On June 30 in the University of Kentucky Veterinary Diagnostic Laboratory's (UKVDL) new stadium-seat auditorium, Erdal Erol, DVM, MS, PHD, UKVDL head of diagnostic microbiology, gave a lecture titled "Current microbiological methods for equine abortion diagnoses and beyond." (Watch the lecture)

During his talk Erol noted that from 2009 to 2011, he found the most likely infectious causative agents for abortion were bacterial, such as Escherichia coli; Streptococcus zooepidemicus; nocardioform actinomycetes (Cr. equi and Amycolatopsis spp); and Streptococcus equisimilis; and viral, such as equine herpesvirus-1 (EHV-1).

Nocardioform-related abortions are restricted to the last trimester. A nocardioform-infected placenta might be thick and heavy with distinctive gross lesions that most commonly occur in the body of the placenta at the bifurcation of the uterine horns. The affected placenta is covered by a thick, light brown, tenacious fluid described by some as "peanut butter."

"Nocardioform bacteria were first reported at the UKVDL in 1986, and the UKVDL remains at the center of research and detection for this major causative agent of abortion," Erol said.

According to Erol, during the 2010-2011 foaling season, the number of confirmed nocardioform cases increased significantly, while the confirmed number of leptospirosis (a bacterial disease that can cause abortion in pregnant mares and chronic uveitis) cases fell dramatically. Erol plotted 12 years of retrospective data, which revealed an inverse change from one disease to the other by year, following a pattern of changing weather conditions from dry to humid. Erol's early hypothesis is that abortions caused by nocardioform rise during dry periods, and abortions caused by leptospirosis, a tropical disease, climb during warm and wet seasons. Erol and a research team from UKVDL and the Gluck Equine Research Center are currently investigating this theory.

Another observation from Erol's team is that resistance by S. equisimilis to gentamicin and tetracycline (two commonly prescribed drugs) is growing. Resistance to these drugs has risen significantly over the past several years. S. zooepidemicus and equisimilis are strains of the strep bacteria that can infect other animals, including humans. The UKVDL is one of the few laboratories in the world that can differentiate between streptococcus strains, Erol said.

Erol also discussed EHV-1, which can cause respiratory disease, abortion, and equine herpes myeloencephalopathy (EHM), a neurologic form of EHV-1. This disease requires a laboratory diagnosis. From 2009-2011, the UKVDL polymerase chain reaction (PCR) to detect 34 EHV-1 cases of fetal abortion, and other laboratory methods such as virus isolation and fluorescent antibody testing confirmed the diagnosis.

Understanding antibody levels, incubation, clinical signs, culture, and serology of abortion causative agents is critical to arriving at the correct diagnosis, Erol said. Major current diagnostic methods include pathological examination, serology assays (monoclonal/polyclonal antibodies, whole lysate/single antigen), culture (usually considered the gold standard), in which the live organism is grown, and PCR, which detects the virus earlier than serology and uses genetic amplification in a molecular way.

Veterinarians must collect and submit to the lab fresh and appropriate clinical specimens in order to maximize the benefit of any tests to be run.

"The specimen should likely yield a causative agent, meaning 'a good swab,' and should be properly taken, stored, and shipped to the lab," Erol explained. "If the swab is stored at room temperature and/or sent without ice packs, there may be too many bacteria present to determine the causative agent."

Karin Pekarchik is an editorial officer in UK's Agricultural Communications Services.

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