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Abstract Background Bovine viral diarrhea virus (BVDV) strains circulating in livestock herds show significant sequence variation. Conventional wisdom states that most sequence variation arises during acute infections in response to immune or other environmental pressures. A recent study showed that more nucleotide changes were introduced into the BVDV genomic RNA during the establishment of a single fetal persistent infection than following a series of acute infections of naïve cattle. However, it was not known if nucleotide changes were introduce when the virus crossed the placenta and infected the fetus or during the acute infection of the dam. Methods The sequence of the open reading frame (ORF) from viruses isolated from four acutely infected pregnant heifers following exposure to persistently infected (PI) calves was compared to the sequences of the virus from the progenitor PI calf and the virus from the resulting progeny PI calf to determine when genetic change was introduced. This was compared to genetic change found in viruses isolated from a pregnant PI cow and its PI calf, and in three viruses isolated from acutely infected, non-pregnant cattle exposed to PI calves. Results Most genetic changes previously identified between the progenitor and progeny PI viruses were in place in the acute phase viruses isolated from the dams six days post-exposure to the progenitor PI calf. Additionally, each progeny PI virus had two to three unique nucleotide substitutions that were introduced in crossing the placenta and infection of the fetus. The nucleotide sequence of two acute phase viruses isolated from steers exposed to PI calves revealed that six and seven nucleotide changes were introduced during the acute infection. The sequence of the BVDV-2 virus isolated from an acute infection of a PI calf (BVDV-1a) co-housed with a BVDV-2 PI calf had ten nucleotides that were different from the progenitor PI virus. Finally, twenty nucleotide changes were identified in the PI virus of a calf born to a PI dam. Conclusions These results demonstrate that nucleotide changes are introduced into the BVDV infecting pregnant cattle at rates of 2.3 to 8 fold higher then during the acute infection of non-pregnant animals.

The objective of this retrospective study was to characterize the relative prevalence of diagnoses and location of lameness lesions in beef cattle. Medical records from 2005 to 2012 were reviewed and 745 cases of beef cattle that had presented for lameness were identified. Information regarding signalment, lesion location, and cause of lameness was analyzed. The cause of lameness was localized to the foot in approximately 85% of cases; a hind limb was affected over 70% of the time. The lateral claw was most commonly affected in cases of both fore- and hind-limb lameness. The most common diagnoses of noninfectious etiology were screw claw, vertical fissure, and interdigital fibroma. Infectious foot disease accounted for only 20% of foot lameness. Routine foot trimming may be warranted in some herds to improve weight-bearing balance and alleviate lameness. L'objectif de cette étude rétrospective était de déterminer la prévalence relative des différentes lésions à l'origine d'une boiterie chez des bovins de boucherie admis dans un hôpital universitaire vétérinaire. Les dossiers médicaux datant de 2005 à 2012 ont été examinés et 745 cas de boiterie ont été identifiés. Les renseignements concernant le signalement, la localisation de la lésion et l'origine de la boiterie ont été analysés. La boiterie a été attribuée à une pathologie du pied dans approximativement 85 % des cas. Dans de tels cas, un membre postérieur était affecté dans 70 % des cas. L'onglon latéral était le plus souvent affecté qu'il s'agisse d'une boiterie d'un membre antérieur ou postérieur. Les lésions d'origine non infectieuse les plus souvent identifiées étaient une concavité de la muraille (pied enroulé ou pied chinois), une fissure verticale et une hyperplasie interdigitale. Les lésions d'origine infectieuse représentaient seulement 20 % des cas de boiterie liés à une lésion du pied. Un parage fonctionnel régulier est probablement nécessaire dans certains troupeaux de bovins de boucherie afin d'améliorer la répartition des charges entre les onglons et l'incidence des boiteries. [ABSTRACT FROM AUTHOR]

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