Nocardioform Placentitis Concerns for Kentucky Foal Crop
A surge in nocardioform placentitis—type of placental infection that results in late-term abortion or small, underdeveloped foals—cases in Central Kentucky’s 2011 foal crop caused concern among practitioners, farm owners and managers, the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL), and the horse industry media. Following that year, the number of confirmed cases dropped to levels typically seen in the state. The 2016 foal crop saw a small increase in cases in February 2016, but then case counts dropped quickly.

However, the UKVDL has seen an increase in confirmed nocardioform placentitis cases in the 2017 foal crop, starting with 10 abortions in December 2016 compared to zero abortions in December 2015. In the first two weeks of January 2017, the UKVDL has already had confirmed eight nocardioform placentitis abortions, with more pending.

Nocardioform placentitis testing is available at UKVDL.

Standard tests are:

  • Culture: $17 in-state, $25.50 out-of-state
    5-day, minimum, turnaround time
  • PCR: $35 in-state, $52.50 out-of-state
    24-48-hour turnaround time

Histopathology, included in mail-in necropsy, and necropsies are performed at the UKVDL.

Nocardioform placentitis was first identified in Central Kentucky in the mid-1980s. The term “nocardioform” was adopted due to similarities of the causative agents to the nocardioform actinomycetes. Through sequence analysis of 16S rRNA genes, the most common organisms have been identified as Crossiella equi sp nov, Amycolatopsis spp, and Streptomyces spp.

The pathogenesis of nocardioform placentitis remains poorly understood. Its clinical ramifications range from late-gestation abortions, stillbirths, prematurity, and the birth of live but non-viable foals, to foals that are small and weak but survive. Because even mild cases of nocardioform placentitis were submitted in 2011, a number of foals were healthy and vigorous at birth.

For more information on nocardioform placentitis see:

Gross and histologic lesions of nocardioform placentitis are distinctive. The cervical star region of the placenta is spared and lesions—single or multiple—most commonly occur at the bifurcation of the placental horns. The affected chorion (the outermost placental membrane) is covered by a thick, light brown, tenacious exudate overlying a rough, tan chorion with marked villous loss. Additionally, expansion of the allantoic stroma by nodular masses (adenomatous hyperplasia) is frequently observed. The characteristic histologic lesions include necrosis of trophoblasts, marked villous loss, squamous metaplasia, chronic suppurative inflammation, adenomatous hyperplasia, and intra-lesional gram positive branching bacilli. The bacteria do not reach the fetus and fetal lesions are limited to those of placental insufficiency.

Researchers have not yet identified nocardioform placentitis’ means of transmission. Nocardioform organisms do not behave in a manner similar to either the models of ascending bacterial placentitis or septicemic bacterial placentitis. Because nocardioform placentitis cases tend to occur in waves, with some years having very large numbers of cases while other years have very few cases, scientists are investigating the role of environmental factors in the incidence of disease; thus far, it appears to follow hot, dry weather.

This information was provided by Laura Kennedy, DVM, Dipl. ACVPl Jackie Smith, PhD, MSc, Dipl. AVES (Hon); and Craig Carter, DVM, PhD, Dipl. ACVPM, DSNAP, of the UKVDL.

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