attitude, loss of appetite, difficulty swallowing, swelling under the jaw, and possibly a slight cough.  It is transmitted by material draining from the nose or lymph nodes (which are responsible for the swelling under the jaw and can eventually break open and drain), and by fomites.  The incubation period is 3-14 days.  Horses are usually sick for 10-14 days and can be contagious for three to six weeks after getting well.  Some can remain carriers, meaning they are capable of spreading the disease to others for several months after they have recovered.

Rhinopneumonitis or equine herpes virus (EHV) is a viral disease which can affect the respiratory, reproductive or central nervous systems (CNS).  The respiratory disease is characterized by runny nose, fever, depressed attitude, loss of appetite, and in some cases a cough.  The reproductive disease is characterized by abortion in mares that are 7-11 months pregnant and who show no signs of being sick.  The neurologic disease affecting the CNS usually occurs after two weeks of being sick with the respiratory form and is characterized by a wobbling gait, weakness and possible bladder dysfunction and being unable to stand.  EHV is transmitted by aerosolized droplets produced by nose blowing or coughing, by fomites, and by the fetal tissues after an abortion.  The incubation period is 2-10 days (2-12 weeks for reproductive disease).  The length of time they are sick depends on the system affected and is extremely variable, but after getting well they are contagious for two to three more weeks.  As with herpes in all species, the virus often becomes latent.  This means the horse gets better and is no longer contagious but the virus is still housed in the body, and during times of stress the virus becomes active and the horse is again contagious even without being sick.  Up to 50% of the horse population is latently infected which is why a horse that has traveled a long distance or has been in some other stressful situation should always be quarantined.

Based on the above diseases, three weeks should be an adequate length of time to feel sure your new horse is not harboring any illness before he is turned out with other horses.  However, many larger boarding facilities use four weeks to be on the safe side.  Keep in mind the quarantine time will need to be extended if the horse becomes ill.  With those diseases that can be transmitted by aerosolized droplets, the further you can distance them the better. When a horse coughs or blows its nose, the particles can travel quite a distance.  Some studies have shown disease transmission of up to 35 feet away.

Other problems that may become apparent during the quarantine period are skin parasites such as lice, fleas, or ring worm, and stallion-like behavior from a “gelding” who may not actually be gelded.  This is also a very good time to get the new herd member dewormed and on the same schedule as the others, and to have a Coggins test if there is no record of a recent one.

If your horse shows any signs of the diseases discussed above or develops diarrhea, you should contact you veterinarian who will diagnose and treat the disease and make further recommendations for quarantining based on your particular case.