Disease that threatens foals worries horse industry; 12 cases have been found in Woodford County (updated)

Chart from University of Kentucky Veterinary Diagnostic Laboratory; the current total for 2020 is 121.

This story has been updated to include numbers as of March 7, and corrected monthly numbers.
By Hayley Burris

University of Kentucky School of Journalism and Media

               The horse industry in the Bluegrass is worried about a higher-than-usual number of Thoroughbred mares with a disease that threatens their foals.

               Nocardioform placentitis is a bacterial infection that causes separation of the placenta, keeping oxygen and nutrients from the fetus and causing it to be aborted, born dead or underdeveloped.

               This foaling season, 102 121 cases have been identified by the University of Kentucky Veterinary Diagnostic Laboratory: 76 91 in Fayette County, eight 10 12 each in Woodford and Bourbon counties, two each three in Scott and, two in Harrison, and one in Shelby. Not all the cases involve Thoroughbreds.

               In only five three years since 1991 have the numbers been higher than the number of cases already reported during this foaling season. Other spikes occurred in 1998, 1999, 2003, 2011 and 2017. (See chart.) The highest number, 328 cases, was in 2011. In 2017, 132 cases were identified.

               The number of cases typically peaks before the foaling season peaks, and that seems to be the case this season. In December and January, respectively, there were 28 16 and 57 40 cases. So far this month, there have been 14, and if that rate continued, the month’s total would be 21. In February, there were 61 cases, but only one so far in March.

               The eight Woodford County cases so far through Feb. 19 were have been one abortion, six stillborn foals, and one placenta that was confirmed with the bacteria that cause the disease.

               The Midway Messenger was unable to identify any particular Woodford County farms with cases of the disease. Two of the large farms that were contacted declined to make immediate comment; another said it had no cases. So did one small farm.

               “Analysis of affected farms indicates larger farms with more pregnant mares and higher stocking densities are at great risk,” said Jackie Smith, an assistant professor of veterinary science at UK. “Preliminary data indicate that mares that spend more time in the barns are at risk of developing the disease; increased grazing times appear protective.”

               Smith also said in the interview, “We really don’t know how nocardioform gets into the mares in the first place.”

               To help find an answer, the foundation that supports the Maxwell H. Gluck Equine Research Center at UK recently released extra emergency funding of $132,000 for research on the disease. The money comes from an endowment created to address such emergencies.

               More nocardiform cases are reported from Kentucky for at least two reasons. First, the state has around 9,000 Thoroughbred foals a year, about 40 percent of the foal crop. Second, the state has “highly tuned equine-health surveillance mechanisms” that catch cases, said a UK news release about the university’s response to the outbreak. UK scientists publish every case they identify, while other states may not due to their smaller populations of horses.

               Of the 75 cases identified this season, 14 were from placentas submitted for testing and 61 were foals assumed to be aborted.  The number only includes finalized cases and not any ongoing or pending.  It also does not include unreported cases, such as foals that survived, or cases that were diagnosed elsewhere than the UK lab.

               Also, some small farms may not ask for tests because of the cost. Testing a placenta at the lab costs $100, and the fee for a post-mortem examination is $175.

               UK is starting to provide test kits for veterinarians to use on farms to help them monitor mares in foal.  Veterinarians enroll mares that they think may have the disease, and a mare on the same farm is also tested, as a control for research purposes.

               UK scientists say mares should be constantly checked throughout pregnancy and evaluated after giving birth.

               The UK news release said, “This is an extremely complicated disease, primarily because there does not seem to be a simple causative relationship between the pathogen(s) and the condition. Another contributing factor is that identification of affected mares is difficult and often delayed,” so harm is often done before a case is identified.