The local equine herpes (EHV-1) investigations that started in mid- February ended on March 19, with the Maryland Department of Agriculture (MDA) lifting the last two of the 13 investigative hold orders it had placed around the state. Of concern during these investigations were horses suspected of having contact with a confi rmed herpes case at Leesburg, Virginia’s Marion duPont Scott Equine Medical Center (EMC).

Equine herpes is an infectious virus that usually aff ects the respiratory system, but, as demonstrated in past outbreaks, can sometimes take a dangerous neurologic form. The release of Maryland’s final hold orders occurred when the MDA received the last of 62 negative test results. “These negative tests bring this EHV-1 situation to offi cial closure in Maryland,” State Veterinarian Dr. Guy Hohenhaus said on March 19.

Although the “index” horse at EMC (the first to show signs of and test positive for herpes) was originally from St. Mary’s County, MDA offi cials confi rmed that only one horse tested positive within the state of Maryland: a mare that originated in Fauquier County, Virginia, came through EMC for surgery, and was sent to Harford County, Maryland to recuperate. That horse was euthanized due to neurologic disease during the week of Feb. 19, officials said.

The last two hold orders to be released were at that Harford County facility and at a Carroll County farm that had housed a horse sent back to EMC when it developed a fever.

Meanwhile, at this writing, the Virginia Department of Agriculture and Consumer Services (VDACS) has released six of the 10 quarantines in that state. The quarantine at EMC has also been partially lifted. At last count, six horses originating in Virginia had tested positive for herpes.

Earlier, the Virginia state veterinarian had ordered the cancellation of the Feb. 24 Casanova Hunt Point-to-Point, as well as public horse auctions and sales in Virginia Feb. 28-March 5. Organizers of the Blue Ridge and Rappahannock Point-to-Points postponed their events, with several hunter paces also rescheduled. Two Virginia state parks were closed to horses during the investigations. In addition, the Maryland Jockey Club shut its doors to Virginia horses.

Lessons Learned

Hohenhaus expressed satisfaction with the situation on both sides of the Potomac River. “Interaction was almost seamless,” he said.

This was the fi rst time in Maryland history, he added, that the investigations were so spread out geographically. “We broke the state into three response regions based on where the properties of concern were (circa Frederick, Baltimore and southern Maryland) and allocated appropriate assets to each, based generally on where our staff [members] lived rather than their regular work assignments,” he explained. “This allowed us to spend more time working the issues on the ground and less driving to get there.”

In the end, he said, “We were again reminded that ‘the only thing we have to fear is fear itself’ is as true today as it was 75 years ago when President Roosevelt first said it. Th e industry in Maryland was on the whole very calm and rational about the problem and overreaction was minimal.”

In addition, he noted, “We have been able to adapt the PCR (polymerase chain reaction) technology to accomplish rapid clearance protocols for farms where an exposed but healthy horse was present. Rather than waiting 21 days, we can wait seven from the last exposure and be confi dent that the blood and nasal swabbing of the exposed animal will be a good predictor of whether it is infected and a risk to others, or if it is not infected and the hold can be released.

“Likewise, we have added the option of using the Colorado protocol for more rapidly clearing an infected premise. This is accomplished by aggressive consecutive day testing following 12 days of disease-free time. We did not employ that protocol during this event, but have gained confi dence in it while evaluating it for use at Leesburg.”

Local Reactions 
While the investigations were ongoing, many local horse people conducted their business with a degree of caution. A Virginia state veterinarian recommendation forwarded to Virginia and Maryland hunt clubs by the Masters of Foxhounds Association reportedly prompted the cancellation of some meets. However, by press time, hunting was “all systems go” in the Free State.

In addition, the owners of at least two Maryland boarding stables put their facilities under voluntary hold orders in an eff ort to keep herpes away.

These restrictions were not initiated by the state, and had nothing to do with pending test results. Robert and Gretchen Butts of Waredaca Farm near Laytonsville simply issued a “common sense” recommendation that boarders “stay on the farm and not leave to visit other facilities” for about two weeks. By press time, however, things were back to normal at that facility. “It worked out fine,” said Robert Butts. “But of course at this time of year, ot was not really a great inconvenience for anybody – we were lucky.”

Over at Wyndham Oaks in Boyds, owner Lori Larson imposed similar restrictions until March 20. “Our fi rst priority is to protect our horses and to be proactive,” she explained. “Until more concrete information was available about the sources and extent of the problem, we determined (in consultation with several of the vets managing horses at Wyndham Oaks, as well as the vets at the Equine Medical Center) that the most prudent – albeit conservative – course of action was prevention. The best way to do that is to limit opportunities for exposure.”

As a result, she said, travel in and out of her barns was limited, incoming horses had to have proof of shots and negative Coggins tests, and people coming from other farms were asked to clean their shoes and clothes before entering the premises. “At the end of the day, it’s the owners, not the farms, that are the fi rst line of defense,” Larson noted.

Had it not been cancelled due to snow, the Foxhall Farm Trophy Team Chase March 18 in Monkton would have required its entrants to produce veterinariansigned health certifi cates verifying that they had been vaccinated recently for EHV-1, had not shown symptoms of the virus, and had not come from quarantined barns. A recent temperature reading was also required.

After the last hold order was lifted, no such requirements existed at the following week’s point-to- point, the Howard County- Iron Bridge Races in Brookeville.

County Number of Leesburg Discharged Horses Number of Horses Tested and Date Tested Test Results and Date Hold Order Status
Carroll 1 1 horse 2/22 Negative 2/27 Released 2/28
Carroll 1 3 horses 2/28
2 horses retested 3/24
All negative 2/26
All negative 3/19
Hold Order Released 3/19. The Leesburdg horse was febrile and sent back to Leesburg. Though that horse and all others tested negative, a partial hold order was placed for extra caution.
Carroll 2 (mare/foal) 2 horses on 2/22 All negative 2/27 Released 2/28
Carroll 1 1 horse on 2/23 Negative 2/28 Released 3/1
Charles 1 1 horse on 2/21 Negative 2/28 Released 2/28
Charles 1 1 horse on 2/22 Negative 2/27 Released 2/27
Harford 2 3 horses on 2/21

16 tested on 2/26
17 retested on 3/12

1 positive 2/26 (euthanized 2/22)

2 Negative 2/26
All negative 2.28

Hold order released 3/19
This was Maryland’s only positive case.
Harford 2 (mare/foal) 2 horses on 2/22 All negative 2/27 Released 2/28
Howard 1 4 horses on 2/21
1 retest on 2/27
All negative 2/26
Negative retest 3/2
Released 3/2
Montgomery 1 2 horses on 2/21 All negative 2/26 Released 2/26
Montgomery 1 1 horse on 2/22 Negative 2/27 Released 2/27
St. Mary’s 0 5 horse on 2/22 All negative 2/27 Released 2/27
(This is the home farm of the ehv-1 positive horse initially detected at Leesburg. It has not been discharged from Leesburg. Stable mates are all negative.)
St. Mary’s 1 1 horse on 2/22 Negative 2/27 Released 2/27
13 Locations
15 63 Tests 62 Negative
1 Positive
13 Hold Orders Released