Among the Actinobacillus spp. only A. lignieresii represents a homogenous and well studied taxon.
However, haemolytic and non-haemolytic strains of A. equuli and A. suis are also isolated from a
wide range of diseases in a variety of hosts. These isolates often pose problems in definitive identification.
Consequently, several studies have been published, emphasizing the need for detailed
studies to reclassify various members of this genus and also to assess their disease significance.
We isolated 48 strains of Actinobacillus from clinical cases in horses, cattle, sheep, cat, pigs and
ostrich. In order to investigate the association of various taxa of Actinobacillus in different pathological
conditions in these hosts, the Zimbabwean isolates were characterized in detail and assigned
to the recently described taxa of Actinobacillus. Representative strains of different taxa were also
confirmed at the Department of Veterinary Microbiology, Frederiksburg C, Denmark. Of the 48 isolates,
22 were identified as A. lignieresii, 13 as A. equuli; 8 as A. suis, four as belonging to Taxon 11
and one as belonging to Taxon 9. These two taxa were recently described. Details of pathological
conditions in the respective hosts and the significance of isolation, are discussed. We have reported
for the first time isolation of A. lignieresii from a post-operative wound in a cat and there is also a first
report of isolation from an ostrich. We considered A. equuli to be the primary cause of equine abortion
and septicaemia, and Taxon 9 as causing "sleepy foal" disease. We did not encounter any case
of "wooden tongue", but isolated A. lignieresii from cases of superficial lymphadenitis in cattle and
This appears to be a first report of detailed descriptions of Zimbabwean strains of Actinobacillus spp.
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