Is Nocardioform Placentitis Worse Than It Appears?

When a Lexington-area spike in foal deaths caused by nocardioform placentitis first hit the news at the end of January, there was considerable anecdotal chatter in the Bluegrass region that the number of equine abortions, stillborns and neonate euthanizations might be higher than what is being reported by the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL), the main entity that tracks such cases.

Two weeks ago, when TDN first reported on the outbreak, the number stood at 44. As of Thursday afternoon, Kentucky's nocardioform placentitis death toll was 65. They are all Thoroughbreds, and the casualties continue to be clustered around Lexington.

Dr. Craig Carter, the director of the UKVDL, confirmed to TDN in a phone interview that those casualty totals are, in fact, likely to be higher.

The reasons are twofold: Nocardioform placentitis is not mandated as a reportable agricultural disease. There is also a time lag involved in the period between when a specimen is voluntarily delivered to the lab for testing and when the results appear on the UKVDL's county-by-county interactive map that tracks the outbreak (view it here). That map is a useful tool, but the UKVDL never intended for it to represent a complete, real-time picture of the disease.

However, Carter said he has no doubt that the UKVDL is compiling and making available enough data for veterinarians and farm personnel to use to increase their awareness and vigilance of nocardioform placentitis, which currently has no known cure or preventative measures.

“I've been here 15 years in the trenches doing the diagnostic testing, and I feel really confident that we are getting enough specimens from the field to where we can put out the appropriate alerts,” Carter said. “And that's really all we can do. Here in the lab, all we can do is confirm a specific diagnosis, and then go back to the veterinarians in the field and say 'Here's what you've got.'”

Nocardioform placentitis is a group of organisms that causes separation of the placenta from the mare's uterus. It stops nutrients and oxygen getting from the mare to the fetus, which can damage and be life-threatening to the foal. Foals can either be stillborn or born in a weakened state that requires euthanization. Some diseased foals can be born normally and mature healthily in cases where mares have only a small lesion caused by the disease.

Nocardioform placentitis has thus far stumped equine epidemiologists, because they don't know how it gets into the mares. It is believed to be either soil- or environment-based, and it seems to spike in the foaling seasons after periods of dry, hot weather in late summer and early fall.

The disease is almost exclusively confined to the Bluegrass region of Kentucky, and cases of it most recently spiked in the 2011 and 2017 foaling seasons. The University of Kentucky's Gluck Equine Research Center has studied nocardioform placentitis extensively, but has been unable to reproduce the disease by inoculating mares with the organisms.

“I want to emphasize it's a rare disease,” Carter said. “It's an unusual bug. It's not seen much outside the Bluegrass area. There are very few places in the world that have ever seen anything quite like these nocardioform organisms. I've heard that Florida has reported a couple and maybe Texas might have diagnosed a couple this year. But why is it focused here and what is its drought relationship?

“All I can say is if you look at the scientific literature, there is very little known about this particular bug, and so that just makes it tougher,” Carter continued. “Most of the diseases we deal with here, we're well aware of them. But this one here has never really been seen at all outside of the Bluegrass region.”

Carter explained the UKVDL's role in combating nocardioform placentitis.

“We [compile the database and map] for situational awareness, basically,” Carter said “But it's only based on what people send to us, so it has that limitation.”

Carter added that one diagnostic positive is that unlike in other agricultural settings, the lofty economics of the Thoroughbred breeding industry provide a strong, built-in incentive for farm personnel to want to report these types of diseases.

“In Kentucky's horse industry, when horses are sick and they're dying [owners and breeders] want to know what's gong on,” Carter said. “So we get [reports] of a very high percentage of the problems that are going on. The horse industry is pretty sensitive. A lot of animal agriculture is tightly clustered in eastern Kentucky, so we get a lot more [sampling] that you would in other states. We're kind of fortunate in that way, because we really want to know what is going on out there.”

When a farm has a suspected nocardioform placentitis case that results in a casualty, the UKVDL becomes aware of it when farm personnel or their veterinarian bring in a dead fetus or a placenta for testing. “We can diagnose it from either specimen,” Carter said. “They give a clinical history of what's going on on that farm, and we do the work [to generate] a diagnosis, and then that goes in the database,” which has controls to maintain client privacy.

Carter said the UKVDL recognizes that for some smaller-scale farm owners, the cost of testing could be a disincentive for them to bring in specimens

“We actually try our very, very best to keep all the prices for our tests relating to the post-mortem as low as we can,” Carter said. “We do have to charge a fee to keep our doors open. But we work really hard to keep those fees low so that people are encouraged to bring their animals in and get a diagnosis.”

Although Carter didn't have all the details, he believes the Gluck Equine Research Center is in the process of getting funding approved so that specimen testing kits can be made available to farm personnel for free, which is something that has been done during past nocardioform placentitis outbreaks.

“So that will kind of help solve the problem that's being talked about where people are saying, 'This is a lot worse than everybody thinks it is,'” Carter explained. “If we go out and do more surveillance and we test more specimens, that should help either validate that statement or not. The last time the free kits were made available, I think that about doubled the number of specimens that we were able to look at. That's a good thing. And it's something that we want to do, because that's our mission.”

While waiting for researchers, such as the team at Gluck, to achieve new breakthroughs, Carter said “what we do is try to increase the surveillance for the disease, and that's what we're in the progress of doing. Right now it looks like it could come close to being as big of a problem as it was in 2010-11.”

Asked his prediction for what direction this year's outbreak of nocardioform placentitis might take, Carter said he expects it to follow historical, season-related patterns.

“It usually does tail off,” Carter said. “Spikes [have previously resolved] to bell curves.”