Molecular and pathological investigations of EHV-1 and EHV-4 infections in horses in Turkey.

This research aimed to examine and identify the cause of a series of horse abortions that occurred in Turkey between 2008-2009. Through the use of real-time polymerase chain reaction (PCR) alongside physical examinations and pathological studies, the study found that these abortions were largely due to infections with EHV-1 and EHV-4, scientifically known as Equine Herpesviruses -1 and -4.

Methodology

• The researchers used molecular techniques and pathological examinations to investigate the cause of these abortions.
• A total of ten lungs, three brains, and one nasal swab from ten different aborted fetuses were included in the study along with six nasal swabs and three vaginal swabs from the horses that had miscarried.
• Two of the fetuses were also necropsied – a procedure similar to an autopsy – and the histopathological findings were reported.

Findings

• Researchers were able to isolate EHV-1 in the lung, liver, and brain of one aborted fetus. Furthermore, EHV-1 DNA was detected in the lungs, livers, and spleens of two necropsied fetuses and in three lungs from ten fetuses submitted for diagnosis.
• A brain from one of the aborted fetuses was also positive for EHV-1 DNA.
• EHV-4 DNA was only detected in the nasal swab of one tested fetus.
• No EHV-1 or EHV-4 DNA was detected in the swabs from the aborting horses.

Sequence Analysis

• The research team performed a sequence analysis of the glycoprotein B of the strains, and generated a phylogenetic tree – a branching diagram showing the evolutionary relationships among various biological species.
• Results indicated that 4 of the 5 Turkish EHV-1 strains (TR02, TR03, TR04 and TR05) fell under the same cluster, hinting at the possibility that they rose from a common ancestor. The fifth strain (TR01) was slightly removed from the group and appeared to cluster with EHV-1 from other locations.
• The study failed to detect single nucleotide polymorphisms (SNP in ORF30) — a DNA sequence variation — associated with neuropathogenesis (the generation of disease affecting the nervous system) in any of the strains.

Necropsy Observations

• At necropsy, the researchers observed sub-millimeter focal necrosis (cell death) in the liver and spleen.
• Microscopic examinations showed focal coagulation necrosis, and marked eosinophilic intranuclear and intracytoplasmic inclusion bodies in the hepatocytes (liver cells) around the necrotic areas in the liver.
• Severe coagulation necrosis in white pulp of the spleen was also observed.