The importance of diagnostics for disease detection, surveillance, and monitoring in swine herds is widely appreciated, and has increased the quality of animal health over the years with a significant impact on animal welfare and production.
Every day, diagnostic laboratories process hundreds of samples that have been collected in the field to aid in the diagnostic process.
However, proper and specific sample collection may not always be easy to accomplish.
Mycoplasma hyopneumoniae is a swine respiratory pathogen that can affect animals at any age. The disease can be extremely difficult to diagnose at the early and late stages of infection.
M. hyopneumoniae multiplies at a very slow rate within the pig, taking a long time to generate clinical signs, which is characterized by a dry cough. It is localized on the lower sections of the respiratory tract (trachea, bronchia, bronchiole), where it can reside for an extremely long period of time (over 7 months).
While serum samples may be tested for antibodies to M. hyopneumoniae, detection in live pigs during the early stages of infection is challenging, and other type of samples are preferred. The best samples for detection of the pathogen are those collected from the lower respiratory tract, which may imply a somewhat invasive and not-so-simple sample collection process.
However, pig-friendly tools have been designed and developed over the last few years to target sampling for specific pathogens in order to minimize invasion and save time. For example, collection of oral fluids by using rope sampling in pig pens is a common practice with highly successful results when it comes to identifying certain pathogens circulating in swine herds. Unfortunately, sensitivity of the detection of M. hyopneumoniae during early stages of infection is limited when using this technique. Consequently, other types of sampling procedures are recommended to be employed for this purpose during the early infection stage.
Nasal swabs are widely used for detection of M. hyopneumoniae. These samples are fairly practical to collect in the field, and individual animals are sampled this way. However, nasal swabs are not very sensitive for detection of M. hyopneumoniae during the stages when pigs are not showing clinical signs (early or late infection), which means results may seem inconsistent at times.
At the Veterinary Diagnostic Laboratory of the University of Minnesota we have tested the use of laryngeal swabs and tracheobronchial lavages (in live pigs) for detection of M. hyopneumoniae, along with nasal swabs and oral fluids.
We have found that more infected pigs can be detected as positive for the bacterium when samples are collected via laryngeal swabs. Colleting laryngeal swabs in pigs may require more training for the personnel in order to make sure that the sample is collected in the right location and the pigs are properly handled.
Sample collection can be done extremely fast, actually taking a shorter time to be collected, compared with a blood sample. For laryngeal swabs to be collected, pigs may be restrained simply with a snare, whereas the use of a mouth gag and a laryngoscope (as seen in Figure 1) is recommended for personnel safety and to better visualize the area to be swabbed.
Tracheobronchial lavages, on the other hand, have shown a lower sensitivity compared to laryngeal swabs and require more training and a slightly longer time for collection.
Once collected, samples should be properly stored and transported to the diagnostic laboratory as soon as possible for processing.