Epidemiologic, pathogenic and molecular analysis of recent encephalomyocarditis outbreaks in Belgium

In 1991 EMCV was isolated for the first time in Belgium from the offspring of a sow with reproductive failure. From August 1995 until December 1996, E MCV was diagnosed in 154 Belgian pig holdings in association with myocardia l failure and sudden death in fatteners and suckling piglets or with reprod uctive failure in sows. To clarify some epidemiological aspects 3 EMCV isol ates characteristic for the different clinical pictures and outbreaks were studied. Field observations and animal experiments indicated that the patho genicity induced by each isolate is specific for one age category and that the spread of the virus is limited. The presented data also suggest that ro dents may play a role in the transmission of EMCV but that pig-to-pig trans mission is at least as important. Molecular analysis of two separate region s on the genomes of the respective EMCV isolates showed that the 1995-96 EM CV epizootic in Belgium was due to a new virus introduction. Furthermore, t he VP1 coding gene is proposed as a marker of virulence.