Amyloid Arthopathy in Chickens: a Metabolic Disease?

摘要

In some domestic and caged wild birds, especially waterfowl, reactive or AA amyloidosis is a well recognized pathological disorder and an important cause of death. Its regular occurrence in Galliformes has been recognized more recently, where amyloid deposits occur mainly in the joints in contrast to other species studied so far. In commercial brown layer chickens AA amyloid arthropathy was first described in 1994 as a clinical problem associated with growth depression and lameness. Analysis of field cases showed that the condition mainly affected brown layers, while it was seldomly found in their white counterparts. Enterococcus faecalis was the major pathogen isolated from amyloidotic joints positive on bacteriology in brown layers. It was shown that of a number of microbial agents (E. faecalis, Salmonella Enteritidis, Staphylococcus aureus, Escherichia coli, Mycoplasma synoviae, chicken anaemia virus, reovirus and Freund's adjuvans) tested, the ability to elicit extensive amyloid arthropathy in brown layer pullets is reserved primarily to E. faecalis and Freund's adjuvans, while marked differences between E. faecalis isolates were found. More recently, however, amyloid inducing M. synoviae isolates were detected in the Netherlands. The first articular amyloid deposits were observed 5 days after injection of high doses E. faecalis. In internal organs, deposits were encountered from day 13 onwards. On intra-articular injection, amyloidosis developed particularly in the target joint and in the internal organs. Indications for clonal spread of amyloidogenic and amyloid-associated E. faecalis isolates from several European countries were found after strain typing by restriction endonuclease fragment analysis of chromosomal DNA by pulsed-field gel electrophoresis (PFGE). In pathogenesis studies it was shown that amyloid arthropathy can be elicited in six-weeks-old pullets after intravenous, intra-articular and intraperitoneal inoculation of high doses (10~9 cfu), however not through intramuscular, oral and intratracheal inoculation. Similarly, oral inoculation of day-old chickens with high doses did not cause any pathology, but intramuscular inoculation with 10~6 cfu resulted in severe growth retardation and arthritis in half of the birds, and joint amyloidosis in approximately 40%. Transmission of arthropathic and amyloidogenic E. faecalis to day-old chicks might occur through intramuscular vaccination with Marek's disease vaccine as samples of hatchery air, Marek's disease vaccine suspensions and injection needles were found to be contaminated with varying and sometimes high levels of E. faecalis. If vaccine suspensions and injection needles were contaminated with arthropathic and amyloidogenic strains, then amyloid arthropathy could be induced at least in those birds injected with ≥ 10~6 cfu, although arthritis already developed in some birds injected with lower doses (165 cfu). In egg transmission studies egg albumen inoculation with low doses led to E. faecalis arthritis transmission to 1 out of 6 hatched chicks, indicating the possibility of transoviductal transmission, although transmission through eggshell contamination was also achieved. Indications for vertical transmission of arthropathic and amyloidogenic E. faecalis at a small scale were found after inoculating intravenously brown layer parent birds with high doses (10~9 cfu).