Obliterative vasculitis caused by ovine herpesvirus type 2 in cattle

Background: Malignant catarrhal fever (MCF) is a frequently fatal viral infection that affects various wild and domestic ruminants and even pigs, as recently reported. It is a disease characterized by lymphoproliferation, vasculitis and erosiveulcerative lesions in mucosa and skin. In Brazil, the virus that circulates and causes the disease has been identifi ed as OvHV-2. The aim of this study is to describe the clinicopathological changes in a cow with obliterative vasculitis caused by OvHV-2. Case: A two-year-old Gir cow with a history of intermittent diarrhea and progressive weight loss for approximately a year, which had not improved with antibiotic therapy, was euthanized and subjected to necropsy. In the necropsy, the liver was enlarged, fi rm, and had a marbled aspect all over the capsular and cut surfaces (light striations intercalated with dark areas). Cut surfaces also revealed thickening of the vessel walls, which exhibited a branched pattern. There was marked thickening of the small and large intestinal walls. The hepatic, mediastinal and mesenteric lymph nodes were enlarged. The samples were fi xed in 10% phosphate-buffered formalin, routinely processed for histology, embedded in paraffi n, cut 5-µm sections, and stained stained with hematoxylin and eosin. Additionally, sections of the liver and ileum were subjected to Masson’s trichrome staining. The main microscopic alterations were found in the vessels (arteries and veins) of the liver and intestine. Periportal fi brosis and marked pericholangitis which would sometimes form bridges were observed in the liver. Transmural and perivascular fi brosis; the muscular layer was ruptured and there was proliferation of the intima, which caused obliteration of the lumen were also present. The lymph nodes’ medullae exhibited intense infi ltration of macrophages and plasma cells with areas of fi capillary proliferation, and atrophy of medullary cords. Neovascularization and marked infl ammatory infi ltrates composed of lymphocytes, plasma cells, macrophages and eosinophils were also present. Masson’s trichrome staining revealed areas of fiThe tissue samples of the carotid rete mirabile, brain and liver were submitted for identifi cation of OvHV-2 by nested polymerase chain reaction (nPCR) tested was positive for ovine herpesvirus type 2. Discussion: The main histological fi ndings (obliterative vasculitis observed in the small and large intestines, liver, and lymph nodes) plus the detection of viral DNA of OvHV-2 in fragments of the carotid rete mirabile, brain, and liver by nPCR confi rmed the diagnosis of malignant catarrhal fever. Chronic cases of MCF in cattle are not often described. The disease is usually manifested in a hyperacute or acute form which culminates with death. The most frequent clinical presentation is the head and eye form, which is characterized by corneal opacity, and ocular, nasal, and oral serous discharge. Bovines with MCF usually exhibit macroscopic and microscopic changes in various organs due to the pansystemic characteristic of the virus, which causes vasculopathy and lymphadenopathy. In this report, the changes were restricted to the intestines, liver, and lymph nodes. The obliterative vasculitis seen in this case is similar to the changes described in cases of chronic. Other herpesviruses which cause lesions to the vascular wall can also cause hyperplasia of the muscular layer with progression to obliterative arteriopathy. This paper reports a presentation of MCR not previously described in Brazil. PCR was an important tool for the conclusion of this case.