Horse diseases for third quarter of 2008

January 13, 2009

The usual suspects continued to make their presence felt in the latest roundup of equine diseases.

The International Collating Centre, Newmarket, England, and other sources reported the following disease outbreaks, according to the University of Kentucky's Gluck Equine Research Centre's Equine Disease Quarterly newsletter.

Cases of anasplasmosis (Anasplasma phagocytophila) and Borreliosis (Borrelia burgdorferi) were diagnosed among non-thoroughbred horses in Switzerland. Contagious Equine Metritis was confirmed in two horses in France and a non-thoroughbred stallion in Switzerland.

Two cases of Eastern Equine Encephalitis (EEE) were diagnosed among non-Thoroughbred horses in Ontario, Canada. The US Department of Agriculture (USDA) reported 157 cases of EEE during 2008, with 81 in Florida and 22 in Georgia as of November 10.

Cases of equine herpesvirus (EHV) infection were reported from Ireland, South Africa, and the United Kingdom (UK). In Ireland, Coital Exanthema (EHV-3) was diagnosed in a pony stallion; EHV-1 was isolated from a Thoroughbred mare with neurological signs; and EHV-4 was isolated and identified by polymerase chain reaction (PCR) from an ataxic trotter mare. In the UK, one horse was euthanized due to severe neurological disease; serology utilizing Complement Fixation (CF) testing identified moderately high titers to EHV-1 and EHV-4. Several in-contact animals seroconverted to both viruses, although none of them exhibited respiratory or neurological signs. Respiratory disease attributable to EHV-4 was confirmed by serology in a single animal and a case of EHV-1 abortion was diagnosed in the UK. Ten abortions attributable to EHV-1 were diagnosed on four premises housing Thoroughbred and Warmblood mares in South Africa.

Equine infectious anemia was diagnosed in two non-Thoroughbred horses in France and three horses in Germany. Japan reported a single case of equine influenza in a draft horse on July 1, with no cases subsequently identified despite extensive surveillance. Equine influenza was confirmed on two premises in the UK. Influenza virus isolated in Switzerland during November 2007 has been characterized as a member of the Eurasian lineage of equine subtype-2 (H3N8).

Cases of piroplasmosis were reported in United Arab Emirates, South Africa, and Spain, where the disease is considered endemic. One case of piroplasmosis in a non-Thoroughbred horse was reported from Switzerland. A clinical case of piroplasmosis was confirmed during August in a 7-year-old Quarter horse in Florida, USA. Subsequent serological testing of 25 horses on the premise identified four additional positive animals. Testing of other in-contact and surrounding premises revealed 14 positive animals on six premises. Transmission of the infection is considered to have occurred as a result of needle transmission and not via tick vectors. All positive animals were linked to two horses that entered Florida from Mexico. As of November 5, six premises were under state quarantine awaiting repeat serological test results.

Strangles was reported on four premises in Denmark, five in France, 20 in Ireland, five in South Africa, several premises in Sweden, and four in Switzerland.

West Nile Virus (WNV) infection was diagnosed among two non-Thoroughbred horses in Ontario, Canada; two non-Thoroughbred horses in France; and 16 horses on 11 premises in Italy. As of November 10, the USDA reported 138 cases of WNV infection among horses in the United States during 2008, with 40 in Washington and 23 in California.