• Bovine respiratory disease is a widespread and costly disease.
• Both morbidity and mortality are significant.
• Animals are particularly at risk during periods of stress such as transport, weaning etc, overcrowding, poor ventilation and when new animals are bought in.
• Nasopharyngeal swabs can be utilized when a sample is required for:
  • Bacterial culture.
  • Virus isolation.
  • Fluorescent antibody testing.
• The most common viral respiratory pathogens are:
  • Bovine Respiratory Syncytial Virus (BRSV).
  • ParaInfluenza 3 Virus (PI3).
  • Infectious Bovine Rhinotracheitis (IBR)/ Bovine Herpes Virus 1 (BHV-1).
  • Bovine Respiratory Corona Virus (BRCoV) .
  • Bovine Viral Diarrhea virus (BVDV).
• The most common bacterial respiratory pathogens are:
  • Mannheimia haemolytica – may be a commensal.
  • Haemophilus somnus.
  • Pasteurella multocida – may be a commensal.
  • Mycoplasma bovis.
  • Mycoplasma disbar.
• It may be worth swabbing in contact clinically well animals, as subclinical infections can lead to further economic losses from reduced growth rates/ failure to thrive etc.

Uses

• Nasopharyngeal swabs are usually not utilized as the first course of action. They are more likely to be carried out as a result of treatment failure, to allow more specific directed treatment.
• They may be used to determine the pathogen when no losses have occurred and post mortem examination isn’t an option.
• They may be used to monitor the response to treatment.

Advantages

• Simple technique.
• Performed on standing animal.
• Relatively inexpensive.
• Quick procedure.
• More likely to isolate a respiratory pathogen than if just a nasal swab were performed.

Disadvantages

• Isolates may not indicate disease- results must be interpreted with care.
• Potential pathogens may be present in healthy animals, and be causing no problems, as part of the normal bacterial flora.
• Potential pathogens harvested from the nasopharynx may not reflect the pathogens causing disease lower down the respiratory tract.
• Nasopharyngeal swabs may be less reliable at isolating pathogens causing disease in lower respiratory tract than other techniques such as Bronchoalveolar lavage Bronchoalveolar lavage (BAL) and transtracheal wash.

Alternative techniques

• BAL.
• Transtracheal wash.
• Paired serum sampling.

Time required

Procedure

• Passage of swab: 5 minutes.

Decision taking

• Test in the acute phase of an outbreak.
• Test a reasonable number of animals:
  • Number to test will vary from farm to farm and will be affected by factors such as the affected population size and the farmer’s budget.
  • Speak to your local laboratory before you take the samples and be guided by them.
• Test unaffected animals as well as those showing signs of disease.
• Where possible, samples should be taken prior to starting antimicrobial treatment.