Infecção natural pelo vírus da diarreia viral bovina (BVDV) em bovinos de corte no Estado do Pará

Abstract

Background: Bovine viral diarrhea virus (BVDV) is a pathogen that causes great economic losses in dairy and beef herds.The main disturbances caused by this virus are related to abortion, fetal malformation and mummification, and the birth ofweak calves. In addition, this disease may result in persistently infected animals, as well as individual immune tolerance tothe virus. However, the symptoms are nonspecific and variable, and dependent on the age of affected animal. The objectiveof the present study was to report three cases with clinical signs of BVDV infection, with subsequent confirmation of thediagnosis by reverse transcription - polymerase chain reaction technique (RT-PCR).Cases: In a beef production farm located at the state of Para, Brazil, three animals presented severe diarrhea; the feces wereliquefied and greenish-yellow in color; crusted lesions were visible and scattered over various parts of the animals’ bodies,including the muzzle, nostrils, periauricular region, and hooves; the tongue mucosa was undergoing an intense desquamationprocess. One of the affected animals, a 6-month-old calf, was euthanized following the recommendations of the “Brazilianguide to good practices for animal euthanasia” of the Ethics, Bioethics and Animal Welfare Committee / Federal Council ofVeterinary Medicine. After euthanasia, this calf was necropsied and some of its organs, including the tongue and skin, weresent to the Biological Institute of Sao Paulo State for histopathology examination (HE) and identification and isolation of thevirus. Positive samples for the presence of BVDV were diagnosed by RT-PCR, confirming the suspicion and explaining thesigns observed in that animal and reported in other dead animals of the farm. Because RT-PCR was performed in ulcerativelesions present in the tongue, negative reactions were detected for bovine herpesvirus (BoHV) and positive reactions forBVDV. The cutaneous tissue was marked with lymphocytic infiltration, observed in both epidermis and dermis, which refersto crusted lesions distributed in several regions of the animal’s body. In the lungs, we observed rare areas of emphysema andmarked lymphocytic interstitial pneumonia with hemorrhagic spots, correlated with symptoms of respiratory disease. Also,marked renal damage and spleen lesions were identified, indicating glomerulonephritis and lymphocytic splenitis.Discussion: This study evidenced the occurrence of BVDV in two calves and one adult animal, which is in agreementwith the described higher incidence of symptomatic infection in young animals. Clinical signs of severe greenish-yellowdiarrhea and crusted lesions distributed throughout several regions of the animals’ bodies, including the muzzle, nostrils,periauricular region, and hooves were described, with intense tongue epithelium desquamation, which is a particular andcharacteristic symptom of Mucosal Disease - the classical form of the physiopathogeny caused by bovine viral diarrheavirus. The clinical findings of severe diarrhea are possibly related to the histopathological results, which showed hyaliniza-tion of the intestinal mucosa and rare mononuclear cells in the liver nodules. Pulmonary histopathological findings of rareareas of lymphocytic interstitial pneumonia, severe emphysema, and hemorrhagic foci refer to respiratory diseases. Basedon the clinical signs and laboratory findings, we conclude that the affected animals showed classic symptoms of bovineviral diarrhea. This diagnosis highlights the presence of the disease in cattle raised in the state of Para, Brazil.