RESUMEN
The molecular epidemiology of Pasteurella multocida has rarely been studied at the farm level in cattle. The aim of this study was to determine whether single or multiple strains of P. multocida tend to exist within farms. Molecular characterisation was carried out on isolates obtained from nasal swabs from 105 calves from 32 randomly selected beef and dairy farms located throughout Scotland, and from 131 calves from 20 farms in the Mayenne region of France, where sampling occurred in response to respiratory disease outbreaks. P. multocida isolates were characterised by random-amplified polymorphic DNA (RAPD) typing and pulsed-field gel electrophoresis (PFGE) using restriction enzyme ApaI. In addition, isolates representative of each farm/RAPD profile combination were typed by multilocus sequence typing (MLST). Among 105 Scottish isolates, 15 RAPD profiles were distinguished. The majority of farms (27/32) had indistinguishable profiles in all positive animals. Five farms had two profiles. Among 140 French isolates, 23 RAPD profiles were distinguished. More within-farm heterogeneity was observed although 10/20 farms had just one profile (E4) in sampled calves. Profile E4 accounted for 60% (84/140) of French isolates. PFGE was more discriminatory than RAPD but confirmed results with respect to within farm homogeneity or heterogeneity of strains, whereas MLST was not discriminatory enough for farm level epidemiology. As in other host species, either several strains or one dominant strain of P. multocida may exist within farms, with evidence for a role of management factors such as movements onto the farm in the number of strains detected.
Asunto(s)
Enfermedades de los Bovinos/epidemiología , Bovinos/microbiología , Brotes de Enfermedades/veterinaria , Infecciones por Pasteurella/veterinaria , Pasteurella multocida/aislamiento & purificación , Animales , Técnicas de Tipificación Bacteriana , Enfermedades de los Bovinos/virología , ADN Bacteriano/genética , Electroforesis en Gel de Campo Pulsado , Francia/epidemiología , Epidemiología Molecular , Tipificación de Secuencias Multilocus , Nariz/microbiología , Infecciones por Pasteurella/epidemiología , Pasteurella multocida/clasificación , Pasteurella multocida/genética , Escocia/epidemiologíaRESUMEN
The prevalence of Pasteurella multocida, a cause of bovine respiratory disease, was studied in a random sample of beef suckler and dairy farms throughout Scotland, by means of a cross-sectional survey. A total of 637 calves from 68 farms from six geographical regions of Scotland were sampled between February and June 2008. Deep nasal swabs were taken, and samples that were culture-positive for P multocida were confirmed by PCR. Prevalence of P multocida was 17 per cent (105 of 616 calves); 47 per cent of farms had at least one positive animal. A higher prevalence was detected in dairy calves than beef calves (P=0.04). It was found that P multocida was associated with Mycoplasma-like organisms (P=0.06) and bovine parainfluenza type 3 virus (BPI-3) (P=0.04), detected by culture and quantitative PCR of nasal swabs, respectively. Detection of P multocida was not associated with bovine respiratory syncytial virus (BRSV), bovine herpesvirus type 1 (BoHV-1) or bovine viral diarrhoea virus (BVDV). Mycoplasma-like organisms, BPI-3, BRSV, BoHV-1 and BVDV were detected in 58, 17, four, 0 and eight calves, on 25, five, two, 0 and five of the 68 farms, respectively.