Chlamydial infections in animals

Chlamydophila psittaci


C. psittaci strains isolated from different avian species consist of many different serovars which may be differentiated by experimental host range and their ability to cause disease (Schachter & Caldwell, 1980). Currently, there are eight established serovars from a variety of avian hosts which can be differentiated by serovar-specific monoclonal antibodies (Andersen, 1997; Vanrompay et al., 1993). These serovars are as follows:

Serovar Comment / Distribution
A psittacine birds; endemic; often systemic but can be inapparent; sporadic zoonotic disease in humans
B pigeons; endemic; also from turkeys; also caused abortion in dairy cattle
C duck, turkey, partridge; specific avian host not identified; zoonotic risk to poultry workers and people in contact
D turkeys, seagull, budgerigar, humans; zoonotic risk to poultry workers and people in contact
E ducks, pigeons, ostriches and rheas; specific avian reservoir not identified; first isolated from cases of pneumonitis in humans
F parakeets; single isolate in this serovar
G isolated from a disease outbreak in muskrats and hares
H isolated from enteritis in cattle

Some C. psittaci strains carry an extrachromosomal plasmid [see: chlamydial plasmids], and several strains are infected with bacteriophages (Storey et al., 1992; see: Genes.ChlamydialPhages). Monoclonal antibodies against the chlamydial lipopolysaccharide (LPS) and major outer membrane protein (MOMP) antigens have been used to distinguish between avian C. psittaci and mammalian chlamydial strains (Fukushi et al., 1997). C. psittaci isolates from birds have also been differentiated in restriction mapping of gene encoding chlamydial MOMP (Sayada et al., 1995). In an analysis of 65 avian isolates, seven groups were found which did not correspond to host or geographic specificity. Again, these groups were all distinguishable from mammalian chlamydial strains.

Phylogenetic analyses have also been carried out on avian chlamydial strains based on 16S rRNA gene sequences (Takahashi et al., 1997). This study identified four genetic groups among a range of avian and mammalian isolates within the previous C. psittaci taxon. These authors concluded that the 16S-23S intergenic spacer regions, which are more variable than 16S rDNA, could be used for more precise identification / differentiation. In a further development, which led to the proposed reclassification of the order Chlamydiales, Everett et al., 1999 reported phyllogenetic analyses of 16S and 23S rRNA chlamydial genes [see Classification.EverettAndersenClassification]. All avian chlamydial strains were placed in the Chlamydophila psittaci taxon, for which the type strain is 6BC (ATCC VR125).

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Topic revision: r5 - 2011-04-02 - MeWard
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