Necrotizing Enteritis and Hyperammonemic Encephalopathy Associated With Equine Coronavirus Infection in Equids

Abstract

Equine coronavirus (ECoV) is a Betacoronavirus recently associated clinically and epidemiologically with emerging outbreaks of pyrogenic, enteric, and/or neurologic disease in horses in the United States, Japan, and Europe. We describe the pathologic, immunohistochemical, ultrastructural, and molecular findings in 2 horses and 1 donkey that succumbed to natural infection with ECoV. One horse and the donkey (case Nos. 1, 3) had severe diffuse necrotizing enteritis with marked villous attenuation, epithelial cell necrosis at the tips of the villi, neutrophilic and fibrinous extravasation into the small intestinal lumen (pseudomembrane formation), as well as crypt necrosis, microthrombosis, and hemorrhage. The other horse (case No. 2) had hyperammonemic encephalopathy with Alzheimer type II astrocytosis throughout the cerebral cortex. ECoV was detected by quantitative polymerase chain reaction in small intestinal tissue, contents, and/or feces, and coronavirus antigen was detected by immunohistochemistry in the small intestine in all cases. Coronavirus-like particles characterized by spherical, moderately electron lucent, enveloped virions with distinct peplomer-like structures projecting from the surface were detected by negatively stained transmission electron microscopy in small intestine in case No. 1, and transmission electron microscopy of fixed small intestinal tissue from the same case revealed similar 85- to 100-nm intracytoplasmic particles located in vacuoles and free in the cytoplasm of unidentified (presumably epithelial) cells. Sequence comparison showed 97.9% to 99.0% sequence identity with the ECoV-NC99 and Tokachi09 strains. All together, these results indicate that ECoV is associated with necrotizing enteritis and hyperammonemic encephalopathy in equids.

Gastritis, Enteritis, and Colitis in Horses

“…The diagnosis is confirmed by detection of equine coronavirus in intestinal contents or feces by PCR, in tissues by immunohistochemistry, or by direct electron microscopy of intestinal contents or affected intestinal tissue. 61,62 Parasitic Diseases Protozoa Cryptosporidiosis Cryptosporidium is an apicomplexan protist that is found mostly on the epithelium of the gastrointestinal, biliary, and respiratory tracts of mammals, birds, reptiles, and fish. 8 Cryptosporidium parvum is responsible for cryptosporidiosis in immunologically normal and immunosuppressed foals between 5 days and 6 weeks of age.…”

Clinical Pathology in the Adult Sick Horse

“…16 Hyperammonemia of gastrointestinal origin also has been reported as a cause of neurologic signs and high fatality rates in horses infected with equine coronavirus. 17,18 Ammonia concentrations in blood samples rapidly increase with storage after collection and, therefore, special handling is required for accurate measurement. Blood should be drawn into EDTA or heparin anticoagulant tubes and centrifuged and plasma separated from red blood cells immediately.…”

Diagnosis and Treatment of Undifferentiated and Infectious Acute Diarrhea in the Adult Horse

“…Lesions include necrosis and sloughing of enterocytes in the intestinal villi, dilated crypts filled with necrotic debris, and mucosal inflammation. 25,26 Hematologic abnormalities include leukopenia, characterized by neutropenia and/ or lymphopenia. 25 The most common clinical manifestations of ECoV infection include anorexia, lethargy, and fever.…”

“…25 Neurologic signs associated with ECoV infection have been described and seem to be associated with hyperammonemic encephalopathy with Alzheimer type II astrocytosis in the cerebral cortex. 26 Diagnosis of ECoV colitis is currently based on PCR of feces, gastrointestinal contents, or tissue samples. In one study there was no significant statistical difference in absolute ECoV quantification between positive sick and positive healthy horses.…”