Grayson-backed study targets silent placentitis with blood test for mares

A simple blood draw could change how Thoroughbred farms handle one of breeding’s most costly blind spots. Grayson-Jockey Club Research Foundation has kept funding a Louisiana State University project led by Shavahn Loux that is building a blood-based test for nocardioform placentitis, a disease that can move quietly through pregnancy and surface only after the damage is done.

The target is a problem the American Association of Equine Practitioners says was first diagnosed in central Kentucky in the mid-1980s and has ranged from scattered cases to outbreak years there ever since. Outside Kentucky and the United States, it has mostly shown up as isolated cases. AAEP says the disease is commonly linked to actinomycetes, especially Amycolatopsis species and Crossiella equi, with Streptomyces species also implicated, and that 4% to 14% of suspected cases can still test negative on PCR and culture even when the classic lesions are present.

That diagnostic gap is what makes Loux’s work matter. The phase II project, listed in Grayson’s 2026 funding slate as “Novel Method for Diagnosis of Nocardioform Placentitis - Phase II,” uses peripheral blood mononuclear cells from a routine blood sample, then exposes them in a 96-well plate to antigens tied to the organisms most often associated with the disease. Loux adapted the concept from a human tuberculosis test because the organisms sit in the same broad class of Actinobacteria. Grayson’s funding round authorized $1,835,879 for 13 new projects and 13 continuing projects at 16 universities, plus three career development awards.

For breeders, the stakes are immediate. Nocardioform placentitis is considered the most common cause of late-term abortion in the mare and can cost the industry millions of dollars a year. It can end in abortion, stillbirth, or the birth of a weak premature or term foal, and AAEP says gestation is shortened by about 20 days on average. Premature mammary gland development may appear in as many as 55% of affected mares, while vaginal discharge is uncommon because the lesions often form far from the cervix.

The disease is also frustratingly hard to catch early. AAEP says the period from exposure to clinical signs is usually three to five months, with increased occurrence tied to low rainfall and high temperatures during August and September in central Kentucky. Suspected mares are often treated empirically with antibiotics, anti-inflammatories, steroids, and supportive drugs, and many farms already put high-risk mares on monthly antibiotics whether signs are visible or not. A better blood test could sharpen those decisions, reduce guesswork, and help preserve pregnancies before the foal’s chances turn on timing alone.