Balasuriya Focuses on EVA and EHV-1 Research at the Gluck Equine Research Center

Equine arteritis virus (EVA) and equine herpesvirus-1 (EHV-1) are the two main topics of research for Udeni Balasuriya, BVSc, MS, PhD, associate professor of virology at the Gluck Equine Research Center.

Balasuriya, who joined the Gluck Center in 2005, focuses on characterizing the molecular epidemiology and molecular basis of pathogenesis of EAV and EHV-1 infections in horses. EAV is the causative agent of equine viral arteritis (EVA), which is characterized by upper respiratory tract disease in adult horses, abortion in mares, and pneumonia in young foals. Stallions can become long-term carriers of the virus and transmit the virus during breeding. EHV-1 also causes upper respiratory tract disease and abortion. Some EHV-1 strains have the ability to cause neurologic disease that could lead to paralysis and even death.

"Both of these viruses pose a significant threat to the global equine industry as there has been an increase in the number of outbreaks of EVA and the neurologic form of EHV-1 in the U.S. and around the world," Balasuriya said. "Furthermore, there is increased global dissemination of EAV and rise in the incidence of EVA due to the rapid national and international movement of carrier stallions for breeding and competition. In 2006 and 2007, a multi-state occurrence of EVA was confirmed for the first time in Quarter Horses in the U.S. The recent outbreak of EVA in Quarter Horses increased awareness among horse owners and breeders of a disease that can have significant financial repercussions, especially for the breeding sector of the nation's equine industry."

Clinical signs of EVA include respiratory illness, nasal discharge, fever, limb and ocular edema, skin rash, swelling of mares' mammary glands, swelling of stallions' genital areas, abortion, and pneumonia in young foals. EAV is transmitted by the respiratory and the venereal routes. Recently, it has been shown there is a risk of EAV transmission associated with in-vivo (in the live horse)embryo transfer from a donor mare inseminated with EAV infective semen.

"This laboratory is one of the very few laboratories in the world that is dedicated to EAV research, and our ongoing research projects are focused on the molecular characterization of the virus, viral pathogenesis, virus-host interaction, and molecular epidemiology as well as development of improved diagnostic and vaccine technologies," Balasuriya said.

While Balasuriya would like to conduct further research on EAV, funding is limited. Balasuriya's earlier research at the Gluck Center focused more heavily on EAV and in recent years has expanded to also include EHV-1. EHV-1 is highly contagious and responsible for significant economic losses due to respiratory illness, abortion, neurologic (paralytic) disease and death in horses. The increase in incidence of neuropathogenic EHV-1 strains in recent years has given rise to considerable concern among horse industries and governmental agencies responsible for equine health around the world.

"EHV-1 continues to pose a major threat to equine health and, for the benefit of our relationship with the equine industry, it is vital that we maintain the 60-year-old tradition of conducting pioneering research on these viruses within the Department of Veterinary Science at the University of Kentucky," Balasuriya said. "This need is even more pressing in the absence of Dr. (George) Allen, who was the driving force behind EHV-1 research at the Gluck Center for many years. There is an urgent need to continue some of Dr. Allen's research that was in progress at the time of his death.

"To this end, I have joined with Drs. Frank Cook and Peter Timoney (faculty members at the Gluck Center) to continue some of the equine herpesvirus research," Balasuriya continued.

Ongoing research projects on EHV-1 are focused on the following areas:

  • Molecular epidemiology and evolution of EHV-1.
  • Identification of virulence determinants of EHV-1 using reverse genetic technology. This involves cloning the full-length genome of a neuropathogenic EHV-1 strain into a bacterial artificial chromosome (BAC) and reconstitution of infectious virus and genetic manipulation.
  • Molecular mechanisms of EHV-1 pathogenesis and host immune response to the virus.
  • Development of improved diagnostic assays and vaccines against EHV-1.

"EHV-1 infection is difficult to prevent because the virus can establish latent infection and protective immunity is only relatively short-lived following a clinical episode," Balasuriya said. "Therefore, horses may suffer a recrudescence of infection (virus becomes active again after a dormant period) or can become reinfected from another carrier animal once protective immunity wanes. In common with natural infections, the currently available vaccines do not stimulate long-lasting protective immune responses. The ongoing studies in our laboratory will yield important benefits for the equine industry in terms of improved diagnostics and more accurate predictions of the clinical consequences associated with detection of specific neuropathogenic and non-neuropathogenic EHV-1 strains."

In recent months Balasuriya has received three grants to further his research on EHV-1. Those grants are:

  • Comparison of in vitro (in the laboratory) antiviral activity of herpesvirus DNA polymerase inhibitors against neuropathogenic and non-neuropathogenic strains of equine herpesvirus-1 from the Kentucky Horse Racing Commission;
  • Molecular characterization of neurovirulent EHV-1 strains from the Grayson-Jockey Club Research Foundation.

"I would like to thank all the private organizations for funding our research projects on EHV-1. These studies will enable us to better characterize the molecular epidemiology of EHV-1 infection to gain a greater understanding of the genetic basis of emergence of neurologic herpesvirus strains and evolution of EHV-1," Balasuriya said.

"In addition, these studies will also allow us to develop better guidelines governing the intrastate and interstate movement of horses during and/or following EHV-1 disease outbreaks. Findings from these studies could eventually impact control programs designed to prevent EHV-1 infection among Thoroughbred and other horse breeds in the U.S., as well as development of improved molecular-based diagnostic tests and more effective vaccines. Furthermore, testing of antiviral drugs with the potential to relieve suffering and prevent the spread of EHV-1 will provide the utmost benefit in terms of horse well-being and the financial health of the equine racing industry."

Studies in his laboratory are also focused on developing improved recombinant vaccines to prevent infection of horses with EAV and EHV-1, as well as developing improved tests to diagnose other equine respiratory viruses.

Balasuriya also spends a considerable amount of time training and supervising postdoctoral fellows and visiting scientists and graduate and undergraduate students at the Gluck Center. His goal is to provide one-on-one instruction of graduate and undergraduate students and afford a multi-disciplinary-based training environment for their benefit.

"My principal goal is to provide leadership, guidance, and support to qualified undergraduate and graduate students, and postdoctoral fellows undertaking viral research that utilizes state-of-the-art molecular virology techniques," he said.

A postdoctoral scholar and three graduate students are currently working on EAV research projects, while another postdoctoral scholar and another graduate student are working on EHV-1 projects. In addition, two undergraduate students and two research staff members work in Balasuriya's laboratory.

Jenny Blandford is the Gluck Equine Research Foundation Assistant at the Gluck Center.


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