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Epidemiology and pathogenesis of tenosynovitis in chickens

Kibenge, Frederick Stephen Bethuel (1982) Epidemiology and pathogenesis of tenosynovitis in chickens. PhD thesis, Murdoch University.

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Tenosynovitis/viral arthritis is a significant cause of lameness (leg weakness) in broiler-breeder chickens in Australia. This thesis reports an investigation of clinical tenosynovitis with emphasis on the epidemiology and pathogenesis of the disease.

The current situation with regard to the role of avian reoviruses and Staphylococcus aureus in "leg weakness" in chickens is reviewed with special consideration to the epidemiology and pathogenesis of the two organisms as a potential cause of tenosynovitis.

Field studies were conducted on six commercial poultry farms on which outbreaks of tenosynovitis occurred. A detailed clinico-pathological description and aetiological investigation is reported. The lesions observed in clinically affected chickens were suggestive of a bacterial infection. The results of microbiological investigations indicated that in Western Australia S. aureus was a common isolate from clinical cases of tenosynovitis. The isolation rate of S. aureus from tendon tissue of affected chickens varied considerably in different outbreaks, from 51.9% to 97.8%, and bacteria other than S. aureus were recovered from a lower proportion of chickens. Adenoviruses and reoviruses, other potential aetiological agents, were also recovered from tendon tissue of chickens, some from chickens with a concurrent bacterial infection. There was serological evidence of avian reovirus, adenovirus and infectious bursal disease virus infections in all outbreaks where this was examined. There was no evidence of a concurrent Mycoplasma synoviae or M. gallisepticum infection.

A system of classification was developed for the differentiation of strains of S. aureus isolated from poultry in Australia using phage typing and cultural examination. It was evident that sufficient differentiation of strains of S. aureus of poultry origin would require a combination of phage typing and cultural examination until such a time as a complete international set of avian phages were available. Based upon the susceptibility to bacteriophages and cultural characteristics the Australian strains of S. aureus were classified into 3 major groups and 9 subgroups. From this classification it was possible to examine the relationship of S. aureus strains involved in different outbreaks of tenosynovitis on commercial poultry farms in Western Australia. It was shown that similar phage types of S. aureus could be isolated from lesions of affected chickens and from chickens without lesions. It was demonstrated that a predominant phage type existed in the lesions of affected chickens on each farm but that several principal phage types were present in the different outbreaks. The results indicated that the occurrence of the disease in Western Australia was not associated with a particular type of S. aureus and that the occurrence of tenosynovitis was not due to the transmission of particular strains from farm to farm.

Staphylococcus hyicus was shown to be among the minor phage types associated with clinical tenosynovitis. Some characteristics of these strains are described. The possible association of lysogeny with variation in properties of S. hyicus is commented upon.

Attempts were made to reproduce the clinical disease using reovirus. adenovirus and bacteria. The reovirus and adenovirus strains used produced only localized lesions when inoculated into the foot pad. Lesions induced by the reovirus were of greater severity than those induced by the adenoviruses. Experiments were conducted to compare the virulence and tropism for tendon tissue of the principal and minor phage types of S. aureus associated with naturally occurring tenosynovitis. The results demonstrated significant differences in virulence between the principal and minor phage types of S. aureus which were isolated from tenosynovitis-affected chickens. Infection with the principal phage types produced gross and histopathological changes in tendons and tendon sheaths indistinguishable from naturally occurring tenosynovitis. However, the clinical course of the experimental disease following infection with S. aureus differed to that observed in natural tenosynovitis. In chickens experimentally infected with varying doses of S. aureus the clinical signs were indicative of an initial septicaemia with secondary tenosynovitis; in natural cases the initial signs were characterized by tenosynovitis with a secondary septicaemia. There was no specific tropism of S. aureus for tendon tissue in experimentally infected chickens. Experiments with S. hyicus, as a minor phage type, confirmed that these bacteria were of low virulence but pathogenic for chickens.

Attempts were made to create "moderate" conditions under which minimal S. aureus infection might localize in tendons. These conditions were attempted by pre-inoculating chickens with avian reovirus. Under the conditions used, pre-infection of the foot pads of chickens with reovirus did not enhance the subsequent S. aureus infection and it was not possible to experimentally reproduce the same lesions as observed in naturally occurring tenosynovitis. Possible explanations for this are discussed.

The considerable heterogeneity in the type of bacteria associated with tenosynovitis, and the differences in the nature of the disease following S. aureus infection compared with that observed in naturally occurring cases of tenosynovitis, indicated that bacteria were not primary pathogens in tenosynovitis in Western Australia. It was concluded that the natural disease was most probably the result of an initial subclinical virus infection, most probably avian reovirus. of susceptible chickens, followed by secondary infection with bacteria. principally S. aureus, leading to the development of clinical tenosynovitis.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Wilcox, Graham and Pass, David
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