Successful eradication of Mycoplasma hyopneumoniae from the Norwegian pig population - 10 years later.

Background: Mycoplasma hyopneumoniae (Mhyo) is the causative agent of enzootic pneumonia in pigs which adversely affects animal health and welfare, in addition to causing considerable economical losses. This paper presents the implementation of the national Mhyo eradication program in Norway, the subsequent population wide surveillance and documentation on the current freedom from Mhyo in the Norwegian pig population. In 1994, the Board of The Norwegian Pig Health Service decided on conducting a national surveillance and eradication program for Mhyo. The program aimed for population wide freedom from Mhyo, based on serological surveillance. A partial depopulation program was initiated in all Mhyo positive farrow-to-feed and farrow-to-finish herds. Total depopulation was performed in all positive finisher herds.

Results: From 1994 to 2009, a total of 138,635 pigs in 3211 herds were serologically tested for the presence of antibodies against Mhyo. Of these, 5538 (4%) individual samples and 398 (12.4%) of the herds were defined as positive. In 2009, the Norwegian pig population was declared free from Mhyo, and has been so since then. From 2009 through 2019, a total of 44,228 individual serum samples have been analyzed for the presence of antibodies against Mhyo and found negative in the National surveillance program.

Conclusion: Eradication of Mhyo infections has resulted in improved health and welfare of the Norwegian pig population. The success of the strategy is based on numerous factors, such as moderate to low prevalence of the agent, well documented and effective eradication protocols, accurate diagnostic tests, relatively small herds, low herd density in most parts of the country and negligible import of live pigs. In addition, economic benefit due to a premium on pigs marketed from herds free from Mhyo, a well-structured commercial pig population, and finally, the loyalty and significant effort of farmers, abattoir employees and veterinarians were crucial factors. To maintain the infection-free status at national level, a continuous alertness is required in the future to discover possible Mhyo infections and ensure rapid sampling and diagnostics. Any findings of Mhyo positive pig herds in Norway will result in immediate eradication.