Quarantine is one of the oldest infectious disease control measures. Formal use of quarantine dates back at least to the 14th century in Italy, where city officials banished people infected or exposed to people with plague ("black death") for 30 days. This was termed "trentino." Later extension of this to 40 days led to the term "quarantino," which evolved into our current term, "quarantine."

The first use of quarantine in horses is unknown, but historically this practice has been used to control various diseases, with variable success. Quarantine is still used, including quarantine of newly arrived horses on farms, of horses upon arrival to certain countries, and isolation of horses known or suspected to be carrying certain infectious diseases. Specific quarantine practices vary with the infectious agent(s) of concern, but they typically involve physical separation of quarantined horse from other horses, restriction of movement on and off the farm, and specific protocols for handling horses. These are designed to detect early signs of disease in quarantined horses and prevent transmission of infection, should horses be carrying infectious agents. Quarantine can be a highly effective practice when developed and used properly.

horse quarantine at event
One of the major problems with quarantine is poor compliance. This was clearly demonstrated by the recent situation in which three horses were broken out of piroplasmosis quarantine.

By its nature, quarantine can make life difficult, ranging from inconvenient restrictions to significant economic losses. The adverse effects of quarantining a horse, farm, or region certainly cannot be overlooked, which is why quarantine guidelines need to be clear, evidence-based, and properly communicated. Human nature, perhaps, leads to a desire to break quarantine when negative quarantine impacts are more apparent than benefits. The need for quarantine and potential implications of breaking quarantine are easy to demonstrate. Breaks in quarantine can cause disease, ranging from sporadic infections affecting in-contact horses to national outbreaks. A break in quarantine is suspected to have caused the massive equine influenza outbreak in Australia that affected thousands of horses and cost in excess of AU$1 billion (US$900 million).

Quarantine measures are put in place to protect the horse (and sometimes human) population, and owners have an ethical obligation to follow them. If ethical issues are not enough to convince someone to abide by quarantine, perhaps legal liability will. Anyone willingly breaking quarantine, leading to infection of other horses, could be responsible for treatment and replacement costs. If their actions result in quarantine of other facilities, they could be responsible for all associated economic losses. If their actions result in broader quarantine and export restrictions, the consequences grow exponentially.

While the legal implications of this have not been tested in court, it is plausible that someone could be found liable if they willingly break quarantine. Having a horse with an infectious disease is not a crime, evidence of poor conduct, or a sign of poor horse care. Infecting other horses by not taking the appropriate precautions could be considered all of those.

Solid evidence supporting quarantine use and clearly defining necessary quarantine practices is largely lacking. Therefore, quarantine practices need to be designed using the most current information, along with general disease transmission and infection control methods.

Typically, quarantine measures err on the side of caution to reduce disease transmission risk, but this can result in unnecessary or excessive practices.

As long as quarantine is based on scientific evidence and implemented in good faith, there is no reason to even consider breaking it. Willful disregard of quarantine is unethical, illogical, and in some cases illegal.

Taking three horses with piroplasmosis from quarantine is completely unacceptable and could have drastic consequences on other horses and horse owners throughout North America.

Originally appeared in the September 2009 issue of The Horse: Your Guide To Equine Health Care.

J. Scott Weese, DVM, DVSc, Dipl. ACVIM, is an associate professor in the Department of Pathobiology at the University of Guelph's Ontario Veterinary College in Canada.