Fourth Quarter 2023 International Report on Equine Infectious Diseases

Horse receiving a vaccination against an infectious disease.
Horse receiving a vaccination against an infectious disease. Kondrashov MIkhail Evgenevich

Newsdate: Friday, January 19,  2024 – 11:30 am
Location: LEXINGTON, Kentucky

This report collates information provided by diagnostic laboratories in Lexington, Kentucky, University of Kentucky Veterinary Diagnostic Laboratory and Equine Diagnostic Solutions, Inc. (EDS). We are also grateful to IDEXX laboratories, Germany, for sharing their quarterly PCR respiratory panel results with this community.

Horse in Belize receiving medical treatment by military veterinarian.

Horse in Belize receiving medical treatment by military veterinarian.

This report collates equine health information provided by diagnostic laboratories in Lexington, Kentucky,
© 2005 by MC2 JOSHUA KARSTEN New window.

We have further included information from the International Thoroughbred Breeders’ Federation, the International Collating Centre (ICC) in Newmarket/Cambridge, United Kingdom, and information from the American Association of Equine Practitioners’ Equine Disease Communication Center (EDCC). This report summarizes heightened activity of several relevant contagious or environment-linked diseases among equids. We encourage everyone to report laboratory-confirmed (toxico) infectious disease of Equidae to the ICC or EDCC.

For North America and Europe, there is steady reporting of Strep. equi spp. equi (Strangles) cases. Several North American states and provinces report single cases of EIA (exception: Texas with eight), while there is a single ‘Old World’ report from Bulgaria.

While the third quarter experienced a true surge of West Nile virus (WNV) infections in California and the U.S. Rocky Mountain states, the situation has cooled a little. New cases have been reported scattered across the U.S. and from the eastern Canada provinces.

The same holds for Eastern equine encephalitis virus (EEEV) infections, which decreased during fall/winter due to decreased mosquito activity. The Mediterranean Basin also reports WNV cases (28 from southern Europe and two from northern Africa). Two more endemic regions for WNV have emerged: Berlin region, Germany, and Vienna, Austria.

Combined, they report close to 10 cases of WNV infections in horses. Interesting is the slow spread of WNV cases into neighboring regions. Noteworthy is the report of two Western equine encephalitis (WEE) virus cases from a bordering region between Uruguay and Argentina.

Incidental Equine Influenza cases/outbreaks have been reported from Ontario, Tennessee and the Pacific Northwest; a few more reports reached us from Northern Europe.

Vesicular Stomatitis virus (VSV) infections in horses in the U.S. is still very present in California.

As Northern Hemisphere-bred broodmares enter their third trimesters of pregnancies, the season for EHV-1 (EHV-4) abortions has begun, and we received reports of incidental abortions. Cases of EHV-1 neurologic disease (EHM) in North America and Europe have also been reported.

Several countries in continental Europe report outbreaks of Atypical Myopathy (AM), the result of Sycamore seeds and seedling ingestion, which can trigger a severe and life-threatening form of type-1 (oxidative) muscle myopathy. Outbreaks of AM follow a seasonal and severe weather pattern during winter and spring.

Kentucky laboratories and the laboratory in Germany report high incidence of Strep. equi spp equi and EHV-1 positive samples. EDS (Kentucky) reports a small number of Equine Influenza positive samples with sample origin from the Eastern United States.


Report by Lutz Goehring Edward O. Olajide - Gluck Equine Research Center – Department of Veterinary Science - University of Kentucky

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