The role of various agents in chicken amyloid arthropathy

Resistance to chicken amyloid arthropathy is associated with a dysfunctional mutation in serum amyloid A

Chicken amyloid arthropathy is a debilitating disease with a major impact on animal welfare. Since the disease is triggered by bacterial infection, preventative treatment also contributes to the widespread overuse of antibiotics. Bacterial infection initiates an acute phase response including increased serum amyloid A (SAA) production by the liver. SAA accumulates at sites of infection and in particular in large joints of affected birds. Interestingly, white egg-laying chickens (WL) are resistant to the disease whilst brown egg-laying chickens (BL) are most affected. Disease susceptibility has an immunological basis but the possible contribution of underlying genetic risk factors is not understood. Using a whole genome sequencing approach, we discovered a novel variant in the SAA gene in WL, which is predicted to result in an arginine to serine substitution at position 90 (SAA.R90S). Surprisingly, when overexpressed in chicken hepatocellular carcinoma cells, SAA.R90S was expressed at a higher rate and secreted to a greater degree than the wild-type SAA protein. Moreover, RNASeq analysis showed that the R90S mutant exerted a differential effect on the expression of core transcription factors linked to cell fate determination and cell differentiation. Comparative analysis of gene expression in murine CD4 T-cells stimulated with IL-6/SAA, suggests that SAA.R90S might block an induced cell fate change toward pro-inflammatory T helper 17 cells, which are required for immunological protection against pathogenic bacteria during an acute phase response. Our results provide first mechanistic insights into the genetic resistance of WL to amyloid arthropathy and could be applied to commercial layer breeding programs to improve animal welfare and reduce the negative effects of the overuse of antibiotics.

Review on skeletal disorders caused by Staphylococcus spp. in poultry

Lameness or leg weakness is the main cause of poor poultry welfare and serious economic losses in meat-type poultry production worldwide. Disorders related to the legs are often associated with multifactorial aetiology which makes diagnosis and proper treatment difficult. Among the infectious agents, bacteria of genus Staphylococcus are one of the most common causes of bone infections in poultry and are some of the oldest bacterial infections described in poultry. Staphylococci readily infect bones and joints and are associated with bacterial chondronecrosis with osteomyelitis (BCO), spondylitis, arthritis, tendinitis, tenosynovitis, osteomyelitis, turkey osteomyelitis complex (TOC), bumblefoot, dyschondroplasia with osteomyelitis and amyloid arthropathy. Overall, 61 staphylococcal species have been described so far, and 56% of them (34/61) have been isolated from clinical cases in poultry. Although Staphylococcus aureus is the principal cause of poultry staphylococcosis, other Staphylococcus species, such as S. agnetis, S. cohnii, S. epidermidis, S. hyicus, S. simulans, have also been isolated from skeletal lesions. Antimicrobial treatment of staphylococcosis is usually ineffective due to the location and type of lesion, as well as the possible occurrence of multidrug-resistant strains. Increasing demand for antibiotic-free farming has contributed to the use of alternatives to antibiotics. Other prevention methods, such as better management strategies, early feed restriction or use of slow growing broilers should be implemented to avoid rapid growth rate, which is associated with locomotor problems. This review aims to summarise and address current knowledge on skeletal disorders associated with Staphylococcus spp. infection in poultry.

Chicken embryo lethality assay for determining the lethal dose and virulence of Enterococcus faecalis

Enterococcus faecalis is the major pathogen found in field cases of amyloid arthropathy in chickens. Given the need for a better understanding of the virulence mechanisms of the causative strains, the embryo lethality assay (ELA) is proposed in the present study as a model to evaluate the virulence of E. faecalis strains, specifically the pathogenic avian strain K923/96, which was previously related with amyloid arthropathy. Hence, 0.2 ml of five doses of the cited strain (from 2.5 to 2500 colony-forming units (CFU) per ml) were inoculated into the allantoic cavity of 10-day-old embryos. The embryo mortality rate (EMR) was determined by daily candling of the eggs over a period of seven days and based on this information the median lethal dose (LD₅₀) was calculated. The ELA was repeated four times on a sample of 3443 eggs. The infectious dose showed a significant effect on the EMR. The EMR with the doses of 2.5, 5, 25, 250 and 2500 CFU/ml was 43%, 45%, 63%, 90% and 93%, respectively. The estimated dose at LD₅₀ was 6.6 CFU/ml. As expected, the higher the infectious dose, the greater the EMR and the lower the embryo survival time. The highest EMR was recorded after three and four days post-inoculation in all doses. In conclusion, these results can be used as a basis for further researches on the E. faecalis virulence. In order to corroborate its model capacity to predict the virulence of this bacterium, more ELAs with different E. faecalis strains are required.

Systemic Clinical and Metabolic Diseases

Like other animals pet and companion birds are also prone to systemic illness. This is presented in the form of certain clinical signs and symptoms which is known as “ sick-bird syndrome.”

Validation of a previously developed quantitative polymerase chain reaction for the detection and quantification of Mycoplasma synoviae in chicken joint specimens

A quantitative polymerase chain reaction (qPCR) was validated for the detection of Mycoplasma synoviae (PCR equivalents of colony-forming units [CFU eq.]) in chicken joint specimens with time and compared with direct mycoplasma culture. Joint specimens were obtained from 70 layer pullets inoculated intravenously with M. synoviae at 6 weeks of age. Ten control birds were injected intra-articularly with Freund's complete adjuvant. Macroscopic joint lesions were observed in 54 infected birds, of which 11 showed positive M. synoviae culture. The specificity of direct mycoplasma culture was high (100%, 95% confidence interval [CI] = 74 to 100), but its sensitivity low (16%, 95% CI = 8 to 26). Most positive results were obtained during the first 2 weeks after onset of joint swelling using synovial fluid. The qPCR was positive in 26 of 28 synovial fluid samples and in 51 of 70 joint swabs. The sterile joint samples obtained from Freund's complete adjuvant-injected birds were negative in the mycoplasma culture. The specificity and sensitivity of the qPCR for synovial fluid samples were 100% (95% CI = 65 to 100) and 93% (95% CI = 77 to 99); for joint swabs they were 100% (95% CI = 74 to 100) and 73% (95% CI = 61 to 83), respectively. Positive qPCR results (10(0.3) (to) (4.6) CFU eq./ml) were found until the end of the experiment (12 weeks post inoculation). At the end of the study, eight out of 16 joint swabs from birds without macroscopic joints lesions were positive in the qPCR (10(2.0) (to) (2.8) CFU eq./ml). Under the conditions of this study, the sensitivity of the qPCR was higher than that of direct mycoplasma culture (P< 0.0001) during the acute, subacute and chronic stages of arthritis.

Chicken amyloid arthropathy: serum amyloid A, interleukin-1beta, interleukin-6, tumour necrosis factor-alpha and nitric oxide profile in acute phase (12th hour)

Acute phase response (APR) is part of the early defense system, which is triggered by different stimuli including, infection, trauma, stres, inflammation and neoplasia. The APR complex is a reaction which induces homeostasis and recovery. In this research, serum amyloid A (SAA), interlaukin (IL)-1beta, IL-6, tumour necrosis factor alpha (TNF-alpha) and nitric oxide (NO) levels were measured 12 hours following injection. For this purpose, Thirty-two 5 weeks old laying chicken were allocated into four groups and intra-articular injections of Freund's adjuvant were used to induce amylod arthropathy in Groups II, III and IV. Vitamin A in group II, and methylprednisolone in group IV were added to enhance and to reduce the severity of amyloidosis, respectively. At the end of the research, it was observed that TNF-alpha and NO increased significantly (P < 0.05) in vitamin A and methylprednisolone groups whereas SAA decreased significantly (P < 0.05) in all groups. It was also observed that IL-6 increased (P < 0.05) in vitamin A group and decreased in all other gorups however, IL-1beta decreased in vitamin A and methylprednisolone groups, while it was increased in the control group. The results of this study suggest that there is a positive correlation between serum TNF-alpha levels in acute and chronic phase in chickens with amyloid arthropathy.

Investigation of serum amino acid and serum amyloid A concentrations in chickens with amyloid arthropathy

BACKGROUND

Increased proteolytic cleavage of serum amyloid A (SAA) may potentially contribute to the development of AA amyloid deposition.

OBJECTIVE

To study the possible relationship between amyloid artropathy and expression of SAA and some serum amino acids.

ANIMALS AND METHODS

Values of 15 serum amino acids and SAA were investigated in chickens with experimentally induced amyloid arthropathy. Thirty-four, 5-week-old chicks were allocated into two groups: one group was injected intra-articularly with 0.25 mL complete Freund's adjuvant at the left tibio-metatarsal joint to induce amyloid arthropathy, whereas the other group served as control. All pullets were necropsied 13 weeks after injection. Collected tissue samples were examined histopathologically. Blood samples were collected and SAA concentrations were measured with enzyme-linked immunosorbent assay. High-performance liquid chromatography was used to assess the amino acid concentrations in serum.

RESULTS

Amyloid accumulation in joints occurred only in the experimental group (89%). SAA concentrations of 166 ± 17 and 423 ± 39 (SD) ng/mL were found in the control and experimental groups, respectively (p < 0.001). In the experimental group, an increase was observed in all examined amino acid concentrations except for citrulline. The most significant (p < 0.001) increases were noticed in serine (from 159 ± 15 to 360 ± 29 µmol/L), glycine (from 151 ± 20 to 279 ± 16 µmol/L), isoleucine (from 48 ± 2 to 80 ± 6 µmol/L), and phenylalanine (from 49 ± 2 to 90 ± 3 µmol/L).

CONCLUSION

The results of this study suggest that there is a positive correlation between some serum amino acid values, especially serine, glycine, isoleucine, and phenylalanine, and the high concentrations of SAA in chickens with amyloid arthropathy.

A concise review of amyloidosis in animals

Amyloidosis refers to a group of protein misfolding diseases characterized by deposition of a particular amyloid protein in various organs and tissues of animals and humans. Various types and clinical forms of amyloidosis, in which the pathology and pathogenesis is diverse depending upon the underlying causes and species affected, are reported in domestic and wild animals. The clinical findings are also quite variable consequent to the variation of the tissues and organs involved and the extent of functional disruption of the affected organs in various animal species. The affected organs may be enlarged and exhibit variable pallor grossly, or the amyloid deposit may be discernible only after microscopic examination of the affected tissues. Amyloid appears as a pale eosinophilic homogenous extracellular deposit in tissues. However, microscopic examination and Congo red staining with green birefringence under polarized light are needed to confirm amyloid and differentiate it from other apparently similar extracellular deposits such as collagen and fibrin. Identifying the type of amyloid deposit needs immunohistochemical staining, ultrastructural characterization of the amyloid fibril, and if feasible also genetic studies of the involved species for clinical and prognostic purposes. This paper provides a concise review of the occurrence of amyloidosis in domestic and wild animals.

Transmission and genetic diversity of Enterococcus faecalis among layer chickens during hatch

BACKGROUND

Studies on transmission of Enterococcus faecalis among chickens during hatch have not been carried out so far. Information about vertical transmission and subsequent spreading and colonization of the cloacal mucosa through cloacal 'drinking' during hatch are important to understand the epidemiology of E. faecalis infections. In the present investigation vertical transmission and subsequent spreading and colonization of the cloacal mucosa of chickens by E. faecalis through cloacal 'drinking' were examined.

METHODS

Two different batches of layer chickens originating from 45 weeks old Brown and White Lohmann parents, respectively from the same farm were sampled in the hatcher. Isolates were confirmed to be E. faecalis by polymerase chain reaction (PCR) and further by multilocus sequence typing (MLST) to state their population structure and comparison made to sequence types previously obtained from chicken.

RESULTS

A total of 480 chickens were swabbed from the cloacae just after hatch and after 24 hours. A total of 101 isolates were confirmed as E. faecalis by a species specific PCR. The prevalence of E. faecalis increased from 14% at 0 h to 97% after 24 h for the Brown Lohmann chickens and from 0.5% to 23% for the White Lohmann flock. The 84 isolates analysed by MLST were distributed on 14 sequence types (ST). Three ST (401, 82 and 249) accounted for 64% of all isolates analysed by MLST after 24 h. ST 82 has previously been reported from amyloid arthropathy and other lesions in poultry.

CONCLUSIONS

The present findings demonstrated a high potential of a few contaminated eggs or embryos to rapidly facilitate the spread of E. faecalis to almost all chickens during hatch.

Arthropathic and amyloidogenic Enterococcus faecalis infections in brown layers: A study on infection routes

Intravenous, intra-articular and intraperitoneal inoculation of 6-week-old brown-layer pullets with an arthropathic and amyloidogenic strain of Enterococcus faecalis resulted in amyloid arthropathy, while intramuscular, oral and intratracheal inoculation did not. Oral inoculation of 1-day-old chickens did not cause any pathology. However, intramuscular inoculation with 10⁶ colony forming units resulted in severe growth retardation and arthritis in 60% of the birds, and amyloid arthropathy in approximately 40%. In egg transmission studies, neither egg dipping nor inoculation of the air chamber with E. faecalis reproduced the condition, although a few chicks became septicaemic. Yolk sac inoculation of 6-day-old embryos caused embryonic death within 2 days. In contrast, egg albumen inoculation with E. faecalis led to arthritis in one of six of the progeny, indicating the possibility that vertical transmission of E. faecalis by the oviductal route could lead to arthritis. The presence of antibodies to E. faecalis was confirmed by enzyme-linked immunosorbent assay in 14/15 of experimental birds that had developed arthritis.

Real-time PCR detection of Enterococcus faecalis associated with amyloid arthropathy

AIMS

To develop a RT-PCR method for detection of the multilocus sequence type 82 of Enterococcus faecalis associated with amyloid arthropathy (AA) in layers.

METHODS AND RESULTS

Bacteria were selected from lesions including AA in layers. The primers were designed based on the phosphate ATP binding cassette transporter (pstS) and xanthine phosphoribosyltransferase (xpt) genes and first tested against three isolates with known base pairs at the specific sites. Subsequently, 12 isolates were selected from our collection by one researcher, and RT-PCR was performed blinded. The sequence type (ST) was then confirmed by multilocus sequence analysis. Two single-nucleotide polymorphisms in the pstS and xpt genes allowed an unambiguous identification of ST82. As an alternative to DNA extraction, a boiling method for release of DNA from cells was used.

CONCLUSIONS

The real-time PCR targeting ST82 enables rapid screening of Ent. faecalis cultured from suspect cases with results available after a few hours, much faster than multilocus sequence typing and pulse field gel electrophoresis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The new method allows a rapid screening of isolates with results available after only few hours. This RT-PCR method could be a useful tool for molecular epidemiological studies on the spread of arthropathic and amyloidogenic Ent. faecalis within and between birds more efficiently.

Characterization of small-colony variants of Enterococcus faecalis isolated from chickens with amyloid arthropathy

In this study we report the isolation and characterization of normal-sized and small-colony variants of Enterococcus faecalis from outbreaks of amyloid arthropathy in chickens. Postmortem examinations of 59 chickens revealed orange deposits in the knee joints, typical for amyloid arthropathy. Bacterial cultures from 102 joints and 43 spleens exhibited pure (n = 88) and mixed (n = 11) cultures of normal (n = 60) and pinpoint (n = 28) colonies of E. faecalis. Pulsed-field gel electrophoresis of 62 isolates demonstrated seven different band patterns with at most two band size variations, and multilocus sequence typing demonstrated two different sequence types, sharing six out of seven alleles, suggesting a close evolutionary relationship between isolates obtained from four outbreaks. In addition, all isolates were clonally related to an amyloid arthropathy reference strain from The Netherlands, previously shown to be globally dispersed. Initial investigation of the isolated small-colony variant phenotype revealed no difference in whole-cell protein profiling between normal and pinpoint colonies. However, the pinpoint colony isolates appeared to be more virulent in an in vivo challenge model in chickens than their normal-sized-colony counterparts. In addition, pinpoint morphology and associated slow growth were expressed without reversion after in vitro and in vivo passage, suggesting a genuine altered phenotype, and in some instances normal colonies converted to pinpoint morphology postinfection. In conclusion, small-colony variants of E. faecalis are described for the first time from veterinary clinical sources and in relation to amyloid arthropathy in chickens.

The role of chicken IL-1beta, IL-6 and TNF-alpha in the occurrence of amyloid arthropathy

In this study, the roles of IL-1beta, IL-6 and TNF-alpha in amyloid arthropathic chickens with variable amounts (severe, moderate and mild) of amyloid accumulation were investigated. The presence and the levels of cytokines were evaluated in serum and in joint tissues by using ELISA and immunohistochemistry, respectively. One hundred brown layer chicks were allocated into four groups and intra-articular injections of Freund's adjuvant were used to induce amyloid arthropathy in Groups II, III and IV. Vitamin A in group II, and methylprednisolone in Group IV were added to enhance and to reduce the severity of amyloidosis, respectively. At the end of the study, a positive correlation was observed among the incidence and severity of amyloidosis, the serum amyloid A levels and the IL-1beta values both in the serum and tissues. Elevation in the tissue TNF-alpha levels in parallel with the severity of amyloidosis has also been noted. As a conclusion, IL-1beta appears to play an important role in avian AA amyloidosis either alone or in combination with TNF-alpha. Further investigation is needed for understanding the role of the pro-inflammatory cytokines in avian AA amyloidosis.

The effects of vitamin A, pentoxyfylline and methylprednisolone on experimentally induced amyloid arthropathy in brown layer chicks

The effects of vitamin A, pentoxyfylline and methylprednisolone on experimentally induced amyloid arthropathy were investigated. In this study, 175 1-day-old brown layer chicks were used. Throughout the study Group II (vitamin A) received high doses of vitamin A (75,000 IU/kg), whereas Group I (negative control), Group III (positive control), Group IV (pentoxyfylline) and Group V (methylprednisolone) received normal levels of vitamin A in the diet. At the fifth week, the experimental Groups II, III, IV and V were injected with Freund's adjuvant intra-articularly to induce amyloid arthropathy. Group IV received pentoxyfylline and Group V received methylprednisolone (10 mg/kg, intramuscularly) once. Joint and blood samples were examined 13 weeks after the injections. The values in Groups I, II, III, IV and V, respectively, were as follows: amyloid arthropathy formation (%), 0, 100, 87, 76, 66; serum amyloid A (ng/ml), 166+/-17, 607+/-40, 423+/-39, 342+/-27, 293+/-22; serum retinol (microg/dl): 59.75+/-3.8, 42.72+/-3, 59.24+/-3.6, 102+/-9.1, 101.3+/-12.3; heterophil/lymphocyte ratio: 0.504, 0.75, 0.75, 0.087, 0.44. In conclusion, it was observed that vitamin A enhanced the development of amyloid arthropathy and there were positive associations between amyloidosis, increased levels of serum amyloid A and increased numbers of tissue infiltrating macrophages. Methylprednisolone had a more successful inhibitory effect on amyloid arthropathy than pentoxyfylline.

Molecular epidemiology of unilateral amyloid arthropathy in broiler breeders associated with Enterococcus faecalis

Although symmetrical polyarticular amyloidosis has been described extensively in brown layers, spontaneous unilateral amyloid arthropathy has not been described previously in chickens. Birds from nine flocks of broiler parent stock (PS) had unilateral lameness associated with severe swelling of the left hock joint and the caudal aspect of the metatarsus. Gross pathology was restricted to the left hock joint and the left digital flexor tendons in almost all cases, suggesting an association with administration of Marek's disease vaccine. Amyloid deposits were found in 83% (25/30) of affected joints by histological examination of Congo red stained sections. Systemic amyloidosis, involving mainly the liver and spleen, was found in 59% (10/17) of birds. Enterococcus faecalis was isolated from joints in 77% (23/30) of cases and Staphylococcus aureus was isolated from the joint in one case (1/30). Thirty-five E. faecalis isolates from joints, tendons and blood samples from birds in five affected PS flocks were compared using pulsed-field gel electrophoresis (PFGE) to separate genomic fragments after digestion with SmaI. All but one isolate had identical or closely related restriction endonuclease digestion (RED) patterns that were very similar to a known arthropathic and amyloidogenic E. faecalis isolate. A further 30 E. faecalis isolates from seven grandparent stock (GPS) flocks and two isolates from two unaffected PS flocks of the same genetic background were analysed by PFGE. Among these isolates, 11 originating from four GPS flocks had RED patterns identical to or closely related to the reference amyloid-inducing strain. Moreover, one E. faecalis isolate from amyloidotic joints of brown layers housed in California, USA was included in the analysis and appeared to be identical to the reference strain. This study showed that the E. faecalis isolates involved in these outbreaks of unilateral amyloid arthropathy in broiler breeders belonged to the same clone as that responsible for outbreaks in brown layers.

Epidemiology: Study on the vertical transmission of arthropathic and amyloidogenicEnterococcus faecalisin a flock of brown layer chickens

Enterococcus faecalis-related amyloid arthropathy was diagnosed in a sample of birds from a flock of brown layer parent chickens aged 57 weeks. E. faecalis was isolated from amyloidotic knee joints and from blood samples from lame birds. From this flock a smaller one was kept for production purposes to study the vertical transmission of arthropathic and amyloidogenic E. faecalis. Three batches of non-soiled and thoroughly disinfected eggs, to prevent egg-shell contamination, were collected for 6 weeks and submitted for incubation every 2 weeks. No joint pathology was found in the offspring chicks (n = 458) monitored for joint disease until 16 or 21 weeks of age. Fresh and candled eggs (infertiles and dead embryos) obtained at day 18 of the incubation period had negative results at bacteriological examination of the yolk sac, except one non-hatched egg (late embryonal death in shell) from which E. faecalis was isolated. Genotyping by pulsed-field gel electrophoresis (PFGE) of all E. faecalis isolates obtained from blood and joints (except one) of the parent birds and of the non-hatched egg after Sma I digestion showed that all isolates were genetically closely related or identical to a known arthropathic and amyloidogenic E. faecalis strain. In this study, vertical transmission of E. faecalis, although it may occur on a small scale as shown by PFGE, did not seem to play a significant role. Conversely, the chronicity of the condition and the development of an immune response may have affected the efficiency of its transmission.

Leukocyte responses in two breeds of layer chicken that differ in susceptibility to induced amyloid arthropathy

Amyloid arthropathy in chicken can be induced by intravenous inoculation of an arthropathic and amyloidogenic Enterococcus faecalis in susceptible breeds. The commercial brown layer hybrids (BL) are more susceptible to the disease compared to their white counterparts (WL). The precursor of amyloid-A protein, which is serum amyloid-A (SAA), is identical in WL and BL. To investigate the factors involved in the breed-restricted susceptibility to amyloid arthropathy, we studied the type of leukocyte response and inflammatory reactions in E. faecalis-induced disease. In the BL, a significant dose dependent peripheral leukocytosis mainly by heterophils, and plasma cell infiltration in arthritic joints was found. In contrast, secondary lymphoid nodular aggregates in the synovial membrane were prominent in the WL. The aggregates consisted mainly of CD8+ T cells. The high number of circulating leukocyte and prolific plasma cell responses in the BL predict extensive humoral and acute phase reactions. This is in agreement with literature data on suppressed T-cell function in casein-induced amyloid-susceptible mice strains. The difference in leukocyte response and type of inflammation between WL and BL, when arthropathic and amyloidogenic bacteria induce infection, in conjunction with susceptibility to amyloid arthropathy, is discussed in view of the murine T-helper responses.