Isolation, characterization, and antibiotic sensitivity assessment of Gallibacterium anatis biovar haemolytica, from diseased Egyptian chicken flocks during the years 2013 and 2015.

Gallibacterium anatis biovar haemolytica constitutes a part of the normal microflora in the upper respiratory and genital tracts of healthy chickens, but it is also associated with different pathological conditions. In the current study, 102 commercial chicken flocks suffering from respiratory disease and/or drop in egg production were investigated for the presence of G. anatis during 2013 and 2015. These flocks comprised 8 breeder, 32 layer, and 62 broiler flocks. By culture method, 20 flocks were found positive: one isolate derived from broiler breeders, 6 isolates from layers, and 13 isolates from broilers. G. anatis biovar haemolytica was identified by phenotyping and PCR. Additionally, partial genome sequencing of 11 isolates (5 layer isolates of 2013 and 6 broiler isolates of 2015) based on 16S rRNA and 23S rRNA gene sequences was performed and revealed 96.5% to 100% genetic relatedness. Antibiotic sensitivity of these isolates revealed that the 2013 isolates were highly susceptible to florfenicol while the isolates of 2015 were highly susceptible to cefotaxime. Gallibacterium anatis biovar haemolytica is a newly introduced bacteria in Egypt causing salpingitis, peritonitis, drop in egg production, and/or respiratory signs.

Pharmacokinetic/pharmacodynamic evaluation of marbofloxacin as a single injection for Pasteurellaceae respiratory infections in cattle using population pharmacokinetics and Monte Carlo simulations.

Population pharmacokinetic of marbofloxacin was investigated with 52 plasma concentration-time profiles obtained after intramuscular administration of Forcyl® in cattle. Animal's status, pre-ruminant, ruminant, or dairy cow, was retained as a relevant covariate for clearance. Monte Carlo simulations were performed using a stratification by status, and 1000 virtual disposition curves were generated in each bovine subpopulation for the recommended dosage regimen of 10 mg/kg as a single injection. The probability of target attainment (PTA) of pharmacokinetic/pharmacodynamic (PK/PD) ratios associated with clinical efficacy and prevention of resistance was determined in each simulated subpopulation. The cumulative fraction of response (CFR) of animals achieving a PK/PD ratio predictive of positive clinical outcome was then calculated for the simulated dosage regimen, taking into account the minimum inhibitory concentration (MIC) distribution of Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni. When considering a ratio of AUC0-24 hr /MIC (area under the curve/minimum inhibitory concentration) greater than 125 hr, CFRs ranging from 85% to 100% against the three Pasteurellaceae in each bovine subpopulation were achieved. The PTA of the PK/PD threshold reflecting the prevention of resistances was greater than 90% up to MPC (mutant prevention concentration) values of 1 µg/ml in pre-ruminants and ruminants and 0.5 µg/ml in dairy cows.

A multiplex PCR assay for molecular capsular serotyping of Mannheimia haemolytica serotypes 1, 2, and 6.

Mannheimia haemolytica is an important respiratory pathogen of ruminants. Of the 12 capsular serovars identified, 1 and 6 are most frequently associated with disease in cattle, while 2 is largely a commensal. Comparative analysis of 24 M. haemolytica genomes was used to identify unique genes associated with capsular polysaccharide synthesis as amplification targets in a multiplex PCR assay to discriminate between serotype 1, 2, and 6 strains. The specificity of serotype specific gene targets was evaluated against 47 reference strains representing 12 known serovars of M. haemolytica and 101 field isolates identified through antisera agglutination as serotypes 1, 2, or 6. The results suggest this simple and cost-effective serotype specific PCR assay can be used as an alternative to agglutination based techniques to serotype the majority of M. haemolytica collected from bovines, thus averting the need to use animals and invest in expensive sera development for agglutination assays. In addition, the gene targets identified in this study can be used in silico to identify serotype 1, 2, and 6 strains in sequenced M. haemolytica isolates without the need for culture based analysis.

Rumen temperature change monitored with remote rumen temperature boluses after challenges with bovine viral diarrhea virus and Mannheimia haemolytica.

Remote rumen temperature monitoring is a potential method for early disease detection in beef cattle. This experiment was conducted to determine if remotely monitored rumen temperature boluses could detect a temperature change in steers exposed to bovine viral diarrhea virus (BVDV) and challenged with a common bovine respiratory disease pathogen, Mannheimia haemolytica (MH). Twenty-four Angus crossbred steers (BW = 313 ± 31 kg) were allotted to 1 of 4 treatments: 1) no challenge (control); 2) challenge by a 72-h exposure to 2 steers persistently infected with BVDV; 3) bacterial challenge with MH; and 4) viral challenge by a 72-h exposure to 2 steers persistently infected with BVDV followed by bacterial challenge with MH (BVDV + MH). Remotely monitored rumen temperature boluses programmed to transmit temperature every minute were placed in the rumen before the time of exposure to steers persistently infected with BVDV. Rectal temperatures were taken before MH challenge (0) and at 2, 4, 6, 12, 18, 24, 36, 48, 72, and 96 h after MH challenge. Rumen temperatures were recorded 3 d before (-72 h; period of BVDV exposure) through 14 d after (336 h) MH challenge. Rumen temperatures were analyzed as a randomized complete block design with a 2 × 2 factorial arrangement of treatments and a first-order autoregressive covariance structure for repeated measures. A treatment × day interaction was observed for average daily rumen temperature (P < 0.01). A treatment difference (P < 0.01) was observed on d 0, when MH-challenged steers had greater rumen temperatures than steers not challenged with MH. There was no BVDV × day interaction (P > 0.01). Rumen temperatures averaged every 2 h resulted in a BVDV × hour interaction (P < 0.01) and an MH × hour interaction (P < 0.01). The BVDV × hour differences occurred at h -18 to -14, 40 to 46, 110, 122, and 144 to 146 (P < 0.01). The MH × hour difference occurred at h 4 to 24 (P < 0.01). Maximum rumen temperature was increased (P < 0.01) for BVDV (0.8 °C), MH (1.2 °C), and BVDV + MH (1.3 °C) compared with the control. On average, rumen temperatures measured by the boluses at the same time points as the rectal temperatures were 0.13 °C less than rectal temperatures, and the 2 body temperatures were highly correlated (r = 0.89). Rumen temperature boluses appear to have potential as a tool for detecting temperature changes associated with adverse health events such as exposure to bovine respiratory disease and BVDV.

Effects of exposure to calves persistently infected with bovine viral diarrhea virus type 1b and Mannheimia haemolytica challenge on animal performance, nitrogen balance, and visceral organ mass in beef steers.

Bovine viral diarrhea viruses (BVDV) have been isolated alone or in combination with other viral and bacterial pathogens in animals diagnosed with bovine respiratory disease (BRD), a disease causing major economic loss to the feedlot industry. The objective of this experiment was to determine the effects of Mannheimia haemolytica challenge after short-term exposure (72 h) to bovine viral diarrhea virus type 1b (BVDV1b) persistently infected (PI) calves on performance, N balance, and organ mass in finishing cattle. Treatments (6 steers/treatment; initial BW = 314 +/- 31 kg) were 1) steers not exposed to steers PI with BVDV nor challenged with M. haemolytica (control; CON); 2) steers exposed to 2 steers PI with BVDV1b (BVD) for 72 h; 3) steers intratracheally challenged with M. haemolytica (MH); or 4) steers exposed to 2 steers PI with BVDV1b for 72 h and challenged with M. haemolytica (BVD+MH). There were 12 h between exposure to PI steers and challenge with M. haemolytica. Steers were housed in metabolism stanchions during the first 5 d after the M. haemolytica challenge and on d 7 to 11, 28 to 32, and for 5 d before slaughter (average 119 d on feed) to determine N balance and were weighed every 28 d. At slaughter, carcass and organ mass data were collected. Data were analyzed as a randomized complete block design with a 2 x 2 factorial arrangement of treatments, and steer was used as the experimental unit. From d -3 (beginning of PI steer exposure) to 4, steers challenged with M. haemolytica had less (P = 0.04) ADG than steers not challenged with M. haemolytica. In addition, steers exposed to steers PI with BVDV tended (P = 0.09) to have less ADG and G:F across the entire finishing period than steers not exposed to BVDV. Before slaughter, retained N expressed as grams per day (P = 0.03) and as a percentage of N intake (P = 0.04) was less in BVD steers compared with steers not exposed to BVDV. There were no effects (P > 0.10) of BVDV exposure or M. haemolytica challenge on empty BW (EBW) or carcass characteristics. Expressed as a percentage of EBW, HCW was less (P = 0.02) and total offal weight was greater (P = 0.02) for steers challenged with M. haemolytica compared with steers not challenged. Results are in agreement with those reported in larger scale finishing studies and suggest that acute exposure to BRD-related pathogens can have long-term effects on animal performance.

Effects of exposure to calves persistently infected with bovine viral diarrhea virus type 1b and subsequent infection with Mannheima haemolytica on clinical signs and immune variables: model for bovine respiratory disease via viral and bacterial interaction.

The objective was to determine effects of an intratracheal Mannheimia haemolytica challenge after 72-h exposure to bovine viral diarrhea virus type 1b (BVDV1b) persistently infected (PI) calves on serum antibody production, white blood cell count (WBC), cytokine concentrations, and blood gases in feedlot steers. Twenty-four steers (initial BW = 314 +/- 31 kg) were randomly allocated to 1 of 4 treatments (6 steers/treatment) arranged as a 2 x 2 factorial. Treatments were 1) steers not exposed to steers PI with BVDV nor challenged with M. haemolytica (control; CON); 2) steers exposed to 2 steers PI with BVDV for 72 h (BVD); 3) steers intratracheally challenged with M. haemolytica (MH); and 4) steers exposed to 2 steers PI with BVDV for 72 h and challenged with M. haemolytica (BVD+MH). There were 12 h between exposure to PI steers and challenge with M. haemolytica. Rectal temperature was increased (P < 0.001) for MH and BVD+MH during the initial 24 h after the M. haemolytica challenge. For MH and BVD+MH, total WBC count was increased (P < 0.01) at 36 h post M. haemolytica challenge compared with CON, whereas in BVD steers, WBC count was decreased (P < 0.01). Total lymphocyte count was increased (P = 0.004) during the initial 72 h post BVDV exposure for the BVD and BVD+MH groups compared with MH and CON, and this difference remained at 96 h post M. haemolytica challenge. An increased (P < 0.001) total neutrophil count was observed during the initial 36 h for the MH group and at 72 h for the BVD+MH challenge group. Interleukin 1beta, IL-6, and tumor necrosis factor alpha (TNFalpha) concentrations were greater (P

Development of a multilocus sequence typing (MLST) scheme for Mannheimia haemolytica and assessment of the population structure of isolates obtained from cattle and sheep.

Mannheimia haemolytica is an important veterinary pathogen affecting cattle and sheep. Previous typing methods, including restriction enzyme analysis, pulsed-field gel electrophoresis and multilocus enzyme electrophoresis (MLEE) have indicated a clonal population structure. Multilocus sequence typing (MLST) has now almost replaced MLEE and is a definitive and portable typing method, allowing global data exchange. The purpose of this study was to develop a MLST scheme for M. haemolytica. A collection of isolates from 10 countries, including the type strain and reference strains for all recognized serotypes were included in the study. Partial sequences of the housekeeping genes adk, aroE, deoD, gapDH, gnd, mdh and zwf were used to define the MLST scheme. The 95 isolates demonstrated 34 different sequence types (ST) of which 19 were connected in three clonal complexes (CC). ST1 constituted more than one-third of the isolates and was most frequently demonstrated among isolates from bovine sources. The analysis indicated a common evolutionary origin of 33 isolates from the French alps, collected from domestic and wild animals and demonstrating several related STs. An analysis of 17 isolates from the USA demonstrated the same ST in 14 of the isolates. In conclusion, an unambiguous typing scheme is presented for M. haemolytica and results obtained confirm previous observations of a clonal population of the organism.

Effects of commingling beef calves from different sources and weaning protocols during a forty-two-day receiving period on performance and bovine respiratory disease.

The study objective was to determine health and performance of ranch calves from different preconditioning strategies during a 42-d receiving period when commingled with calves of unknown health histories from multiple sources. Steer calves from a single source ranch (RANCH) were weaned and immediately shipped to a feedlot (WEAN, initial BW = 247 +/- 29 kg); weaned on the ranch for 45 d before shipping, but did not receive any vaccinations (WEAN45, initial BW = 231 +/- 26 kg); or weaned, vaccinated with modified live viral vaccine, and held on the ranch for 45 d before shipping (WEANVAC45, initial BW = 274 +/- 21 kg). Multiple-source steers were purchased through auction markets (MARKET, initial BW = 238 +/- 13 kg), and upon receiving, a portion of ranch-origin steers from each weaning group was commingled with a portion of MARKET cattle (COMM). The experimental design was completely randomized with a 2 x 3 +1 factorial arrangement of treatments. Factors were RANCH vs. COMM and weaning management (WEAN vs. WEAN45 vs. WEANVAC45) as the factors; MARKET cattle served as the control. Calves of WEAN, WEAN45, and MARKET were vaccinated on arrival at the feedlot. Ranch-origin calves tended (P = 0.06) to have greater ADG than COMM or MARKET calves, although ADG was not affected (P = 0.46) by weaning management. Across the 42-d receiving period, DMI was not affected (P = 0.85) by cattle origin. However, MARKET, WEAN45, and WEANVAC45 calves consumed more (P < 0.001) DM than WEAN calves. Gain efficiency was not affected (P > or = 0.11) by treatment. Ranch-origin calves were less (P < 0.001) likely to be treated for bovine respiratory disease than MARKET calves; COMM calves were intermediate. Calves that were retained on the ranch after weaning (WEAN45 and WEANVAC45) were also less likely to be treated (P = 0.001) than MARKET or WEAN calves. As expected, differences in morbidity related to differences in health costs. Calves of WEAN45 and WEANVAC45 had less (P < 0.001) health costs than MARKET and WEAN calves. On arrival, serum haptoglobin concentrations were greater (P < 0.001) in MARKET and WEAN compared with WEAN45 and WEANVAC45 calves. Calves from a single source that are retained on the ranch for 45 d after weaning exhibit less morbidity and less health costs during the receiving period at the feedyard than when cattle are commingled or trucked to the feedyard immediately after weaning.

The acute phase response in calves experimentally infected with bovine viral diarrhoea virus and/or Mannheimia haemolytica.

The aim of this investigation was to study differences and similarities in the acute phase response of calves experimentally infected in the respiratory tract with either bovine viral diarrhoea virus (BVDV) or Mannheima haemolytica (Mh), or with a combination of both (BVDV/Mh). A non-inoculated control group was also included. The acute phase response was measured by serum or plasma concentrations of the acute phase proteins (APPs) haptoglobin, serum amyloid A (SAA) and fibrinogen, and of cortisol, prostaglandin F2alpha-metabolite and interferon-alpha (IFN-alpha) activity. Clinical symptoms were also recorded and were most severe in the BVDV/Mh group. The symptoms were mild to moderate in the BVDV group, while none, or very mild symptoms were observed in the Mh group. In all inoculated groups, a significant acute phase response was observed, with elevated values of haptoglobin, SAA and fibrinogen, while the control group remained unaffected throughout the study. In general, the magnitude of the response was similar, but the duration of elevated concentrations of APPs was significantly longer in the BVDV/Mh group than in the BVDV group, reflecting the duration of the clinical symptoms. However, in the single infection groups, the APP response and the clinical symptoms were not correlated. The IFN-alpha activity increased in all BVDV-inoculated animals, but no response in cortisol and PGF2alpha-metabolite concentrations was observed after infection. Basal levels of serum concentrations of haptoglobin, SAA and fibrinogen were established and may be used for evaluating calf health in herds. The duration of elevated haptoglobin, SAA and fibrinogen values did not differ significantly within groups indicating that their value as indicator of disease is equal.