The Participation of a Malignant Catarrhal Fever Virus and Mycoplasma bovis in the Development of Single and Mixed Infections in Beef and Dairy Cattle With Bovine Respiratory Disease

Abstract

The bovine respiratory disease (BRD) complex is a multietiological and multifactorial disease associated with a wide range of viral and bacterial pathogens. This study evaluated the contribution of specific infectious disease agents in the development of BRD in cattle from Brazil and determined if a virus within the malignant catarrhal fever virus (MCFV) group and Mycoplasma bovis, acting individually or in conjunction, can be associated with the development of BRD. Formalin-fixed paraffin-embedded pulmonary sections were used in immunohistochemical assays to determine the intralesional presence of six antigens associated with BRD: bovine alphaherpesvirus 1 (BoHV-1), bovine parainfluenza virus 3 (BPIV-3), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), MCFV, and M. bovis. Pneumonia was diagnosed in 82.7% (120/145) of all cattle evaluated. Interstitial pneumonia (60%, 72/120) and suppurative bronchopneumonia (25.8%, 31/120) were the most frequent patterns of pneumonia identified. Intralesional antigens of MCFV (53.3%, 64/120) were the most frequently associated with BRD, followed by M. bovis (47.5%, 57/120), BVDV (42.5%, 51/120), BoHV-1 (28.3%, 34/120), BRSV (24.2%, 29/120), and BPIV-3 (8.3%, 10/120). Additionally, antigens of BVDV, MCFV, and M. bovis were the most frequently identified agents associated with singular and concomitant infections. The MCFV identified during this study is more likely to be ovine gammaherpesvirus 2 (OvHV-2), since OvHV-2 is the only MCFV identified within the geographical region of this study. Interstitial pneumonia with proliferative vascular lesions may be a useful histologic feature to differentiate MCFV-induced pneumonia from other viral pneumonias of cattle. These results demonstrate that MCFV and M. bovis, in single or mixed infections, can produce pneumonia in cattle and should therefore be considered as primary agents in the development of BRD.

Ovine gammaherpesvirus 2 infections in cattle without typical manifestations of sheep-associated malignant catarrhal fever and concomitantly infected with bovine coronavirus

“…All animals infected with OvHV-2 had distinct patterns of pulmonary diseases, including interstitial pneumonia (animals #2 and #4) and suppurative bronchopneumonia (animal #4); similar findings were identified in cattle with BRD due to infections with a MCFV, more likely, OvHV-2 [ 19 ]. Additionally, necrotizing vasculitis, the hallmark for a histologic diagnosis of MCF [ 1 – 3 ], was only observed in animal #4; suggesting that this histologic alteration should not be the only histopathologic feature used to arrive at a diagnosis of OvHV-2-associated pneumonia.…”

“…Alternatively, cattle without any clinical manifestations, gross, and histologic demonstration of SA-MCF vasculitis contained OvHV-2 DNA [ 45 ]. Furthermore, our group has demonstrated the participation of OvHV-2 in cattle with neurological syndromes but without typical clinical manifestations of SA-MCF [ 15 ], with similar findings in cattle with pulmonary [ 19 , 20 , 22 ] and renal [ 21 ] diseases. Additionally, several reports have confirmed the participation of OvHV-2 in cattle [ 13 , 16 , 45 , 46 ] and the American bison [ 16 – 18 ] without typical clinical manifestations of SA-MCF.…”

“…However, BVDV nucleic acids or proteins were not identified from the lungs or intestine of these calves, suggesting that this viral disease pathogen did not participate in the development of the diseases patterns herein described and that these animals were concomitantly infected by BCoV and OvHV-2. Consequently, the role of OvHV-2 in the development of enteric diseases in cattle, either acting as an innocent bystander or a primary contributor [ 19 ], must be fully investigated, considering that enteric disease is also associated with MCF in bison [ 17 , 43 , 57 ].…”

“…The marked difference between the cases herein presented and those described in cattle [ 11 , 12 ] and bison [ 43 ] was the absence of typical clinical manifestations of SA-MCF in these calves as well as the cows with neurological manifestations [ 15 ]. Although the duration of disease progression was unknown in a retrospective study of BRD, PVLs were significant histologic features to diagnose MCFV-associated pneumonia in cattle with BRD, during which MCFV antigens were identified in 53.3% (64/120) of all cattle with BRD [ 19 ]. Furthermore, since PVLs are considered as the consequence of severe vasculitis [ 12 ] that is characteristic of SA-MCF [ 1 ], these vascular lesions may be essential histologic elements for the histopathologic diagnosis of OvHV-2-associated diseases in the absence of necrotizing vasculitis.…”

“…Additionally, cattle with neurological manifestations [ 13 , 15 ], and healthy cows [ 13 , 15 ] and the American bison, Bison bison [ 16 – 18 ] developed typical SA-MCF histologic lesions but without clinical signs suggestive of MCF. Furthermore, intralesional antigens of MCFV were identified in cattle with bovine respiratory disease, BRD [ 19 ], pulmonary [ 20 ], and renal diseases [ 21 ], but without any clinical manifestation and/or diagnosis of MCF, suggesting that these animals were infected by OvHV-2 but without the characteristic clinical signs of SA-MCF.…”