Research in Veterinary Science 99 (2015) 41–45
Contents lists available at ScienceDirect
Research in Veterinary Science j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / r v s c
Nasal isolation of Mannheimia haemolytica and Pasteurella multocida as predictors of respiratory disease in shipped calves J.D. Taylor a,*, B.P. Holland b,1, D.L. Step c, M.E. Payton d, A.W. Confer a a
Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078-2007, USA Department of Animal Science, Oklahoma State University, Stillwater, OK 74078-2007, USA Department of Veterinary Clinical Sciences, Oklahoma State University, Stillwater, OK 74078-2007, USA d Department of Statistics, Oklahoma State University, Stillwater, OK 74078-2007, USA b c
A R T I C L E
I N F O
Article history: Received 9 July 2014 Accepted 17 December 2014 Keywords: Bovine respiratory disease BRD Mannheimia haemolytica
A B S T R A C T
Three hundred ninety five calves were purchased from sale barns and delivered to the Willard Sparks Beef Research Center. Nasal swabs were collected to determine if presence of Mannheimia haemolytica and Pasteurella multocida in the upper respiratory tract (URT) can facilitate diagnosis of bovine respiratory disease (BRD). Samples were collected at arrival and at treatment for BRD. Clinically healthy control calves were sampled at time of treatment of sick calves. M. haemolytica was more commonly isolated from calves at treatment than at time of arrival or from control calves. M. haemolytica was more common in calves requiring treatment than in those never treated. Need for treatment and number of treatments were negatively associated with average daily gain, supporting the accuracy of diagnosis. These results suggest that URT sampling, when combined with clinical diagnosis, may assist in providing greater diagnostic accuracy, improving ability to evaluate risk factors, interventions, and treatments. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction Despite extensive research and wide-spread adoption of control and treatment efforts, bovine respiratory disease (BRD) remains the primary cause of feedlot morbidity and mortality. One reason for lack of progress is that most research relies upon field diagnosis of undifferentiated BRD rather than confirming the microbial agents involved. It has been asserted that greater effort should be made to elucidate the epidemiology of specific pathogens (Taylor et al., 2010a). Mannheimia haemolytica is the most common bacterial isolate from BRD cases (Fulton et al., 2002), but other implicated species include Pasteurella multocida, Histophilus somni and Mycoplasma species (Haines et al., 2001, and Welsh et al., 2004). Distinguishing among etiologic agents of BRD based upon clinical signs is generally unsuccessful (Haines et al., 2001); thus it is necessary to obtain bacteriologic samples in order to characterize the role each bacterium may play. Collection of isolates from the lungs of affected cattle would be the most informative. However, ante-mortem collection of such samples is logistically challenging, and the typical interval of days to weeks between disease onset and death limit utility of necropsy findings in defining initiating
* Corresponding author. 250 McElroy Hall, Stillwater, OK 74078, USA. Tel.: +1 405 744 7537; fax: +1 405 744 5275. E-mail address: [email protected] (J.D. Taylor). 1 Currently with Merck Animal Health, Volga, SD 57073, USA. http://dx.doi.org/10.1016/j.rvsc.2014.12.015 0034-5288/© 2014 Elsevier Ltd. All rights reserved.
agents. Given the ease of collecting samples from the upper respiratory tract (URT), it is appealing to use nasal swabs for assessing the role of various bacteria in BRD. Yet bacterial agents associated with BRD are frequently found in the URT of healthy cattle (Magwood et al., 1969) and any association between presence in the nasal pharynx and development of lower respiratory disease has been inconsistent. At least two studies (Yates et al., 1983, and Fulton et al., 2002) found no relationship between URT flora and risk of subsequent treatment. However, others (DeRosa et al., 2000, and Godinho et al., 2007) found value in use of nasal swabs in predicting what organisms are present in the lung of sick calves. More recently, research has focused on molecular characterization of isolates, rather than simple speciation. Numerous reports have utilized pulsed-field gel electrophoresis (PFGE) to evaluate isolates obtained from the URT via nasal swabs (Klima et al., 2011, and Klima et al. 2014a), while other work has compared isolates obtained from the URT and the lower respiratory tract (LRT) (Timsit et al., 2013, and Klima et al. 2014b). These works have sought to gain a better understanding of the characteristics of M. haemolytica populations associated with BRD (Klima et al., 2014a); however, such work is only relevant if the isolates obtained from the URT bear some relationship to the disease. The utility of samples obtained via nasal swabs has been staunchly defended by some (Hotchkiss et al., 2010), to predict not only the species present in the LRT but also the strain type. Others have reported results that call into question the usefulness of such approaches due to findings of only moderate concordance between findings in the LRT and URT (Allen et al., 1991,
42
J.D. Taylor et al./Research in Veterinary Science 99 (2015) 41–45
and Timsit et al., 2013). Clearly, additional work is needed to not only evaluate the molecular epidemiology of these organisms, but also the relationship between isolates in the URT and probability of disease. Therefore, the purpose of this study was to examine the utility of nasal swabs for predicting the likelihood of requiring treatment for BRD. Our hypothesis was that prevalence of M. haemolytica and P. multocida in the URT would not differ between calves requiring treatment and those not. 2. Materials and methods 2.1. Cattle Three hundred ninety five (395) calves (mean initial body weight of 218.6 ± 22.4 kg; range 157–287 kg) were obtained through order buyers from two auction markets in central Oklahoma between September 12 and 23, 2005. Included were 49 bulls and 346 steers. Calves were delivered to the Oklahoma State University Willard Sparks Beef Research Center and allowed to rest approximately 12 hours after arrival before undergoing initial weighing, individual identification, and sample collection, including collection of nasal swabs. Cattle were processed approximately 36 (loads 1–3) or 72 (load 4) hours after arrival. Processing included a viral vaccine (Bovishield Gold® 5, Zoetis, Florham Park, NJ), clostridial bacterin/ toxoid (Ultrachoice® 7, Zoetis), and an anthelmentic (Ivomec® Plus, Merial, Duluth, GA). No vaccines targeting bacterial BRD agents were administered. Castration and dehorning were performed at this time, as necessary. Cattle were blocked by weight and assigned into 25 open-air, dirt pens. Calves were monitored by trained personnel throughout the feeding period and identified as potentially suffering from BRD based upon the DART (depression, appetite, respiratory system, temperature) clinical scoring technique (Table 1). Treatment was administered to all calves that received a DART score of three or four. A calf deemed to be mildly clinically ill (having a clinical score of one or two), was treated only if it had a rectal temperature greater than 40 °C. At time of treatment, at least one (and frequently two) clinically healthy cohort(s) (control(s)) was also taken to the treatment area for further evaluation. Calves used for control sampling were from the same arrival and pen as treated calves and had never been treated for BRD prior to use as a control. Rectal temperature was measured for both treated and control calves; control calves were enrolled only if rectal temperature was
Contents lists available at ScienceDirect
Research in Veterinary Science j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / r v s c
Nasal isolation of Mannheimia haemolytica and Pasteurella multocida as predictors of respiratory disease in shipped calves J.D. Taylor a,*, B.P. Holland b,1, D.L. Step c, M.E. Payton d, A.W. Confer a a
Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078-2007, USA Department of Animal Science, Oklahoma State University, Stillwater, OK 74078-2007, USA Department of Veterinary Clinical Sciences, Oklahoma State University, Stillwater, OK 74078-2007, USA d Department of Statistics, Oklahoma State University, Stillwater, OK 74078-2007, USA b c
A R T I C L E
I N F O
Article history: Received 9 July 2014 Accepted 17 December 2014 Keywords: Bovine respiratory disease BRD Mannheimia haemolytica
A B S T R A C T
Three hundred ninety five calves were purchased from sale barns and delivered to the Willard Sparks Beef Research Center. Nasal swabs were collected to determine if presence of Mannheimia haemolytica and Pasteurella multocida in the upper respiratory tract (URT) can facilitate diagnosis of bovine respiratory disease (BRD). Samples were collected at arrival and at treatment for BRD. Clinically healthy control calves were sampled at time of treatment of sick calves. M. haemolytica was more commonly isolated from calves at treatment than at time of arrival or from control calves. M. haemolytica was more common in calves requiring treatment than in those never treated. Need for treatment and number of treatments were negatively associated with average daily gain, supporting the accuracy of diagnosis. These results suggest that URT sampling, when combined with clinical diagnosis, may assist in providing greater diagnostic accuracy, improving ability to evaluate risk factors, interventions, and treatments. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction Despite extensive research and wide-spread adoption of control and treatment efforts, bovine respiratory disease (BRD) remains the primary cause of feedlot morbidity and mortality. One reason for lack of progress is that most research relies upon field diagnosis of undifferentiated BRD rather than confirming the microbial agents involved. It has been asserted that greater effort should be made to elucidate the epidemiology of specific pathogens (Taylor et al., 2010a). Mannheimia haemolytica is the most common bacterial isolate from BRD cases (Fulton et al., 2002), but other implicated species include Pasteurella multocida, Histophilus somni and Mycoplasma species (Haines et al., 2001, and Welsh et al., 2004). Distinguishing among etiologic agents of BRD based upon clinical signs is generally unsuccessful (Haines et al., 2001); thus it is necessary to obtain bacteriologic samples in order to characterize the role each bacterium may play. Collection of isolates from the lungs of affected cattle would be the most informative. However, ante-mortem collection of such samples is logistically challenging, and the typical interval of days to weeks between disease onset and death limit utility of necropsy findings in defining initiating
* Corresponding author. 250 McElroy Hall, Stillwater, OK 74078, USA. Tel.: +1 405 744 7537; fax: +1 405 744 5275. E-mail address: [email protected] (J.D. Taylor). 1 Currently with Merck Animal Health, Volga, SD 57073, USA. http://dx.doi.org/10.1016/j.rvsc.2014.12.015 0034-5288/© 2014 Elsevier Ltd. All rights reserved.
agents. Given the ease of collecting samples from the upper respiratory tract (URT), it is appealing to use nasal swabs for assessing the role of various bacteria in BRD. Yet bacterial agents associated with BRD are frequently found in the URT of healthy cattle (Magwood et al., 1969) and any association between presence in the nasal pharynx and development of lower respiratory disease has been inconsistent. At least two studies (Yates et al., 1983, and Fulton et al., 2002) found no relationship between URT flora and risk of subsequent treatment. However, others (DeRosa et al., 2000, and Godinho et al., 2007) found value in use of nasal swabs in predicting what organisms are present in the lung of sick calves. More recently, research has focused on molecular characterization of isolates, rather than simple speciation. Numerous reports have utilized pulsed-field gel electrophoresis (PFGE) to evaluate isolates obtained from the URT via nasal swabs (Klima et al., 2011, and Klima et al. 2014a), while other work has compared isolates obtained from the URT and the lower respiratory tract (LRT) (Timsit et al., 2013, and Klima et al. 2014b). These works have sought to gain a better understanding of the characteristics of M. haemolytica populations associated with BRD (Klima et al., 2014a); however, such work is only relevant if the isolates obtained from the URT bear some relationship to the disease. The utility of samples obtained via nasal swabs has been staunchly defended by some (Hotchkiss et al., 2010), to predict not only the species present in the LRT but also the strain type. Others have reported results that call into question the usefulness of such approaches due to findings of only moderate concordance between findings in the LRT and URT (Allen et al., 1991,
42
J.D. Taylor et al./Research in Veterinary Science 99 (2015) 41–45
and Timsit et al., 2013). Clearly, additional work is needed to not only evaluate the molecular epidemiology of these organisms, but also the relationship between isolates in the URT and probability of disease. Therefore, the purpose of this study was to examine the utility of nasal swabs for predicting the likelihood of requiring treatment for BRD. Our hypothesis was that prevalence of M. haemolytica and P. multocida in the URT would not differ between calves requiring treatment and those not. 2. Materials and methods 2.1. Cattle Three hundred ninety five (395) calves (mean initial body weight of 218.6 ± 22.4 kg; range 157–287 kg) were obtained through order buyers from two auction markets in central Oklahoma between September 12 and 23, 2005. Included were 49 bulls and 346 steers. Calves were delivered to the Oklahoma State University Willard Sparks Beef Research Center and allowed to rest approximately 12 hours after arrival before undergoing initial weighing, individual identification, and sample collection, including collection of nasal swabs. Cattle were processed approximately 36 (loads 1–3) or 72 (load 4) hours after arrival. Processing included a viral vaccine (Bovishield Gold® 5, Zoetis, Florham Park, NJ), clostridial bacterin/ toxoid (Ultrachoice® 7, Zoetis), and an anthelmentic (Ivomec® Plus, Merial, Duluth, GA). No vaccines targeting bacterial BRD agents were administered. Castration and dehorning were performed at this time, as necessary. Cattle were blocked by weight and assigned into 25 open-air, dirt pens. Calves were monitored by trained personnel throughout the feeding period and identified as potentially suffering from BRD based upon the DART (depression, appetite, respiratory system, temperature) clinical scoring technique (Table 1). Treatment was administered to all calves that received a DART score of three or four. A calf deemed to be mildly clinically ill (having a clinical score of one or two), was treated only if it had a rectal temperature greater than 40 °C. At time of treatment, at least one (and frequently two) clinically healthy cohort(s) (control(s)) was also taken to the treatment area for further evaluation. Calves used for control sampling were from the same arrival and pen as treated calves and had never been treated for BRD prior to use as a control. Rectal temperature was measured for both treated and control calves; control calves were enrolled only if rectal temperature was
