In cattle, especially young ones, infectious bronchopneumonia is a major problem. While herd management and raising conditions are important risk factors, infectious agents ultimately are responsible for these pathologies.
Thus, several viruses such as BRSV, BVDV, BoHV1, BCoV, BPIV-3 and IVD, as well as mycoplasmas (especially Mycoplasma bovis), have the ability to damage the respiratory tract more or less severely and affect its natural defenses.
In addition, the lesions caused to the respiratory tract are likely to be superinfected by opportunistic pathogenic bacteria such as Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Bibersteinia trehalosi or Trueperella pyogenes.
Facing bronchopneumonia problems, the identification of the infectious agents involved (viruses and / or bacteria) allows better understanding of their dynamics within farms and guide the choice of specific preventive and curative measures (vaccinations or treatments).
In recent years, diagnostic methods have undergone remarkable developments. Thus, we now have real-time PCR tests that make it possible to detect most of the important infectious agents sensitively, specifically and quantitatively.
In addition, unlike traditional methods (viral isolation, bacterial culture), these PCRs are able to detect organisms that have not survived during transport to the laboratory and the results are available in a few hours instead of several days.
However, if the antimicrobial susceptibility of certain bacteria is to be assessed, bacterial culture is still required. As the samples are often polymicrobial, the laboratory will ideally use several culture media to maximize the chances of isolation (a “bacterial respiratory profile”).
The most representative samples of bronchopulmonary microbism, tracheal and bronchoalveolar aspirations, are difficult to obtain under regular cattle raising conditions. However, deep nasopharyngeal swabs are an excellent alternative both due to their easy execution and their representativeness of this microbism.
To take these samples, it is important to use long 30-inch double-guarded swabs (usually used for uterine swabs in mares) that allow the deep nasopharynx to be sampled while avoiding contamination of the samples by nasal flora.
If the samples are intended only for PCR examinations, it is unnecessary to place them in a specific transport medium: a saline solution (0.9% NaCl) is perfectly suitable. On the other hand, agar gel transport media that interfere with the extraction of nucleic acids must be prohibited.
Conversely, samples for bacteriological examinations require more precautions. Indeed, most respiratory bacteria die fairly quickly if they are not placed in suitable conditions. It is recommended to use an Amies liquid or agar gel medium, kept refrigerated (but not frozen!) and delivered quickly to the laboratory (<48 hours).
Regarding viruses and mycoplasmas, it is not useful to carry out individual examinations. On the contrary, it is even recommended to examine composite samples (pools of 3 to 5 samples). This reduces costs without significantly affecting analytical sensitivity while increasing diagnostic sensitivity.
The choice of animals to sample is obviously important. They must be at the beginning of clinical signs. Indeed, some viruses (especially BRSV) disappear quickly from the respiratory tract. In addition, animals that have recently been vaccinated with attenuated viruses must be avoided, as some of these viruses can persist for several days in the respiratory tract.
Unlike viruses, bacteriological examinations must be individual because the bacterial flora can vary considerably from one animal to another. If you want to obtain antibiograms, you must first use these examinations. Of course, samples must be taken from animals who have not previously received antimicrobials.
|Biovet provides you with tubes containing Amies liquid transport medium that is suitable for both viruses and bacteria. The same sample (swab) can then be used for both PCR and bacteriology. For the samples to be examined in pool, we recommend submitting the samples individually, the laboratory will take care of constituting the pools.|
In conclusion, when faced with bronchopneumonia problems, laboratory examinations, PCR and/or bacterial cultures, applied to carefully produced and preserved samples, can provide interesting help in determining the infectious agents involved and deploying appropriate preventive or curative measures.
|PCR testing||Bacteriological examinations|
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André Broes, D.V.M., Ph.D., Technical services Manager
- Allen JW, Viel L, Bateman KG, et al. The microbial flora of the respiratory tract in feedlot calves: associations between nasopharyngeal and bronchoalveolar lavage cultures. Can J Vet Res. 1991;55(4):341-6.
- Allerton F. Antimicrobial use: importance of bacterial culture and susceptibility testing. In Practice. November 2021, 500-510
- Capik SF, White BJ, Lubbers BV, et al. Comparison of the diagnostic performance of bacterial culture of nasopharyngeal swab and bronchoalveolar lavage fluid samples obtained from calves with bovine respiratory disease. Am J Vet Res. 2017;78(3):350-358.
- Cooper VL, Brodersen BW. Respiratory disease diagnostics of cattle. Vet Clin North Am Food Anim Pract. 2010;26(2):409-16.
- Cummings DB, Meyer NF, Step DL. Bovine Respiratory Disease Considerations in Young Dairy Calves. Vet Clin North Am Food Anim Pract. 2022;38(1):93-105.
- Doyle D, Credille B, Lehenbauer TW, et al. Agreement Among 4 Sampling Methods to Identify Respiratory Pathogens in Dairy Calves with Acute Bovine Respiratory Disease. J Vet Intern Med. 2017;31(3):954-959.
- Fulton RW, Confer AW. Laboratory test descriptions for bovine respiratory disease diagnosis and their strengths and weaknesses: gold standards for diagnosis, do they exist? Can Vet J. 2012;53(7):754-61.
- Godinho KS, Sarasola P, Renoult E, et al. Use of deep nasopharyngeal swabs as a predictive diagnostic method for natural respiratory infections in calves. Vet Rec. 2007;160(1):22-5.
- Loy JD, Leger L, Workman AM, et al. Development of a multiplex real-time PCR assay using two thermocycling platforms for detection of major bacterial pathogens associated with bovine respiratory disease complex from clinical samples. J Vet Diagn Invest. 2018;30(6):837-847.
- Pardon B, Buczinski S. Bovine Respiratory Disease Diagnosis: What Progress Has Been Made in Infectious Diagnosis? Vet Clin North Am Food Anim Pract. 2020;36(2):425-444.
- Van Driessche L, De Neve CH, Haesebrouck F, et al. Storage time and temperature affect the isolation rate of Mannheimia haemolytica and Pasteurella multocida from bovine bronchoalveolar lavage samples. BMC Vet Res. 2020;16(1):238.
- Van Driessche L, Valgaeren BR, Gille L, et al. A Deep Nasopharyngeal Swab Versus Nonendoscopic Bronchoalveolar Lavage for Isolation of Bacterial Pathogens from Preweaned Calves With Respiratory Disease. J Vet Intern Med. 2017;31(3):946-953.
- Zhang J, Wang W, Yang M, et al. Development of a One-Step Multiplex Real-Time PCR Assay for the Detection of Viral Pathogens Associated With the Bovine Respiratory Disease Complex. Vet. Sci., 2022; 9:1-10.