Antibodies to WNV Common in Arab Emirate Horses

Researchers found antibodies to West Nile virus (WNV) in nearly 20% of horses recently tested in the United Arab Emirates (UAE), according to Ulrich Wernery, DVM, PhD, scientific director of the Central Veterinary Research Laboratory in Dubai and author of the Dubai-based study published in Wildlife Middle East.

The testing was initiated after one horse showed clinical signs of encephalitis.

"We were really astonished, especially to see only one clinical case," Wernery said. "That means to us that we are dealing with a very mild strain."

The horse that showed clinical signs was treated and recovered within a week.

A widespread survey of 750 horses in the UAE--a country that previously had no history of WNV--was launched in late 2007 following diagnosis of the index case in the city of Ghantoot. Results of the enzyme-linked immunosorbent assay (ELISA) antibody test showed that 19.2% of these 750 horses had WNV antibodies. Within the immediate Ghantoot area, 84% had antibodies for the disease. Serum from 11 Ghantoot horses was sent to Cornell University College of Veterinary Medicine for further testing, which revealed that all the horses in the sample had been exposed to the virus at least six weeks prior to the survey. Exact numbers were not released, but Wernery said all the horses showed "very high levels" of antibodies.

"At the beginning we were shocked to see that many horses positive, but now we are relieved (because) they are protected," Wernery said, cautioning that this could not be considered lifelong immunity.

Wernery recommended that veterinarians vaccinate all horses traveling in or out of the UAE--particularly those in transit between the UAE and North America--regardless of their antibody levels.

Approximately two-thirds of American horses have been vaccinated against WNV, making a similar serosurvey in the United States unfeasible, said Frank Hurtig, DVM, MBA, associate director of equine veterinary medical affairs at Merial. However, an estimated 3-10% of unvaccinated American horses develop clinical signs of disease, he said, and 20-30% of those cases result in death.

Wernery said 30% of UAE camels tested were also positive for WNV antibodies. None of the camels have shown any clinical signs of encephalitis.

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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