Variations in the clinical course of EP.
and inconsistencies in the efficacy of vaccination have raised
suspicions that M. hyopneumoniae isolates vary in virulence.
Differences at the antigenic , chromosomal
, genomic
and proteomic levels have
been reported between M. hyopneumoniae isolates and,
finally Vicca et al. (2003) demonstrated differing virulence
characteristics between such isolates. Differences in adhesion
and transmission (Meyns
et al., 2004; Marois et al., 2007) of the organism have been
suggested but not clearly demonstrated.
From an epidemiological perspective, typing M. hyopneumoniae
isolates would facilitate the understanding of the
transmission of M. hyopneumoniae isolates within and
between herds. Recently described molecular typing techniques
(Table 3) suggest that one strain of M. hyopneumoniae
infects a given herd, whereas the strains involved in different
outbreaks vary.