Enzootic pneumonia is one of the most prevalent and economically significant infections in the swine industry. A farm-specific Mycoplasma hyopneumoniae eradication program without a stop in farrowing was implemented in a birth to weaning herd of 700 sows. The weaners (27 days old) were moved weekly to a compartmentalized nursery site and finally, at 11 weeks of age, transfered to all-in-all-out finishing barns.
The nursery and the different fattening units were located at different sites. The diagnosis of enzootic pneumonia was based on clinical symptoms, several laboratory tests (ELISA serology, Polymerase Chain Reaction tests) and slaughterhouse findings. Treatment and control measures over longer time periods were not successful in managing the infection. Despite Mycoplasma hyopneumoniae vaccination of the piglets and frequent use of antibiotics, pigs originating from this breeding herd were still suffering from chronic coughing. Typically, vaccination did not stop mycoplasma colonisation and horizontal spreading among pigs.
Furthermore, Mycoplasma hyopneumoniae was the trigger of the respiratory disease complicated by many other respiratory pathogens like Actinobacillus pleuropneumoniae. Both acute and chronic respiratory symptoms were responsible for major economic losses in the nurseries and fattening units.
The productivity was significantly decreased by impaired daily weight gain and feed conversion rate. A clear increase of the number of days to reach market weight and poor performing pigs was noted along with a higher mortality rate.
The farm management set the short term targe to improve the general health status and technical performance by implementing a feasible eradication program. Total depopulation of the breeding herd and repopulation with specific pathogen-free pigs after thorough cleaning and disinfection of the whole farm would have created an enormous financial outlay and was not considered as a realistic option.
Partial depopulation and strategic medication
An eradication program based on partial depopulation and strategic medication was initiated. This protocaol requires only temporary changes in the pig flow. The cash flow disruption is less significant due to reduced production losses and the maintenance of the genetic potential and parity profile of the sows.
The distance to neighbouring herds was more than 3 km, greatly reducing the risk of airbourne re-infection. The program was initiated in the summertime, which is the ideal season for eradication. Higher temperatures reduce the survival time of the pathogen in the environment and increase the ventilation rates in the pens, both lowering the infection pressure.
The farm specific protocol required full commitment from the staff. Several actions were taken to improve internal and external biosecurity in order to avoid propagation of the infection inside the farm and re-introduction of the disease from outside. Stringent cleaning and disinfection protocols were established. The protocol was based on the combination of strict biosecurity measures and a medication program, both going hand in hand.
Stabilisation of the breeding herd
Pigs in excess of 10 months of age have normally built up high levels of immunity to mycoplasma, lung lesions have healed and shedding of the pathogen is low. On the other hand, pigs younger than 10 months of age are often found to be highly infectious and shed Mycoplasma hyopneumoniae profusely.
All the pigs younger than 10 months of age were removed from the sow herd in order to reduce active shedding and transmission of Mycoplasma hyopneumoniae. Only animals older than 10 months and suckling piglets remained on site. Sick animals showing a lack of appetite were removed from the farm or euthanised before the start of the program. In this multi-site production system, pigs were always removed from the breeding herd at weaning. Hence, in this specific field case a stable sow herd was achieved by the temporary cessation of the purchase of gilts younger than 10 months.
The breeding herd was closed to the introduction of gilts and boars five weeks before the start of teh medication period. All young animals (from weaning to 10 months of age) should be temporarily removed from the breeding herd for eradication in a one- or two-site herd.
Treatment of sows and piglets
After stabilisation, the remaining sows and gilts were treated via feed with tiamulin 100 g/kg microgranulated premix (Vetmulin®) at a daily dose of 8 - 10 mg tiamulin hydrogen fumarate/kg bodyweight for two consecutive weeks. Successful eradication programs have been conducted with tiamulin worldwide. Tiamulin belongs to the antimicrobial class of the pleuromutilins. The minimal inhibitory concentration of tiamulin to inhibit growth of 90% (MIC90) of the Mycoplasma hyopneumoniae strains tested is not more than 0.06 μg/ml. This clearly indicates the highest susceptibility of Mycoplasma hyopneumoniae to tiamulin. Tiamulin does not only show excellent absorption after oral administration but also high tissue concentrations in the lung and bronchoalveolar fluid.
The exposure to tiamulin is 18 times higher in lung tissue compared to plasma. As the survival time of mycoplasma outside the pig's body is reported to be short, a treatment duration of 14 consecutive days was advised. Special attention was paid to correct dosing, mainly for the sows in the lactation units. Sick sows refusing to eat during the treatment period were removed from the herd or injected with tiamulin.
The gilts introduced after the eradication program were certified mycoplasma-free and were housed in a properly cleaned and disinfected quarantine area upon arrival. From one week before until the end of the treatment period of the sows, the suckling piglets received a dose of tulathromycin (2.5 mg/kg bodyweight, intramuscularly) every five days to avoid transmission in the farrowing units. Sick piglets were euthanised. Only pigs originating from sows that were treated for the full 14 days prior to giving birth were considered to be Mycoplasma hyopneumoniae-free and were no longer vaccinated against Mycoplasma hyopneumoniae. These mycoplasma-free pigs were transferred to completely depopulated facilities for weaners and fatteners, that were thoroughly cleaned and disinfected at least one week before transfer.
Monitoring
Mycoplasma monitoring was carried out after the strategic medication to evaluate the eradication program success. All serology tests (ELISA, n = 155) and antigen tests on oral fluids and nasal swabs (PCR, n = 30) were negative for Mycoplasma hyopneumoniae over a time period of 30 weeks (Table 1). Lungs at slaughter check did not show typical mycoplasma lesions (Figure 1).
Impact on technical performance
Clinical signs of enzootic pneumonia were not observed afterwards. A clear improvement of the general health status and technical performance of suckling piglets, weaners and finishers born after the eradication was noted. In addition, the Vetmulin® administration also supported the control of concurrent infections like ileitis, mycoplasma arthritis and pneumonia caused by other bacteria. An enormous performance boost was noted immediately after the eradication program (Tables 2, 3 and 4).
Conclusion
Eradication of enzootic pneumonia is by far the most effective and cost-efficient way to improve herd health status, technical performance and animal welfare long term. In this multi-site production system, Mycoplasma hyopneumoniae was successfully eradicated by a strategic medication program with Vetmulin® in combination with extensive biosecurity and hygiene measures.
This program does not require a total depopulation of the sows or a stop in farrowing and results in a high and quick return on investment. Furthermore, the repeated use of antimicrobials and preventative vaccination against Mycoplasma hyopneumoniae was stopped. Huvepharma is your reliable partner for tailor-made eradication programs suitable for different pig production systems.
