PhD Thesis Demeter Zoltan

structural proteins: the C and V protein (Pardo, 2006). The N encapsulates the viral
RNA (Simon-Martìnez et al., 2007).
Fig. 2: Schematic representation of the ultrastructural morphology and genetic features
3.1.7 Genetic diversity
of CDV (based on Greene & Appel, 2006)
Nucleic and amino acid sequence analysis of CDV has shown that the H gene of CDV
is going through an antigenic drift depending on a geographic pattern (Martella et al.,
2007). Furthermore, in a study made on the P gene and in lesser extent of the H gene
showed that genetic differences of the isolates correlated with the geographic origin
(Bolt el al., 1997). The H gene possesses the highest degree of variation and the F and P
gene are genetically more stable (Bolt el al., 1997). This may be the consequence of the
role the H protein plays in the host’s immune reaction (Pardo et al., 2005). Considering
this fact, the H gene has been the most studied gene to determine phylogenic
relationships between different strains, although the F gene has also been used for this
purpose. Another fact that makes it more advantageous to use the H gene is the higher
number of complete H gene sequences than complete F gene sequences available in
public databases for phylogenic comparison (Pardo et al., 2005). In addition to the H, F
and P genes, studies have also been conducted on the N gene. In contrast to the H and
the F gene, that shows high genetic variation, the N gene is more conserved (Simon-
Martìnez et al., 2007). The mentioned study published results that showed 93-97 %
similarity between their isolates and the Onderstepoort strain used as a reference. For
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