FINAL DIAGNOSIS: EHD virus infection in a Southern Indiana cow

  In August 2007, Heeke ADDL was presented with a 9-year-old Charolais cow with a 7 day clinical history of lethargy, standing in water (suspected fever), poor  appetite and weight loss.  A total of 3 cows in this herd of 42 were exhibiting similar clinical signs, though this was the only cow that had died.

  Grossly, the cow had ulcerative and necrotizing   rhinitis, stomatitis, reticulitis, and teat dermatitis, along with pulmonary congestion and edema and fetal   mummification.  The epithelium of the nares was  markedly reddened and necrotic and had extensive areas where the epithelium was sloughed.  The nasal turbinate mucosa was diffusely reddened but otherwise grossly unremarkable.  The dental pad and the epithelial ridges of the palate were severely sloughed and ulcerated.  The buccal mucosa had multiple 1-2 mm red shallow erosions, often surrounding the buccal papillae.  The gingival mucosa surrounding the lower incisors was yellow-gray and necrotic, with hyperemic margins.  The tip of the tongue was dark, dry, and sunken (necrotic), and the epithelium on the ventral midline of the tongue was white, raised (possible    remnant of a vesicle), and focally sloughed.   The   epithelium of the lower lip was yellow-gray, dry, cracked and necrotic.  A 3-cm area of the mucosa of the reticulum was gray and dry (necrotic) with hyperemic margins.  Esophagus, rumen, abomasum and  intestine were grossly  unremarkable.  The skin of the teats had multiple 1-3 mm red erosions and shallow ulcers.  The uterus contained a 12x14x30 cm mass of fetal bones (severely mummified fetus).

  Histologically, the cow had erosive and ulcerative stomatitis, nasal dermatitis, rhinitis, and reticulitis.  The oral mucosa had multifocal full-thickness necrosis and ulceration with numerous superficial bacilli, marked congestion of the superficial submucosal blood       vessels, and mild perivascular lymphocytic infiltrates.  The tongue had a large focal ulcer, with coagulation necrosis of the underlying vessels.  Some blood     vessels of the tongue contained fibrin thrombi, and colonies of thin filamentous bacilli were present in some of the deeper areas of necrosis.  The nasal tip epidermis had necrosis and separation (sloughing) of the epidermis, marked necrosis of the superficial    dermis, infiltration of degenerating neutrophils into the superficial dermal papillae, and marked congestion of the superficial dermal capillaries.  The nasal turbinate submucosa was congested and edematous, and   heavily infiltrated with degenerating neutrophils.

  Based upon the time of year, the lesions (especially the characteristic dental pad necrosis and teat lesions), and the presence of an epizootic hemorrhagic disease (EHD) outbreak in the local whitetail deer population, infection with EHD virus was strongly suspected.  The differential diagnoses included BVD, IBR, Malignant catarrhal fever, foot-and-mouth-disease and rinderpest.  Tissues were submitted to the Foreign Animal Disease Laboratory at Plum Island, New York, and no foreign animal diseases were detected.  Lip, oral mucosa, tongue, reticulum, teat, lung, spleen, and lymph node were submitted for fluorescent antibody (FA) testing and virus isolation.  FA tests did not detect BVD, IBR, EHD virus in any of the tissues, but EHD virus was isolated from the lung, spleen, lymph node, and oral mucosa.  Post-mortem pericardial fluid was submitted for serologic testing, and was found to be positive for EHD by agar gel immunodiffusion (AGID).  ELISA   testing for Bluetongue virus was negative.  A tissue pool was submitted to the National Veterinary Services Laboratory in Ames, Iowa, and PCR tests were     negative for alcephaline herpesvirus-1 and ovine herpesvirus-2 (the causes of malignant catarrhal fever).  EHD viral RNA was detected in the sample tested by PCR.  EHD virus was then isolated from the pooled tissues by inoculation onto BHK-21 cells and cattle pulmonary artery endothelium cells, and was determined to be EHD type-2 by virus neutralization testing.  No bacterial pathogens were isolated from the lung and liver.  Based upon the characteristic clinical signs and      lesions, and the isolation of EHD virus from the       affected tissues, bovine EHD was diagnosed in this case.

-by Dr. Duane Murphy, Heeke ADDL

Erosion of nasal mucosa	Epithelial erosions of the teats	Erosion of dental pad and hard palate