Colostral immunity as an analytical factor in predicting the development of acute respiratory viral infections in calves

To reduce the incidence of acute respiratory viral infections in cattle, routine vaccination of mother cows is carried out. There is a direct dependence of the passive immunity level in calves on the vaccination efficacy in cows. The paper presents the results of a study of colostral immunity in calves and post-vaccination immunity in cows against the agents of acute respiratory viral infections in agricultural facilities located on the territory of the Ural and Volga Federal Districts. In the farms under study (n = 10), cattle are vaccinated with inactivated vaccines: “COMBOVAC” and “COMBOVAC-R” (OOO Vetbiokhim, Russia), “HIPRABOVIS® 4” (Laboratorios Hipra, S. A., Spain). The study of postvaccinal immunity level in cows showed that the levels of antibodies to infectious bovine rhinotracheitis virus (5.3–8.0 log2), bovine viral diarrhea virus (3.5–4.8 log2), bovine parainfluenza-3 virus (6.8–8.5 log2) and bovine respiratory syncytial virus (4.2-4.5 log2) in cattle confer protection. When evaluating the results of serological diagnostics of passive immunity in calves to acute respiratory viral infections, it was found that the level of colostral antibodies in them is lower than the level of post-vaccination antibodies in cows: to infectious bovine rhinotracheitis virus by 34.2–58.8%; to bovine diarrhea virus by 37.5–45.0%; to bovine parainfluenza-3 virus by 14.7–35.4 and to bovine respiratory syncytial virus by 23.5-42.2%. To ensure epizootic favourable situation, it is proposed to adjust the schedules of vaccination against bovine diseases in herds, infected by acute respiratory viral infections for dairy farms under study.

Performance of multiple diagnostic methods in assessing the progression of bovine respiratory disease in calves challenged with infectious bovine rhinotracheitis virus and Mannheimia haemolytica1

The objective of this study was to evaluate the diagnostic performance of chute-side diagnostic methods for detecting physiological and pathological changes as indicators of early bovine respiratory disease (BRD) in calves experimentally inoculated with infectious bovine rhinotracheitis virus (IBR) and Mannheimia haemolytica (Mh). A challenge study was performed over 14 d in 30 Holstein steers [average weight (±SEM) = 211 kilograms (kg) ± 2.4 kg] inoculated on day 0 with IBR and on day 6 with Mh. Diagnostic methods included clinical illness scores (CIS), lung auscultation using a computer-aided stethoscope (CAS), rectal temperature, facial thermography, pulse oximetry, and bilateral thoracic ultrasonography. Animals were randomized into 1 of 5 necropsy days (days 6, 7, 9, 11, and 13) when the percentage of lung consolidation was estimated. The effect of study day on the results of the diagnostic methods and associations between each diagnostic method’s values with lung consolidation measured at necropsy were determined with mixed models. Values for all diagnostic methods differed significantly (P < 0.01) by day. During the IBR phase (days 0 to 6) calves had “normal” to “moderate” CIS, whereas during the Mh phase (days 6.5 to 13) scores were predominantly “severe” to “moribund.” Similarly, CAS scores were “normal” and “mild acute” during the IBR phase and “mild acute” to “moderate acute” after the Mh challenge. Oxygen saturation did not differ significantly between days 0, 1, 2, 4, and 6; however, significantly decreased 12 h after inoculation with Mh (P < 0.05). Mean lung consolidation between animal’s right and left side recorded by ultrasound was 0.13% (±0.07) before the inoculation with Mh. However, during the Mh phase, mean consolidation increased significantly over time (P < 0.05). The percentage of lung consolidation at necropsy ranged from 1.7% (±0.82) on day 6 to 55.4% (±7.49) on day 10. Clinical illness scores, rectal temperature, facial thermography, oxygen saturation, and ultrasonography were significantly associated (P < 0.05) with lung consolidation at necropsy. In addition, there was a significant trend (P = 0.07) between CAS and lung consolidation scores at necropsy. These chute-side diagnostic methods are useful for detecting disease progression on animals with early stages of BRD.

INVESTIGATION ON BOVINE VIRAL DIARRHEA VIRUS AND INFECTIOUS BOVINE RHINOTRACHEITIS VIRUS IN MONGOLIAN DAIRY FARMS

In this study, 168 blood sera were collected from dairy cows in Selenge and Tuv aimags during 2013 - 2014. The ELISA was carried out for serological detection of antibodies and antigens to Bovine viral diarrhea virus (BVDV), antibodies to Infectious bovine rhinotracheitis virus (IBRV) in dairy cows in Mongolia. The ELISA results of antibodies of BVDV and antigen of BVDV showed that 86.9% and 3.57%, respectively. The seroprevalence of antibodies against IBRV was found to be 60.7%. In order to confirm of BVDV, One Step RT-PCR was performed in ELISA positive cattle serum samples using specific primer for BVDV. The results showed that 294 bp fragment was successfully amplified. Phylogenetic analysis revealed that the nucleotide sequences 5'UTR gene of the isolates belonged to the BVDV1 subtype. Four isolated virus samples were closely related to China, the another isolate was closely related to the Slovenia BVDV1 isolate.