Colorado State Researchers Begin New EHV-1 Study

A Colorado State University (CSU) study will look at how equine herpesvirus type 1 (EHV-1) compromises the immune system immediately upon entering the "gate" of a horse's respiratory system--the airway and throat--allowing it to spread through the body and potentially cause neurological damage, abortion, and possibly death.

The study will specifically concentrate on the lining of the respiratory systems, called the epithelium, which keeps the airway moist and is a barrier to pathogens. The epithelial cells also serve a critical function in shaping the immunological response, including secreting chemicals to attack pathogens and determining and initiating the cascade of immune responses in the rest of the body.

"We believe that the herpesvirus finds a way to 'hide' from the immune response, and we also know that if an immune system doesn't trigger a good response at the first sign of infection, viruses like this one take off," said Gabriele A. Landolt, DVM, MS, PhD, Dipl. ACVIM, assistant professor of equine medicine in the Department of Clinical Sciences and co-lead researcher on the project. "That combination of events may take place in the horse's respiratory system, and if we can crack the equine herpesevirus secret to getting through that gateway and compromising the immune system at that point of entry, we may be better able to find treatments and preventative measures to stop outbreaks of the virus."

"The outcome of this research will also help scientists understand how herpes viruses in all species may impact immune systems," said Gisela Hussey, PhD, assistant professor in the Department of Clinical Sciences and co-leader of the project. "This study is innovative because it is the first study to focus on defining the immune responses at the respiratory epithelium and how the virus controls the immune system."

Equine herpesevirus-1 is spread through nose-to-nose contact and through close contact with contaminated equipment, clothing and water and feed. The pathogen also may spread for a limited distance through the air. There are several types of equine herpesevirus, and there also are herpes strains that impact virtually every species. 

Equine herpesvirus is highly contagious and can cause a variety of ailments in horses, including rhinopneumonitis (a respiratory disease mostly of young horses), abortion in broodmares, and myeloencephalopathy (evident in the neurologic form). The virus is not transmissible to humans. Clinical signs of the neurologic EHV-1 form include fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence.

The researchers are conducting the study on actual equine epithelium cells from deceased horses whose owners have volunteered the tissue for the research. The use of these cells in a model that mimics the actual response in a living horse also is novel in this research area.

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