The titers, duration, and residual clinical protection of passively transferred nasal and serum antibodies are similar among beef calves that nursed colostrum from vaccinated or unvaccinated dams and were challenged experimentally with bovine respiratory syncytial virus at three months of age.

OBJECTIVES: To compare initial titers, duration, and residual clinical protection of passively transferred bovine respiratory syncytial virus (BRSV) nasal immunoglobulin (Ig) G-1 and IgA, and serum neutralizing (SN) antibodies. ANIMALS: 40 three-month-old beef steers born either to unvaccinated or vaccinated cows. PROCEDURES: During the last trimester of gestation, cows were assigned randomly to either vaccinated or unvaccinated groups. Calves were grouped on the basis of whether they nursed colostrum from unvaccinated dams (NO-VACC group; n = 20) versus dams vaccinated with 2 doses of an inactivated BRSV vaccine (VACC group; n = 20). At 3 months of age, calves were challenged with BRSV. Respiratory signs were scored. Nasal BRSV IgG-1 and IgA and SN antibodies were compared before and after the challenge. The presence of BRSV in nasal secretions was evaluated by reverse transcription-PCR assays. RESULTS: Respiratory scores after BRSV challenge were similar between treatment groups. Nasal BRSV IgG-1 and SN antibodies were significantly greater in VACC calves at 48 hours of life; however, by 3 months of age, titers had decayed in both groups. Nasal BRSV IgA titers were minimal after colostrum intake and before the BRSV challenge, and increased in both groups after the challenge. The NO-VACC group had a significantly greater probability of shedding BRSV compared with VACC calves. CLINICAL RELEVANCE: At 3 months of age, titers of passively transferred BRSV antibodies in VACC and NO-VACC calves had decayed to nonprotective levels. Calves born to vaccinated dams had a decreased probability of BRSV shedding; however, this was not related to differences in SN or nasal BRSV antibody titers.

Comparison of levels and duration of detection of antibodies to bovine viral diarrhea virus 1, bovine viral diarrhea virus 2, bovine respiratory syncytial virus, bovine herpesvirus 1, and bovine parainfluenza virus 3 in calves fed maternal colostrum or a colostrum-replacement product.

Colostrum-replacement products are an alternative to provide passive immunity to neonatal calves; however, their ability to provide adequate levels of antibodies recognizing respiratory viruses has not been described. The objective of this study was to compare the serum levels of IgG at 2 d of age and the duration of detection of antibodies to bovine viral diarrhea virus 1 (BVDV-1), bovine viral diarrhea virus 2 (BVDV-2), bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV-1), and bovine parainfluenza virus 3 (BPIV-3) in calves fed maternal colostrum (MC) or a colostrum replacement (CR) at birth. Forty newborn male Holstein calves were assigned to the CR or the MC group. Group CR (n = 20) received 2 packets of colostrum replacement (100 g of IgG per 470-g packet), while group MC (n = 20) received 3.8 L of maternal colostrum. Blood samples for detection of IgG and virus antibodies were collected from each calf at birth, at 2 and 7 d, and monthly until the calves became seronegative. Calves in the MC group had greater IgG concentrations at 2 d of age. The apparent efficiency of absorption of IgG was greater in the MC group than in the CR group, although the difference was not significant. Calves in the CR group had greater concentrations of BVDV neutralizing antibodies during the first 4 mo of life. The levels of antibodies to BRSV, BHV-1, and BPIV-3 were similar in the 2 groups. The mean time to seronegativity was similar for each virus in the 2 groups; however, greater variation was observed in the antibody levels and in the duration of detection of immunity in the MC group than in the CR group. Thus, the CR product provided calves with more uniform levels and duration of antibodies to common bovine respiratory viruses.

Les produits de remplacement du colostrum sont une alternative pour fournir une immunité passive aux veaux nouveau-nés; toutefois, leur capacité à fournir des niveaux adéquats d'anticorps reconnaissant les virus respiratoires n'a pas été décrite. L'objectif de la présente étude était de comparer les niveaux d'IgG sériques à 2 jours d'âge et la durée de détection des anticorps contre le virus de la diarrhée virale bovine de type 1 (BVDV-1), le virus de la diarrhée virale bovine de type 2 (BVDV-2), le virus respiratoire syncitial bovin (BRSV), l'herpesvirus bovin de type 1 (BHV-1), et le virus parainfluenza bovin de type 3 (BPIV-3) chez des veaux nourris avec du colostrum maternel (MC) ou du colostrum de remplacement (CR) à la naissance. Quarante veaux nouveau-nés mâles de race Holstein ont été assignés soit au groupe CR ou MC. Les animaux du groupe CR (n = 20) ont reçu deux paquets de substitut de colostrum (100 g d'IgG par paquet de 470 g), alors que les animaux du groupe MC (n = 20) ont reçu 3,8 L de colostrum maternel. Des échantillons sanguins pour la détection d'IgG et d'anticorps contre les virus ont été prélevés de chaque veau à la naissance, à 2 et 7 j d'âge, et à chaque mois jusqu'à ce que les veaux deviennent séronégatifs. Les veaux dans le groupe MC avaient des concentrations d'IgG plus élevées à 2 j d'âge. L'efficacité d'absorption apparente d'IgG était plus grande dans le groupe MC que dans le groupe CR, bien que la différence ne fût pas significative. Les veaux dans le groupe CR avaient des concentrations plus élevées d'anticorps neutralisants envers BVDV durant les 4 premiers mois de vie. Les niveaux d'anticorps contre BRSV, BHV-1, et BPIV-3 étaient similaires dans les deux groupes. Le temps moyen pour atteindre la séronégativité était similaire pour chaque virus dans les deux groupes; toutefois, de plus grandes variations étaient observées dans les niveaux d'anticorps et la durée de détection de l'immunité dans le groupe MC comparativement au groupe CR. Ainsi, le produit CR a fourni des veaux avec des niveaux d'anticorps contre les virus respiratoires bovins communs plus uniformes et de plus longue durée.(Traduit par Docteur Serge Messier).

Antiviral treatment of calves persistently infected with bovine viral diarrhoea virus.

BACKGROUND: Animals persistently infected (PI) with bovine viral diarrhoea virus (BVDV) are a key source of viral propagation within and among herds. Currently, no specific therapy exists to treat PI animals. The purpose of this research was to initiate evaluation of the pharmacokinetic and safety data of a novel antiviral agent in BVDV-free calves and to assess the antiviral efficacy of the same agent in PI calves. METHODS: One BVDV-free calf was treated with 2-(2-benzimidazolyl)-5-[4-(2-imidazolino)phenyl]furan dihydrochloride (DB772) once at a dose of 1.6 mg/kg intravenously and one BVDV-free calf was treated three times a day for 6 days at 9.5 mg/kg intravenously. Subsequently, four PI calves were treated intravenously with 12 mg/kg DB772 three times a day for 6 days and two PI control calves were treated with an equivalent volume of diluent only. RESULTS: Prior to antiviral treatment, the virus isolated from each calf was susceptible to DB772 in vitro. The antiviral treatment effectively inhibited virus for 14 days in one calf and at least 3 days in three calves. Subsequent virus isolated from the three calves was resistant to DB772 in vitro. No adverse effects of DB772 administration were detected. CONCLUSIONS: Results demonstrate that DB772 administration is safe and exhibits antiviral properties in PI calves while facilitating the rapid development of viral resistance to this novel therapeutic agent.