Epizootic Hemorrhagic Disease
Bluetongue virus (BTV) and Epizootic hemorrhagic disease (EHD), both caused by orbiviruses, are most commonly associated with disease in sheep and deer, respectively. These diseases were diagnosed by the CAHFS laboratory system in sick dairy cows with lesions suggestive of foot-and-mouth disease on 3 dairies in California in August.
The Epizootic hemorrhagic disease virus (EHD) case was a single cow on a large dairy that was presented to the herd veterinarian with ulcers throughout the mouth. The mouth was very painful, and the cow was salivating excessively and off feed. She had sore feet with small erosions in the skin between both front claws, with mild swelling and petechial hemorrhages around the coronary band. The dairy reported one other cow with similar lesions one month earlier. A CDFA foreign animal disease diagnostician performed an investigation with a herd visit and the cow was determined to be unlikely to have Foot-and-mouth disease (FMD) due to the fact only a single animal was affected. Ovine herpesvirus-2 Malignant catarrhal fever (MCF) was the primary rule out. The cow was euthanized and laboratory findings were extensive: stomatitis, glossitis, nasal antrum rhinitis and interdigital dermatitis of the front feet.
A full foreign animal disease testing work-up was performed at the USDA-NVSL foreign animal disease laboratory at Plum Island, including FMD, MCF, Vesicular stomatitis virus and Rinderpest. In addition, the CAHFS Biotechnology section was validating various tests for diseases which could look like FMD, and tested initially for Bovine viral diarrhea virus, MCF and BTV, all of which were negative. Infectious bovine rhinotracheitis virus testing was done by standard fluorescent antibody test at CAHFS-Tulare. At the suggestion of an overseas colleague, EHD testing was initiated and the test was positive by PCR. The PCR product was sequenced and the presence of EHD virus was confirmed.
The CAHFS investigation executed a battery of molecular tests in search of an etiological agent for this dramatic manifestation of a “FMD look-alike” disease that had not previously been reported in cattle in California. This persistent testing, along with the networking with a colleague overseas, highlights the strength and tenacity of CAHFS’ diagnosticians. This is yet another example of CAHFS serving the animal industry and CDFA as the early warning system that helps to protect the health of California’s livestock and poultry.